Our team, 744, has designed a pneumatic stinger for our robot for IRI. The piston we originally tested with was a little bit thicker than the one we have on the robot now, because the original piston was found to have a leak. The piston we have on the robot now works, but it is not as good. Therefore, I was wondering if any team would be willing to lend us a piston similar to the original.
I’m not sure how these are technically measure, but the tube length is 27 inches. The tube diameter is 1.25 inches (a little thicker is ok). And the shaft length is 24.5 inches. If the tube is slightly shorter or slightly thicker that is ok too.
Or, if someone would be willing to show me to a site where we could find a cheap piston like this. I had checked bimba, but the sizing was very confusing to me, any help with that would be greatly appreciated as well. We are on a really tight budget for this trip and the plan did not include very much robot modification.
If you post the part number I am sure an IRI team will be able to help you. Bimba: The part number should be etched on the size of the cylinder. The number refers to the cylinder bore, stroke, action type, & mounting system.
Magnetic Piston - 1.25 inch bore, 24.5 inch stroke - Double Action, Rear Pivot mount
You said piston so many times my head is spinning, the proper term is cylinder
Sounds like you have a 1"-1.25" diameter by 24" stroke cylinder such an animal will not be cheep to purchase (prob at least $70.00 or so.) You could try and find a local company that could get you one at costs. Search for pneumatic supplies.
I have a 1.5" and 2" in the shop and we will more than likely be using the 1.5" cylinder for our stinger. Can you fit a 2" cylinder and provide it enough air?
What was leaking about the first cylinder? If it was a fitting, those can be replaced. Some cylinders can be rebuild. Can you post a picture of find a part number?
haha sorry for the terminology. Words aren’t my specialty.
And neither are pneumatics. Our team has used pneumatics twice in our time as 744. Once in 2006 just for gear shifters (and way before my time) and once last year. But the decision to add pnuematics last year was about 6 days before build season ended. Needless to say, things were a bit crazy.
Anyway, the shaft on the cylinder that we would like to have used seems to have been grabbed by a clamp at one point. We had done our initial testing by just capping the one side and deploying air through the other, so we didn’t realize the problem until we hooked both sides up to the solenoid. The seal holds when it’s deployed, but not when it is retracted. This (older) cylinder seems to be a Packer product and I believe the part number is 1.06DSR24.0.
As far as your 2in cylinder, I am most concerned about the weight. We are really close to the 125 mark with this new system, so, I am skeptical that we would stay under with it.
As far as air goes, we will be installing 2 of those plastic tanks, each holding 44 cu in of air. I would estimate only getting about 1 good shots out of the 2in cylinder, but I don’t know exactly how to calculate that. If you could explain how to do the calculation to figure out how many shots a certain cylinder gets when you have a certain amount of air that would be really cool. My best guess is that since the air is stored at 120 psi, and you are regulated to 60 psi, that you have, in the case of two 44 cu in tanks, 882=176 cu. in. of volume to work with. Then, in the case of the 2in bore 24in stroke cylinder, the volume required to fill the cylinder is 75.4 cu. in. (pir^2*h), and each deploy and retract would use that much of your 176 cu. in. Therefore, you would only get one shot as 150 of your 176 cu. in. would be used up. Is this right? Please correct me if I’m wrong, which I probably am, because, as I said, pneumatics is not my specialty. But I want to learn!
If the problem is near the end of the shaft and you don’t need the full 24" stroke you could use spacers on the shaft so it does not retract all the way into the cylinder and doesn’t get into the bad part of the shaft.
You could also not hook up the retract end and cap the solenoid and use surgical tubing to retract the cylinder instead of air.
Spacers sounds like a really good idea! Whether or not we can do that is dependent on how much we would need to leave deployed because the shaft goes right through our ball pickup, so if it’s only a few inches we should be fine, but anything above 5 inches and we would probably have a problem. Thank you so much for all of your help!! We’re meeting tomorrow, unfortunately the robot is already shipped, but we should be able to figure something out. I’m just happy that we at least have one that works, even if it doesn’t work as well.
And to other teams, if you happen to have something like this lying around it would still be appreciated!
Thank you Arefin! He’s actually on a trip right now, but I’ll have him call you this week. He also won’t be going to IRI (too much family, too little time, completely understandable). But it would be wonderful if you could look. Thank you!