A while back my Soo 320 project SW1 broke a horned ball on it’s front truck drive, while searching for parts I found NWSL had instructions for upgrading the rear truck drive which was somewhat notorious on these models.
It’s basically a rubberish straw, for a closer look:
The NWSL solution is to create a cardan shaft between with the standard horned ball/cup arrangement on either end. You start by cutting a 0.250″ long section from a 2mm diameter shaft.
Press fit the cups onto the shaft making sure they are aligned
And finally installing horned balls on the motor and truck shaft and you’ve go an improved drive (some fiddling about may be required)
As I have two SW1 (which you might have guessed from the pictures it was at this point I started working on the second one. I made it as far as pressing the cups on a shaft when it slipped out of my pliers bounced off my forehead and landed somewhere in the room… yet to be found. I don’t expect to find it until long after I’ve given up and cut another one.
Matt's Railroad Blog 