Re: Boiler water level; Rubys and others (very long version)/Whoops dept.
Whoops! I called Kevin Trent. Sorry Kevin. Phil.P. Reading,PA. (text snipped) > Best regards, > > Kevin > > >
Re: Boiler water level; Rubys and others (very long version)
This is a very good explanation of what happens and should be part of an FAQ. Any one who is fortunate enough to be around the larger scales 1" and larger can observe the water expansion that Kent describes fairly easily as their glasses are larger and they all have relief valves to get more accurate water level readings. Phil.P. Reading,PA. > Thank you to Harry Wade, Clark Lord, and Jeanne Baer for raising the "zippy" > question in the operation of small scale live steam locomotives. Harry > originally wrote that in his experience a '' "low water condition produces > freer steaming thus the locomotive gets "zippier" ". I agree as far as his > observation goes, and I will explain why I think that he is right, but the > question that I was directly answering was "As a fellow post asked, how do > you know when to refill the boiler (Ruby) and by how much". I believe this > question and my subsequent answer are congruent and I stand by it. > (much snipped) > Best regards, > > Kevin > > >
Re: Boiler water level; Rubys and others (very long version)
-Original Message- From: Kevin O'Connor <[EMAIL PROTECTED]> To: Multiple recipients of sslivesteam <[EMAIL PROTECTED]> Date: Sunday, May 27, 2001 2:50 PM Subject: Boiler water level; Rubys and others (very long version) >snip< >"Zippiness" commences at the point that the boiler water level falls low >enough that the potential carryover caused by bursting steam bubbles is no >longer a problem. At this point the boiler/burner is delivering the >"driest" saturated steam to the cylinders that the combination can. The >locomotive will then continue to "zip" right along, running real well, until >the water level drops low enough to start to uncover the top of the >firetube. At this point the locomotive will start to act "tired" (this is >what I said in my original answer) as the firetube's effective steam >generation area starts to fall as the water level goes down. The locomotive >will continue to "tire" until it finally stops when there is no more water >to boil. > >snip< Kevin Your explanation of the phenomenon we all experience is exactly right. The only time a locomotive doesn't operate this way is if it is grossly overfired. When this happens (the Aster Mikado is a perfect example) the locomotive can remain "zippy" from the time carryover ceases until the boiler is almost out of water. In fact, my Mike used to run its absolute "zippiest" at less than 1/4 full--water well below the tops of the flues. I suppose Aster designed the locomotive this way to make it very forgiving of less than perfect attention to boiler water level but the design makes it terribly wasteful of fuel. Now that I've added full control of the firing rate to the burner, it behaves the way it should--following your description exactly. Victor Lacy
Summer Steaming Rules
Mr. Lunkenheimer has received new rules from the Union Steward concerning hours of operation for the summer. Steaming will only be permitted from 1/2 hour before sunset to 2 hours after sunrise, mosquito's permitting. We are having not only the worst drought in over 100 years, forest fires all over the place, but uncommonly HOT weather. Track temperatures yesterday afternoon registered BEEF, RARE on a Taylor Meat thermometer. That's getting near the meltdown temp of those plastic wheels on the 'less than prototypical' pieces of rolling stock. Fuel usage has decreased markedly, the "Rube" ran 25 minutes yesterday afternoon though [all locomotives on The Swamp have shield and spear names, rather than the looking glass variety]. Keep your steam up! Walt & Lunk
Mason Bogie
Will any list member that has had experience with the new Australian Mason Bogie please contact me off list? Thanks, [EMAIL PROTECTED]
Boiler water level; Rubys and others (very long version)
Thank you to Harry Wade, Clark Lord, and Jeanne Baer for raising the "zippy" question in the operation of small scale live steam locomotives. Harry originally wrote that in his experience a '' "low water condition produces freer steaming thus the locomotive gets "zippier" ". I agree as far as his observation goes, and I will explain why I think that he is right, but the question that I was directly answering was "As a fellow post asked, how do you know when to refill the boiler (Ruby) and by how much". I believe this question and my subsequent answer are congruent and I stand by it. To explain the phenomena of "zippiness" we need to start with a mental picture of the cross section of a flue tube model boiler. I intend to ignore the "pot boiler" boiler design for now. It is a cylinder with one, or more, firetubes that start somewhere at the backhead end of the boiler and terminate at the forward, smokebox, tube sheet. For the purposes of this discussion I intend to use the ubiquitous Ruby's boiler cross section as my example as it has only one firetube that passes both through the backhead and smokebox tube sheets. A general rule in the hobby is to fill one's boiler with distilled water equal to no more than 80% of the boiler's internal volume. The remaining 20% of volume is at first made up of noncondensible gas (air) which will soon be replaced with very