I think Carleton should report this to the railroad forum to dispel any notion that measurements in the railroad industry is not nice rounded English only and metric is converted to exact sub-millimeter accuracy. The huge tolerances allow for metric numbers to be just as round.
Jerry ________________________________ From: John M. Steele <jmsteele9...@sbcglobal.net> To: U.S. Metric Association <usma@colostate.edu> Sent: Sunday, March 8, 2009 6:10:42 PM Subject: [USMA:43543] Re: Metric discussion on the railroad list (1) As I said, I couldn't find the details online. However, I would guess that something like that or a little more is a reasonable "as installed" tolerance with the rest of the range reserved for wear over time. --- On Sun, 3/8/09, Jeremiah MacGregor <jeremiahmacgre...@rocketmail.com> wrote: > From: Jeremiah MacGregor <jeremiahmacgre...@rocketmail.com> > Subject: Re: [USMA:43511] Re: Metric discussion on the railroad list (1) > To: jmsteele9...@sbcglobal.net, "U.S. Metric Association" <usma@colostate.edu> > Date: Sunday, March 8, 2009, 6:03 PM > So what this all means is that all of the sub-millimeter > lengths that those opposed to metric would insist on being > there is all nonsense. A 1440 mm gauge would work just as > well as a 1430 mm. > > Jerry > > > > > ________________________________ > From: John M. Steele <jmsteele9...@sbcglobal.net> > To: U.S. Metric Association <usma@colostate.edu> > Sent: Sunday, March 8, 2009 1:50:04 PM > Subject: [USMA:43511] Re: Metric discussion on the railroad > list (1) > > > > My calculator says 37 mm. However, other articles say the > forces tend to widen the gauge, and ultimately that sets the > need for maintenance. So I would guess a fraction of that > is initial tolerance, and part is allowance for widening > over time. I couldn't find details online though. > > Also the shape of the railhead, wheel and flange are all > somewhat complex shapes and controlled. > > > --- On Sun, 3/8/09, Jeremiah MacGregor > <jeremiahmacgre...@rocketmail.com> wrote: > > > From: Jeremiah MacGregor > <jeremiahmacgre...@rocketmail.com> > > Subject: Re: [USMA:43495] Re: Metric discussion on the > railroad list (1) > > To: jmsteele9...@sbcglobal.net, "U.S. Metric > Association" <usma@colostate.edu> > > Date: Sunday, March 8, 2009, 1:28 PM > > Interesting. That is a 27 mm tolerance. The > average of > > the two extremes is 1441.5 mm. This means that the > > railroads track widths can easily be stated as 1440 mm > as it > > will fall within the tolerance. This also means that > > vehicles built for the railroads may also experience > such a > > large tolerance (maybe not as large as 27 mm) and thus > when > > being built can be expressed in round numbers. > > > > Carleton should express this information to his > Railroad > > Engineer forum friend. > > > > > > Jerry > > > > > > > > ________________________________ > > From: John M. Steele > <jmsteele9...@sbcglobal.net> > > To: U.S. Metric Association <usma@colostate.edu> > > Sent: Sunday, March 8, 2009 12:33:57 PM > > Subject: [USMA:43495] Re: Metric discussion on the > railroad > > list (1) > > > > > > > > Assuming Wikipedia is correct, the tolerance of 1435 > mm > > gauge track is 1423 mm to 1460 mm for track rated for > 60 MPH > > travel.. I assume lower grade (lower speed) track is > > allowed a wider tolerance. Thus, that 0.1 mm > confusion in > > nominal is entirely negligible. > > > > I assume the tolerance is asymmetric because the width > can > > not be narrower than maximum wheel flange spacing (the > > flanges are on the inside, and ideally do not touch) > > http://en.wikipedia.org/wiki/Rail_gauge > > > > > > --- On Sun, 3/8/09, Jeremiah MacGregor > > <jeremiahmacgre...@rocketmail.com> wrote: > > > > > From: Jeremiah MacGregor > > <jeremiahmacgre...@rocketmail.com> > > > Subject: [USMA:43489] Re: Metric discussion on > the > > railroad list (1) > > > To: "U.S. Metric Association" > > <usma@colostate.edu> > > > Date: Sunday, March 8, 2009, 11:53 AM > > > Carleton, > > > > > > > Also in the design of railroad equipment, > can you > > tell us > > > what the usual tolerance ranges usually > are? You > > are > > > correct that in the world they don't get > precise > > to > > > sub-millimeter precision unless they have to. > They > > would > > > round everything to whole numbers if it > wouldn't > > effect > > > the outcome or if it falls within acceptable > > tolerances. > > > > > > The standard rail gage in the US is 56.5 inches, > which > > > equals 1435.1 mm. Everywhere else it is equal > to > > exactly > > > 1435 mm. I don't know anything about > railroads > > but I > > > bet that nowhere will one find the tracks > > consistently 1435 > > > mm due to many factors that distance will vary to > some > > > degree. There is constant exposure to heat and > > cold. > > > There are movements in the earth which can shift > > tracks, > > > etc. Thus to worry about sub-millimeter lengths > is > > > ridiculous.
