Problem with CIM-VersaPlanetary Setup (Choo-Choo motor)

[AM694]

Hi, our idea, for the choo-choo motor, was to have a modified CIM motor (shaft cut to approximately 1/2") mounted to a VersaPlanetary 50:1 reduction, and to use the key (approx. .4") as opposed to a set screw, as we thought a set screw would not be able to adequately transfer the torque.

Eventually, after a day of testing, the setup became unable to pull down the Choo-Choo. My gut feeling, from what my ears were telling me, was that something was skipping, as there was this grinding sound that seemed like something was hitting against something else.

This could possibly be because the 2mm key is failing to transfer torque to the gearbox (e.g, it's skipping or breaking somehow), it could be because of a failing CIM motor (on a previous one that broke, the CIM operated almost perfectly, but on occasion, its rotation faltered).

It was very easy to put one's hand on the "output sprocket", and rotate the VP output shaft, albeit with the knocking sound occurring.

We've tried increasing the length of the key (by artificially pushing out the CIM's keyway relative to the keyway of the gearbox with extra face plates), and that helped, but this setup needs to be more sustainable and rugged than it is. What are your thoughts? Did anyone have similar issues? Thanks a lot for your help!