I have an O-27 gauge train set mounted on a table. The oval is approximately 44 inches long and 29 inches wide (inside measurements. Will an oval HO gauge track fit inside the larger (O27)oval? I have been told that it will but in looking at the curves available online the smallest I see is 15 inch radius. If my math is right then the oval would be about 30 inches wide.
Bill Mc
Yes, BUT. Using flex track I have made an oval on a 12 inch by 24 inch layout with HO track. The BUT is finding locomotives and rolling stock to run on sub 15 inch radius track. I found some that will run on my 5 1/2 inch radius, so I’m sure there are some that will run on tight curves inside an O-27 curve. A Dash9 or SD80 ain’t gonna work though. 
Fred
15" may be the smallest commercially available curves available in HO. The only way to do it would be to use flex track. Even a 15" radius is going to limit what could run on the track, so going tighter is probably going to limit the rolling stock to small switchers and cars or trolleys.
And at 15" radius only the smallest stock looks any good on it, loco plus two or three small wagons at the most. Since curves this tight would typically only be found on local branch lines.
Ian
IF you are going to do that why not go to N scale?
Thanks for the replies. I guess I’m going to have to go “back to the drawing board”.
See my reply to your thread in the Classic Toy Trains forum. Think 3D, like Lionel did with their display layouts. Run an overlapping HO oval elevated above the O27. Put one corner/end of the O27 inside a tunnel with the HO on top of the tunnel. You will have to use the O27 trestles or make your own - HO ones will be too short. Or put bases of wood or foam under the HO trestles to get at least 5.5 inches total elevation above the O27. Depending on your O27 table size and HO equipment you intend to run, use either 15 inch or 18 inch radius sectional track for the HO. An added bonus is the ability to run the smaller On30 equipment on the HO track when the fancy strikes you. Brings out the kid in you!
yours in toy train fun
Fred Wright
Fred,
I really like your suggestion about the elevated track. I am confused however by the On30 thing. You said “run the smaller On30 equipment on the HO track”. Isn’t On30 equipment actually O scale that will run on the smaller HO scale track. Or did you mean that some On30 equipment is smaller than others?
Bill Mc
You might be able to find model 19th century locomotives and stock to go around curves this tight. The Bachmann Jupiter and some Overton passenger and freight cars should do the trick. Or if you just wanted something a little more modern, a GE 44 tonner and some ore cars.
Bill Mc
You are correct. On30 is models in O scale of narrow gauge equipment, designed to run on HO track. Only the smaller On30 models are going to go around 15 inch radius curves, though. Most will take 18 inch radius, but the larger On30 models (such as K27s and K28s) require even bigger. I was particularly thinking of the Bachmann Porter steam engines and the small diesel “critters” for 15 inch radius. I believe the Shay and Climax might also make 15 inch radius, but nothing less. At 15 inch radius, I would stick to cars that are 7 inches or less in actual length (28 ft prototype), which likely means no passenger cars.
Enjoy anyway - you have both the 3 rail track, and the HO track which can run either HO or On30. Lots of flexibility and fun!
Fred Wright