Hey y’all,
I have to place an order for two of the BaneBots 42mm gearboxes and I want to order some extra pinions for the Fisher Price motors in the kit. I’m not anywhere near our kit, or I’d just measure it myself, but I’m curious if I ought to be ordering the 3.2mm or 5.0mm bore pinions.
I think I’m after the 3.2mm pinions since the FP motors are a 550-ish can, but better safe than days behind schedule, right? 
3.2mm is roughly the same size as a 1/8" shaft, which I believe is what the FP has.
We ordered 3.2mm for our FP’s and the banebots and they worked, The 5.0mm would be way too big.
3.2mm. I just ordered the same stuff today, and was curious to see what size…so I took out the calipers and measured the shafts of the FP motors. They are exactly 1/8", which is 3.175mm, which will fit the gears.
Make sure you get a gear puller if your dont have one already. Then you can re-use the ones on the 550’s, or have some spare ones lying around (which wouldn’t be a bad idea).
we used the 3.2mm pinions last year for the FP motors and they worked well. We are also moving up to the 42mm gearbox’s this year and hope to have better success with them this year. You will defiantly need a gearpuller, and grab a bunch of extra pinions just incase you burn out any FP’s.