Team 228 turned aluminum pins which were inserted into holes in the frame and held to the frame with hairpin cotter pins from McMaster. The bumpers were held onto the pins with larger hairpin cotter pins as can be seen in this photo:
The bumper brackets were 0.125" aluminum angle bored to the OD of the pins on one flange and bored for deckmate screws into the bumper plywood. This system only required the pulling of 14 cotter pins to remove the bumpers and reinstall. We averaged under 5 minutes to remove/install all the bumpers.
We were fairly happy with this first generation design and had no failures in any component. We will probably change the design slightly so that instead of holding the pins to the frame with cotter pins, the base of the pins will be bored and tapped and bolted to the frame. This will remove the play that can be seen in the photo. We will also design a new bumper bracket to hopefully be produced in CNC sheet metal, like our frame, improving tolerances. These brackets will also hopefully incorporate wrapping the corners of the plywood with aluminum angle.