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Unread 01-02-2010, 03:34
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: non-pneumatic "kicking" mechanism

Since the only arrangement of elements with any structural integrity is the triangle, and since it is more efficient (less material) to apply and direct force via tension ---

Our kicker is an aluminum triangle "pendulum" made of tee-slot channel with gusset plates at corners and a "toe" on low corner for ball contact. Triangle's top corner clamps to 5/8 axle through ball bearings. At low corner of triangle is attached a 1500lb test 1/8 x 1/4 synthetic cable that runs through forward mounted pulley which turns cable rearward, toward bank of bungee cords, pre-tensioned to ~50LBS. Rear corner of triangle has strong travel stop cord attached to solid frame anchor point. It stops the kick at end of travel, and it sustains the minimum pretension force on bungees.

On its path rearward to the bungee group, the kicker cable passes through a winder plate that is driven by a geared down CIM motor to ~12RPM. Winder rotates 0-180 degrees in just over 2 seconds to shorten tension cable up to 12", depending on desired kick strength (bungee tension rises to ~120Lbs at max.). Kick is triggered by instant disengagement of winder cable from the winder plate using 2" of pneumatic cylinder piston travel to actuate the disengagement. The kick can be triggered at any point in the wind up cycle from 0-180 degrees. The trigger design is a very simple medieval-type concept and there are no other masses accelerated during kick, except the kicker & cable, and that is all I can say about it.

We are waiting to finish the gear box setup for the winder to confirm what level of wind torque it can hold while motor is de-energized. If de-energized motor allows winder to UN-wind, another system will be needed maintain the wind up tension/torque while waiting for the right moment to launch a kick.
Will confirm results of gearbox test when finished.

So far, our kicker has consistently placed shots within a 30" dia. circle at 35+ feet. We still need to "possess" balls well enough to maintain this level of accuracy during match play, and this remains the bigger challenge. We do expect to be able to consistently score two or more goals from far end in autonomous mode.
-RRLedford

Last edited by RRLedford : 01-02-2010 at 03:36.