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Unread 23-01-2010, 00:32
RRLedford RRLedford is offline
FTC 3507 Robo Theosis -- FRC 3135
AKA: Dick Ledford
FRC #3135 (Robotic Colonels)
Team Role: Mentor
 
Join Date: Jan 2010
Rookie Year: 2009
Location: Chicago, IL USA
Posts: 286
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Re: kicker idea input

Team 3135 failed miserably with its RAM kicker accelerated by bungies!

Our PVC pipe ram kicker prototype, with 1-1/4" pipe sliding inside 2" pipe was kicked powerfully ONLY when hitting ball dead center, but could not elevate at that contact spot. The end of pipe had a tee in it to hit ball like a hammerhead shark, but even with good speed, hitting much below center killed all the power delivered. It seemed that too much torque and bending was happening as the 1-1/4 pipe extended much beyond the 2" guide pipe. There was no ram wiggle at all, and it was almost frictionless sliding, but this scheme would not elevate at all. This is the nature of compression - it wants to buckle and bend things out of alignment and initiate torque, whereas tension pulls things into alignment with each other.

So we went back to doing a bungee driven two arm pendulum, building a final scheme with metal parts today, and using ball bearing 5/8 swing axle. Already, we are up to 40 feet airborne without even very much optimization. The pendulum kicker produces elevation of kicks SO much more easily than the ram, and it is far simpler to tune for proper ball contact.

We are still intending to use a CIM+gearbox as a winder for bungee pulling to store energy. The winder sits between kicker and bungees, which all have one of their ends anchored on the frame. Cable passes through winder which can shorten cable by from 0-20" with a 0-180 degree cable wind. Cable can be instantly disengaged from winder - AT ANY # DEGREES INTO THE WIND UP CYCLE - allowing snap back to a straight un-wound state, and variable energy release under programmable controll based on how far the winder is rotated before cable is released. This way we have variable kick energy at programmed levels.

Pneumatics can do too, this using a programmed valve open interval to limit level of pressure build up for shorter kicks.

Our design for the winder's pneumatic trigger mechanism for disengaging cable from winder is being tested using wood on Sat. If all goes well, we will be cutting metal to finish kicker bu Thr. Will post results as we progress.
-RRLEDFORD

Last edited by RRLedford : 23-01-2010 at 00:35.