I know this is an old topic, but the problem still exists.
If I was to make a Hi-rail wheel gauge, what would be the defining measurement to check? Would it be back-to-back width of the wheels? For some reason I keep plopping the NMRA 2-rail gauge onto a set of Hi-rail wheels expecting them to drop right in. I've noticed that almost every wheelset I try, the backs of the wheels are "just" too wide, about 1/16" from going in. But they're all consistent. If I took even a scrap piece of brass and made it to slip between the wheels (whatever that measurement should be) then I could check every wheelset against it and it would be easier than holding a ruler up to the wheels.
Another topic...I spent the last 2 days cleaning crud off the wheels of my rolling stock, didn't want to do it but I noticed several wheels had buildup that was 1/32" thick! While cleaning them I noticed a lot of variation between tread angles, a couple of cars had wheel tread where the angle was almost flat but with large flanges. I'm running on Atlas, Micro Engineering, and Signature Switch 2-rail track and have not had any problems, other than thru a couple of my hand-built turnouts where I used too many spikes in the frog area.
Anyway, a while back I stated that, being I was running BPRC, I really didn't need to clean wheels and track because there's no requirement for electrical continuity. But there is a need to keep them clean to prevent derailments so cleaning accumulated dirt/grime off these places is still a necessary evil. Today I get to clean the wheels on all of my engines Woo-Hoo!!! Good thing is all I have to do is turn them over and turn on the switch. Another good thing is I only need to do this once or twice per year.
