11th Hour Question about pneumatic catapult piston arrangement


Tomorrow we are set to attach the pistons to our pneumatic system on the robot. We’ve tested a configuration where the pistons are almost vertical (pics below), but I’ve noticed that just about all of the teams have the pistons in a different formation (more pics below). If we were to try to implement the second formation, we’re wondering if we would get any significant improvement over our current design? The way the robot is right now, we’d only be able to use about 1/2-3/4 of the stroke with the horizontal arrangement, and that would be at a further distance from the axis of rotation that we have currently. That being said, I’m sure there is a reason teams have chosen the horizontal arrangement instead of the vertical arrangement, and I’m asking why here because we’re simply out of time to test a new setup (extensively) before setting it on the robot; however, if we could find a reason here to switch, that would certainly be something we’d do.

Current setup: This isn’t exactly like the robot, but all of the dimensions are approximately the same, +/- about half an inch. As you can see, the pistons are almost vertical and they’re pushing straight up. We’ve since raised that bottom bar (going into the photo) up a few inches so that the pistons start at their 0 extension position and then only extend to about 1/2 of their extension, at which point the entire mechanism is stopped with some rope/pericord. This barely gets the ball over the 6’ mark (truss) (and goes about 3-4’ horizontally, so not much room to adjust the angle), so we’re hoping that we could improve it to get the fabled 18’ across the field shots (more than likely unrealistic 2 days before the district event, but still, no harm in dreaming, right?). This setup also has the effect of ripping the hinges that we’re using apart; a lot of the force being applied initially is being sent straight up, and we’ve noticed (in slow motion video) that the hinges are being bent up and then converting some of the motion to angular motion. We’ve ordered stronger hinges, but we fear the worst for them in this setup.

Proposed setup: There would be a piece of metal/plywood (spray painted grey) which gets mounted underneath the bar going into the picture on the left, along with a new bar that gets mounted going into the picture on the right, as denoted by a light grey box bounded by dark grey lines. The pistons then get mounted using the same hardware in the new position (denoted by red). Hopefully my amazing mspaint skills communicate this new geometry successfully.

We have a setup similar to the bottom one and it is working very well for us. We have the pistons just shy of parallel to the arm of the catapult. We found that the angle actually allows pressure to build up before firing, giving it a spring action. We can get the ball to go 10 or so feet vertically (haven’t actually measured) and through the goal from about 15 feet based on the angle we have ours set at. The ball itself goes about 23ish feet. Feel free to message me and I can send you a picture of our setup. Hope this helps.

I have seen launchers with vertical pistons, but I don’t have experience with them.

Our team has the same 2-pistons quasi-parallel to arm setup that the previous post mentioned though we have slightly less range and height.

I don’t have any pictures of our setup offhand, but if your interested I might be able to dig up a few.

It’s worth noting that our design requires a high flow solenoid in order to get enough power to the pistons in order to make a shot. If you don’t have any, a work around would be to have one solenoid feed to each piston and have them fire simultaneously in code.

We actually have a high flow solenoid feeding each of our pistons, though these just arrived today and were not used in obtaining the numbers for the test above; those came from 1 of the old grey solenoids from 2006(?) feeding each cylinder.

Please people they are not called pistons, they are cylinders!

Harrison: the design actually doesn’t require the high-flow solenoid to score (it was working in prototype-phase with a standard KOP solenoid); in fact, it’s quite robust to decreases in flow rate, which is why we don’t need any downstream tanks with it. We put on the high-flow solenoid because we had purchased it and figured it couldn’t hurt, essentially.

I would like to thank everyone for helping out TheHolyHades1. With your help team 1257 was able to construct, install, and test a pneumatic catapult during our last event before Regionals while never missing a match and finishing the qualifying rounds ranked 18th!

Thanks again for the help, and great job TheHolyHades1 and your build team. I am sure pictures and a video will be coming soon.

Solenoids still need to be a maximum of 1/8" NPT under R77, C.