Temperature Shutoff on Denso Motors?

[Richard McClellan]

Has anyone had any issues with the Denso motors heating up after several minutes of high loading? Our team has a 3-wheel crab drive setup this year, and each module is independently steered. We are using the two Denso motors to rotate the two front modules (directly driven) and a globe motor (directly driven) to rotate the rear module. The whole system works great during driving practice at first, but after about 10 minutes of driving, the rotation of the front modules stops working (the lights on the Jaguars are solid green, the modules aren't rotating, and the denso motors are hot to touch). Then if we wait 5-10 more minutes (which I presume is for the motors to cool down), it will start working again.

At first I thought there might be some large side loading on the output of the window motor, or binding in the lazy susans we are using for rotation, causing it to bind, but we've taken the modules apart many times and can't seem to find any issues. A picture of our robot can be seen here.

Our sister team, 2881, is also using their denso motors to drive some belts for their lift and they are experiencing the same behavior (freezing up after 10-15 minutes of driving.

Has anyone else ever experienced issues like this with the denso motors? Is there an internal temperature shutdown such as an auto-reset breaker of some kind? We are thinking of making some heat sinks to attach to these motors, but if anyone knew where we could buy some that were about the right size, that would be a lot easier.