Building radial couplers by stereolithography

Radial coupler with radius bar (red) and drawbar (orange)

Functional radial couplers in H0 scale are rare to find as spare parts and hard to built from scratch. So it was natural to engineer them within the 3D print project. Weighting pros and cons, I decided that the coupler mount must be part of the car body and not of the frame. For two reasons: the radius bar is positioned close to the buffer, and the drawbar support close to the doorsteps. Both are part of the body shell.

I designed a drawbar who has a little nose who is overrunning the radius bar under the buffer. The general geometry is strictly to scale. As separate small parts cannot be 3D printed, I integrated the coupler inside the monotlithic car body as internal bars, avoiding warping of the body during printing. They must be cut out of the shell and sanded a little, together with the radius bar. Screw holes are pre positioned.

The production model of the wooden combine -  to be released soon - will have two coupler bars per shell. One is ready for Kadee NEM coupler heads, the other is spare.

2 drawbars are "cast" in the carbody

The coupler bar is working well with trailers, even in push mode through S-curves, despite the tendancy to jackknifing. This radial coupler will be mounted to all my future models,  and the older box cars will be redesigned as well.