FTC 7314 build November 2013
At Oxford, it was observed that when we attempted to hang, arm elements rotated to prevent hanging. We pinned the pivot tube clamps at the competition, but the steel drive shaft then spun.
Disassembled arm in order to:
- Increase the effective arm drive power by using a larger-diameter steel drive shaft with a keyway (and using keys).
- Abandoning the 4-bar arm to allow more arm movement, thereby enabling scoring in baskets "behind" the robot; need to turn around to score eliminated.
23-November DAR FLL Scrimmage
FTC 7314 (Sab-BOT-age) & 4399 (Autobots) robteers volunteered for this event, helping to make it a big success.
Mechanical: Rebuilt the arm drive by replacing the original 4.7mm D-shaft with a 0.25" diam steel shaft with 3/32" keyway cut its entire length. His change required the following:
- Bore out the driven brass worm gear to 0.250" ID
- Broach a 3/32" keyway in the worm rear ID
- Drill the output shaft bushing holes on the worm gearbox to 3/8" (from 8mm)
- Replace output shaft bushings with 0.25" ID bronze flange bushings (1/2" long)
- Cut (3) 3/32" keys: for worm gear and (2) for Hubs
- Assemble output worm gear and shaft w/ key
- Re-assemble input shaft with dual motors and worm
- Bore (2) driven Hubs to 0.250" ID and broach 3/32" keyways
- Reassemble arm drive shaft (including tubing portion)
- 1/4" diam 4140 alloy steel shaft such as McMaster-Carr 8927K18 - with keyway cut and cut to 3" length - R04
- (2) SAE 841 Bronze Flanged-Sleeve Bearings for 1/4" shaft diam, 3/8" OD, 1/2" length McMaster-Carr 6338K414 - R05l
- (3) keys cut from steel standard key stock 3/32" x 3/32" McMaster-Carr 98535A125 - R04