O 3 rail coupler height gauge 

3 Rail O gauge may be built to standards, but unlike Scale O and HO etc, there are no coupler height gauges that I have found.   There is no standard unless you can measure it. 

After doing some checking on my cars I believe the .688" +-.031" Center line height of the coupler appeared to be correct for the 3 rail as well as O scale.    To make sure all my 3 rail cars are adjusted correctly, I needed a master gauge.   Since I have a 3D printer, no problem. 

Designing a gauge, just for height, should not have been too tough.  Except I forgot on 3 rail the center rail on tubular track is "higher" than the outer rails.  The insulation paper does that.  Also make sure you make the coupler the correct direction.  After a couple of iterations I came up with this.

After printing check the height from where it sits on the track to the top of the large face, it is designed to .688".  This is the center of the coupler which is .360 tall.   It printed to .685 center height using PETG.  Well within the +-.031" for "center".

Testing with one of  the non-adjustable Lionel cars it looks good.

For files see the O Gage Forum 3d Printing Catalog 

Now I can adjust my cars to a master instead of car to car. 

Last update Oct 5 2022