Re: newspaper coverage of next week's NASS conference

[tloc54452]

 The article lists a "cordon" steel.  I believe that would be Cor-ten.

John B





Sent: Sat, Aug 7, 2010 11:44 am

See http://is.gd/e7Kyq for a newspaper article about next week's NASS
conference.

Fred Sawyer




 
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Re: Cantilever gnomon

[tloc54452]

 I should add that the sudden change where the tube comes up out of the 
concrete will cause a stress concentration.  The factor can be up to 3 times.  
One way to handle the problem is with a compliant mount, but that will lead to 
the gnomon moving to unforeseen positions.  Better, I think, would be to 
reinforce the tube below ground and above ground for the first couple of feet 
with another tube fitted inside.  Preferably press fitted or shrink fitted, but 
a glue-in should do the job also.

John




 


 

-Original Message-
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Fri, 3 Oct 2008 4:19 pm
Subject: Cantilever gnomon











 John C,



OK, just got back from meetings.  Five minutes gives me the attached.  I bumped 
the wall thickness to 1/8" as suggested.  Good plan.



It would be an air roar to say the 12' cantilever is stiffer or stronger than 
the 24' gnomon rigidly supported at both ends.  However, a perfectly 
satisfactory cantilever gnomon can be made with your specs.  Just keep steel 
strength in excess of 100,000 psi.  Consult me when you get down to real 
hardware.  The key word to keep in mind here is "mushroom".



John B





 







 



-Original Message-

From: [EMAIL PROTECTED]

To: [EMAIL PROTECTED]

Sent: Fri, 3 Oct 2008 10:45 am

Subject: Re: Long Rod Canceled!















 Hi John C,





Not to worry, po
liticos are often frightened by such things.  Comes from lack of practical 
experience or from innumeracy, though of course, you will often find both in 
the same politician.  That's why many people treat them like mushrooms.  C'est 
la vie.





We should look at the equations for a cantilever beam next.  Cantilevers are 
not nearly as strong as simply supported beams which in turn are not nearly as 
strong as rigidly supported beams.  However, in this instance, you have the 
huge advantage of having only half the length!





I have some meetings, but will compute stress & deflection for you later.  
Obviously, almost anything will do.  Just keep the tube's wall thick enough to 
keep it from getting dented, and Bob's your uncle.








 


John B











 





-Original Message-


From: John Carmichael <[EMAIL PROTECTED]>


To: [EMAIL PROTECTED]


Sent: Fri, 3 Oct 2008 9:18 am


Subject: Long Rod Canceled!
































Hi Guys:







 







Well, you won’t believe it, but after all that work
that you did to help me, the “committee” just informed me that now they
don’t want the extra long rod gnomon that goes into the ground!  They
say they don’t like the look of it!  But I think the real reason is that
they are really scared of the bending problem, because I’ve been keeping t
hem
informed of our great discussion.







 







This is typical of the way this project has been going. 
I spend20hours making my drawings and models and writing to you, and then they
go and change everything and I have to go redo it all.







 







Now they want the minimum length gnomon that will suffice for
the SW dial, and it will only be attached near the face.   The artist
decided on a 3” tube that will be 12 ft long.  We’re still
going to have a second sundial on the ground, but we’re going to use a
different piece of the sculpture to be its gnomon.







 







I loved our discussion nevertheless and it taught me things
that will surely come in handy for some other project.  I bet you all
learned some new things too that might help you. I’ve saved all your
letters, spreadsheets and drawings that you sent me in a special folder for
future reference.







 







Thanks guys,







 







John C







 







 







 







  







John L. Carmichael







Sundial Sculptures







925 E. Foothills Dr.







Tucson AZ 85718-4716







USA







Tel: 520-6961709







Email: [EMAIL PROTECTED]








 







My Websites:







(business) Sundial Sculpt
ures: http://www.sundialsculptures.com








(educational) Chinook Trail Sundial: 
http://advanceassociates.com/Sundials/COSprings/







(educational) Earth & Sky Equatorial
Sundial: http://advanceassociates.com/Sundials/Earth-Sky_Dial/ 








(educational) My Painted Wall Sundial:
http://www.advanceassociates.com/WallDial








(educational) Painted Wall Sundials: 
http://advanceassociates.com/WallDial/PWS_Home.html








(educational) Stained Glass Sundials: http://www.stainedglasssundials.com








(educational) Sundial Cupolas, Towers
& Turrets: http://StainedGlassSundials.com/CupolaSundial/index.html








 












 







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browse - Download Now! 





 






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McCain or Obama? Stay updated on coverage of the Pre

Cantilever gnomon

[tloc54452]

 John C,

OK, just got back from meetings.  Five minutes gives me the attached.  I bumped 
the wall thickness to 1/8" as suggested.  Good plan.

It would be an air roar to say the 12' cantilever is stiffer or stronger than 
the 24' gnomon rigidly supported at both ends.  However, a perfectly 
satisfactory cantilever gnomon can be made with your specs.  Just keep steel 
strength in excess of 100,000 psi.  Consult me when you get down to real 
hardware.  The key word to keep in mind here is "mushroom".

John B


 



 

-Original Message-
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Fri, 3 Oct 2008 10:45 am
Subject: Re: Long Rod Canceled!











 Hi John C,



Not to worry, politicos are often frightened by such things.  Comes from lack 
of practical experience or from innumeracy, though of course, you will often 
find both in the same politician.  That's why many people treat them like 
mushrooms.  C'est la vie.



We should look at the equations for a cantilever beam next.  Cantilevers are 
not nearly as strong as simply supported beams which in turn are not nearly as 
strong as rigidly supported beams.  However, in this instance, you have the 
huge advantage of having only half the length!



I have some meetings, but will compute stress & deflection for you later.  
Obviously, almost anything will do.  Just keep the tube's wall thick enough to 
keep it from getting dented, and Bob's your uncle.






 

John B







 



-Original Message-

From: John Carmichael <[EMAIL PROTECTED]>

To: [EMAIL PROTECTED]

Sent: Fri, 3 Oct 2008 9:18 am

Subject: Long Rod Canceled!



























Hi Guys:





 





Well, you won’t believe it, but after all that work
that you did to help me, the “committee” just informed me that now they
don’t want the extra long rod gnomon that goes into the ground!  They
say they don’t like the look of it!  But I think the real reason is that
they are really scared of the bending problem, because I’ve been keeping them
informed of our great discussion.





 





This is typical of the way this project has been going. 
I spend20hours making my drawings and models and writing to you, and then they
go and change everything and I have to go redo it all.





 





Now they want the minimum length gnomon that will suffice for
the SW dial, and it will only be attached near the face.   The artist
decided on a 3” tube that will be 12 ft long.  We’re still
going to have a second sundial on the ground, but we’re going to use a
different piece of the sculpture to be its gnomon.





 





I loved our discussion nevertheless and it taught me things
that will surely come in handy for some other project.  I bet you all
le
arned some new things too that might help you. I’ve saved all your
letters, spreadsheets and drawings that you sent me in a special folder for
future reference.





 





Thanks guys,





 





John C





 





 





 





  





John L. Carmichael





Sundial Sculptures





925 E. Foothills Dr.





Tucson AZ 85718-4716





USA





Tel: 520-6961709





Email: [EMAIL PROTECTED]






 





My Websites:





(business) Sundial Sculptures: http://www.sundialsculptures.com






(educational) Chinook Trail Sundial: 
http://advanceassociates.com/Sundials/COSprings/





(educational) Earth & Sky Equatorial
Sundial: http://advanceassociates.com/Sundials/Earth-Sky_Dial/ 






(educational) My Painted Wall Sundial:
http://www.advanceassociates.com/WallDial






(educational) Painted Wall Sundials: 
http://advanceassociates.com/WallDial/PWS_Home.html






(educational) Stained Glass Sundials: http://www.stainedglasssundials.com






(educational) Sundial Cupolas, Towers
& Turrets: http://StainedGlassSundials.com/CupolaSundial/index.html






 









 






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McCain or Obama? Stay updated on coverage of the Presidential race while you 
browse - Download Now! 



 





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n/listinfo/sundial




 



gnomon-cantilever_tube.xls
Description: Binary data
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Re: Long Rod Canceled!

[tloc54452]

 Hi John C,

Not to worry, politicos are often frightened by such things.  Comes from lack 
of practical experience or from innumeracy, though of course, you will often 
find both in the same politician.  That's why many people treat them like 
mushrooms.  C'est la vie.

We should look at the equations for a cantilever beam next.  Cantilevers are 
not nearly as strong as simply supported beams which in turn are not nearly as 
strong as rigidly supported beams.  However, in this instance, you have the 
huge advantage of having only half the length!

I have some meetings, but will compute stress & deflection for you later.  
Obviously, almost anything will do.  Just keep the tube's wall thick enough to 
keep it from getting dented, and Bob's your uncle.


 
John B



 

-Original Message-
From: John Carmichael <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Sent: Fri, 3 Oct 2008 9:18 am
Subject: Long Rod Canceled!






















Hi Guys:



 



Well, you won’t believe it, but after all that work
that you did to help me, the “committee” just informed me that now they
don’t want the extra long rod gnomon that goes into the ground!  They
say they don’t like the look of it!  But I think the real reason is that
they are really scared of the bending problem, because I’ve been keeping them
informed of our great discussion.



 



This is typical of the way20this project has been going. 
I spend hours making my drawings and models and writing to you, and then they
go and change everything and I have to go redo it all.



 



Now they want the minimum length gnomon that will suffice for
the SW dial, and it will only be attached near the face.   The artist
decided on a 3” tube that will be 12 ft long.  We’re still
going to have a second sundial on the ground, but we’re going to use a
different piece of the sculpture to be its gnomon.



 



I loved our discussion nevertheless and it taught me things
that will surely come in handy for some other project.  I bet you all
learned some new things too that might help you. I’ve saved all your
letters, spreadsheets and drawings that you sent me in a special folder for
future reference.



 



Thanks guys,



 



John C



 



 



 



  



John L. Carmichael



Sundial Sculptures



925 E. Foothills Dr.



Tucson AZ 85718-4716



USA



Tel: 520-6961709



Email: [EMAIL PROTECTED]




 



My Websites:



(business) Sundial Sculptures: http://www.sundialsculptures.com




(educational) Chinook Trail Sundial: 
http://advanceassociates.com/Sundials/COSprings/



(educational) Earth & Sky Equatorial
Sundial: http://advanceassociates.com/Sundials/Earth-Sky_Dial/ 




(educational) My Painted Wall Sundial:
http://www.advanceassociates.com/WallDial




(edu
cational) Painted Wall Sundials: 
http://advanceassociates.com/WallDial/PWS_Home.html




(educational) Stained Glass Sundials: http://www.stainedglasssundials.com




(educational) Sundial Cupolas, Towers
& Turrets: http://StainedGlassSundials.com/CupolaSundial/index.html




 






 





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Re: Preventing Rod Gnomon Bending

[tloc54452]

 Maybe everyone understands a double elastic hinge, but in case there is one 
person who doesn't, sketch attached.  Thinner plates are welded to a base 
plate.  Not shown, the gnomon tube goes through the holes in the thinner plates 
and is welded to them.  As I was saying, this thing could be covered if it 
doesn't fit with the aesthetics of the rest of the design.

John C, looks like that guy can do anything with metal.  Cool!


 
John B




 

-Original Message-
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Thu, 2 Oct 2008 9:49 am
Subject: Re: Preventing Rod Gnomon Bending











 Most tubes aren't perfectly straight, so it behooves one to rotate the tube 
until the high point is up.



I agree that axial compliance is needed.  However, sockets tend to be a little 
loose, and so you might lose your rigid support status.  (Rigid supports cause 
three bends in a bar while simple supports only cause one so rigid is much 
stiffer and stronger.)  So how about a double elastic hinge?  Everyone know 
what that is?  Maybe I should sketch it when I get a chance.  A double elastic 
hinge would keep the axes of the ends of the tube pointing at each other while 
allowing for expansion and contraction.  I think I would put the solid 
connection at the lower end of the gnomon and the double elastic hinge at the 
upper end where it would be less attractive to monkey with.  If it doesn't fit 
the aesthetics, it
 could have a cover over it.



John B





 





 



-Original Message-

From: Larry Bohlayer / Celestial Products <[EMAIL PROTECTED]>

To: 'Sundial List' <[EMAIL PROTECTED]>

Sent: Wed, 1 Oct 2008 7:44 pm

Subject: RE: Preventing Rod Gnomon Bending






































John,





 





In the structural engineering of bridges,
I believe that beams are often produced with a calculated curvature such that
when in place the flexure under its own weight puts it into straight line. Such
might be possible with your gnomon as well, BUT I think you will have to design
one of the end supports to allow for expansion/contraction movement. This could
simply be a socket welded to vertical face that allows the gnomon rod to slide
inside the socket.





 









Larry Bohlayer





Celestial Products





P.O. Box 801





Middleburg, VA 20118





540-338-4040





[EMAIL PROTECTED]









 





















From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On
Behalf Of John Carmichael


Sent: Wednesday, October 01, 2008
2:47 PM


To: 'Sundial List'


Subject: Preventing Rod Gnomon
Bending









 





Hi
Guys:





 





I’m
designing a large 15 foot tall southwest declining nearly vertical dial that
will have a very long20polar axis oriented rod gnomon.  But I’ve come
across a potential problem that I’ve never had to deal with before and am
seeking your expert advice or suggestions.





 





Setup:





The
gnomon rod will be unusually long because one end will be attached near the
sundial face and the other end will go down and be firmly attached to the
ground.  The reason 
that it will go all the way to the ground is because a
second horizontal dial will be on the ground that will use the same
gnomon.  The original specs have the gnomon rod diameter as 2 inches, but
it can be made wider if need be.  The gnomon length will be about 25
feet.  We have not decided if the gnomon will be a hollow tube (like a
metal pipe) or a solid metal rod.  We want to avoid using any gnomon
support struts and we want to prevent bending.   





 





Problem:





Since
I’m not a metal structural engineer, I am concerned that the 2”
diameter, 25 foot long gnomon might sag under its own weight or bend if kids
hang on it.  Keep in mind that it is attached at both ends, which should
help prevent bending.  Here are my questions:





 





1. Do hollow pipes bend easier than solid
rods? (I’m
 guessing they do, but I’m not sure.)





2. Can a hollow pipe be made to bend less
if it is filled with concrete? Or will the added weight just make
bending worse
? (This idea occurred to me because I’ve noticed that the
metal pipe collision barriers around gas station pumps are filled with
concrete.  Is this to prevent them from bending if a car hits them?)





3. Would increasing the diameter of the
gnomon give it added strength and prevent bending?





 





Any
help much appreciated!





 





Thx





&
nbsp;





John





 









 






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Re: Preventing Rod Gnomon Bending

[tloc54452]

 Oh, I concur wholeheartedly.  If it's an end attachment it's one thing, but if 
you want to fill the tube with it so as to make the tube stiffer, there are 
actually better ways.  I also agree with the guy who said don't make your wall 
too thin.  If it's too thin, it's not dent resistant.  A dent is a kink 
starter, so very bad thing.  If you want to fill the tube with something to 
help it keep its form, I'd suggest high density foam.  At a few pounds per 
cubic foot, it weighs nothing compared to the steel, but should help ward off 
collapses somewhat.  Also, someone suggested extruded aluminum tube with built 
-in reinforcement.  Good stuff, but not very straight in long lengths.  If you 
can't find it in the size you want, extrusion dies aren't too many thousands of 
$.  Of course, that's more than foam-filled aluminum or steel would be.  You 
should check into lengths of pipe very soon.  It can be hard to get just what 
you want in a very long length.


 
John B



 

-Original Message-
From: John Carmichael <[EMAIL PROTECTED]>
To: 'Roger Bailey' <[EMAIL PROTECTED]>; [EMAIL PROTECTED]; [EMAIL PROTECTED]
Sent: Thu, 2 Oct 2008 10:30 am
Subject: RE: Preventing Rod Gnomon Bending

























 



Hi Roger:



 



This comment of yours is most important, and if it’s true, then
that would be the way to go.  I trust you, so I’ll probably do wha
t you say.



 



You said:



John C, I would not put a box section
inside the round tube. Unless welded all the way along, the benefit is just
additive. You gain much more for the same weight with a thicker pipe where the
benefit is based on the difference in the fourth power of the
diameters. Thicker pipe is also cheaper and easier.



 



Thanks
Roger!  I hope the other guys agree with you.



 



John
C



 



 



 



 









From: Roger Bailey
[mailto:[EMAIL PROTECTED] 

Sent: Thursday, October 02, 2008 10:02 AM

To: [EMAIL PROTECTED]; [EMAIL PROTECTED];
[EMAIL PROTECTED]

Subject: Re: Preventing Rod Gnomon Bending









 






Hello
John B , John C and all,









 









The
spreadsheet is excellent. I agree. "Don't speculate, calculate. The
spreadsheet simply and elegantly calculates for round hollow pipe very well. I
have added a few lines for standard pipe 2" & 3" Sch 40 and
80 as these are commonly available.









 









My
comments speculated on different shapes without looking closely at the math. A
square hollow  hollow box is slightly better than a round hollow tube
of the same OD and ID as the factors multiplying the length to fourth power are
1/12 for the box and Pi/64 for the pipe.  









