Modifying S scale rolling stock and passenger cars with O Gauge trucks

I am an S gauger and have a very wide selection of S gauge equipment. Here are my thoughts.

First, some of the Gilbert S gauge items were made with 3 rail O gauge trucks from 1939 through 1941. These would be a quick and easy start for your equipment expansion. They are fairly easy to find and not expensive.

Second there is a reasonably wide range of S gauge items available. One brand of interest might be the S Gauge K-Line cars. These were originally O gauge and were released with S gauge trucks. the original mounting holes for the O gauge trucks are still in the chassis. There are a lot of these, they are about 1/60th scale, maybe a little larger.

In the Gilbert and Lionel AF line any boxcar with a sheet metal chassis can accept an O gauge truck and navigate O-31 curves. The earlier Gilbert S gauge boxcars (made through about 1950) have diecast chassis with underbody details. The wheel flanges on an O gauge truck will hit the detail going around O gauge curves unless your minimum curve is O-38 or larger. Remember, all the Gilbert and then Lionel cars were designed for a minimum S gauge radius of 20". Anything with steps like gondolas, hoppers, cabooses, most passenger cars will need at least O-38 unless the steps are cut off. Look for items with a sheet metal chassis to be safe.

I would avoid the American Models and S Helper Service cars. These have a lot more low hanging separately applied details, and bolsters that will not easily accept standard 3 rail O gauge trucks.

Here is a picture of the underside of three cars. The boxcar in the middle is what you want. The caboose may work with a spacer between the truck and car body so the coupler arm clears the steps. Same with the hoppers, tank cars and gondolas with steps.

Thanks, Tom, for many great ideas I never thought of. Because so much S stuff is available, I don't think I'd hurt the value of a highly collectible piece by converting it. Most items can be found for under $20, and junk Marx 4-wheel trucks are inexpensive as well. Plus, it gives me something to tinker with to adapt to my needs.

Retrucked 633 boxcar.  The trucks are from prewar 3/16" O cars.  Attached to the frame with #8 x 3/4" round head machine screws.  The truck needs to be shimmed with a #8 washer to keep the truck from interfering with the car body.

I have been using 10-32x3/4” socket head screws with nylon insert locknuts and #8 washers for mounting replacement trucks on Gilbert and Lionel AF cars. The socket head fits perfectly into the well on hoppers and mounts under the trucks on other cars. Black anodized can be ordered, I just used stainless steel and made them black with a felt tip paint marker. Pictures below.

The bottom picture shows an S gauge K-Line boxcar chassis. They just drilled a second hole in the O gauge chassis and put thread locker on the screw threads to mount the S gauge trucks.