Not a bad idea Tom. I will use a zip tie. Then I will engineer a quick release function that allows me to disconnect the plastic retaining device. Then I can calculate the speed of rotation based on the distance the plastic retaining device travels from the rotating shaft assembly. I will of course take into consideration wind resistance/inertia and some amount of error in the timing of the release.

Or, I could just stomp on the gas, if the clicks don't speed up as fast the truck, that would be indicitive of slipping, meaning it is just some light amount of friction in the coupling portion.