 









John
C, I would not=2
0put a box section inside the round tube. Unless welded al the
way along, the benefit is just additive. You gain much more for the same weight
with a thicker pipe where the benefit is based on the difference in the fourth
power of the diameters. Thicker pipe is also cheaper and easier.









 









To
show how the shear stress has to be carried through the material, try this
experiment with a couple of 2x4s. Lay a 2x4 between two supports and stand
on the middle of the span. Laid flat it really bends. On edge it bends
much less. One 2x4 on edge bends less that two 2x4s laid flat one on top of the
other.









 









Base
on the formula for the second moment of area for a rectangle, 1/12 x b x h^4,
one on edge is twice as stiff as two laid flat. 









 









Regards,
Roger









 









 









   















From: [EMAIL PROTECTED]










Sent: Thursday, October
02, 2008 7:21 AM









To: [EMAIL PROTECTED]
; [EMAIL PROTECTED]
; [EMAIL PROTECTED]










Subject: Re: Preventing Rod
Gnomon Bending















 









All of the
"scary equations" were hidden in the spreadsheet I sent out. 
Hidden so as not to scare anyone.  Did the spreadsheet arrive
unreadable?  Unfathomable?



John
 B









 









 






-Original Message-

From: Roger Bailey <[EMAIL PROTECTED]>

To: John Carmichael <[EMAIL PROTECTED]>;
'Sundial List' <[EMAIL PROTECTED]>

Sent: Wed, 1 Oct 2008 8:29 pm

Subject: Re: Preventing Rod Gnomon Bending









Hi
John,









 









In
general, a tube is stiffer than a rod if you are looking at bending from the
weight.  This is why structures are made from I beams not solid chunks of
steel. Engineers use the moment of inertia (second moment of area) to calculate
the effect of weight distributed at a distance from the center. An I beam is
best, a tube is next best, a rod with all that weight in the middle not
contributing to the strength is the worst. A round rod is not as stiff as a
square or rectangular bar for the same reasons. As noted, anything in the tube
only contributes by keeping the sides apart and adds weight. Ditto internal
structures. They only add weight close to the center. Thickness of the tube is
very important. For scary equations see 
http://en.wikipedia.org/wiki/Second_moment_of_a

Re: Preventing Rod Gnomon Bending

[tloc54452]

 Most tubes aren't perfectly straight, so it behooves one to rotate the tube 
until the high point is up.

I agree that axial compliance is needed.  However, sockets tend to be a little 
loose, and so you might lose your rigid support status.  (Rigid supports cause 
three bends in a bar while simple supports only cause one so rigid is much 
stiffer and stronger.)  So how about a double elastic hinge?  Everyone know 
what that is?  Maybe I should sketch it when I get a chance.  A double elastic 
hinge would keep the axes of the ends of the tube pointing at each other while 
allowing for expansion ad contraction.  I think I would put the solid 
connection at the lower end of the gnomon and the double elastic hinge at the 
upper end where it would be less attractive to monkey with.  If it doesn't fit 
the aesthetics, it could have a cover over it.

John B


 


 

-Original Message-
From: Larry Bohlayer / Celestial Products <[EMAIL PROTECTED]>
To: 'Sundial List' <[EMAIL PROTECTED]>
Sent: Wed, 1 Oct 2008 7:44 pm
Subject: RE: Preventing Rod Gnomon Bending

































John,



 



In the structural engineering of bridges,
I believe that beams are often produced with a calculated curvature such that
when in place the flexure under its own weight puts it into straight line. Such
might be possible with your gnomon as well, BUT I think you will have to design
one of the=2
0end supports to allow for expansion/contraction movement. This could
simply be a socket welded to vertical face that allows the gnomon rod to slide
inside the socket.



 






Larry Bohlayer



Celestial Products



P.O. Box 801



Middleburg, VA 20118



540-338-4040



[EMAIL PROTECTED]






 
















From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On
Behalf Of John Carmichael

Sent: Wednesday, October 01, 2008
2:47 PM

To: 'Sundial List'

Subject: Preventing Rod Gnomon
Bending






 



Hi
Guys:



 



I’m
designing a large 15 foot tall southwest declining nearly vertical dial that
will have a very long polar axis oriented rod gnomon.  But I’ve come
across a potential problem that I’ve never had to deal with before and am
seeking your expert advice or suggestions.



 



Setup:



The
gnomon rod will be unusually long because one end will be attached near the
sundial face and the other end will go down and be firmly attached to the
ground.  The reason that it will go all the way to the ground is because a
second horizontal dial will be on the ground that will use the same
gnomon.  The original specs have the gnomon rod diameter as 2 inches, but
it can be made wider if need be.  The gnomon length will be about 25
feet.  We have not decided if the gnomon will be a hollow tube (like a
metal pipe) or a solid me
tal rod.  We want to avoid using any gnomon
support struts and we want to prevent bending.   



 



Problem:



Since
I’m not a metal structural engineer, I am concerned that the 2”
diameter, 25 foot long gnomon might sag under its own weight or bend if kids
hang on it.  Keep in mind that it is attached at both ends, which should
help prevent bending.  Here are my questions:



 



1. Do hollow pipes bend easier than solid
rods? (I’m guessing they do, but I’m not sure.)



2. Can a hollow pipe be made to bend less
if it is filled with concrete? Or will the added weight just make
bending worse? (This idea occurred to me because I’ve noticed that the
metal pipe collision barriers around gas station pumps are filled with
concrete.  Is this to prevent them from bending if a car hits them?)



3. Would increasing the diameter of the
gnomon give it added strength and prevent bending?



 



Any
help much appreciated!



 



Thx



 



John



 






 





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Re: Preventing Rod Gnomon Bending

[tloc54452]

 All of the "scary equations" were hidden in the spreadsheet I sent out.  
Hidden so as not to scare anyone.  Did the spreadsheet arrive unreadable?  
Unfathomable?

John B


 



 

-Original Message-
From: Roger Bailey <[EMAIL PROTECTED]>
To: John Carmichael <[EMAIL PROTECTED]>; 'Sundial List' <[EMAIL PROTECTED]>
Sent: Wed, 1 Oct 2008 8:29 pm
Subject: Re: Preventing Rod Gnomon Bending
















Hi John,


 


In general, a tube is stiffer than a rod if you are 
looking at bending from the weight.  This is why structures are made from I 
beams not solid chunks of steel. Engineers use the moment of inertia (second 
moment of area) to calculate the effect of weight distributed at a distance 
from 
the center. An I beam is best, a tube is next best, a rod with all that weight 
in the middle not contributing to the strength is the worst. A round rod is not 
as stiff as a square or rectangular bar for the same reasons. As noted, 
anything 
in the tube only contributes by keeping the sides apart and adds weight. Ditto 
internal structures. They only add weight close to the center. Thickness of the 
tube is very important. For scary equations see 
http://en.wikipedia.org/wiki/Second_moment_of_area 


 


Regards, Roger Bailey  PEng*


 


*Unfortunately my PEng only applies for chemical 
engineering nor sundial or other structural design.







From: John Carmichael 


Sent: Wednesday, October 0
1, 2008 11:46 AM


To: 'Sundial List' 


Subject: Preventing Rod Gnomon Bending










Hi Guys:


 


I’m designing a large 15 foot tall southwest declining nearly 
vertical dial that will have a very long polar axis oriented rod gnomon.  
But I’ve come across a potential problem that I’ve never had to deal with 
before 
and am seeking your expert advice or suggestions.


 


Setup:


The gnomon rod will be unusually long because one end will be 
attached near the sundial face and the other end will go down and be firmly 
attached to the ground.  The reason that it will go all the way to the 
ground is because a second horizontal dial will be on the ground that will use 
the same gnomon.  The original specs have the gnomon rod diameter as 2 
inches, but it can be made wider if need be.  The gnomon length will be 
about 25 feet.  We have not decided if the gnomon will be a hollow tube 
(like a metal pipe) or a solid metal rod.  We want to avoid using any 
gnomon support struts and we want to prevent bending. 
  


 


Problem:


Since I’m not a metal structural engineer, I am concerned 
that the 2” diameter, 25 foot long gnomon might sag under its own weight or 
bend 
if kids hang on it.  Keep in mind that it is attached at both ends, which 
should help prevent bending.  Here are my questions:


 


1. 
Do hollow pipes bend
 easier than solid rods? (I’m guessing they do, but 
I’m not sure.)


2. 
Can a hollow pipe be made to bend less if it is filled with concrete? Or 
will the added weight just make bending worse? (This idea occurred to me 
because 
I’ve noticed that the metal pipe collision barriers around gas station pumps 
are 
filled with concrete.  Is this to prevent them from bending if a car hits 
them?)


3. 
Would increasing the diameter of the gnomon give it added strength and prevent 
bending?


 


Any help much appreciated!


 


Thx


 


John


 











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Re: Preventing Rod Gnomon Bending

[tloc54452]

 John C,

OK, here's a better deal for you.  See attached spreadsheet.

Change the figures in black to reflect the tubing you like and can get.  
Outputs are in red or blue according to whether your tube is simply supported 
or rigidly supported.  The truth will be in between.

Stresses and deflections are additive.  If the stress from gravity is 6000 psi 
and the stress from the miscreant is 60,000 psi, then the total stress is 
66,000 psi.  If people will be around the thing, you must have a safety factor 
of four on the ultimate strength for ductile material.  So your material must 
be good for 4 * 66,000 = 264,000 psi.  You would have to be rich!  

Deflections are also additive.  If the deflection from gravity is 2" and the 
deflection from the miscreant is 16", the total deflection is 18".

The spreadsheet presently calculates for steel.  If you use another material, 
you must change the Young's modulus and the density.  For instance, the density 
for aluminum will be 0.1 lb/cubic inch and the Young's modulus will be 1E7 psi.

Have fun.

John B



 


 

-Original Message-
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Wed, 1 Oct 2008 5:46 pm
Subject: Re: Preventing Rod Gnomon Bending











 Hi John C,



Off the top of my head, 25' between supports is going to be a bit long for 2" 
outside diameter in steel.  4" might do it, will have to lay some numbers on it 
and quit guessing.
 Glad to hear it is supported at both ends.  Supported in the middle might be 
easier, but we like a challenge, right?  Besides, the engineering must follow 
the aesthetics where possible.



OK, you are supported at both ends by welding to something that is steel.  Is 
that steel substantial?  The reason I ask is there are two types of supports.  
One is simply supported, as if the two ends were up on wheels.  The other way 
is rigidly supported, but that takes a helluva stiff support.  Real world 
supports tend to fall in between these two extremes.  So by giving me a feel 
for how stiff these supports are, or telling me something about them so I can 
decide for myself, I can guess where these supports might lie on the continuum 
between simple and rigid.



One more thing - we need definitions for what's acceptable.

1) How much deflection under its own weight is tolerable?

2) How much child weight must it be able to support without permanent 
deflection?  Also, any chance the miscreant will bounce on the thing rather 
than gently hang from it?



John B



PS: BTW, this is a power function, so if it's 24' 6" and not 25', that will 
help tremendously.





 

PPS: Yes!  32.5 degrees up from the horizontal will help.









 



-Original Message-

From: John Carmichael <[EMAIL PROTECTED]>

To: [EMAIL PROTECTED]; [EMAIL PROTECTED]

Sent: Wed, 1 Oct 2008 4:36 pm

Subject: RE: Preventing Rod Gnomon B
ending






























Hi John B:





 





The minimum diameter of the gnomon is 2” (5cm) because if it’s
any thinner the shadow will be too narrow.  But it could be as thick as 4”
(10cm).  It will be close to 25 feet (7.6meters) long.  Both ends w
ill be
welded to solid steel.  It’ll be at an angle of 32.5 degrees to horizontal, if
that helps.





 





Can you really help me figure this out?  There must be some sort
of mathematical formula to use.





 





By the way, my first thought was to use a stranded steel cable
with a counterweight to maintain tension (sort of like my stone dials), but the
design does not allow for it.  It’s gotta be a tube or a rod.





 





I hope this is enough info for you.  If you know how to crunch
the numbers, can you see if the 2” diameter tube or rod will work?





 





Thanks ever so much!





 





John





 





 





 









From:
[EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of [EMAIL PROTECTED]


Sent: Wednesday, October 01, 2008 4:10 PM


To: [EMAIL PROTECTED]


Subject: Re: Preventing Rod Gnomon Bending









 









Hi
John,





You actually have two questions here, and several engineers 
on the list to
answer them.





1) What should I do to prevent its deflection under its own weight?


2) What should I do to make it resistant to permanent deformation?





The answer to the second one is easy: make it out of the thinnest music
wire.  You can bend music wire in a tight circle and it will spring back
to its original shape without harm.  (Tongue in cheek: you can also make
it out of nitinol, then if it's bent, you heat it, and it will spring back to
its original shape.)





The answer to the first one is also easy: make it as hefty as you can. 
Solid does bend less easily than cored, but you pay a heavy weight premium with
consequent increased deflection under its own weight.  The purpose of
filling a tube, whether with sand, foam, or concrete, is to keep the walls
apart so that maximum stiffness is realized.  Without a filler, you kink
the tube, the walls are next to each other, and stiffness is gone.

Re: Preventing Rod Gnomon Bending

[tloc54452]

 Hi John C,

Off the top of my head, 25' between supports is going to be a bit long for 2" 
outside diameter in steel.  4" might do it, will have to lay some numbers on it 
and quit guessing.  Glad to hear it is supported at both ends.  Supported in 
the middle might be easier, but we like a challenge, right?  Besides, the 
engineering must follow the aesthetics where possible.

OK, you are supported at both ends by welding to something that is steel.  Is 
that steel substantial?  The reason I ask is there are two types of supports.  
One is simply supported, as if the two ends were up on wheels.  The other way 
is rigidly supported, but that takes a helluva stiff support.  Real world 
supports tend to fall in between these two extremes.  So by giving me a feel 
for how stiff these supports are, or telling me something about them so I can 
decide for myself, I can guess where these supports might lie on the continuum 
between simple and rigid.

One more thing - we need definitions for what's acceptable.
1) How much deflection under its own weight is tolerable?
2) How much child weight must it be able to support without permanent 
deflection?  Also, any chance the miscreant will bounce on the thing rather 
than gently hang from it?

John B

PS: BTW, this is a power function, so if it's 24' 6" and not 25', that will 
help tremendously.


 
PPS: Yes!  32.5 degrees up from the horizontal will help.




 

-Original Message--
---
From: John Carmichael <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
Sent: Wed, 1 Oct 2008 4:36 pm
Subject: RE: Preventing Rod Gnomon Bending

























Hi John B:



 



The minimum diameter of the gnomon is 2” (5cm) because if it’s
any thinner the shadow will be too narrow.  But it could be as thick as 4”
(10cm).  It will be close to 25 feet (7.6meters) long.  Both ends will be
welded to solid steel.  It’ll be at an angle of 32.5 degrees to horizontal, if
that helps.



 



Can you really help me figure this out?  There must be some sort
of mathematical formula to use.



 



By the way, my first thought was to use a stranded steel cable
with a counterweight to maintain tension (sort of like my stone dials), but the
design does not allow for it.  It’s gotta be a tube or a rod.



 



I hope this is enough info for you.  If you know how to crunch
the numbers, can you see if the 2” diameter tube or rod will work?



 



Thanks ever so much!



 



John



 



 



 






From:
[EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of [EMAIL PROTECTED]

Sent: Wednesday, October 01, 2008 4:10 PM

To: [EMAIL PROTECTED]

Subject: Re: Preventing Rod Gnomon Bending






 






Hi
John,



You actually have
 two questions here, and several engineers on the list to
answer them.



1) What should I do to prevent its deflection under its own weight?

2) What should I do to make it resistant to permanent deformation?



The answer to the second one is easy: make it out of the thinnest music
wire.  You can bend music wire in a tight circle and it will spring back
to its original shape without harm.  (Tongue in cheek: you can also make
it out of nitinol, then if it's bent, you heat it, and it will spring back to
its original shape.)



The answer to the first one is also easy: make it as hefty as you can. 
Solid does bend less easily than cored, but you pay a heavy weight premium with
consequent increased deflection under its own weight.  The purpose of
filling a tube, whether with sand, foam, or concrete, is to keep the walls
apart so that maximum stiffness is realized.  Without a filler, you kink
the tube, the walls are next to each other, and stiffness is gone.



As you can see, the two answers are in conflict.  Shall we start with an
example?  Give me some rough dimensions, including telling me where and
how the rod is supported, and we can try various things.



Best,

John B









 









 






-Original Message-

From: John Carmichael <[EMAIL PROTECTED]>

To: 'Sundial List' <[EMAIL PROTECTED] i-koeln.de>

Sent: Wed, 1 Oct 2008 11:46 am

Subject: Preventing Rod Gnomon Bending













Hi Guys:









 









I’m designing a large 15 foot tall southwest declining
nearly vertical dial that will have a very long polar axis oriented rod
gnomon.  But I’ve come across a potential problem that I’ve never had to
deal with before and am seeking your expert advice or suggestions.









 









Setup:









The gnomon rod will be unusually long because one end will
be attached near the sundial face and the other end will go down and be firmly
attached to the ground.  The reason that it will go all the way to the
ground is because a second horizontal dial will be on the ground that will use
the same gnomon.  The original specs have the gnomon rod diameter as 2
inches, but it can be made wider if need be.  The gnomon length will be
about 25 feet.  We have not decided if the gnomon will be a hollow tube
(like a metal pipe) or a so

Re: Preventing Rod Gnomon Bending

[tloc54452]

 Hi John,

You actually have two questions here, and several engineers on the list to 
answer them.