saturated steam. The initial heating of this trapped air is what causes the false pressure spike on a pressure gauge fitted locomotive. Once this hot trapped air is released to the atmosphere the steam pressure gauge will again read zero and the next movement of the gauge will reflect the real raising of steam pressure. What is conveniently ignored is that water expands in volume when it is heated (or freezes) and so the 20% of "free space" over the boiler water level is now compressed to something less as the level of boiler water rises. This fact is most easily observed in model locomotives like the Aster/LGB Frank S. and the Hyde Shay both of which have "port hole" water gauges on the backhead tube sheet. If you fill a Frank S. boiler to halfway up the porthole you will have a 3/4 full reading after the boiler pressure reaches 2kg/cm2 (28psig). It is more difficult to see this change on model locomotives fitted with 5mm, or less, diameter sight glasses. Let's now visualize what is happening in the model boiler as it reaches operating pressure. The water level is well above the top of the firetube (gas flue), and as the water expands, due to being heated, it is compressing the trapped air at the top of the boiler into a space less than the original 20% of volume. The trapped air may or may not be vented off by the operator, but at some point, as the temperature of the of the heated water exceeds 212F, steam will begin to be present in the space above the boiler's water level. The boiler's pressure will continue to rise until the pressure relief device opens. At this point Ruby's ready to go! When the operator opens the throttle the steam delivery line and the cylinders will fill with condensate (hot water) untill they warm up. Once the cylinders are cleared of condensate the locomotive will start to run on its own. At this point one will notice that the exhaust steam appears to be very wet. This is caused by the surface of the boiling water efferescing water into the steam in the top of the boiler as the water boils and steam bubbles to the surface. Some of this hot water is carried over (it's called carryover in full scale practice) with the steam flowing to the cylinders. The water cools as it flows through the steamline and the cylinders. It does not "flash" into steam, and it degrades the performance of the locomotive until the boiler water level drops low enough so that caryover stops. In model locomotives like the Ruby the steam turret is located at the top of the backhead. This is an additional source of carryover because every time the locomotive bumps itself running with a full water level some of the water surges rearward and is forced up into the throttle valve passage and hence to the cylinders. This is one reason that piston valved engines seem to run better in reverse. This rapid and explosive boiling action of the water in a model boiler has been documented both by myself and Larry Bangham as we both worked on perfecting boiler water level electrical sensors that would tell a pump when to turn on and off to maintain a constant water level irrespective of the locomotive's speed and load. Eventually the sensors were designed to cancel out the chaotic and unpredictable boiler water surface conditions that are prevalent in these tiny boilers. This rapid and unpredictable boiling can be observed by looking at the porthole type water gauge on the backhead of a Frank S. locomotive. "Zippiness" commences at the point that the boiler water level falls low enough that the potential carryover caused by bursting st
Re: Ruby
Great Trent, Let me know what you think when you see it! Geoff Geoff, > > Hello. I'm Trent, and I'm a Rubyholic. > > Thanks for the heads up on the pictures in National Geographic. Without you >pointing them out I would have missed it. > I too looked around their web site and and did several searches on their "in >house" search engine and turned up nothing. > Off to the local bookstore! > >Later, >Trent > > >Geoff Spenceley wrote: > >> Lst, attention Ruby fans!! >> >> In the current issue of National Geographic, about the 12th page (no >> number), there is a double page photo of a circa 1900 loco rusting in >> Alaska, titled; "Running to Rust", a sad picture indeed, especially since >> it must, and I say Must! be the prototype ancestor of "Ruby"!! Remarkable >> ! The cab is missing but you can get one from Vance!! >> >> I went to: http://www.nationalgeographic.com/ but couldn't find it there, >> however I suspect it is to be found--somewhere! >
Re: Ruby
Geoff, Hello. I'm Trent, and I'm a Rubyholic. Thanks for the heads up on the pictures in National Geographic. Without you pointing them out I would have missed it. I too looked around their web site and and did several searches on their "in house" search engine and turned up nothing. Off to the local bookstore! Later, Trent Geoff Spenceley wrote: > Lst, attention Ruby fans!! > > In the current issue of National Geographic, about the 12th page (no > number), there is a double page photo of a circa 1900 loco rusting in > Alaska, titled; "Running to Rust", a sad picture indeed, especially since > it must, and I say Must! be the prototype ancestor of "Ruby"!! Remarkable > ! The cab is missing but you can get one from Vance!! > > I went to: http://www.nationalgeographic.com/ but couldn't find it there, > however I suspect it is to be found--somewhere!
