Bearing Stack

1Place the two parallel plates

Drop two 1/8" plates into a fresh assembly. Use a layout sketchA separate sketch in the assembly that holds the master dimensions every part references. Change a number once, and everything driven by it updates. to set the gap — typical FTC shafts run 1.5" to 2" plate-to-plate.

Lock the plates with a Fastened mate so they don't wander while you work on the shaft.

2Press the bearings into the plates

Insert two flanged bearings. Mate each one with a Fastened mateAlways Fastened — never Revolute. The bearing's outer race doesn't spin; the inner race does, which is on the shaft. Mating the wrong race is the most common assembly bug. to the outer face of each plate, flange-out, hole concentric.

If the flange is on the wrong side, the bearing will pop through the plate the first time the shaft sees load.

3Drop in the hex shaft

Insert a 6mm hex shaft and mate it Revolute through the two bearing inner races. The shaft should rotate freely with zero axial play once you constrain it.

Length matters: leave 2–4 mm of shaft sticking out past each plate for the shaft collar or clipA shaft collar (set-screw) or e-clip captures the shaft axially so it can't slide out under impact. Without one, a hard hit will walk the shaft right out of the bearings..

4Add spacers to set the wheel position

Slide in plastic spacersSpacers control where the wheel (or gear, or pulley) lives along the shaft. Stack them in 1mm/2mm/5mm increments — keep a notebook of which stack gives you the right wheel center. on each side of the wheel position. The goal is zero side-load on the bearings and the wheel exactly where the layout sketch says it should be.

5Cap it with shaft collars

Add a shaft collar (or e-clip) outboard of each bearing. Mate Fastened to the shaft — that's what keeps the whole stack together when the robot takes a hit.

Spin it in Onshape's Play view. The shaft should rotate cleanly; the plates and bearings shouldn't move at all.