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 <[email protected]> To: U.S. Metric Association <[email protected]> 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 <[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.
