Model Railroading > Intermountain wheels: semi-scale vs. scale

Want to order some HO wheel sets from Intermountain and noticed they have 2 types of wheel sets for each.
questsion: What is the difference between semi-scale and scale wheels?

Thanks!

Shannon Crabtree
Fredericksburg, VA
Virginia Midland Railroad Blog

Regular wheels are .110" tread width and semi-scale is .088" tread width. The semi-scale wheels look closer to prototype tread width but don't require 100% perfect trackwork.

Lee Ryan - Rio Grande Fan
Denver, CO



Edited 1 time(s). Last edit at 01/25/13 09:05 by RioGrandeFan.

As long as your track is properly gauged, and you aren't using switches with excessively wide flange ways, you should be OK.

Well, to answer the question, "semi-scale" wheels, aks Code 88 are, as already mentioned, .088 in wide. Scale wheels in HO are .063 in wide. Most standard wheelsets in HO are .110 in.

Elizabeth

Thanks for clearing this up!

Shannon Crabtree
Fredericksburg, VA
Virginia Midland Railroad Blog

.088 semi-scale wheels.

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Scale wheels meet the standards of Proto:87 modelers. The flanges are much smaller - smaller than even prototypically scalled wheels. More discussion here:

http://www.proto87.org/p87/journal/n7/page3.html

The net result is difficulty with NMRA standard trackwork. The flangeway in frogs (at crossings and turnouts) and guard rail spacing is too big on NMRA standard trackwork, resulting in unreliable operation.

Code 88 (semi-scale) is supposed to be a good compromise, but I've had problems with Code 88 wheels. I blame the piss-poor trackwork on my club's modules, and modelers too lazy to correctly lay, or correct poorly laid trackwork. I know I'm not alone in these problems. Good trackwork is no problem, but I was blamed for my own equipment derailing where others with code 110 wheels had no problem, even when I showed that the issue was things like wide flangeways and other track maladies. "Well, I don't have a problem with my equipment, so it must be yours that's the problem."

I encourage anyone to adopt better, finer standards, but be advised, it's an uphill battle in a social setting like a model railroad club. Especially one that pretends to be "inclusive" by catering to the lowest common denominator, thus alienating fine scale modelers.

The math is this: Code 66 wheels (0.066" wide) scale out to 5-3/4". That's dead center the prototype standard wheel width of 5 to 6-1/2" wide. The standard Code 110 RP-25 wheel (0.110" wide), scales out to a little over 9-1/2" wide. That makes it about 50% too big, or about right for S-scale. What do you think about running HO trains with S-scale wheels? Well, there are many who say this is a necessary compromise, and a vocal minority who prove that wrong.