[tim-tim]

I will echo some of the same things Clinton has mentioned.

The CIM motor not mounting flush will cause a lot of issues. I would look into that. This is one of the main reasons for using a thicker sidewall, to keep the bearing flush with the outer surface. A quick solution you could do to keep this gearbox/prototype is to create a shim/spacer for the CIM mating surface to move the CIM off the sidewall and bearing. This would require very minimal changes to what has already been fabricated.

The cost of bearings adds up over time, surprisingly. A round bearing vs hex bearing is around 1/2 price. That is a savings of ~$2/bearing; and only requires minimal effort from what is depicted.

How is this being mounted to the robot? Are you using the 4 bolts that hold the transmission together? I would loo into ways for keeping the assembly as a whole unit and pick up a few other points. This makes it easier for hot swapping and changing in the heat of the battle (based on my experiences anyway).

If you want to really look at some weight savings, eliminate all the extra shaft lengths that are not needed. Replace the screws retaining the bearings with an aluminum rivet or two.

Where is the encoder mounting? At the the end of the long turned down hex shaft? That is a lot of added weight for an encoder. Could you integrate the encoder in another spot? Maybe off another shaft?

Hope this helps. This is a good start and has probably taught you many valuable lessons. Keep iterating!