Minimum radius for traditional AF?

The 1962 Gilbert catalog shows the Casey Jones 4-4-0, F9, C&NW Pacific, PA1 and a Hudson set being sold with Pikemaster track.

Rusty

Pretty much any freight car will work. In addition to the above engines the short step version of the C&O GP7 works as well as the Atlantic steam engines. The streamline passenger cars work but not the older heavyweights.

OK, thanks guys. I have loads of old O27 track so I could try removing rails and regauging them for S gauge to do some trials on nominal 12.4" radius. AF flanges are probably big enough to manage tubular track.

You might take a router and cut the radius in a piece of scrap wood insert your rail and give it a try.

I doubt many engines will handle 12.4"

Good luck

Gunny

I can tell you the only rolling stock on which the trucks can pivot far enough would be reefers and box cars. On all the others the couplers will hit the steps on the bodies first. Gilbert two rail flanges are much smaller than Lionel wheel flanges and are designed for the Gilbert flat top, prototype profile rail. I suspect a cut of cars may stringline when attempting to pull them around an 027 curve on Lionel round top rail.

An Atlantic engine may go around an O27 curve without derailing. Keep in mind all the Gilbert trains are full 1/64th scale length, the passenger cars just model 70' cars. Even when these 1/64th scale trains were introduced by Gilbert pre war in O gauge they were not designed to run on O27 or O31 track. Gilbert prewar O gauge three rail track was 40" in diameter.

The best way to test smaller radii would be to get a couple pieces of S gauge GarGraves flex to bend to small test curves.

Perhaps buy 1 or 2 pieces of GarGraves AF (S-gauge) 3' flex to experiment with.   I've heard that they can bend fairly tight if you are careful and go slowly.  First cut a plywood jig for the radius you want, then form the track around it.

Dave, that was my recommendation as well. GarGraves S gauge flex is easy to bend, nothing like 3 rail O gauge. I built an entire S gauge layout with GarGraves by bending it around my waist. that gave me about a 12"radius. I then just carefully widened it to match the track centerline marked on the layout and tacked it down. Resulted in very smooth curves and a slight easement at the tangents.

@Drummer3 posted:

Perhaps buy 1 or 2 pieces of GarGraves AF (S-gauge) 3' flex to experiment with.   I've heard that they can bend fairly tight if you are careful and go slowly.  First cut a plywood jig for the radius you want, then form the track around it.

@AmFlyer posted:

Dave, that was my recommendation as well. GarGraves S gauge flex is easy to bend, nothing like 3 rail O gauge. I built an entire S gauge layout with GarGraves by bending it around my waist. that gave me about a 12"radius. I then just carefully widened it to match the track centerline marked on the layout and tacked it down. Resulted in very smooth curves and a slight easement at the tangents.

What, GarGraves flex is easy to bend???  When did that happen?  It has been about 30 years since I've bent any GG, but compared to AM, SHS/MTH, and what I see in FV flex -- I've always wondered why anybody would use GG.  AM flex is not that friendly to bend, but a pleasure after GG.  GG does not cut easily (at least when it was tubular) -- again, compared to what is out there now.  Don't know how they compare cost wise or if GG turnouts have been made to finally work.  Then there is appearance...

2¢

Tom Stoltz

in Maine

I am not recommending GarGraves, That is merely a cheap and easy way to determine a minimum usable radius. Way easier than trying to regauge Lionel O27 curves. In my opinion GarGraves is easy to curve and cut. I used a reinforced cutoff disc in a Dremel Mototool. My permanent layout uses MTH flex with handlaid turnouts because someone named Tom quit making turnouts before I could place my order.

The reason for GarGraves flex in the old days was because I was using a mixture of Gilbert turnouts and R-O-W Industries turnouts.

The reason the 21234 C&O GP7 steps were shortened was to enable the steps to clear the pikemaster switches. Any GP7 should work if there are no switches.

@gunny posted:

I doubt many engines will handle 12.4"

Good luck

Gunny

I agree. Let's remember that the "typical nominal" track radius in HO scale is 18".

FWIW, my Flyer Pacifics and even the Enhorning F unit I have are just fine on the sectional 42" (21"R) Gargraves that I'm currently using. Obviously I would prefer a larger radius, but like most of us, my space is limited.

Mark in Oregon

There is a lot of MTH S gauge flex track on eBay. You could buy one or two pieces and try it out to see how tight your trains can go.

Have you considered bump outs on each end of your layout, in order to have wider turns?