Re: 2073 Pneumatic Catapult
 

WOW! That is an elegant solution to the FRC pneumatics flow limitations. Your TDC latch is brilliant. Thank you for sharing the design. We made a copy today (no accumulator) and it worked beautifully. As my son said: "those guys rock!"

Re: 2073 Pneumatic Catapult
 

We couldn't get the shot we want out of ours, so we scrapped it and are working on other designs. But thanks so much for sharing the general idea!

Re: 2073 Pneumatic Catapult
 

Have you tried making or buying a proportional control valve (AKA I/P)? We made one that worked pretty well but was a modified regulator, so illegal. You could turn knob w/ gearmotor & multi-turn POT.

One of the students said today that a "Quick Exhaust Valve" or "Dump Valve" is legal this year. This is a shuttle valve on the exhaust port that charges from solenoid and dumps to atmosphere. Anybody know about this?

Re: 2073 Pneumatic Catapult
 

The day after we shot the first video we made another with some wider angles.
http://youtu.be/Zfx2kwGwvEg

Re: 2073 Pneumatic Catapult
 

Just had an idea you guys. Every time the video goes to slow motion, put in a different Dubstep drop, but no music on the regular speed parts. That would be funny to me for some reason.

Re: 2073 Pneumatic Catapult
 

Sorry it took so long, but I finally had a chance to test out the collectors on our shooter. I made two videos. The first one had the collectors in line:

http://www.youtube.com/watch?v=hNUfE...BwU5QuFBVQGPyg

The second one has the collectors removed:

http://www.youtube.com/watch?v=4HNRL...re=c4-overview

Both videos were take with the front of the robot 9 feet away from the goal.

It looks like the shoot just gets higher. What that means for this shooter is that the arm is traveling though its arc faster. Is it something we are going to pursue? We aren't' sure yet. We like our shot the way it is without.

Re: 2073 Pneumatic Catapult
 

Quick exhaust valves are illegal according to recent Q and A...

http://www.chiefdelphi.com/forums/sh...hreadid=124806

Re: 2073 Pneumatic Catapult
 

This is specifically why we are experimenting with adding an accumulator on the exhaust side as well. It acts as a buffer to allow less restriction to the exhausting air, at least in principal.
Once our final catapult is built, we will test and see if it makes any measurable difference. But, so far, it appears it doesn't really make much difference at all. It may be that the air hoses are the biggest restrictions.

Re: 2073 Pneumatic Catapult
 

again, with our quick tests, we found of the difference to be noticeable. This is with the old metal 16in^3 tanks in line on both sides of the piston.

Re: 2073 Pneumatic Catapult
 

Thanks Joe for the info, much appreciated. Maybe next year...

Re: 2073 Pneumatic Catapult
 

We just rigged up a test of this set up.
Works OK. Just needs some tweaking... the rig was from an elastic catapult the kids were prototyping that we repurposed. Probably should build a new catapult.
http://youtu.be/W3DGCs-57xU

Re: 2073 Pneumatic Catapult
 

Have you looked into "rolling release" vs. your "cup" holding method? Here's a link to a paper: http://arxiv.org/ftp/arxiv/papers/1005/1005.0176.pdf

Re: 2073 Pneumatic Catapult
 

While I was on the plane this morning, did some video analysis on those two videos I posted earlier.

our normal shot has a velocity of 6.1 m/s. With the 16in^3 collectors on both sides of the cylinders the velocity was 6.6 m/s.