1) What should I do to prevent its deflection under its own weight?
2) What should I do to make it resistant to permanent deformation?

The answer to the second one is easy: make it out of the thinnest music wire.  
You can bend music wire in a tight circle and it will spring back to its 
original shape without harm.  (Tongue in cheek: you can also make it out of 
nitinol, then if it's bent, you heat it, and it will spring back to its 
original shape.)

The answer to the first one is also easy: make it as hefty as you can.  Solid 
does bend less easily than cored, but you pay a heavy weight premium with 
consequent increased deflection under its own weight.  The purpose of filling a 
tube, whether with sand, foam, or concrete, is to keep the walls apart so that 
maximum stiffness is realized.  Without a filler, you kink the tube, the walls 
are next to each other, and stiffness is gone.

As you can see, the two answers are in conflict.  Shall we start with an 
example?  Give me some rough dimensions, including telling me where and how the 
rod is supported, and we can try various things.

Best,
John B



 


 

-Original Message-
From: John Carmichael <[EMAIL PROTECTED]>
To: 'Sundial List' <[EMAIL PROTECTED]>
Sent: Wed, 1 Oct 2008 11:46 am
Subject: Preventing Rod Gnomon Bending






















Hi 
Guys:



 



I’m designing a large 15 foot tall southwest declining
nearly vertical dial that will have a very long polar axis oriented rod gnomon. 
But I’ve come across a potential problem that I’ve never had to
deal with before and am seeking your expert advice or suggestions.



 



Setup:



The gnomon rod will be unusually long because one end will
be attached near the sundial face and the other end will go down and be firmly
attached to the ground.  The reason that it will go all the way to the
ground is because a second horizontal dial will be on the ground that will use
the same gnomon.  The original specs have the gnomon rod diameter as 2
inches, but it can be made wider if need be.  The gnomon length will be
about 25 feet.  We have not decided if the gnomon will be a hollow tube
(like a metal pipe) or a solid metal rod.  We want to avoid using any gnomon
support struts and we want to prevent bending.   



 



Problem:



Since I’m not a metal structural engineer, I am concerned
that the 2” diameter, 25 foot long gnomon might sag under its own weight
or bend if kids hang on it.  Keep in mind that it is attached at both
ends, which should help prevent bending.  Here are my questions:



 



1. Do
hollow pipes bend easier than solid rods? (I’m guessing they do,
but I’m not sure.)



2.
Can a hollow pipe be made to b
end less if it is filled with concrete? Or
will the added weight just make bending worse? (This idea occurred to me
because I’ve noticed that the metal pipe collision barriers around gas
station pumps are filled with concrete.  Is this to prevent them from
bending if a car hits them?)



3.
Would increasing the diameter of the gnomon give it added strength and prevent
bending?



 



Any help much appreciated!



 



Thx



 



John



 






 





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Re: Welcome to summer

[tloc54452]

 Whoa, where'd spring go?

John B


 











...and, we are closer to the sun in our winter than
they are:)

Simon


--- Chris Lusby Taylor <[EMAIL PROTECTED]>
wrote:

> I believe the sun crossed the equator earlier today,
> so it's now summer here
> in the Northern Hemisphere. Commiserations to all of
> you in the Southern
> Hemisphere, especially as our summer is longer than
> yours.
> Chris Lusby Taylor
> 51.4N 1.3W










 

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Re: Brass sundial and girl

[tloc54452]

That's beautiful!  Does it seem like the girl's torso might block light to the 
dial?

John B


 


 

-Original Message-
From: Александр Болдырев <[EMAIL PROTECTED]>









Hi!

My friend Dr N. Mishik has found out in the Internet a very nice sundial 
located 
in Polotsk (Byelorussia).  Please, press the link for higher resolution. 

http://www.fotku.ru/?p=sf&f=0

Aleksandr
- - - - - - - - -
www.sundials.ru














More new features than ever.  Check out the new AOL Mail ! - 
http://webmail.aol.com
---
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direct south recliner

[tloc54452]

I'm working on a direct south recliner for my latitude.
Since I don't have a PC, I don't have a sundial-
drawing program.? I used the low end of Vellum's 
offerings to draw the attached which shows me 
the proportions of the dial.? This is for 37.72N
and it reclines 25 degrees to give me an extra 
hour of readings near the summer solstice.
Vellum's CAD programs work on a lot of platforms,
which is handy.

Best,
John B



Email and AIM finally together. You've gotta check out free AOL Mail! - 
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Re: A simpler statement?

[tloc54452]

 Hi Fer,

Thanks!? People like you make all the difference.
I started years ago with just Waugh's book.? Did
not know of this mailing list.? Then when I had a 
realization (an "Aha!"), I did not know if was right
or not.? It might be a very long time before I was 
sure.

John




 


 

-Original Message-
From: fer de vries <[EMAIL PROTECTED]>
To: sundial@uni-koeln.de; [EMAIL PROTECTED]
Sent: Tue, 4 Sep 2007 4:55 am
Subject: Re: A simpler statement?
















Hi John,


?


Indeed, this is a simplification of the formula for 
a sundial.


?


In stead of phi I prefer another letter for the 
style height but that's just a choice. I use v.


Phi then still is the latitude.


?


It also is my practice to start with the 
calculation of the styleheight for any planar sundial.


I take care of the right sign which tells me if the 
equivalent horizontal dial is at northern or southern latitude.


I then know if the hourlines run 
clockwise or anticlockwise or are parallel.


I also know if the polestyle points to the north or 
south pole or is parallel to the sundial's plane.


?


If you also calculate the hourangle of the substyle 
(ts as I use) the formula for any dial is:


?


tan z = tan ( t - ts ) * sin v.


?


This is the simplification as you propose but now 
for any planar dial.


?


You can read more about this at our website 
at


http://www.de-zonnewijzerkring.nl/eng


?


Follow the links


Calculate and construct


Extensive version.


?


Look at the paragraph notes and how the program 
ZW2000 uses this principle.


?


Best wishes, Fer.


?



?



Fer J. de Vries


?


De Zonnewijzerkring
http://www.de-zonnewijzerkring.nl


?


Molens
http://www.collsemolen.dse.nl


?


Eindhoven, Netherlands
lat.? 51:30 N? 
long.? 5:30 E






  
- Original Message - 

  
From: 
  [EMAIL PROTECTED] 

  
To: sundial@uni-koeln.de 

  
Sent: Tuesday, September 04, 2007 1:05 
  AM

  
Subject: A simpler statement?

  


According to various 
  books, one lays out the hour-line angles 
of a horizontal dial for the 
  latitude, one lays out the hour-line 
angles of a direct-south vertical 
  dial for the co-latitude, and 
one lays out the hour-line angles of a 
  reclining direct-south 
dial for the co-latitude minus the angle of 
  reclination.

I wonder if it would be simpler to say (for northern 
  latitudes) that:
1) The style of the gnomon always points to the (ideal) 
  north star
2) Hour-line angles are laid out by 
?D = ARCTAN (TAN t 
  * SIN phi)
?where
?D = hour-line angle
?t = solar hour 
  angle
?phi = angle of style to dial plate

This is the usual 
  equation, but I have redefined phi.

John B


  

  


  Email and AIM finally together. You've gotta check out free AOL Mail!


  

  




  

---
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Email and AIM finally together. You've gotta check out free AOL Mail! - 
http://mail.aol.com
---
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A simpler statement?

[tloc54452]

According to various books, one lays out the hour-line angles 
of a horizontal dial for the latitude, one lays out the hour-line 
angles of a direct-south vertical dial for the co-latitude, and 
one lays out the hour-line angles of a reclining direct-south 
dial for the co-latitude minus the angle of reclination.

I wonder if it would be simpler to say (for northern latitudes) that:
1) The style of the gnomon always points to the (ideal) north star
2) Hour-line angles are laid out by 
?D = ARCTAN (TAN t * SIN phi)
?where
?D = hour-line angle
?t = solar hour angle
?phi = angle of style to dial plate

This is the usual equation, but I have redefined phi.

John B



Email and AIM finally together. You've gotta check out free AOL Mail! - 
http://mail.aol.com
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Re: Hi Def Photo settings?

[tloc54452]

 To pick a nit (though not sure if one's there to pick)
1080interlace is what's broadcast but 1080progressive


 is what comes off a high def DVD such as Blu Ray.


 
John B




-Original Message-
From: Brooke Clarke <[EMAIL PROTECTED]>
To: John Carmichael <[EMAIL PROTECTED]>; [EMAIL PROTECTED]
Sent: Sun, 15 Jul 2007 10:43 am
Subject: Re: Hi Def Photo settings?










Hi John:

This morning I was reading about the different video systems. In the U.S. the 
old standard is now called 480i and the progressive scan version 480P.
HDTV can be called 720P or 1080i.  The interesting thing is that the image 
format is from the Motion Picture Engineering Group (MPEG) the same folks who 
brought you JPEG for still images.  It's my understanding you can store images 
in .jpg format on a DVD (or web page) and a DVD players will access them.  But 
I haven't tried it.

The photoshop print size is based on 72 DPI which at one time was the common 
printer resolution.  If your DPI setting is not 72 then the actual print size 
photoshop displays will be incorrect.

Forget about the print size and just set the pixel dimensions where you want 
them.  Note that the horizontal and vertical pixel counts are locked together. 
  If you want to get a 16:9 format you need to crop the image.  If you did it 
by changing the pixel counts the image would become distorted.

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com



John Carmichael wrote:
> Hello to the webmasters & photo buffs amongst us:
> 
>  
> 
> In this new age of High Definition Wide Screen Television and computer 
> monitors and high speed internet connections, more and more people will 
> want to see photos and movies in Wide Screen High Definition.  (Have you 
> seen a slide show on a large HDTV?  They are great!  And so convenient- 
> a lot easier that setting up a projection screen and a projector) I’m 
> thinking about providing access to hi def jpg. sundial photos on the 
> websites that I am involved with.  But I have a technical question about 
> what resolution and dpi settings I should use when resizing original 
> photos using PhotoShop Elements.
> 
>  
> 
>  
> 
> Ideally, the photo should completely fill the screen of the HDTV with no 
> black blank spaces on the sides.  Usually, the original photos I get are 
> taken with digital cameras set at the highest max resolution settings 
> but they do not have the correct wide screen aspect ratio.  They are 
> shaped like traditional photos with different aspect ratios (4” x  6”, 
> or 8” X 10”, or 11” X 17”, etc.) So to make them fit the screen, they 
> need to be cropped.  (For artistic and copywrite reasons, I won’t to do 
> it to old photos, but it could be done.)  Fortunately, most of the newer 
> cameras have hi def wide screen image size settings (16:9 aspect 
> ratio).   So new photos can be easily shot in wide screed hi def and 
> don’t need resizing or cropping.
> 
>  
> 
> In Photoshop, the resize tool lets you pick the image size (height x 
> width dimensions in pixels) and the document size (resolution in 
> pixels/inch). Modern digital cameras allow you to set the image size for 
> widescreen hi def viewing.  These photos measure 1920 x 1080 pixels and 
> Photoshop says that they have a resolution of 72 dpi.  So I assume that 
> this is the ideal photo size and resolution for viewing on a hi def 
> monitor or TV.  Is this correct?
> 
>  
> 
> Until now, I have been resizing the website photos to a height of 900 
> pixels at a resolution of 150 dpi.  Since the dpi is more than double 
> the new camera res of 72 dpi, even though the height is less, then 
> couldn’t I increase the size of these photos to a height of 1080 and a 
> dpi of 72 without loss of quality?
> 
>  
> 
> Any thoughts on this?
> 
>  
> 
> Thx
> 
>  
> 
> John
> 
>  
> 
> John L. Carmichael
> 
> Sundial Sculptures
> 
> 925 E. Foothills Dr.
> 
> Tucson AZ 85718-4716
> 
> USA
> 
> Tel: 520-6961709
> 
> Email: [EMAIL PROTECTED] 
> 
>  
> 
>  
> 
> My Websites:
> 
> (business) Sundial Sculptures: http://www.sundialsculptures.com 
> 
> 
> (educational): Earth & Sky Equatorial Sundial: 
> http://advanceassociates.com/Sundials/Earth-Sky_Dial/ 
> 
> (educational) My Painted Wall Sundial: 
> http://www.advanceassociates.com/WallDial
> 
> (educational) Painted Wall Sundials: 
> http://advanceassociates.com/WallDial/PWS_Home.html
> 
> (educational) Stained Glass Sundials: 
> http://www.stainedglasssundials.com 
> 
> (educational) Sundial Cupolas, Towers & Chimneys: 
> http://StainedGlassSundials.com/CupolaSundial/index.html 
> 
> 
>  
> 
> 
> 
> 
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
> 


-

Re: Help Oscar!

[tloc54452]

One might argue that the single page of cutouts 
now provided is indicative of the level of effort 
the school wishes to put into this subject.

Perhaps, then, we should design that page and 
also provide two pages of explanatory material 
for the teacher.? I think this is the best for which 
we can hope.

If we want to volunteer in the schools, and they 
will make time for us, more time can be spent 
on the subject with better result.? (In which case
I would _definitely_ utilize Tony's prepared material.)
Pursuant to this, should we form a pedagogue-
recognized group, e.g. The Sundial Missionary Society?

John B




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Re: Help Oscar!

[tloc54452]

Perhaps for a child of 8, a single-page explanation/illustration with cutout 
dial at the bottom is the ticket.? Can it be done?? Then how about two pages?

John B



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Re: Poncet or Equatorial platforms

[tloc54452]

That's cool.? The fellow with a Dobsonian wants a
low-height platform underneath his apparatus, and 
so do thee and me.? So instead of a long arcuit 
surface, he uses two short arcs.? Very nice.

Personally, I'm more of a purist, but for a fellow
who wants to match his watch time, this is a great
solution.

John B


 


 

Mac Oglesby wrote:


For an excellent site to visit without registration, look at:

http://www.biophysik.uni-freiburg.de/Reiner/ATM/atm_e.html

(click on "eq platform" at left edge)





 



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Re: Poncet Platform

[tloc54452]

Hi Peter,

One more image, of the pivot alone?? Can't quite make it out in that second 
view.? The rest is quite clear.

Question: Is it still a Poncet platform if it utilizes a cylindrical surface 
rather than a planar surface?

Best,
John B


Peter Mayer wrote:








?

Hi,?
?

?  I've tried to send a couple of small jpgs of my crude Poncet 
Platform, but they've been blocked by the server, too large.  I may have 
to try in stages.?
?

best wishes,?
?

Peter?
?




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Re: Glynne replica dial

[tloc54452]

 4/25.4 = .1575 inch
8*13+60 = .164 inch

That's not much difference at all.
(These are nominal, both will be under)
I would tap it out to 8-32.? It would
be easy to do with so little metal 
to remove.? You're lucky it's close
to 32 TPI. (25.4/32 = 0.79 mm)

To get gnomons on in a repeatably
correct position, I've been doweling
the gnomon to the dial plate.? 
(Pressing dowels into the gnomon
with matching holes in the plate.)
By having one dowel between the
screw holes and one outside, the
gnomon can't be put on backwards.

More about pinning: I screw the 
gnomon to the dial plate, adjust 
its position, then drill the dowel 
holes (match drill, since it's already 
assembled).? After drilling, I dis-
assemble and ream the holes in
the gnomon for a press fit and the
holes in the dial plate for a slip 
fit.? Press in the dowels and Bob's 
your uncle.? I hope this doesn't
sound difficult; it's terribly easy.

John B



 


 

-Original Message-
From: Richard M Koolish <[EMAIL PROTECTED]>
To: sundial@uni-koeln.de
Sent: Thu, 7 Jun 2007 6:42 am
Subject: Glynne replica dial










I have been given a sundial that may be a Glynne replica
drawn by Fer deVries.  I found it at a friends house in
the suburbs of Boston, Massachusetts USA.  The gnomon was
mounted backwards.  There are some pictures at:

http://www.dickkoolish.com/rmk_page/pictures_060407.html

The screws were steel and rusted, and I had to drill the heads
off in order to remove them.  When I went to replace them, I
discovered that they were not a standard english or metric thread.
The dial plate is about 12" in diameter and the gnomon angle
is 54.5 degrees.  It says Fer J. deVries 1982 under the gnomon.
An old message in the sundial archive mentions a similar but
smaller dial.

http://www.mail-archive.com/sundial@uni-koeln.de/msg04470.html

The old screws are the same diameter as a 4mm metric screw, but
the thread is .8 pitch or 32/in, so an 8-32 is too big
and a 4mm-.7 is too fine a thread, so I'm wondering what
to do about re-attaching it.

Also, it looks like the dial plate was once glued to the
marble base disk, but the adhesvie has long since dried
out and failed.  I assume glue was used to prevent the
thin dial plate from being lifted and bent. So, should
adhesive be used, and what kind?

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Re: spherical geometry question

[tloc54452]

 Many thanks, Fer and Gianni!
 
 You are right, Fer, I did mean 5 am to 7 pm. My mistake. I meant to ask for 
plus or minus 5 hours, 6 hours, and 7 hours from noon.
 
