High torque that can be purchased.

[s_forbes]

High reduction spur gearboxes are fairly simple to make (and a fun design project!) if you have appropriate tools.

We lucked out this year and had the opportunity to get parts made on a milling machine with DROs (digital read outs). We designed a high reduction gearbox to work with unmodified AndyMark toughbox gears and output shaft, which we happened to have a bunch of from past robots. The parts that needed to be fabricated were the two plates for the gearbox, the standoffs that hold the plates apart, and the idler shafts (toughbox shafts were too short).

Due to our uncertainty we designed it to work as either a 3 stage (max reduction 53:1) or a 4 stage (190:1). Additional gearing options would be possible with the different gearsets offered by Andymark. We ended up going with the 3 stage configuration driven by CIMulators and a 12:60 chain drive to the arm sprocket, giving a total reduction of about 717:1 from the RS-775s to the arm.

I've been hoping for a while that AndyMark would come out with a spur gearbox scheme similar to this that would accept FP/Banebots motors on one of the plates. This year we made our own plates, but we would have bought them in a heartbeat if we could!