wheel gauge?

On Lionel tubular track the the gauge, 1.25”, is measured at the narrowest place which is some distance below the top of the rail. Since the flange is tapered, the flange contacts the narrow point of the track below the tread, but above the tip of the flange.   When Lionel measures the wheel gauge, the point it is measured where the tread contacts flange, which is not at the track gauge point. In the few cases where Lionel provided a gauge number, it  is less than the track gauge because of the tapered flange.  Think that is confusing, the real railroads face the same problem.  So they measure the distance between the backs of the wheels.

To measure the gauge of Lionel and Lionel clone equipment, you need a digital calipers so you can get the gauge dimension on the wheel where the flange contacts the tread.  That number will probably be something like 1.235”.   Best way to check for out of gauge is comparing the problem wheels to wheels of a similar design that run properly. 

The Kadee wheel gauge is probably for O scale wheels and is not appropriate for three rail wheels. 

I just went into the train room and snapped a couple of pictures to help illustrate what I was saying. The truck is a postwar GG-1 truck.  For the track the caliper is upside down. It is a little hard to read, but the reading is 1.250”.

thanks david.

Track gauge is track gauge - ie both scale and 3 rail stuff use 1.25 gauge track.    This is equivalent to 5 scale feet.    2 rail evolved from different sources in the 1920s and 30s and some were 17/64 scale and some 1/4 scale and some use 3 rail track and what not.    I think that as many 2 railers used or converted 3 rail equipment, they accepted the slightly too wide gauge and it became the standard.   

So the track gauge is the same, but the flanges for 3 rail are much deeper.    That makes it harder to use a 2 rail gauge, but not impossible, just use common sense and make sure you are checking to where the flange hits the tread.

On a separate note, there is a small group of modelers who model "proto-48" and build their track and equipment to 4 ft 8 1/2 inch gauge.