I use a drill bit in mine and so do a lot of others. I've heard of other people using allen keys that they've sanded round.
I haven't had problems with the drill bit in mine, just make sure it's tight enough to not fall out.
i read an article in r/c car action and they say to heat the shaft and input gear in the oven, did you have to do all that or did you just shove the drill bit in? thanks for the quick response!
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It's "Dr. _paralyzed_" actually. Not like with a PhD, but Doctor like in Dr. Pepper.