[Joe3]

Yeah, to tell the whole story on this. There was a long progression of arm-related failures that occured from week 4 of build until this past weekend.

First, we have the two F-P motors and gearboxes powering a further 16-1 reduction that goes out to the arm.

1. Thursday night, end of week 4, we go to hang for the fist time. Arm buckles.

Result: Thicker tubing on the arm

2. Sunday night, end of week 5, we go to hang, gearbox mounts tear through chassis.

Result: Have the gearbox contain the tension of the chain. (larger gearbox), and beef up the chassis in the area.

3. End of week six, split a copy of the sproket you see on right there in half when going to hang.

Result: Replace with a less lightened copy.

4. NJ Regional, Arm is keyed to that 1/2 shaft. A battle is fought when we try to hang for the first time between the arm, shaft, and key. The arm lost, and the keyway was destroyed.

Result: Increase contact area on the keyway from .5" at both ends of the arm (left and right) to 2" on both ends of the arm attaching the the shaft.

5. Testing on practice 'bot before Philly Regional, strip teeth off many 'a gear.

Result: Double up gears to decrease the point load put on each tooth.

6. Testing before nationals on the practice 'bot, buckle the shaft near where that shear happened at PARC. When going for the hang.

Result: Add more bushing blocks for support.

So, this has been a year long developing problem, where it seems we just keep moving the weak link. Finally we got to a point where I dont think that we will improve the design, but rather replace that shaft and be more gentile with it from now on, as we cant go to a stiffer material (It's already steel) and to increase the diameter would require a redesign that just isn't worth the work at this point.

But there you go. No you have all been fully informed.