Having done some thinking about Proto:87 and the extra work and “special” wheels involved, and all the fine, fine layout pics I’ve seen with normal wheels, I’m thinking about using the “Semi-scale” wheels.
So, which companies make these?
Also, I assume they theoretically work on all trackwork that the standard HO wheels work on. Is this correct?
I’d like to use them as much as possible, but then not worry if it’s difficult to convert an engine or two.
I’m hoping with a mixture of semi-scale wheels and standard wheels, my equipment will be totally compatible with others layouts, and anyone could run their stuff on my layout (except for Proto:87).
Just wanted to open up some discussion on these semi-scale wheels. Northwest short line’s version of them have .088" wide treads.
I use semi scale wheels on my tank, and hopper cars ,along with my other cars wich have standard wheels sets,with no problems.
Intermountain makes them in 28",36",33",38" http://www.imrcmodels.com/ho/hoacc.htm
The only thing I’ve noticed about the semi-scale wheels is that they are more prone to drop into some turnout frogs. Adding some filler material to turnouts with too-deep flangeways helps. I use an NMRA gauge to check the depth. The semi-scale wheels do look really good, a nice compromise without all the work of exact scale, and I haven’t noticed that they are any more prone to derail than regular wheels.
I’ve been converting rolling stock, including locomotives, to 88’s for a little while. There has been no noticeable difference in tracking, and the difference in appearance is terrific. For locos I use NWSL wheelsets, and I generally use Intermountains for cars.
I use Intermountain metal semi-scale wheelsets (generally I don’t allow a car on my layout that doesn’t have 'em), and the only problem I note is the frog drop mentioned above–Peco switches are more vulnerable to this problem. The added weight and precision otherwise results in very reliable operation.
I’m starting to realize that semi-scale wheels may really require turnouts constructed specifically for them so the wheels don’t drop down into the frog.
It seems there is a tradeoff to going directly to semi-scale wheels. It seems good looks = rougher ride over frogs, or specially built turnouts.
Alrighty, so to run both RP25 as well as semi-scale wheels, my frogs need to provide clearance for .027" flanges (.002" of “slop” built in for semi-scale).
Flange widths: I’ll use the NMRA gauge, and have an extra .005" of side-to-side slop for guard rails.
That extra .005" of flange clearance probably leads to some “dropping into the Frog” that I’ve heard rumors about with semi-scale wheels.