I think I understand the difference but can someone explain it. Is it just for looks or does each specific set of wheels need a specific type of track?
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Thanks for posting this question. It's one I always wanted to ask and just never hit the submit button. Terry
Wheel Flange, and i rolled a 2 rail wheel on a Hi-Rail track and it has a little fun going through the switches that I have at one of the groups I belong to
Scale wheels are 2R flanges and Hi-Rail wheels are 3R pizza cutters.
Scale wheel locomotives also have fixed pilots with full length handrails, and generally require a minimum of 072 curves.
Scale wheel locomotives also have fixed pilots with full length handrails, and generally require a minimum of 072 curves.
There are three key differences:
- Tread width. Hi-rail wheels are just under 1/4" thick (.250) while the standard scale wheel is between .115 (fine scale) and .172 (early). This also means that the flanges on scale wheels are farther out than on a hi-rail wheel.
- The flange depth on a hi-rail wheel is higher. There's a nickname of "pizza cutter flange" which kinda gives you the idea of some wheels, but the flanges modernly are between 1/16" and 1/8" depending on the wheel. Scale wheels have much smaller flanges of under 1/16". Hi-rail wheels on rolling stock are also contoured in a "fast-angle" configuration which exaggerates the prototypical wheel taper that allows trains to negotiate curves more smoothly. Scale wheels are tapered as well, but it is much more subtle. Scale wheels (most of them) are also cut to an NMRA wheel RP25 (recommended practice) standard. About 10 years ago, I posted a thread suggesting we dump the fast-angle wheel in favor of an RP25 code 172 wheel with a slightly larger flange that was "less than well received."
- Most important, hi-rail wheels are NOT insulated because they don't need to be since the hot is coming from the center rail. Scale wheels are insulated on at least one side since the hot comes from one rail and grounds on the other in a 2-rail operation.
If you're using "flat-top" track like Atlas, Gargraves, FasTrack or MTH, you can run rolling stock with scale wheels and Kadee couplers provided you have wide enough curves, usually 36" Radius (O/72) is sufficient with some exceptions. I do this at the club all the time.
You can even run modern hi-rail wheels on Code 148 2-rail track with a third rail added, but 2-rail turnouts will be problematic. You can't run hi-rail wheels on 2-rail track fed in a 2-rail manner because they're not insulated.
Good description Matt. I believe, but am not sure, that a flange gauge will be tighter for a 3-rail wheel.
Bob, you are correct about the flange. Matt did mention it in his post.
"This also means that the flanges on scale wheels are farther out than on a hi-rail wheel."
Same meaning just a different way of saying it.
I noticed that the flanges were not the same on 2 rail and 3 rail equipment when I tried to build a display case that would have grooves for the flanges. I wasn't easy but eventually I found a happy medium that worked with both types.
The thing that has always bothered me with this question is are scale wheels really scale? There is the discrepancy with the track gauge, which is 5 foot if the scale is 1 in 48. For post war hi rail the gauge of the wheel sets is 1.260". This is measured at the intersection of the flange and tread. It is wider than the track gauge, which works because of the shape of the tubular rail. Information on modern hi rail wheel gauge is harder to get and may very from supplier to supplier. But if post war wheel sets are run on modern flat top rail, and the gauge is 1.25", there should be a problem.
On real railroad wheels sets there is about 3/4 inch clearance between the wheels and the rail. Both the wheels and the rail are gauged at a point that is not at either the tread or top of the rail. 4 ' 8 1/2" is the track gauge, not the wheel set gauge. The discrepancy is rarely noticed because wheels sets are always measured back to back, about 53 3/16", and no one ever pays any attention to the actual gauge.
On on a hi rail wheel the flange is straight. On a real wheel there is no straight line on the gauge side of the flange. The flange is only one inch tall, which would only be 0.021" in 1:48.
"The thing that has always bothered me with this question is are scale wheels really scale? There is the discrepancy with the track gauge, which is 5 foot if the scale is 1 in 48."
If you want exact scale wheels on correct gauge you can use P48( proto 48). Contrary to first glance it tracks very well since the 1/48 scale flanges are about the same as common HO scale flanges and with more weight holding them on the track in O scale.Here's a Lionel hopper with P48 wheel sets installed....DaveB
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So then David measures the opposite.
He is correct - the only truly scale wheel discs are the .115, used predominately by Proto-48. I would think that the best and most expensive models would be true Proto-48, but the market is not there.
I like the looks of the old .172 wheelsets. Irrational, i am sure, and part of the reason I really should understand why lots of folks like the looks of the center rail. I am trying . . .
So does P48 use 1 1/4" track gauge?
Originally Posted by David Johnston:
So does P48 use 1 1/4" track gauge?
No. The gauge is slightly narrower -- I believe 1.177 instead of 1.125. The wheelsets are also narrower (.115) and the flanges are seriously smaller than 2-rail O scale.
Originally Posted by Hudson J1e:
Bob, you are correct about the flange. Matt did mention it in his post.
"This also means that the flanges on scale wheels are farther out than on a hi-rail wheel."
Same meaning just a different way of saying it.
I noticed that the flanges were not the same on 2 rail and 3 rail equipment when I tried to build a display case that would have grooves for the flanges. I wasn't easy but eventually I found a happy medium that worked with both types.
I have a board around somewhere I cut grooves in for painting purposes and I made double cuts with the table saw to widen the grooves to handle hi-rail wheelsets. The reason the scale wheelsets have a wider "back gauge" is simply because the wheels are substantially narrower and in compliance with the flangeway specs under RP25. Hi-rail wheels by virtue of their overall thickness and the flange size/countour have a tighter back gauge which is what makes them incompatible with standard 2-rail turnout guard rails and flangeways.
By the way, one of the best tools I have is a Kadee Coupler height gauge which has a flange checker, a height gauge, a trip pin gauge, and can give you a good idea of whether your track is in gauge.
Originally Posted by AGHRMatt:
I have a board around somewhere I cut grooves in for painting purposes and I made double cuts with the table saw to widen the grooves to handle hi-rail wheelsets. The reason the scale wheelsets have a wider "back gauge" is simply because the wheels are substantially narrower and in compliance with the flangeway specs under RP25. Hi-rail wheels by virtue of their overall thickness and the flange size/countour have a tighter back gauge which is what makes them incompatible with standard 2-rail turnout guard rails and flangeways.
Way back in my carpet-central days I acquired a half-dozen or so of the 2-rail Atlas switches (they were cheap--something like $6-8 each when Lionel 027's were going for upwards of $40+. I added Code 148 rail for the center rail (after the tactic of soldering wire atop a line of brads hammered into the ties didn't work out so well):
You can see how I addressed the guard rail issue:
i.e. I whacked them. The cars do behave themselves over the frogs, as my numerous YouTube videos attest.
---PCJ
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