 Using 37.72N rather than 38N, the results are
 +/- 5 hours 21.46 from vertical or 68.54 above horizon
 +/- 6 hours 52.28 from vertical or 37.72 above horizon
 +/- 7 hours 83.11 from vertical or 6.89 above horizon
 
 This is exactly what I wanted to know! I want something that is like a wall 
dial (for near ground level at the north center of my daughter's yard), so 
perhaps about 30 degrees from vertical will be my limit. I will have to 
sacrifice the other summer hours in order to be able to read the dial without 
having to stand near it as you do with a horizontal dial. This little bit of 
tilt still gives some improvement compared to my vertical wall dials, and 
that's what I want. Obviously I could instead put up two joined vertical dials 
with the proper dihedral angle between them, but I wanted to do this with a 
single dial face.
 
 Thanks again, you guys,
 John
 
 

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spherical geometry question

[tloc54452]

 This is pretty simple, but rather than damage anything delicate by actually 
thinking, I thought I'd just ask.
 
 In the summer, obviously I lose the morning and evening hours on my direct 
south vertical dials.
 
 How far back would I have to recline a direct south dial to pick up 6 am and 6 
pm at the summer solstice if I live at 37.72 N? How about 5 am / 5 pm?
 
 If there is a way to think to think about this without doing spherical 
geometry, I would like to know it.
 
 Thanks!
 John
 
  

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From the AWAD mailing list

[tloc54452]

  -Original Message-
  From: [EMAIL PROTECTED]
 To: [EMAIL PROTECTED]
 Sent: Wed, 18 Apr 2007 9:02 PM
 Subject: A.Word.A.Day--gnomon
  This week's theme: words for odds and ends.

gnomon (NO-mon) noun

   1. The raised arm of a sundial that indicates the time of day by its
  shadow.

   2. The remaining part of a parallelogram after a similar smaller
  parallelogram has been taken away from one of the corners.

[From Latin gnomon (pointer), from Greek gnomon (interpreter), from
gignoskein, to know. Ultimately from the Indo-European root gno- (to know)
that is also the root of knowledge, prognosis, ignore, narrate, and normal.]

Today's word in Visual Thesaurus: http://visualthesaurus.com/?w1=gnomon

-Anu Garg (words at wordsmith.org)

  "Eighty-six years in the making, one of the world's largest sundials has
   finally been installed at Place de la Concorde, as part of the Year 2000
   festivities of the City of Paris. It takes an approach more cerebral than
   celebratory. The sundial's pointer, or gnomon, is the 109-foot Obelisk of
   Luxor. Its base is the northern half of Place de la Concorde."
   Rose Marie Burke; Sundial Aids Millennium Countdown; The Wall Street
   Journal (New York); Oct 26, 1999.



There are two things to aim at in life; first to get what you want, and
after that to enjoy it. Only the wisest of mankind achieve the second.
-Logan Pearsall Smith, essayist (1865-1946)

Slang -- Degradation or reinvigoration of the language? Join us in an online
chat with lexicographer Grant Barrett, editor of The Official Dictionary of
Unofficial English. Apr 22, 6 pm Pacific (GMT -8) http://wordsmith.org/chat

Pronunciation:
http://wordsmith.org/words/gnomon.wav
http://wordsmith.org/words/gnomon.ram

Permalink: http://wordsmith.org/words/gnomon.html


   

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Re: A trap for the unwary.

[tloc54452]

Re: PDF size

Tony,

There is an option in the PDF writer to select the percent at which it 
is printed.  I use it sometimes to print very large drawings to 8.5x11. 
  It can also be used to print a slightly-large drawing to a smaller 
sheet of paper.  I wonder if that could be what you're running into.  
The 100% PDF is still in the document, it's just that there are printer 
instructions also.

John Bercovitz

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Re: Google Earth's geographic grid

[tloc54452]

 Jim and John,
 
 You know, I have questions about the orientation of the sat maps also. The 
other day my wife was asking where something was on a hillside in a global 
sense so she'd recognize that same hillside when we drive the curvy road in a 
nearby park. So I got out my trusty Leica (nee Leitz) laser rangefinder and 
found a white rock on that hill lies 650 yards away. Then I shot the rock with 
my magnetic compass. I'd dialed in the mag dec and checked it against the 
gnomon on my south-facing wall dial and also against the north star with 
compensation for the clocking of the star about the pole, and so I know the 
compass isn't bad. Then I went to google earth and drew a line from where I was 
on our property to the white rock. I captured that image and imported it into 
Ashlar-Vellum's Graphite and measured the angle. It was almost exactly 2 
degrees in error. I guess the next step is to walk over to the rock with my 
Garmin and see where it is. Unfortunately, the land is posted and where I'd!
  be walking would be in clear view of half the neighborhood. So there is 
another layer of effort before I can walk out there. Or a stealthy midnight 
sneak? 8-) Oh, wait... Why not just take my trusty Garmin to two different 
_accessible_ locations and follow the same procedure? Almost the same thing.
 
 John

 -Original Message-
 From: [EMAIL PROTECTED]
 To: [EMAIL PROTECTED]; sundial@rrz.uni-koeln.de
 Sent: Fri, 26 Jan 2007 9:52 AM
 Subject: RE: Google Earth's geographic grid
 
  To Jim and anyone who measures wall declinations: Ever since Roger Bailey 
told us about his idea for getting an approximate wall declination measurement 
by using a Google satellite image, I have been using a variation of it for 
measuring walls in distant locations that I can't measure physically. It is 
also a great way to double check a traditional physical measurement. Here is 
the technique that I use. I think is more precise and easier: Instead of using 
the Google geographic grid and a protractor, I can let Delta Cad give me an 
exact measurement without using paper printouts and a protractor with their 
inherent lack of precision. Here is the technique that I use. I think is more 
precise and easier: 1) Import a jpg. picture of the Google satellite image into 
Delta Cad. 2) Then draw a line along the wall I wish to measure. 3) Click the 
"Edit" button then click on the line. 4) Read the angle value of the line on 
the Edit popup window. 5) Determine the wall's declination fro!
 m the angle value. Done!  I have compared the results of this technique with 
actual physical measurements of my house and the results were within just one 
degree of the actual measurements.  I think this is pretty good and is probably 
good enough to design most declining wall sundials using this technique. This 
can really simplify your life if you are designing a wall dial for a far off 
location that you can't measure yourself using traditional techniques. I still 
don't trust my clients to make this measurement themselves using traditional 
declination measuring techniques! John   Jim Tallman wrote: Hello All, I 
periodically use Google Earth to check rough declination at remote  locations. 
When a Spectra sundial customer contacts me and is unsure  about the 
direction/orientation of their home, I can get a really good  idea by looking 
at their location with Google Earth. By turning on the  geographic grid, making 
a printout of their neighborhood/house, and  using a protractor!
  I can usually get pretty close...close enough for  what I am doing, s

ince the Spectra will not be physically mounted to a  wall, etc...it can simply 
be rotated a bit to compensate for any small  amount of declination error. 
Sometimes I wonder about just how accurate Google Earth is, especially  their 
mapping of the satellite photos and maps to the coordinate grid.  I do not need 
to split hairs and be perfect - when precision is needed I  have remote 
customers drop a plumb line, mark a shadow, and send me the  appropriate 
time/solar measurement at their location, should they wish  to do so. I guess I 
am not entirely willing to automatically accept their output  as 100% 
perfect...and I wonder if anybody on the list has any  interesting thoughts or 
practical experience re: Google Earth and the  accuracy of their geographic 
grid. 
 Best, Jim Tallman http://www.artisanindustrials.com 
http://www.spectrasundial.com [EMAIL PROTECTED] 
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Re: The Compendium

[tloc54452]

 Hey Fred,
 
 Wow! That's great! Works so easily on both my PC _AND_ my Mac!
 
 Thanks,
 John Bercovitz 

 -Original Message-
 From: [EMAIL PROTECTED]
 To: sundial@uni-koeln.de
 Sent: Fri, 24 Nov 2006 3:18 PM
 Subject: The Compendium
 
  The December issue of The Compendium is about to go out. The print and CD 
editions will be mailed early next week.Instructions for the downloadable 
edition will go out to subscribing NASS members this weekend. As recently 
requested, the file to be downloaded will be a zip file rather than a Windows 
executable. Although this change should make this a more appealing option for 
Mac users, please note that it does mean that users will have to have a 
zip/unzip utility (and these are of course available all over the Internet).   
With this modification, we're happy now to invite all those who urged its 
adoption to join NASS! For more information, go to http://sundials.org and 
click on Join NASS.   Fred Sawyer  
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fair use, DMCA, and the list

[tloc54452]

Well, I didn't want to get into this, but I have to comment that here we go again - stuff that definitely would not be a problem in person, that would be easily worked out, turns into a problem on the internet because people can't understand each other correctly from a few written words.  We should all know this by now.  If you knew John C in person, you'd know he's just trying to help the rest of us become better educated as to what's out there.  He's excited about educating us and he puts a great deal of effort into it.  I sure got educated!  I had no idea all those wonderful dial images were out there until John posted those images, and I never would have unless he'd done it.  We all owe John bigtime.  Sure he says stuff you might not like, in a manner you might not like (who doesn't do that on occasion?), but you gotta realize he is putting it out there for comment and is open to comment (as opposed to attack).  Just li!
 ke the rest of us posting here.  Hell, you want to see tactless, talk to _me_ some time, in person!  I'll show you tactless!

OK, all you other guys are right about the copyright law I'm sure.  Technically.  But just to see what a lawyer would say, I asked my son.  His comment is, "Not necessarily."  (Is nothing necessarily true in law?)  He says John must always respect the takedown law for copyrighted material obtained from the web (take it down if asked by the owner), but depending on how he's using it, he could be perfectly within his rights.  No permission or attribution required.  My son directed me to a law site which we can all access:
http://caselaw.lp.findlaw.com/casecode/uscodes/17/chapters/1/sections/section_107.html 
where it says:
Laws: Cases and Codes : U.S. Code : Title
17 : Section 107Section 107.  Limitations on exclusive rights: Fair use
  Notwithstanding the provisions of sections 106 and 106A, the fair
use of a copyrighted work, including such use by reproduction in
copies or phonorecords or by any other means specified by that
section, for purposes such as criticism, comment, news reporting,
teaching (including multiple copies for classroom use),
scholarship, or research, is not an infringement of copyright. In
determining whether the use made of a work in any particular case
is a fair use the factors to be considered shall include - 
(1) the purpose and character of the use, including whether
  such use is of a commercial nature or is for nonprofit
  educational purposes;
(2) the nature of the copyrighted work;
(3) the amount and substantiality of the portion used in
  relation to the copyrighted work as a whole; and
(4) the effect of the use upon the potential market for or
  value of the copyrighted work.

The fact that a work is unpublished shall not itself bar a finding
of fair use if such finding is made upon consideration of all the
above factors.

This section makes copyright law sound more human and understanding than I thought it was.

Best,
John B



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Re: Slightly off-topic: names of geomteric shapes

[tloc54452]

There are a limited number of entries at the bottom of this page which may be of help.

http://www.geom.uiuc.edu/docs/reference/CRC-formulas/

John B 



 
 
-Original Message-
From: [EMAIL PROTECTED]
To: sundial@uni-koeln.de
Sent: Sat, 14 Oct 2006 7:25 PM
Subject: Slightly off-topic: names of geomteric shapes
















Good afternoon everyone,


 


This is a bit off-topic, but given the range of expertise available on the 
Sundial List, I think I can get an answer ...


 


I need names for some geometric shapes for some research I am doing. Two 
are not a problem:


 


Sector: a part of a circle bounded by the circumference and two radii 
meeting at the centre of the circle. 


Segment: a part of a circle bounded by the circumference and a chord.


 


But is there a simple one- or two-word name for a piece of a pipe? Imagine 
a pipe cut lengthwise with two radial cuts to give a long piece which in cross 
section is bounded by two arcs, joined by the radii. Is there a formal name for 
this shape? It's only the two-dimensional shape that interests me, i.e. the 
cross-section of the bit cut lengthwise out of the imaginary pipe. I guess it 
could be a "pipe sector" , but this doesn't sound very mathematical!


 


More generally, does anyone know of a web source with diagrams of numerous 
geometric shapes and their names? I think I will have a few more odd 
cross-sections come up in the next few months, and I will need names for 
them.



Cheers, John


 


John Pickard
[EMAIL PROTECTED]


 




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Re: NASS Compendium sample issue

[tloc54452]

 I'm one of many more Mac users on this list than you know,
but I also have a PC; call me bilingual.  There's one more problem
solved by going to zip and that's that the computer gurus at our
computer division really hate it when we download an executable. 
These are some of the foremost IT guys in the world and they're really
paranoid, but as a consequence we have a super-low attack rate on our
PCs (and ~0 on our Macs, but they can't claim credit for that) at our
national lab.  They think downloading executables is a really poor
idea.  So to avoid running afoul of them, I just don't tell
them.  If Fred changes, I won't get caught.



John B



 

-Original Message-

From: [EMAIL PROTECTED]

To: [EMAIL PROTECTED]

Cc: [EMAIL PROTECTED]; sundial@uni-koeln.de

Sent: Fri, 6 Oct 2006 2:13 PM

Subject: Re: NASS Compendium sample issue



The question isn't whether Mac users will be drawn to join by the
change, the question is whether PC users will be driven to quit. If
current subscribers are unaffected, and if it is convenient for Fred
and the NASS, then what is there to lose? 

 

John 

 



On Oct 6, 2006, at 5:07 PM, Reinhold Kriegler wrote: 

 

> Dear Fred, 

> 

> I have my doubts whether really some MAC users will join. So I
> expect a list of the names of the real new subscribers after this
> Compendium-mode-change in the SML. 

> My experience is: There is much lip service in the world ... 

> 

> Saludos! 

> Reinhold 





> - Original Message - 

> From: "John Goodman" <[EMAIL PROTECTED]> 

> To: "Fred Sawyer" <[EMAIL PROTECTED]> 

> Cc: "Sundial List"  

> Sent: Friday, October 06, 2006 10:48 PM 

> Subject: Re: NASS Compendium sample issue 

> 

> > Thanks for considering a change, Fred. If it's not too much trouble 

> > for you, it will make it easier for more subscribers. 

> > 

> > Best wishes, 

> > John 





> > On Oct 5, 2006, at 11:55 AM, Fred Sawyer wrote: 

> > 

> >> Yes, perhaps I should have clarified when I said that the 

> >> Compendium download was an executable file - it is a Windows 

> >> executable. 

> >> 

> >> That was a restriction that I believe once was imposed by the 

> >> software at our ISP - but things appear to have changed and a zip 

> >> download would be possible. It would require a few other changes 

> >> to procedures, but I'll consider it for future issues. 

> >> 

> >> Fred Sawyer 

 



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Re: Leybourn Layout in Sample Compendium

[tloc54452]

Dear wecirp,



I'm not sure precisely what you're asking, sorry about my confusion, so
I'll just say a bunch of stuff and you can pick what you need and then
ask for what you _really_ wanted to know.  May seem silly, but may
save time.



This is a horizontal dial so it should be installed such that two crossed levels on top of the dial plate will both read level.



The angle of the gnomon is equal to the latitude where the dial is
placed.  So if you live at 30 degrees north, the gnomon is a
triangle with 30 degrees included angle at the pointy end.



The pointy end of the gnomon goes where a line from 6 am to 6 pm
intersects with a line drawn perpendicular to the 6-6 line from the
noon mark.  The big end of the gnomon points to noon.  The
gnomon is perpendicular to the plate.  The plane of the gnomon
contains a north-south line at the dial's location.



Best,

John B



 
 
-Original Message-
From: [EMAIL PROTECTED]
To: sundial@uni-koeln.de
Sent: Thu, 5 Oct 2006 3:02 PM
Subject: Leybourn Layout in Sample Compendium









Is there any specific information on the gnomon for this layout, 
like location, size, orientation, etc.?  Or, the complete design?

Thank you.

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Re: A Projection Dial Question

[tloc54452]

Hi John C.



OK, right - that was the point about using a ball lens.  A ball is
symmetrical in all directions so it will focus equally well whatever
the azimuth & elevation of the sun.  Here I'm envisioning a
ball lens atop a slender rod, so there is no blocking of the sun's rays
regardless of the sun's position.  Now, if you put the ball lens
in an opaque plate to cast a shadow for more spot contrast, as Fred did
with his aperture/tower/cylindrical dial, the plate may occlude a few
of the sun's rays depending on its orientation.  However, the ball
lens will still focus; it will just have fewer input rays.



In a way, calling it a ball lens, as everyone does, is a contradiction
in terms.  If I recall correctly, the word "lens" derives from the
shape of a lentil bean.  This ain't no lentil bean; it's a pea!



Best,

John B. 





-Original Message-
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Cc: sundial@uni-koeln.de
Sent: Tue, 29 Aug 2006 9:41 AM
Subject: Re: A Projection Dial Question
















Hi John B:


 


Ok, I think I understand the point you made about 
the benefit of using a lens in the aperture nodus:


 


"With a lens in the aperture nodus, the projected 
spot of light will always be brighter and smaller than the diameter of the lens, 
and therefore will give more precise sundial readings than a simple aperture 
without a lens."


