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Unread 29-01-2008, 01:28
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TheOtherGuy TheOtherGuy is offline
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Re: 1726 Prototype Testing

Quote:
Originally Posted by Frank Neuperger View Post
Nice job. It appears that the ball develops a rearward spin with this design as it rolls off the catapult forks. This is elegant. It seemed to roll back towards the bot after the shot.

The mechanism illustration suggests an "over center" latching scheme where actuators initially pressurize with the force vector of the actuators aimed just below center of the mechnism fulcrum. As such it will not fire unless somthing bumps them above the fulcrum. Possibly the small gizmo at the far left of the illustration does this. Getting both actuators "over center" at the same time may be a challenge due to build tolerances and mechanism flex.

I wonder about the shot to shot repeatability in terms of height and trajectory. To be shooting on the move, the shot to shot repeatability would be important.
Actually, I'm just really bad at making drawings I believe this picture from our gallery demonstrates it best:

the point where the piston attaches is just above the line created by the front pivot point and the end of the flinging arm. When the cylinders are pressurized, the catapult "slowly" begins moving because of that slight height. The end pieces you see are just mechanical stops so the catapult arms are always under the point where the piston attaches.

As for the ball-picker-upper, we simply use a pneumatic piston right now, but may end up switching to a motor to conserve air for the catapult:
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Last edited by TheOtherGuy : 29-01-2008 at 01:33. Reason: added links to larger images