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.