 


But please excuse me if I'm wrong, I 
think this is only true if the sun's ray hit the lens straight on.  I 
still don't believe aperture lenses will function at all times on 
a typical sundial that has low solar angles.  What about the fact that the 
sun hits the lens at many different angles throughout the day and the 
seasons?  Sometimes, the sun's rays will hit the lens at a perpendicular 
angle, straight on, and the focusing will work great. But at most other times 
(i.e.. late afternoon on a south wall dial) the sun's ray will hit the lens from 
a low angle.  This affects the "cone of light" and distorts 
it.  Lenses don't work very well if they are not positioned perpendicularly 
to the sun's rays, do they? 


 


I just did a little experiment with a lens.  I 
tilted the lens so that the sun hit it at low angles, and the spot of light grew 
to a big blob of dim unfocused light.


 


What do you think about this?


 


John C.


 


  
- Original Message - 

  
From: 
  [EMAIL PROTECTED] 

  
To: [EMAIL PROTECTED] 

  
Sent: Monday, August 28, 2006 7:46 
  PM

  
Subject: Re: A Projection Dial 
  Question

  



  
Hi John C.

Fascinating web page.  Found a little 
  typo:
Shows both Standard (Dutch: Wintertijd) and Daylight Saving Time 
  (Dutch: Wintertijd).  


  

OK, so how do you keep it focus for varying distances?  Simple: 
  you don't.  What you do is settle for a long converging cone.  This 
  converging cone is smaller in diameter than the diverging cone from a pinhole 
  at all places along its length except both are equal in diameter where the 
  cones emerge from the apertures.  So this special ball lens, if it works 
  out, is not a magic bullet.  It's just a lot better than a pinhole!  
  (Brighter and smaller spot).

I could have the ray tracer draw a light 
  cone from a "pinhole" and from the special ball lens and put them on the same 
  page if you like.

 
John B.



-Original 
  Message-
From: [EMAIL PROTECTED]
To: 
  [EMAIL PROTECTED]
Sent: Mon, 28 Aug 2006 10:30 AM
Subject: Re: A 
  Projection Dial Question


  

  
Hi John B.

  
 

  
It's a very interesting topic that of using 
  lenses for gnomons.  Have you see the webpage of glass sundials?  It 
  has a photo collection of some amazing glass sphere dials.  See: http://advanceassociates.com/Sundials/Stained_Glass/sundials_EGP.html  
  Even one for the blind.

  
 

  
But nobody yet has answered the main question and 
  the biggest doubt I have:  How do you solve the problem of keeping the 
  sunspot in focus as the projection distance changes.  For example, if the 
  focal length of the sphere (or lens) is 3 inches, how do you keep the spot in 
  focus if the projection distance is 30 inches? The projection distance on 
  a dial would constantly be changing as the sun moves through the sky.  
  HOW DO YOU KEEP THE SPOT IN FOCUS!

  
 

  
John C.

  
 

  
 

  

- Original Message 
- 


From: 
[EMAIL PROTECTED] 



To: [EMAIL PROTECTED] 



Sent: Saturday, 
August 26, 2006 10:30 AM


Subject: Re: A 
Projection Dial Question




Hi John C,

I also contacted an optical engineer buddy 
(well, that's really his sideline - writing optical programs like the one I 
used; really he's an astrophysicist and an astronaut and a space-telescope 
designer, sort of your basic overachiever).  Anyhow, he said the whole 
thing was a fascinating idea and he'd never heard of anyone using 
aerogel.  So if it works, cool, we got a new thing.  If it 
doesn't, we'll always say it shoul

Re: A Projection Dial Question

[tloc54452]

I got to thinking about refractive index on a theoretical basis. 
Usually the way you beat refractive index down below the normal limits
is with porosity that is so fine that the light doesn't see it (e.g. AR
coatings).  So what has high, fine porosity?  Long period of
thought...  Doh!  Silica aerogel!  It's normally a kind
of pale yellow color.  Sort of a scattering effect, I think. 
Refractive index is probably TOO low.  I have a buddy in that
racket.  I will ping him as to what density could be delivered and
so what refractive index.  Then we also need to know what the
transparency vs density is.  He should know.  Silica aerogel
is fragile and is always covered with something.  In thermal
panes, for instance, it has glass on both sides of it.  I wonder
if it couldn't just be sprayed with clear Krylon.  Or cast into a
hollow glass sphere?  Again, he will know.  I know it's an
evaporative process that leaves the aerogel behind, so it just might
work.



John B  (mechanical engineer, somewhat off the reservation as usual)






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Re: A Projection Dial Question

[tloc54452]

image


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hollow_glass_sphere.gif
Description: GIF image
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Re: A Projection Dial Question

[tloc54452]

Hi Edley,









I did not have succes with a hollow glass sphere.  Seemed like it
ought to have worked.  Maybe I should take another look at
it.  Glass has an index of about 1 & 1/2, water about 1 &
1/3, so water might fix what I ran into.  Or I messed up.














Hi John C,









Jah, that's why I was saying if you can find something with a low
enough refractive index.  But I couldn't.  So then I thought,
well liquids might be about right, but not much luck there either (see
scale drawing, attached).  I'm not fond of liquid hydrogen because
some nattering nabob of negativism will always say it will leak and
everyone will be incinerated, and the nabob will be right, of
course.  Hey, it's the chance you take.  LN is a
distant-second-place possibility if you are at a cryogenics plant and
don't mind a double window glass sphere with evacuated gap.  I'll
assume your installation isn't at a cryogenics plant.  That leaves
us with common liquids, water being a good example.  Water doesn't
work so good.  I think this here plan gang agley.









John Bercovitz



Update: the 35k image brought the total message size to 62k which
cuased an automatic bounce.  I will try to send the image all by
its lonesome.  If it bounces too, it will require moderator
(different time zone) approval to go through.



 


 


  
- Original Message - 

  
From: 
  [EMAIL PROTECTED] 

  
To: [EMAIL PROTECTED] 

  
Cc: sundial@uni-koeln.de 

  
Sent: Friday, August 25, 2006 2:33 
  PM

  
Subject: Re: A Projection Dial 
  Question

  



  
Hi John C,

I'd be tempted to use a ball lens if I could find one 
  made of a material of a low enough refractive index (and a high enough Abbe 
  number).  Searching on "ball lens", I found a simple explantion:
http://www.edmundoptics.com/techSupport/DisplayArticle.cfm?articleid=245

The 
  trouble with a PCX or DCX is limited field, meaning the total number of hours 
  of useful image-spot time would be limited.

Best,
John B


  
 
 
-Original Message-
From: 
  [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Cc: 
  sundial@uni-koeln.de
Sent: Fri, 25 Aug 2006 8:59 AM
Subject: A 
  Projection Dial Question


  

  
Hello Fred (cc. Sundial List):

  
 

  
I received an email from Chris Coulter in 
  Colorado.  He is the general contractor who I worked with to make the 
  equatorial dial.  He has a new project in mind that is very similar to 
  your wonderful new Tower Sundial in Connecticut.  He saw a website that 
  describes an existing projection dial at Kent Denver Science Building in Cherry 
  Hills Village, Colorado that uses a glass lens to focus the sunspot on the 
  walls of a circular indoor rotunda.  See this: http://www.lorisandassociates.com/pages/pbuild.htm

  

I 
  was wondering if you could help clear up a technical question.  It seems 
  to me that this type of dial SHOULD NOT have a glass lens.  Perhaps there 
  is an error in this website and there is no lens, but just a flat piece of 
  glass to keep the rain out.  Since glass lenses have a fixed, unchanging 
  focal length and since they only work when in linear alignment with the sun, 
  the lens and the spot of light, I don't think that a lens would 
  work.  Imagine your projection sundial tower with a lens in the aperture 
  nodus.  It surely could not function, could it?

  
 

  
The spot of light projection distance is highly 
  variable in your tower, being long in the summer and short in the winter. A 
  lens would only function if the projection distance were equal to focal length 
  of the lens, wouldn't it?

  
 

  
Am I correct or am I missing 
  something?

  
 

  
Thanks Fred,

  
 

  
John



  




  

  
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Re: A Projection Dial Question

[tloc54452]

Hi John C,



I'd be tempted to use a ball lens if I could find one made of a
material of a low enough refractive index (and a high enough Abbe
number).  Searching on "ball lens", I found a simple explantion:

http://www.edmundoptics.com/techSupport/DisplayArticle.cfm?articleid=245



The trouble with a PCX or DCX is limited field, meaning the total number of hours of useful image-spot time would be limited.



Best,

John B



 
 
-Original Message-
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Cc: sundial@uni-koeln.de
Sent: Fri, 25 Aug 2006 8:59 AM
Subject: A Projection Dial Question
















Hello Fred (cc. Sundial List):


 


I received an email from Chris Coulter in 
Colorado.  He is the general contractor who I worked with to make the 
equatorial dial.  He has a new project in mind that is very similar to your 
wonderful new Tower Sundial in Connecticut.  He saw a website that 
describes an existing projection dial at Kent Denver Science Building in Cherry Hills 
Village, Colorado that uses a glass lens to focus the sunspot on the walls of a 
circular indoor rotunda.  See this: http://www.lorisandassociates.com/pages/pbuild.htm



I 
was wondering if you could help clear up a technical question.  It seems to 
me that this type of dial SHOULD NOT have a glass lens.  Perhaps there is 
an error in this website and there is no lens, but just a flat piece of glass to 
keep the rain out.  Since glass lenses have a fixed, unchanging focal 
length and since they only work when in linear alignment with the sun, the lens 
and the spot of light, I don't think that a lens would work.  
Imagine your projection sundial tower with a lens in the aperture nodus.  
It surely could not function, could it?


 


The spot of light projection distance is highly 
variable in your tower, being long in the summer and short in the winter. A lens 
would only function if the projection distance were equal to focal length of the 
lens, wouldn't it?


 


Am I correct or am I missing 
something?


 


Thanks Fred,


 


John








 




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Re: finding true north

[tloc54452]

Daylight Saving Time?



John



 
 
-Original Message-
From: [EMAIL PROTECTED]
To: sundial@uni-koeln.de
Sent: Thu, 10 Aug 2006 1:17 PM
Subject: finding true north
















Hello everyone!


I am constructing my first sundial 
in my garden. I am having a problem finding true north. 


"The Dialist" computer 
progream tells me that solar noon is at 11:53.


The shadow method tells me that 
solar noon is 12:43ish.


I also employed the compass method 
and also I tried finding north by looking at the "north star". 


The direction for true north is 
different for each of the methods I try. 


Yesterday I laid out the sundial 
using the direction of true north I found using the compass method. The latitude 
here is 47.0019 degrees N. Longitude is 117.0854 degrees W. Apparently the 
declination is 15 - 16 degrees here. So I compensated for that (I lined up true 
north 16 degrees to the left of magnetic north). 


Today I tested the sundial, and it 
seemed that each hour was off by one hour1:00 pm on the clock shows 12:00 pm 
on the dial; 12:00 on the clock shows 11:00 am on the dial; and so on. 



I used a MS Excel spread sheet that 
I found on the internet to calculate the hour placements and date scale 
placement - corrected for longitude.


I would appreciated any help at 
all. Thank you.


Tracy

 




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Re: Delta Cad workshop?

[tloc54452]

Ah, another PC terrorist.  But long before PCs copied the
look and feel of Macs, and even before AutoCAD, Apple's software
division created Claris CAD which will does more or less what Delta CAD
does, and guess what?  It works well on 7.6 or earlier and also on
the latest classic.  In between are problems which are not
insurmountable.  They're not going to port classic to the
Intel-Mac (part of Apple's
no-backward-compatibility-because-it-hurts-forced-sales policy), so
there you're stuck.  It's so long since Claris last sold their
CAD, I wonder if they care about the copyright.



John B





 

Dave Bell wrote:



> Perhaps this? 


> http://www.draftingdeals.com/draftingdeals/finditem.cfm?itemid=7324 



>

> sorry! :{) 

>

> Dave















Willy Leenders wrote: 
 

> Delta Cad is only applicable for Windows. Is there a good 
> alternative for Macintosh? 

> 

> Willy LEENDERS 

> Hasselt Flanders (Belgium) 
 



 




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Re: another decorative sundial

[tloc54452]

Simon illustratingshadows wrote:


A number of those dials are poorly made, however some
of them have quite good workmanship. That good
workmanship is spoiled by consistently screwing up the
latitude scale, as well as other things. If they go to
the trouble to do good metal work, why not use working
designs.


Exactly!  The metalwork was mediocre, as one would
expect for that many assembled components for that price,
but it would cost no more to put the markings in the right
places!  Aggravating.  The saleslady sounded absolutely sure
when she said then dial was made correctly, but I would
only believe that if she had said she belonged to the
NASS or the BSS.  I was just hoping...

John

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another decorative sundial

[tloc54452]

I am returning a compass sundial I received mail order today.
Markings and numbers for time and latitude are in the wrong
places.  The bubble level is defective.  The damping of the
compass needle is too low (that ain't ALNICO).  I questioned
closely when I placed the order to determine if it was made
correctly and was assured it was.  So I'm out postage.  I don't
want anyone else to be misled into thinking this is other than
a decorative piece, hence  this warning.

John B


Details:

www.stanleylondon.com

Stanley London
22345 La Palma Ave.
Suite 103
Yorba Linda, CA 92887  USA

Description: Premium Quality Brass Sundial Compass w/Case
Weight: 2.9 Lbs.
Price: $95.00
Quantity: 1



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Re: "ClearCoat" - Your beautiful painted dial

[tloc54452]

Would the clear coat have the same specular-diffuse quality as the 
original paint or does it have its own type of reflectivity, 
supplanting that of the underlying paint?


John B

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Re: tried hard anodizing?

[tloc54452]

If your weather includes years of wind with dirt in it, or godferbid a 
desert sandstorm, I speculate the extra thickness of Al2O3 buffered by 
compliant PTFE should hold up better than many things against the 
kinetic SiO2, which I think is probably lower on the Moh's scale.


John B


-Original Message-
From: hannes <[EMAIL PROTECTED]>
To: Sundial Mail List 
Sent: Thu, 18 May 2006 19:25:59 +
Subject: AW: tried hard anodizing?

  (german) wikipedia states that the process of hard anodizing uses 
cooled electrolytes, so much higher current can be used. usually the 
protective layer is 25-50µ, half of which adds to the thickness of the 
piece.

with very pure alloy layers of 200µ can be produced.

 I wonder if the thicker layer is more weather resistant, or if proper 
sealing is more important (which is what I would expect).


hannes

--
hannes kühtreiber
[EMAIL PROTECTED]
http://www.datenmull.at.tf

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Re: tried hard anodizing?

[tloc54452]

Tony Moss wrote:


I must admit that this is the first time I have encountered the term
'hard' anodising and the webpage referred to gave only general
information of the process.


Hard anodizing is still Al2O3, it's just extra thick.  Can't get that
thickness by ordinary methods.  I think by ordinary methods the
coating starts to lose mechanical integrity as it gets thicker.  So
they have a process for extra thick which is what I used for wear
surfaces because it lasts longer.  In that sense, it's just as good for
a sundial as it is for a rubbing surface.

For those unfamiliar with Al2O3 (alumina), it is very hard, I think
more than Rc 60, Moh's 9, and in a parallel lives is used as an 
abrasive,

among other things.

Aluminum naturally anodizes itself, but the natural coating is thin
and ratty and doesn't have much integrity.

Anodizing is sort of trees or bushes growing off the surface.
You seal it to keep stuff from getting in the branches.  Lots
of seals available, but boiling water is decent and cheap.

TMI (more than you ever wanted to know) from John B
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taxonomy?

[tloc54452]

Is there a formal taxonomy for sundials?

I like:
http://sundials.org/faq/
select:
6. What types of sundials are there?

I was thinking about my bowstring equatorial.  It's also an 
equinoctial, right?  So what takes precedence?  Seems like it would 
help the new guy ('tis I) to be able to look at the "formal" name of a 
dial and then imagine almost exactly what it is.  I don't know if such 
a system would work with all the new inventions that come from people 
on this list & al, but perhaps it would.


John B
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bronze casting materials

[tloc54452]

Can you tell I'm recently retired, with feverish mind?  Or more 
prosaically, I'm exploring fabrication methods now that I have more 
time.  But I digress.


I just recalled that our local park district has amongst its many 
facilites a place to cast jewelry by lost wax.  The hobbiest can do 
gold and silver, but they practice with bronze and sometimes do small 
artworks.  Aha!, sez I.  Perhaps they can do larger.


What's a good casting alloy?  (I'm more familiar with wrought copper 
alloys.)  I'd be looking for good color and weather resistance, which 
might mean a marine alloy.  As a pensioner, I'd be looking for 
inexpensive.  As an investment caster, I'd be looking for fluidity and 
low shrinkage.  In addition, I might well want good soldering/silver 
brazing.  I'm thinking something in the CDA 900 series, but I'm really 
out of my league here.


What have you folks been using?  And while we're at it, suggested 
patination methods if your secrets aren't too dear?


Thanks,
John B
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Re: Sundial Motif to Be Featured on New Canadian $10 Coin

[tloc54452]

Now if they'd just put the a.m. VI diametrically opposite the p.m. VI...

John B

-Original Message-
From: Robert Terwilliger <[EMAIL PROTECTED]>
To: 'Steve Lelievre' <[EMAIL PROTECTED]>; sundial@rrz.uni-koeln.de
Sent: Wed, 17 May 2006 09:48:08 -0400
Subject: RE: Sundial Motif to Be Featured on New Canadian $10 Coin

 The new coin can be seen here:

http://makeashorterlink.com/?Z1CA21F1D
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Re: tried hard anodizing?

