When it is stated that a locomotive or rolling stock has 42, 36 or 33 inch wheels, what is measured in that diameter
The tread. Flanges have a higher diameter.
When a wheel develops a flat spot it can be trued up, thus reducing the diameter.
1 At what diameter is it too small to be trued up again?
2 Can an undersize 36" wheel be turned down to a 33" wheel?
At what point of the tread is the diameter measured?
The diameter is measured at the largest point of the tread, in other words, just before the fillet for the flange.
Ol’ Ed
And if a wheel is turned down (say to correct a flat spot), is the angle of the tread kept the same? Is that angle the same for all wheel sizes?
When wheels are trued, both are turned to the same size and matching contour. 36" cannot be turned to 33". There is a limit to turning and it is not very much. This is why wheels are scrapped.
In the old days and maybe still in some locomotive cases there is a tire ((a steel ring around the wheel that is machined with a tread and flang)), this can be replaced without scrapping the whole wheel. Today the use off tires is rare, I think they do exist on some old switchers. Tires were used on steam locos and other equipement.
Measured in the center of the tread. Hollow worn tread is a measurable defect. A 40" wheel is 40 inch nominal , some are fat 40’s actually 42.5 inch plus . Normally a wheel has about a two inch rim thickness so a true 40" wheel can be turned to a 38 inch wheel . A fat 40 has 2.5" rim thickness so there is much more wear in a fat wheel and they will last a bit longer . The downside is that they will not always fit in the locomotives trucks , (like a GE with underslung brake cylinders) .I prefer a fat wheel to a true wheel . I also prefer wide flange wheels, but that is another story.
Randy
as late as 1992 the Belt Railway of Chicago was using tires on their engines as this road is mostly switching and thats hard on flanges. i watch tires being sweated on the 1225 back in 91 in the old Ann Arbor shops in Owosso MI man talk about something to watch lol heat and hammers
Randy.
Are all wheels on the truck turned to the same diameter?
Federal law states that the wheels cannot vary more than 3/4 inch , on older locomotives this will work but on newer engines the wheel slip system will not operate properly if the wheel varience is more than 1/2 inch . On locomotives with six axles if the wheels are more than 1/2 inch , shims must be installed between the pedastal springs and the journal boxes to equalize the weight on the drivers. If you do not install shims yuou will have no end to the wheel slip problems.
Randy
Presently it is very difficult to get wheels , sweating on tires is becoming a viable option again.
Randy
“Sweating,” as in adding metal(moltan metal) to the existing wheel to increase its diameter?
Tires are not “sweated”. Sweating is a process where a lower temperature filler such as solder or brazing alloy flows into a gap between the parts. Tires are shrunk on to the wheel. The tire is heated causing it to expand. When placed over the wheel and allowed to cool it will grip the wheel by whatever interference was machined into it. A 36 inch wheel could easily be thirty thousanths smaller than the wheel OD and grip as a solid piece of metal.
Youv’e never put em on a hot day !!! trust me … you sweat !!
Thanks, guys, for the information. Another question crosses my mind, though. Do they harden the wheel tread as they do the track? And if so, how? Nitride?