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 <[email protected]> wrote: > From: Jeremiah MacGregor <[email protected]> > Subject: Re: [USMA:43495] Re: Metric discussion on the railroad list (1) > To: [email protected], "U.S. Metric Association" <[email protected]> > 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 <[email protected]> > To: U.S. Metric Association <[email protected]> > 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 > <[email protected]> wrote: > > > From: Jeremiah MacGregor > <[email protected]> > > Subject: [USMA:43489] Re: Metric discussion on the > railroad list (1) > > To: "U.S. Metric Association" > <[email protected]> > > 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.