[tloc54452]

Larry McDavid wrote:


 I have a 1-inch thick 6061 machined aluminum tooling plate
mounted in a polar plane in a local desert at 4500 feet elevation
where the UV exposure is extreme. This plate was hard black
anodized and Teflon impregnated when fabricated 23 years ago.
Today, it is still shiny and a slightly lighter dark gray than the
original color.


Wow!  This sounds good!  By tooling plate you mean -T651?
Good stuff.  6061-T651 has always made me happy.  Who did
the anodizing?  Still in business?  I had one up here (SF Bay Area)
I used to use, but they went out of business (ecological disaster
zone), and I don't think my local guy actually does hard anodizing.

High desert.  Apple Valley?  (Call me nosey.)  I'm surprised the
PTFE can take that much UV.

Thanks, Larry.

John Bercovitz
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tried hard anodizing?

[tloc54452]

Has anyone tried hard anodizing?  I used to use tefloned hard anodizing 
on 6061 for mechanical parts subject to sliding.  It has a duller, 
grayer finish.  I wonder how it does in the weather.  I have regular 
anodizing, water sealed, on my 12" (30 cm) bowstring equatorial.  Fine 
weather resistance, but...  The equatorial surface is really a concave 
cylindrical mirror, so it's pretty darn bright to the eye from some 
norrmal viewing positions.  Hard anodizing might be the cure.  Anyone 
tried it?


For those unfamiliar with hard anodizing, but curious, googling found:
http://www.techplate.com/hard_anodize.htm

Thanks,
John B
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Re: azimuth of the axis

[tloc54452]

Hi Joe,

By plan view of the earth's orbit, I meant the plane of the earth's 
orbit is in the piece of paper we are looking at.  The axis of the 
earth is tilted with respect to the orbital plane, therefore it will 
project a line onto this piece of paper.  So my question was, where is 
this line pointing?  Off list, someone told me that the line points at 
the sun at the solstices, which are not far in time from aphelion and 
perihelion.  Before he said that, my shoulders were sloped from 
shrugging from not knowing; now my forehead is sloped from slapping it 
when I got the answer which I should have known!


My apologies that my phraseology was not up to par and thanks for the 
interesting information!


John B


-Original Message-
From: Joe Montani <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]; sundial@uni-koeln.de
Sent: Tue, 16 May 2006 16:47:27 -0600
Subject: RE: azimuth of the axis

 John,

I don't exactly understand the phrasing of the question.

The picture or geometry is exactly described by the apparent place
of the sun at the time of interest, and by the fact that the axis of
 the earth is, for the purpose of this conceptual picture, fixed in 
space.


Therefore, all angles, however defined, can be calculated. It will be
easy, if just the right question(s) is (are) asked.

But I do not know what you mean in your use of the term "azimuth"
of the axis of the earth. Azimuth usually refers to the angle between
the north cardinal point and the bearing of an object in the horizon-
coordinate system. Usually, we reckon from North, through East. So,
due East would be Azimuth = 90 deg; SW would be 225 deg; etc.
(Some folks, such as the Chileans with whom I worked, measure through
WEST, so one must be thorough in defining terms, for surety).

But the axis of the earth does not have an azimuth because it is not
an object in the sky or on the earth.

Yet, thinking ahead to what you may want to know, I offer the tidbit
that, when the earth is furthest from the sun, we are about at about
 July 4th on the calendar (July 5 this year, I think). Now, that is 
about

2 weeks after the June Solstice, so the Sun will still be at a strong
northern Declination of close to +23.44 deg, or more correctly about
+22.8 deg at the date of aphelion. To get back to your "pointing-at"
question with regard to the axis of the earth, and the sun, the axis
will thus miss "pointing-at" the sun by about 90.0 minus 22.8 deg on
the date of aphelion, or by about 67.2 deg. Another way to say this,
 or to visualize it, is to say that the line of sight to the sun will 
make an

angle of 22.8 deg at that date with the plane of the earth's equator.

Maybe you have something else in mind, though. And forgive me if I'm
completely missing your point.

 Perhaps you mean to phrase your question in terms of Longitude of the 
Sun

on the Ecliptic, instead.

--Joe / Tucson, AZ / USA

 >What is the azimuth of the axis when the earth is farthest from the 
sun, >calling the sun at 0 degrees?? In other words, how far off is it 
from >pointing directly at the sun? [snip]


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azimuth of the axis

[tloc54452]

I am in need of the help of a big-brained list member, as I can't quite 
figure this.  I know of the ecliptic and the celestial equator and the 
precession of their crossing and such, so I presume I have necessary 
but insufficient background.


OK, earth's orbit, plan view, looking down at the north pole of the 
earth, but of course off axis by 23.44 or .45 degrees.  An ellipse with 
the sun at one of the foci.  When earth is farthest from the sun 
(aphelion), the north pole is pointed toward the sun.  But not 
precisely.  What is the azimuth of the axis when the earth is farthest 
from the sun, calling the sun at 0 degrees??  In other words, how far 
off is it from pointing directly at the sun?  (So we need to choose an 
epoch; let's say 2000.)


I just want to know in order to have a more complete picture in my head.

Thanks!
John B

PS: If it's something intuitively obvious to the most casual observer, 
please be kind.


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RE: Dial at Filoli Center

[tloc54452]

After looking at the dial plate closely, I was able to see where the 
gnomon had originally been, many many years before.  I agree that it 
was probably set where it is now by a repairman with more aesthetic 
than sciatheric sense.


I'm leaning more toward your point of view - a friend suggested that if 
they want a correct dial, I should make them one for another location 
on site and leave that one alone.  It really is a very nice dial as is; 
it is at least historically correct, as pertains to its own history; it 
is not screaming, "Release me!'  ;-)


In addition, if I were to "fix" the dial, it still wouldn't be perfect 
since the hour lines aren't dead on.  So again, what's the point?  I 
think you've convinced me.


I'll attach my best-fit hour line worksheet.  I ignored gnomon 
thickness; it's pretty thin and presently rounded on top, though that 
doesn't appear original either.  In left-right mirror-image symmetry, 
the angles from noon agree fairly well to exactly, so I've taken the 
average of the two where they differ.


John





Sun, 14 May 2006 09:30:04 -0700
Roger Bailey wrote:

These days, looking good is important. To me, the Filoli Center dial is 
an
excellent example of this "form over function" philosophy. To "fix" the 
dial

would be to destroy it.

The dial is obviously not designed for the Filoli location but 
transported
or copied from an English garden. The gnomon is displaced and the angle 
is
wrong but the support feet on the gnomon seem to fit the inner circle. 
To

move the gnomon would destroy the balance and aesthetics of the dial.

The only thing that looks gnomically correct is the orientation of the 
dial.

I assume it is aligned away from the axis of the brick path to be true
north. It will then show true solar noon.

Since solar time is not clock time and this dials rarely works for solar
this , my only suggestion for improvement is to go all the way, looking 
good
California style. Re-align the dial and pedestal away from north and 
along

the axis the brick sidewalk.

Regards,

Roger Bailey
Walking Shadow Designs
N 48.6  W 123.4
(closer to the design latitude of the Filoli Center dial)


FiloliDialLats.pdf
Description: Adobe PDF document
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Dial at Filoli Center

[tloc54452]

Yesterday I visited the 15-inch-diameter bronze dial at the Filoli 
Estate in Woodside, now run by Filoli Center in conjunction with the 
National Trust for Historic Preservation.


I found that the best fit to the dial's hour lines is 50 N.  The gnomon 
appears to have been cut down to 46.5 N (upper edge filed half-round, 
for safety?).  The gnomon has also been attached in the wrong spot to 
the dial plate with steel socket-head flat-head screws.  Presumably 
reattached after some mishap.


I'm talking to the all-volunteer army that runs the place right now in 
case they'd like to have the dial corrected.  I suspect they won't be 
terribly enthused about a 12.5 degree wedgeplate under the dial, 
though.  Might confuse the public.


Pix at the bottom of ny sundial page:
http://www.angelfire.com/ca2/tech3d/sundial.html

John B
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Re: Buyer's Guide

[tloc54452]

I think this an outstanding idea well done, especially with addenda of 
contributors of this list.


Next hurdle: how to get the information out there in this 
information-overload age?


There are obvious multiple benefits if we can think of how best to do 
it.


John B
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Re: book: Sundials at Greenwich

[tloc54452]

Continuing on the subject of that same dial, in the following passage, 
why "on the meridian of Nuremberg, latitude 49 degrees"?  This is a 
portable dial and it seems to me the analemma ought to be as good at 
one location as another.  What am I missing?


Thanks,
John Bercovitz

http://www.nmm.ac.uk/collections/explore/object.cfm?ID=AST0368&picture=1#
content

"...and a scale for the equation of time is displayed graphically as a 
figure of eight in the centre.  [...]  An inscription along the North 
side of the hour-plate reads, ‘A new horological invention from the 
tables of Lord Johann, philosopher of Wurtzelbau indicates the equation 
of time during the course of the day on the meridian of Nuremberg, 
latitude 49 degrees’."


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book: Sundials at Greenwich

[tloc54452]

This looks like a nice book.  Very expensive, though.  Does any of you 
have it?

There is supposed to be more information about the equinoctial shown at
http://www.nmm.ac.uk/collections/explore/object.cfm?ID=AST0368&picture=1#
content
in this book, but I wonder how much more.  Are there more photos or 
just the one shown on the website?


Thanks,
John B

Sundials at Greenwich
– Hester Higton 
A Catalogue of the Sundials, Horary Quadrants and Nocturnals in the 
National Maritime Museum

ISBN 0-19-850877-8
Published: 2002
Publisher: Oxford University Press and the National Maritime Museum
Edition: 1

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encyclopedia britannica

[tloc54452]

A friend send me the article under "Dial" in the 1910 edition.  
Interesting several-page article.  I looked in my 1771 repro edition 
and found another interesting article.  Are these generally available 
on line?  I wonder what the legality of scanning them and putting them 
on a website for others might be.


John Bercovitz
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Re: Measurers - Hendrik van Balen

[tloc54452]

This is fascinating.  What is the central figure doing?  What methods, 
instruments, is he using?  Why does he have two great toes on one foot? 
 But seriously, I am interested in old methods; just don't know much 
about them.


Thanks,
John Bercovitz
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Re: SunZoner, was site examiner

[tloc54452]

Here on this computer the following hot links don't work, but cutting 
and pasting the URLs does.


> peephole facing up
> http://www.angelfire.com/ca2/tech3d/images/SunZoner1.jpg
>
> peephole facing up
> http://www.angelfire.com/ca2/tech3d/images/SunZoner2.jpg
>
> peephole facing more toward the observer
> http://www.angelfire.com/ca2/tech3d/images/SunZoner3.jpg

 John Bercovitz 
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SunZoner, was site examiner

[tloc54452]

I named it "SunZoner" because on Google,  that seems like the only name 
not yet taken.  It took me just over half a day to make it from scraps 
in my shop, and I let the scraps be my design guide.  The build 
requirement of a half a day means economics is no way to justify 
building this over buying a modern version of a horizontoskop.  
However, I retired Friday and I must have fun!


I used a made-in-China Ace Hardware 200 degree peephole for the door.  
Best they had & seems good enough.  Actual angle of view is 170 
degrees; I think they must have rounded off to the nearest 100 degrees. 
  The top and bottom almost-semicircular occluder plates are of 1/8" Al 
sheet.  The square rod that separates the occluders is 1" sq x 3.5" 
long and has the peephole through the center of it.  The occluders 
occlude all but +/- 23 3/4 degrees (added 1/4 degrees for the 
half-angle of the sun's disk).  Every two hours is a 1/8" diameter Al 
welding rod through both occluder plates, crimped on each end to keep 
it from falling out (pretty crude, huh?).  Note that +/- 23 3/4 degrees 
is measured from the pupil of the peephole.


I took three pictures, incandescent flood lamp, fluorescent tubes 
behind diffuser, on-camera flash.  I haven't made a web page for this, 
but I can give you direct links to the JPEGs:


peephole facing up
http://www.angelfire.com/ca2/tech3d/images/SunZoner1.jpg

peephole facing up
http://www.angelfire.com/ca2/tech3d/images/SunZoner2.jpg

peephole facing more toward the observer
http://www.angelfire.com/ca2/tech3d/images/SunZoner3.jpg

Note the arm coming off the 3/4 x 1 rect bar stock that serves as the 
polar axis.  It has a 1/4 Diam dowel coming up out of it and that dowel 
engages one of three holes in the lower occluder plate.  That way I can 
re-register the occluders and keep the hour lines on solar hours.


I turned down the end of the 3/4 x 1 rect stock to 1/2" and bored one 
end of the 1" sq stock to .502.  You might say that's a loose fit, but 
it's Al against Al and I didn't want to worry.  The extruded angle 
provides a natural place to inscribe latitude lines.  I put a bullseye 
bubble level and my 50 year old (gulp) Boy Scout compass on the angle 
with double stick tape.  Our local  magnetic declination setting has 
changed a lot since I was a boy socut.  Fasteners are non-magnetic 
stainless.


OK, seems easy enough to use on a high tripod.  I think at much lower 
latitudes than mine (37.72) it would be inconvenient.


John Bercovitz
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Re: Sundial house

[tloc54452]

Enough to make anyone covetous.  I wonder what the optics inside the 
"oculus" are.  Seems to have a healthy aperture and a very wide angle.  
Also, at noon there seems to be a dark streak in the middle of the 
beam.  Might be a rod crossing the optic at some distance.

Cool!
John Bercovitz


Robert Terwilliger <[EMAIL PROTECTED]> write:
 An article in USA Today
"Architects' family basks in the sundial effect"
http://www.usatoday.com/tech/news/2006-03-30-sundial-house_x.htm
Bob

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Re: site examiner

[Tloc54452]

Yes, several people sent pix of the horizontoskop, and I like it very very much, but it looks like I'd have to purchase cards for every latitude, and some cards may not be available, though close enough, I think.   So then I thought perhaps a wide-angle mirror (convex mirror) or mirror garden ball with lines scribed on it and tilt it correctly and restrict the position of the observer's eye.   Problem is that the position of the image is at the center of curvature, hence the restricted eye position to correlate with the externally-scribed lines.   Then I started wondering how close I could get to the horizontoskop's capabilities in something I could actually build.    

If the horizontoskop and its cards were cheap and readily available, I would purchase one, but it's not that trivial to make, I think.

John Bercovitz
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Re: site examiner

[tloc54452]

I've gotten a number of comments off list on the gadget.  Let me first 
say thanks to all.


While designing, I was thinking along the lines of something Dick said 
off list which is that there was something S&T sold which was a polar 
axis with a sight-along pointer pivoted on it and you could set dec and 
RA, if I understood him correctly.  I combined that thought with 
something Tony showed me that a friend of his had devised.


It just occurred to me, following up on another reply and taking a 
geocentric view, that you could say the sun rotates about a point on 
the earth's axis.  You find that point by dropping a perpendicular form 
the center of the sun to the earth's axis.  At the equinoxes, the sun 
is broadside to the earth, so it is rotating about the center of the 
earth.  During the solstices, it is rotating about a point high or low 
on the axis of the earth.  This way of thinking mimics my device.


Best,
John
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Re: site examiner

[tloc54452]

Just got a chance to sketch up a thought that might be easy to build.
At the bottom is a clampable pivot used to set the red pole axis to 37
degrees, in this case.  The blue semicircle is clamped to the red pole
axis and does not rotate about it.  The blue semicircle has times 
printed

on it, noon in the middle.  The magenta line is attached to quarter
circles of various colors which are in turn attached to black vees which
all pivot together around the red pole axis.  The magenta line can
point at any time on the blue semicircle.  The cyan line crossing the
red pole axis is the axis of the optic which might be a pinhole and it
might be a wide-angle view optic for a door from Stanley Hardware,
which has almost a 180 degree field of view.  $10

The colored hoops are the solstices and equinoxes, as you might
imagine.  In use, set the pole axis angle, make it point north-south,
and swing the eyepiece and hoops as required to see the range of
the zone the sun will be in.

What do you think?  Might work?  I ain't proud - if you don't like
it or it's stupid, tell me what you would do about it.

If the description and graphic are unclear, I'll make one and shoot a 
picture.


John Bercovitz


SunRange.gif
Description: GIF image
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site examiner

[tloc54452]

Here in northern California, seems like we have lots of trees.  Few 
good sites for sundials in populated areas near me because of this.  I 
was thinking I need a sundial "site examiner".  This would be a device 
that would scan the path of the sun over the sky looking for 
obstructions.  It would have tripod levelling, a magnetic compass in 
the base, a way to set the pole axis angle, a +/- 23.44 degree tilt for 
the seasons, and be able to swing whatever to cover the hours.  From 
this you'd know what per cent of the time the sundial would be 
effective.  We can all imagine numerous incarnations of such a device.  
I think I'll build one.


Does anyone have any experience with what the public finds acceptable 
utitlity?


Thanks,
John
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Re: Terminator

[tloc54452]

Douglas Bateman <[EMAIL PROTECTED]> wrote:

I have a site on my browser, www.mapmaker.com/shadowfacts/sunweb.asp
that shows the terminator throughout the year. It is fascinating to 

see how

rapidly the shape changes,  


Already the sunclock shows the light is broadening in the northern 
hemisphere.

Not even one full day into spring.   Hmmm...

