Additional questions about improving pneumatic catapult

[Christopher149]

I have no particularly good pictures offhand, but here's something:

early prototype video
picture from before first event, I think

We have two cylinders (I'm not sure of bore size) that are 8-10 inches stroke, I believe. The up and down strokes are powered by separate SMC double solenoids like http://team358.org/files/pneumatic/S...alOverride.jpg from kits past, so not particularly high flow. This allows the shot to only vent the topside from atmospheric instead of 60psig. Also, only one downstroke port is connected; the other has no fitting. These push a bar of c-channel whose fulcrum is a bolt. The cylinders point just above the fulcrum, allowing pressure to build before overcoming the weight of ball and bar. The ball is held in place over the bar by the surrounding 80/20 bars. It can make the truss and the high goal from in front of the low goal.

It took a while of playing with dimensions and number of cylinders to get right. There have been several tweaks since these images: a little spacer to elevate the arm at the rear, moving the connection between arm and cylinders a couple holes forward, adding the second valve to not fight pressure on top half of cylinder. Presently, we have 7 accumulators (of at least 3 models, darn space problems) to store air and have an on-board Viair compressor.

Compared to the OP, the shooter is quite close to the ground, so the power is available for a good shooter.

It was finalist at 16-3-0 (11-1-0 through quals) at Traverse City.


Does this help?

Edit: summary of my suggestions: place cylinders more in line with fulcrum, try to use more of stroke, lighten the arm, eliminate flex, keep the ball steady. Use at own risk