Questions about teams experiences with single acting cylinders

I have never used single acting cylinders before, although may implement them in my design this time around. I have a few questions regarding other teams experiences with single acting cylinders to decide whether or not I should use them or stick with double acting.

First of all, in my design the cylinder is going to be extended by default for long periods of time. I have some concerns about this affecting the internal spring. Have any teams had issues with the spring wearing out after using their pneumatics for a while?

Second of all I have a question about air consumption. With the single acting cylinders, I am going to make the air pressure as low as possible in order to conserve air. Although with the spring the air pressure does have to be higher in order to counteract the weight of the spring, if I am using a low air pressure mechanism, does it really save air to use single acting if the air pressure needs to be higher than if I was using single acting cylinders due to the internal springs?

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I used a single-acting cylinder for our clamp last season, and I plan to use multiple single-acting cylinders for our robot this year. I have never had any issues with the spring wearing out in the single-acting cylinders. Overall, it saves air using a single-acting versus a double-acting cylinder. I would recommend using a regulator to reduce the air pressure to find a good sweet spot between saving air and still having enough power to do whatever task needs to be accomplished. Another plus side of single-acting cylinders is that you can fit them in tighter spaces, because the only air inlet is at the back of the piston, versus double-acting cylinders which have air inlets at both ends of the cylinder. Let me know if you have any other specific questions.

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I had several single acting cylinders on my robot last season, but over time i replaced them all with double-acting. While they did work on a clamp and other mechanisms, double acting always just ended up being better. I had 6 cylinders on the bot last year that were guaranteed to be used, and i know many others had more. I personally never ran out air, and since it was never an issue I ended up using all double acting cylinders because they were better in the situations I was using them in. That said, you can certainly use single acting, but if your only reason is air conservation and it would be (even marginally) better with double acting id just use those. As for the spring, I’d be surprised if it wore out, as youll only ever have it extended for the 2:00 the match takes. at all other times itll be contracted, so id bet it wouldn’t be an issue. Just a hunch though

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Right, they are definitely more versatile.

Yes, if you have a problem having enough air. But you can always use double-acting cylinders as if they were single acting just by leaving one port in the air cylinder open, and plugging the extra port in the solenoid.

tl;dr
You’ll probably not break a spring in VEX, but I have real-world experience breaking single-acting cylinder springs. When I first began designing pneumatic systems, I thought single-acting cylinders might be a good idea, mainly because they reduce the amount of piping required. As a young engineer (many years ago) I looked at the 1,000,000 cycle estimated life of the spring and though “no problem.” But the problem was that I was building test equipment for La-Z-Boy chairs at the time, and a typical functional test is 50k to 100k cycles per test…so it didn’t take more than a couple months for internal springs to start breaking. So…don’t use single acting cylinders industrially unless you have a good handle on what lifecycle you need.

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