There was comment about the terminator being a great circle in actual 
fact.
A Mercator projection shows lines of longitude parallel so the light 
and dark

bands have straight lines between them at the equinoxes.

But is the terminator really a great circle and can we tell the 
difference on the
sun clock?  The sun is not infinitely far away and on that account less 
than half
the globe would be illuminated.  However, the sun's disk subtends ~1/2 
degree

at the earth which would make more than half the globe illuminated.
Finally, due to refraction by the curved atmosphere, we see some piece 
of

the sun's disk before said piece is over the horizon.

My question: what is the sum of these effects (and any I have 
forgotten)?
What fraction of the earth's surface can see some part of the sun's 
disk at

any given time?

Thanks,
John
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Re: high-latitude dial

[Tloc54452]

Chris Lusby Taylor <[EMAIL PROTECTED]> wrote: 

> It seems to me it would work, but I can't see any 
> advantages over a cylindrical gnomon.

Aha!   It dawns on me now what you were saying.   I 
thought you meant tell time by the center of the 
shadow of a small-diameter gnomon, but you're 
suggesting one could as well tell time by one edge 
of the shadow of a large-diameter gnomon.   Sounds 
right to me.

I just tried the shadows of a knife edge and of a 
3/4" diameter rod and they look about equally sharp.   
I should do a more careful experiment, but to first 
order, it appears to be true.

Perhaps there is an advantage in that laying out the 
dial in quadrants may be easier than laying out dial 
lines tangent to a cylinder.   (Would be using my 
methods unless it's an equatorial dial.)   And some
may have an aesthetic preference one way or the other.
But I agree - same thing.

John B
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Re: high-latitude dial

[tloc54452]

Chris Lusby Taylor <[EMAIL PROTECTED]> wrote:


It seems to me it would work, but I can't see any advantages over
a cylindrical gnomon.


I was thinking an edge would give better definition of the position
of the shadow, at least for a stout gnomon.  But outside of that,
I agree with you.

The idea of having four styles is to avoid gaps or overlaps in the
dial line layout.

John B
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high-latitude dial

[tloc54452]

This is really a gedanken experiment as I know no one at high latitude 
needing a dial, but here's what I came up with for a dial primarily for 
high latitude.  The dial has a square gnomon and four sets of hour 
lines, one set for each style.  I'd be interested in the list's 
comments on its practicality.  Last time I had an idea, I was told by 
the list that the dial was invented in 832 BCE, and approximately 
400,000 have made each year since then.  No, seriously, I'm naturally 
curious if it's already been done.


After drawing this, I googled "square gnomon" and got one hit - from 
one of the list's own luminaries, John Carmichael!  So something like 
the idea is out there, at least.


Thanks,
John


Hi-lat.gif
Description: GIF image
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Re: Paint on stainless steel plaques

[tloc54452]

I second the motion to experiment.  I have heard that black-oxided 
stainless is no longer rust resistant.  Am dying to know if this is 
actually true.


John Bercovitz


-Original Message-
From: tony moss <[EMAIL PROTECTED]>
To: Sundial Mail List 
Sent: Sat, 4 Mar 06 23:35:31 +
Subject: RE: Paint on stainless steel plaques

 >

Hello David,

A black oxide coating might work. Stress relieving typical stainless 

steels
results in an adherent black oxide coating on the surface. Brushing 

after
heat treatment may return the metallic shine to the stainless and 

leave the

black oxide in the etched areas. I haven't tried this myself but the
chemistry seems right. Test it on a piece of scrap to see how it 

works. The
stainless will have to be heated to red heat in air to developed the 

black

oxide surface.


That sounds promising but I would be wary of distortion resulting from
this 'stress relieving' of the metal.  Experiment first!

Tony Moss
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Re: Numb3rs

[tloc54452]

I didn't reply before because I hadn't gotten a chance to think about 
it until I got stuck in a traffic jam this morning  There actually is a 
closed-form solution using subsolar points.  In the attached sketch, A 
and B are the subsolar points associated with the date-and-time stamps 
on the two photos.  The red circle and cyan circles are all the points 
at the shadow angles of the A and B photos from their associated 
subsolar points.  There are two interesection points, C and D.  From 
other information, we can select C.


Now we have a spherical triangle, ABC which has sides a, b, and c.  
There are ways to solve this triangle using spherical trig.  Here are a 
couple of Wolfram sites:

http://mathworld.wolfram.com/SphericalTrigonometry.html
http://mathworld.wolfram.com/NapiersAnalogies.html
We have all the side lengths, a, b, and c - these are the angles 
between points B and C, between points A and C, and between points A 
and B as subtended at the center of the earth.  A, B and C also 
represent the angles between azimuths from a point to the other points 
on the triangle.  Since we have a, b, and c, we can find A, B, and C.


QED

John Bercovitz


numb3rs.GIF
Description: GIF image
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Re: Numb3rs

[tloc54452]

I'm embarrassed to say I still don't get it.  When they first showed 
two different photos, I thought, "two equations, two unknowns" but then 
later there were a bunch of words and the sun going 'round the earth in 
two circles almost touching and I got all messed up.


So let me tell you how I would solve it and then you can tell me, "Hey, 
that's the same thing only different, yuh retard!" only out of 
consideration for the gentility of the list, you can omit the "yuh 
retard" bit.


Say you have a shadow angle A at 10 am and a shadow angle B at 1 pm.  
So first you go to the standard line of longitude two hours east of 
your standard line of longitude and lay the analemma on it and find the 
subsolar point for the date.  Then around the subsolar point you draw a 
circle on the surface of the earth which is the locus of all points at 
an angle A from the subsolar point as measured from the center of the 
earth.  That circle has all the places which have the first (10 am) 
shadow length.  Then you go to the standard line of longitude one hour 
west of your standard line of longitude and do the same thing mutatis 
mutandis for the 1 pm shadow angle.


So now you have two circles drawn on the surface of the earth and where 
they intersect are the only two possible loci (relative to the standard 
line of longitude) of the abode of him who done the dirty deed.


Is there an intuitive way to get from my earthbound way to solve it to 
how they solved it on the show?


Thanks,
John Bercovitz

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Re: Numb3rs

[tloc54452]

Fred Sawyer wrote:

Tonight's episode of Numb3rs (CBS 10EST) is a repeat of "Obsession" - 
the episode that includes mention of the North American Sundial Society 
and a problem relating to finding a location based on shadows.


Thanks, Fred; I'd missed it the first time.

Would anyone care to discuss the method?  It went by a little fast for 
me.  I suppose we assume that bricks are laid so that their tops lie in 
the same plane, that all bricks and the mortar between them have a 
known and unvarying size and perhaps are perfectly rectangular for this 
discussion, that the yard is perfectly level, that the orientation of 
the brick field and hoop are unknown, that the basketball hoop's 
diameter and elevation are known to high precision, and the time stamp 
on the photos is right on the money (would this be relative to each 
other or zulu time?).  Have I overspecified the necessities?  OK, then 
what do we do to compute latitude and longitude to a hundredth of a 
degree?


Thanks,
John Bercovitz
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Laser cutting Stainless Steel

[tloc54452]

John Carmichael  wrote:

 I heard that you can't laser cut stainless steel because the light 

reflects back into the machine

 and it either doesn't cut or it doesn't cut well. Is that true?


Steel and especially stainless are pretty good because they are dull 
enough.  Aluminum is more trouble but you just bump the power up to 
cover the lower absorptivity (higher relfectivity).  Maybe you were 
thinking of torching stainless?


John Bercovitz
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Re: Is the USA 'Daylight-Saving' period to be extended ?

[Tloc54452]

In a message dated 2005/04/19 12:23:22 PM, [EMAIL PROTECTED] writes:

> Yes, the U.S. Congress is presently discussing whether to extend DST 
> from the first Sunday in March to the last Sunday in November -- an 
> increase in the duration of DST by about two months.  

I hope they pass the extended DST.  Then we can lobby for year-round DST.  
Then we can lobby to set the clocks to standard time (but start the day at an 
earlier hour).  Works for me.  Just because B. Franklin couldn't get up before 
12 doesn't mean the rest of us can't (deliberately inflammatory tongue-in-cheek 
remark).

John Bercovitz
-

Umbrae, Penumbrae and Equatorial dials

[Tloc54452]

Well, here's another question.  I've been thinking (again) about
what a proper shadow would be for a bowstring equatorial or a
hemisperium or hemicyclium.  I made up a dumb little spreadsheet
which is at the URL below to thrash about with the numbers some.
Parts of that spreadsheet are shown below.  From the output, you
can see how I've been thinking, but how _should_ I be thinking
about this problem?  What _is_ a proper shadow?

Thanks,
John Bercovitz


http://www-eng.lbl.gov/~bercov/math/Sundials/UPE.xls

Umbrae, Penumbrae and Equatorial dials 

dramatis personae
d - diameter of rod or sphere
D - distance of center of rod or sphere from where you read the shadow
A - angular subtense of the sun in radians (32' = .0093 radians)
U - umbra width or diameter (for rod or sphere respectively) = d - .0093D
P - linear or radial width of penumbra = .0093D
S - highly fictitious "sensitivity" = D/U
Angle is small enough that small-angle approximation applies

dD   AUPS
0.1256   0.0093   0.0692   0.0558   86.70520231
0.250   12   0.0093   0.1384   0.1116   86.70520231

0.2506   0.0093   0.1942   0.0558   30.89598352
0.500   12   0.0093   0.3884   0.1116   30.89598352

When D/d is large, is it too hard to find where the umbra is within the shadow?
When D/d is small, is it too hard to find where the center of the umbra is?
If the shadow-caster is a sphere instead of a rod, must the umbra be relatively 
larger?


-

Equinox and east-west line

[Tloc54452]

Hi,

I stuck a tall nail perpendicularly in a horizontal board 
for the equinox and I marked the position of the shadow of 
the nail's head several times the day before and the day 
after the equinox (the equinox was in the middle of the 
night for California).  I got two parallel tracks very close 
together (which show that my house errs from being east-west 
by a little over a degree).

Since the sun heads north at about a minute of angle per 
hour, is the east-westedness of my tracks off by a minute 
of angle per hour divided by 15 degress per hour or one part 
in 900 (about 4 minutes of arc)?  Can it be that simple?  

Thanks!
John Bercovitz
-

Declination approximation?

[Tloc54452]

Is there an approximate formula for the declination of the
sun vs day number?  I just tried the obvious
=23.44*SIN[(day number)*360 degrees/365.2422]
but it's not too shiny - misses by a degree or two at times.

Thank you,
John Bercovitz

38 hours, 35 minutes & counting...
-

Advantages and disadvantages by dial type?

[Tloc54452]

I was thinking about another dial, one that does date and 
time whenever the sun is up.  I came to the conclusion that 
a hollow hemisphere with its lip in a horizontal plane and 
nodus at the center of the hemisphere would do it, and might 
not be too difficult if I could make the hemisphere from 
something commonly available.  Assuming you wanted just 
Local Apparent Time, would all the date and time lines on 
the inside of the partial sphere be great circles?  That 
fact, if it is a fact, might make construction fairly easy.

Then I wondered if there is another type of dial which will 
give date and time whenever the sun is up.  So I started 
trying to find a list of advantages and disadvantages of 
different dial types.
Something like:
- horizontal garden dial - good anytime sun is up, generally no date, but 
limited date with nodus
- equatorial dial - good only from 6 to 6 else won't show some hours at 
equinoxes, generally no date
- equatorial-cylindrical with nodus bead - can do all dates and times if top is 
cut off level with nodus?
- armillary dial - blocks itself at times
- nodal dial, time & date on horizontal plane - sometimes the time/date are 
impractically distant from the nodus
- nodal dial, time & date on part of sphere - does it all and it maintains 
constant shadow size

I looked around for such a list, and of course visited Frans 
Maes' site where I found the following passage -

Frans writes:
"The most natural type of dial is the nodal sundial. The 
shadow of any fixed point traces a projection of the above 
pattern on the background, the dial face. That may be a 
hollow sphere, in which case the projection is a 1:1 
replica. That type of dial was known already in Antiquity. 
Other shapes are easier to produce, like a hollow cone, or a 
plane surface of arbitrary orientation.  The principle is 
the same, though."

So it sounds like a portion of a sphere with nodus has been 
around a long time, but it's not made often because it's too 
difficult.  Is that correct?  

Is this sundial close to ideal?
Frans Maes' site
http://www.biol.rug.nl/maes/zonnewijzers/welcome-e.htm
nodal dial
Smit Transformer Manufacturing Co., Nijmegen

Thanks,
John Bercovitz

-

leap second insertion questions

[Tloc54452]

Thanks for the pointer to GPS-Nv99_Innov.PDF

It was gratifying to learn that UTC and sundials
always agree well, given the usual corrections
between sundial time and UTC.

I didn't quite understand the advantage of periodic
insertion of leap seconds vs aperiodic for the 
correction of the ~2msec per day increase in period 
of the earth's rotation.  Why does the GPS system
care if it's periodic or aperiodic?  Also, why 
would the update sometimes become large?  Isn't
that just a matter of making the period of correction
reasonably short?

Thanks,
John B

Quotations from GPS-Nv99_Innov.PDF :



...


-

Re: RE: BBC radio program(me) on sundials on 13 Dec.

[Tloc54452]

Many thanks to all!  Just checked - nothing happening  at 198 kHz except 
heterodynes and voice I can't make out at this time here at 37.7N, 122.1W.
(not that I seriously expected to be able to hear anything in the longwave 
bands at this distance)

Thanks again,
John
-

Re: BBC radio program(me) on sundials on 13 Dec.

[Tloc54452]

In a message dated 2003/11/27 02:50:54 PM, [EMAIL PROTECTED] writes:

> BBC Radio 4  will carry a 30-minute show on sundials on Saturday, 13 
> December at 1530 GMT.
>
> It's of course easy to hear in the UK, but anyone with a Web 
> connection who can stream audio can also listen at
>
> http://www.bbc.co.uk/radio4/
>
> or through the ether on long wave at 198 meters. 

I have a shortwave receiver that picks up BBC on 5975 kHz rather 
well.  Will the program be at that frequency also?  (This ancient
computer won't handle streaming audio.)

What would the frequency of 198 m be?  Is that a band, rather
than a frequency?  Haven't heard of that band, but I'm a rank novice 
at this sort of thing.  Let's see... 299792458/198 = 1514 kHz  (Not
correcting for the refractive index of air.)  Have I messed that up?

Thanks!
John Bercovitz

-

Re: Stabilizing a plinth?

[Tloc54452]

For those interested in a report, I laid two courses of brick last weekend
(which made me a weakened weekend warrior).  I figure the first course
will settle and then I can shim the gap between the first and second courses.
The plinth was actually an annulus, a short section of thin-walled tube, so
no wonder it kept pitching to and fro.  With layers of brick under it, the 
load
(pressure in this case) will not be so high.

The gnomon and wedge seem to be spot on.  I'm within a couple of minutes
at all times which is about all I'd expect out of a small, old, cast bronze 
dial
with line placement not to the standards of this august body (that's youse 
guys).

Again, thanks for your help,
John Bercovitz
-

Re: Stabilizing a plinth? - Thanks!

[Tloc54452]

Many thanks to all for the great suggestions as to how to 
stabilize a plinth and still be able to remove the installation.

Also, Tony Moss' discussion about that dead spot in the dial
when the gnomon doesn't have a knife edge or zero thickness
was timely.  When I was figuring the dial plate's latitude, I 
_thought_ some of the angles near noon were sort of funny 
as figured from the intersection of the 6 to 6 line and the 
centerline of the gnomon.  Now it's embarrassingly obvious 
what the cause of that was!

Many thanks,
John Bercovitz
-

Re: "camera obscura" dials - Diameter of the hole

[Tloc54452]

> ., I would be interested in what they

> consider the optimal dimensions for the pin hole vs. the

> size etc.  I will install one tomorrow at my home,

> commemorating the Spring Equinox.

Here is perhaps a different way of thinking about the 
problem of the hole diameter vs its distance from the
plane on which the spot of light lands.

As the hole becomes smaller, physical optics makes the
spot of light larger.  However, as the hole becomes larger,
geometric optics makes the spot of light larger.  So I think
the thing to do is set the equations for these two diameters
equal to each other to find the minimum*.  When I do that, I 
get:

D = .03 SQRT L
where
D = diameter of hole, in mm
L = distance from hole to image plane, in mm

Since one equation is going up and the other down, the belly
of the curve which is their sum is very broad.  Therefore, I
would increase the .03 figure to .04 to get much more light
through with no visible degradation of the fineness of the
spot.

Reworking the equation, we can see that the angle the spot 
subtends becomes smaller as L becomes larger.  This argues
for a large L.

On the other hand, the human eye is very good at finding 
the center of a spot of light, so perhaps I am attacking 
entirely the wrong problem!!

Best,
John Bercovitz

* I used the diameter of the first dark ring in the diffraction
pattern.  I used the sodium D line for the wavelength.  I used
a point object (not the sun, which subtends half a degree);
however, what I'm actually trying to do is sharpen the image 
of the sun, so believe my approach is correct.
-

Re: intentional rust finish

[Tloc54452]

In a message dated 2002/10/19 10:06:03, [EMAIL PROTECTED] writes:

>Similarly, what about the steels (I don't recall the type
>name) used for sculptural works, that quickly develop a dark brown
>"rust" layer, which supposedly protects the underlying steel (just as
>aluminum, titanium, and stainless steels do) from further progression?

