I happened on a photo of the Tomix/Tomytec 3-stall roundhouse. With minor changes, it looks like it would make a good US-style roundhouse. Anybody have one of these? How long are the stalls?
Checking at a Japanese site I found 30 X 29 X 10.5 cm. Or converted I believe is 11.8 X 11.4 X 4.1 inches. What I can't tell is whether that is the entire footprint with the base or just the structure footprint. Either way it looks like it could accommodate locos like an F unit or GP-7 or a small steamer like a 2-8-0.
I had one of these I picked up some time ago. The structure been around for awhile. It was the only roundhouse at the time that seemed to be set up for the Atlas turntable. I ended up taking off the base and just using the structure, the base being held on with multiple screws. The structure comfortably houses Bachman Light Mountains and Kato Heavy Mikados. Part of the internal space is taken up by a buffer that automatically closes the doors when the locomotive runs into it. Mark
15 degrees. This may be of some help: http://www.trainweb.org/tomix/control/TomixTurntables.htm Rich K.