[KrazyCarl92]

Abiding by the rules is a necessity. None of them are optional; they are all strict design constraints that MUST be met in order to compete. Although a good shooter may be more of a differentiating factor between good and bad robots than good bumpers, existing and legal bumpers are more of a necessity to be on the field than an existing shooter is.

As for technical stuff: avoid shoulders, grooves or other features on live shafts that concentrate stress between the driving torque and the load. Putting a snap ring groove between a driving sprocket and arm hub is asking for the shaft to fail where a spacer would do perfectly fine.