Possibly COR-TEN?  (Sometimes spelled corten or cor ten.)
It was used in WWII to make amphibious vehicles.  We had
tons of it left over from WWII in a factory at which I once 
worked.  It sat in the weather but never seemed to acquire
deep pitting.

John Bercovitz

Rust never sleeps.
-

2nd attempt at a sundial

[Tloc54452]

I had to back off on my grandiose plans, which you folks kindly
commented on earlier, and scale the thing down to something I
could easily build.  Results, for the curious, are in the sundial
section of my website:

http://www.angelfire.com/ca2/tech3d/sundial.html

Comments always welcome!

John B

Re: Commercial Offerings

[Tloc54452]

> The photo-3d list people maintain a different list sell-3d for
> commercial postings.

That was a long time ago and I'm trying to remember why I did that.
I think it was for two reasons.  The primary reason was that the
main list was overloaded with a horrendous amount of traffic.  A 
secondary reason was for the convenience of those who were 
primarily buyers and sellers.  We also spun off tech-3D because of
complaints from general readers about "math heads" overloading
the list.  Before we spun off the lists, we allowed "informational"
posts regarding current and new products, but that wasn't enough for 
the wheelers and dealers who wanted to move very quickly with
their resales.

On another list, we tried subject-line prefaces.  If you were posting
something for sale, your subject began with FS:  If you had a technical
post, it began with TECH:  or CALC:  Then with a good mail tool, one 
could sort a single list's posts by subject line into bins.  I thought
this approach worked exceptionally well, though unfortunately,
some posters had difficulty remembering to add a preface.

John B

Re: How DO they do that?

[Tloc54452]

I love this list's digressions!  8-)

Trivia question:
You can't join a straight road to a circular road tangentially
else the third derivative (d/dt of the centripetal acceleration)
will be infinite.  So, what curve is used to join the straight
road to the circular road?  

If no one knows, I don't remember the answer but can find it.

John Bercovitz

Re: numerals

[Tloc54452]

>  If brass numbers are epoxied to marble stone, will
>  their different coefficients of thermal expansion
>  break the bond?

Sorry to be coming in so late on this.  Work pressures - 
got to go there five days a week and work eight hours (or 
more) too.  Ridiculous!

This is a transient thermal problem but let's say the brass 
temperature follows the stone's temperature well because the 
glue is thermally conductive enough to sink it.

Ordinary brasses' coefficients of thermal expansion (CTEs) 
hover around 20E-6 per degree C.

The CTE of granite is 7E-6 per degree C. +/- 10%.  I think 
it's true that granite weathers better than marble, though 
its aesthetics may leave something to be desired in your 
application.

Marble can be a bit anisotropic, but below is a typical 
maximum value.  Marble also displays some hysteresis, so 
you can heat it once and expect a lower CTE thereafter.  
The CTE of marble is 10E-6 per degree C in the maximum 
expansion direction and near zero in the other direction.

As suggested previously, a compliant form of epoxy will 
help handle the shear from the differing CTEs.  You can 
make epoxy more compliant by adding ascorbic acid or you 
can buy it that way.

Another thing that helps compliance is to make sure the 
bond line is thick enough.  Epoxy is available with glass 
beads in it to set bond line thickness precisely, but you 
could simulate that with strategically-placed shims.  Just 
don't put shims near the edge of a bond.  A thicker bondline 
is better even though it will weaken the bond, because bond 
strength isn't your problem here.

The edge of the bond is where rips start.  A good rip-stop is
a chamfer on the edge of the letter.  About a 10 degree angle
is good.   Since a radian is about 60 degrees, 10 degrees 
would be an angle of about 1 in 6.  Try to at least double
the bondline thickness at the edges.  Also, leave the 
curve of epoxy at the edge in place if you possibly can.
This is also great rip-stop protection.  If it is naturally 
too big and unsightly, wipe the excess off while the epoxy 
is still "wet".

Your marble could easily get to 80 C if it's sitting in the 
sun.  That should also help the compliance.

So let's say you bonded at 25 C because epoxy sets up better 
and faster when it's warm.  In use the temp settles out at
80 C.  Difference is 55 C.  The difference in CTEs is either
20E-6/C or 20 - 10 = 10E-6/C and we pick the larger figure.
Your numeral is maybe 25 mm at its largest extent, so asuming
the center of the numeral stays put, the distance to the
farthest edge is 12.5 mm.  Then that farthest edge moves
(55C)*(20E-6/c)*(12.5 mm) = .014 mm = .0005 inches.

OK, so the shear strain (gamma) is .014 mm divided by your 
bond line thickness, which is maybe 0.14 mm: .014/.14 = 0.1  
By Hooke's law, stress and strain are proportional.  For 
tension and compression, the proportionality constant is E, 
and for shear, the proportionality constant is G.

For Dexter Hysol 9309.3NA, a compliant epoxy
Modulus of rigidity, G, is 855 Mpa or 124 ksi
The maximum allowable shear stress, tau, is 29 MPa or 4200 psi
These figures are for 25C and I'm having the devil of a time 
finding G for elevated temp, though max stress falls to 6.9 MPa 
or 1000 psi at 82C.  I'd assume G would also fall, maybe faster 
than allowable stress, so we can probably get away with using 
the 25C figures.

For Dexter Hysol 9394, a rigid epoxy
G is 1204 MPa or 148.5 ksi at 25C
Tau max is 29.0 MPA or 4200 psi @ 25C  (same as for 9309.3NA)
Tau max is 20.7 MPA or 3000 psi @ 82C  (better than 9309.3NA)

The elegant way would be to look at the allowable strain for 
each epoxy.  Maximum allowable stress (tau) divided by G will 
give us maximum allowable strain (gamma).  Whatever allows the 
most strain is best in the respect we've been discussing.

For Dexter Hysol 9309.3NA, a compliant epoxy @ 25C
gamma max = tau/G = 29 MPa / 855 Mpa = .034

For Dexter Hysol 9394, a rigid epoxy @ 25 C
gamma max = tau/G = 29 MPa / 1204 Mpa = .024

Neither of these make the grade with the .14 bondline thickness
so we have to triple or quadruple the bondline thickness to get
strain down to what we can live with.

Conclusion.
You need half a millimeter (.020") or more bondline thickness 
to pull this off, based on this cursory examination.  That's a 
thick bondline.

Summary.  
The amount of movement is related to the difference in the CTEs 
and the temperature change.  The amount of movement divided by 
the bondline thickness is the strain.  The maximum allowable 
strain is related to the maximum allowable shear stress and the 
modulus of rigidity.

What else can you do?  Well, titanium's CTE matches granite's 
pretty darned well.  How about gold-plated Ti on granite?  8-)  
Other than that, I'd take Bill Gottesman's advice, but check the 
suggested adhesives at 80C, just in case.

John B

decimal & metric

[Tloc54452]

In a message dated 2000/02/15 01:44:39, [EMAIL PROTECTED] writes:

>The way to cut the Gordian knot is to throw out everything and start
>over with a base 12 numeral system.  Then the scientific calculations
>and the everyday divisions by 2, 3, 4, and 6 are *both* easy.

Hear hear!  The greatest tragedy of the metric system is that it uses  
decimal base.   Bring back base 12: one, dozen, gross.  How did we lose 
it in the first place?  Was it that Arabic mathematicians were so much 
more advanced than their European counterparts?

John B

metric system

[Tloc54452]

Like most engineers in the US, I use both systems.  Here are some 
random observations from a few decades of engineering.

There are very few arguments in favor of American (nee Englsih) 
units other than avoidance of the the cost of conversion. However, 
it is interesting that the English system just growed and so is 
user-friendly.  Actual values often lie in the user-friendly 1 to 
100 range.  Derived units are also convenient.  Your house water 
pressure may be 40 psi (pounds per square inch) or 275 kilopascals 
(unless you're using some secondary unit like bars). 

On the down side of the English system, the man on the street gets 
confused between mass and weight when talking about pounds.  
However, it seems like the metric man on the street gets confused 
between mass and weight when talking about kilograms, though it's 
my impression that the metric man may be slightly less confused.

For those who are accustomed to using the metric system, but must 
occasionally use the English system, I'll tell you the secret.  
It's really very easy.  The key is g.  (g being 32.174 f/s/s or 
9.80665 m/s/s, not 392 Hz)  In the English system, wherever an 
equation should not have g, insert it.  Wherever it should have g, 
omit it.  8-)  It's as simple as that. 

Me personally, yeah, I favor one system.  I don't care which 
system, just one system.  8-)  I'm tired of having to carry around 
constants in two systems and the conversion factors between them 
(.2248 pound = 1 newton).  What a waste of my limited memory!

Well, sure, it would be more comfortable for me to stay with the 
English system since the metric system was a curiosity when I went 
to school.  However, any discomfort from using only the metric 
system pales in comparsion with the present situation of having to 
use both systems day in and day out.

I live in California.  Admittedly California communists are often 
confused, but our beloved (former) Governor Moonbeam once said 
about government that less is more.  So it ain't just us 
conservative refugees from a geriatic ward that think that.

John B

Re: optical resolution tables

[Tloc54452]

> When I first started using cables for my styles I thought a lot about what
> would be the correct diameter cable.  On one hand, I wanted the cable to be
> as thin as possible, because a thin shadow gives a more precise time reading
> than a thick one.  On the other hand, if the shadow is too thin, it makes
> for difficult time readings from a distance.  Not knowing the resolution
> formulas that some of you have mentioned, I determined the cable diameter by
> experimentation.

I'm not sure how to solve this problem mathematically.  
Maybe that Compendium article does it.  I just tried
different diameter rods the design distance from a 
piece of sheet metal until I got a combination of umbra 
and penumbra that I felt was best for accurate reading.  
Exactly what you did.  I ended up using 1/8" (3.175 mm) 
diameter rod to cast the shadow on the hour ring of my 
armillary sort of sundial (still at the machinist's, 
lo these many moons).  The inside diameter of the ring 
is 6" (152.4 mm).

The mathematical treatises presented of late are intended
for line width and letter size rather than shadow size.
I'm not sure how one would apply them to shadow size.

John B

Re: optical resolution problem

[Tloc54452]

>Do you know of any kind of formula to estimate the proper proportions for 
>seeing high or distant dial lines, letters etc. clearly? I suspect 
>architects, engineers and advertisers (billboards) must have some way of 
>knowing what will be clear to a given eye at a given distance.

The best the average corrected eye can do is about a minute of arc.  That's
with very high contrast like truly black lines on a truly white background.
For low contrast objects, you'd want more like 3 minutes of arc.  I'm talking
about spacing of lines here where the line width and the space width are 
equal.  

One example which might help would be the Snellen eye test chart.  The lines
in the letter E for 20-20 vision (when it's the correct distance away - no 
cheating) are 1 minute and the spaces are 1 minute so this has a 2 minute 
spacing.  With corrected vision, that letter E should be easy.

So all in all, I think I would try a minimum of 3 or 4 minute spacing because 
not 
everyone's been to his optometrist or ophthalmologist recently.  Of course if 
you 
have the space, by all means do increase the size for more legibility.  Also 
to make 
it faster to read - no one has to puzzle over it.

As far as isolated lines, that's another thing.  Here you just need high 
contrast
and some width.  As an example of very high contrast, think of power lines
against a bright sky.  You can see them for miles even though the angle they 
subtend is well below what your eye is "diffraction limited" at.  So seeing an
isolated line is strongly a matter of contrast as well as angle subtended.  
I'd
still go for a minute or two of angle even with high contrast, though.

John B

Re: Moonbase Alpha, (Space 1999).

[Tloc54452]

In a message dated 99/12/11 10:53:47, [EMAIL PROTECTED] quotes:

>Since a full moon on the winter solstice is occurring in conjunction
>with a lunar perigee (point in the moon's orbit that is closest to
>Earth), the moon will appear about 14% larger than it does at apogee.
>This will make it appear brighter. Also, this will be the closest lunar
>perigee of the year. 
>
>The Earth is also several million miles closer to the sun, than in the
>summer.  Thus the sunlight striking the moon is about 7% stronger,
>making it still brighter.

Laying a coupla numbers (from the CRC) on it:

earth, in kilometers
apogee  1.5207E8
perigee 1.4707E8

(1.5207/1.4707)^2 = 1.069

moon, in kilometers
apogee  4.0551E5
perigee 3.6330E5

(4.0551/3.6330)^2 = 1.246

total 1.069*1.246 = 1.288

ln 1.288 / ln 2 = .37 stops

I don't know if you can see .37 stops difference or not.
So it will appear brighter but I think a clear night 
would be more important to brightness.  Of course if 
there is snow on the ground, then dark objects will have
high contrast and contrast is the name of the game in
resolution.  So with the increased contrast and the
reflectance of the snow, the night may appear much 
brighter.

John B

PS: 4.0551/3.6330 = 1.116, rather than 1.14

The great jet experiment

[Tloc54452]

Well, that was fun,... and useless.  I took a miniature 
fire hose nozzle which fits on a garden hose and measured
flow rate when it was in the water in the bucket and out of 
the bucket.  No difference.  I measured reaction force when 
the tip was at various depths in the water and when it was 
out of the water.  No difference.  It surprised me that it
was only 20 ounces (1.25 lb) in all test situations.  Felt 
like more.  For reference, the pressure at the nozzle was 
30 psi when the nozzle was flowing (there was a long section 
of hose ahead of it).

Flow rate was 1150 cubic inches per minute into the 3 gallon 
bucket.  Nozzle exit diameter is .190 inches.  So the exit 
velocity was 

v = 1150/[(pi/4)*.19^2] = 40560 inches per minute = 676 inch/sec


mass flow rate was

m dot = [(1150/1728)*62.4]/60 = .69 lbm/sec

  (.69 lbm/sec)/(386 in/sec^2) = .0018 lb-sec/in


reaction = m dot * delta v = .0018 * 676 = 1.22 lbf

What have I proven?  The jet reaction is real, and measures 
as predicted, but seems to have nothing to do with the Moss
effect.  The Moss effect must depend on the configuration of 
the spray coming out of the nozzle.  Also shown was that in 
this case, the flow around the nozzle while it was in the 
bucket was not a part of this problem.  Indeed, the water in 
the bucket looked completely turbulent.

John B

PS to the rational countries: The American system of units
is very simple.  Just throw in the acceleration of gravity
(386 in/sec^2) wherever it is not needed and omit it wherever
it is needed.  Once you have that down, it is an easy system
to use.  My tools were American system so rather than converting...

jet boats & other sundial-related stuff

[Tloc54452]

I had a spare moment at work so I looked up jet boats
in Mark's Standard Handbook for Mechanical Engineers.
The thrust is m dot *(Vjet - Vboat).  This is derived
from impulse-momentum which is a sort of rearrangement
of the common formula from Sir Isaac,

F = m * a
to:
f = m * dV/dT
to:
f dT = m * dV
from which:
f = m/dT * dV
or:
f = m dot * change in velocity

In air, the force would be just m dot * V because the
total change in velocity is V because the water comes
to rest.  In the case of a boat, the change in velocity
may not be so high because the boat actually may be moving!  
8-)

So now we just need to know what the final velocity of
the water in the bucket is as well as the m dot I 
mentioned the other day.  The m dot is easy because that's
the fill rate.

I would say that at this point, one goes empirical and
just measures stuff.  Obviously the water flow in the
bucket may resemble the exterior of a torus and so one
measures the velocity of the water near the hose but
upstream of its exit to get the equivalent of Vboat.

I can't remember what the other sundial-related stuff
is just now.

John B

accepted convention?

[Tloc54452]

In my Britannica Atlas, I ran into a convention I haven't 
seen before.  The number after the decimal point is the 
minutes of arc.  So my latitude would be listed as 37.42
whereas I would call it 37 degrees, 42 minutes or 37.70
degrees.  Is this atlas' convention common?

John B

PS: Well, Tony, I've often noticed what you say and never
thought about it.  Some of us have dull minds and are
therefore content.  8-)  I wonder what the fill rate is 
with the hose in and out of the water.  If the fill rate 
is significantly reduced, then the velocity is reduced and
the jet's force is reduced since the jet's force should 
be something like m dot * v (mass flow rate times velocity)
I would imagine:

Kg/sec * m/sec = Kg-m/sec^2 = newton

Yes, that works out (I hope).

EoT and decl

[Tloc54452]

As I mentioned the other day, I typed the figures from Waugh's book into 
a spreadsheet (Excel) so I could play with them.  Not nearly as neat as 
the programs you folks have been mentioning, I'm sure, but if you enjoy 
making the magic happen yourself, I have put the spreadsheet up at my 
website.  You can retrieve it from the bottom of the page,

http://www.angelfire.com/ca2/tech3d/sundial.html

if it happens to be working.  8-)

You can strip off the columns to the right in the spreadsheet where I did 
some doodling and put in your own columns.

John B

Re: February 29

[Tloc54452]

Many thanks, Patrick, for your reply.  Checking further, I find that 
Waugh has done something similar for Feb 29th and EoT.  Also, I did 
find one error in the EoT table.  For April 21, the EoT is listed as 
1 00 but going by the adjacent data, 1 09 would be more correct. Just
a typesetting error, I am sure.

I keyed the data for both the EoT and decl. tables into Excel so I can
fool around with it a little.  It's easy to spot anomalies if you plot.

John B