Is single acting pistons still good for clamping on to a mobile goal on a lift?
Yes, my team uses one. You only need strong force when clamping, not necessarily when releasing, so I don’t think a double acting piston would help in any way (for a simple design at least)
That depends on how you want the claw to grab the goal. Our team prototyped two designs using single-acting cylinders (“piston” refers to the actual moving part inside the cylinder, people like kmmohn have made sure to make this point known) that grabbed the base of the goal and they both worked well. Our “active open” (using the pressure to hold the claw open), rubber band close claw won us our first competition, but we are currently switching it out for an active close design. We originally went with the active open claw due to the ease of adjusting the clamping force (add or remove rubber bands), but it used more pressure (due to having to hold against the force of the rubber bands) than our new active close design. The rated “Max Force: 54 N (12 lb force)” found on the VEX product page seems to be strong enough to hold on to a goal, but this design has not been tested in conjunction with heavy defense.
A word of warning: Our designs take up a decent amount of space (more than what would be used with a dual-acting cylinder), so I would recommend looking into a design similar to Xenon27’s Fall Reveal. However, if you only have single-acting cylinders, or have some extra space, a single-acting cylinder based design is not a bad choice.
I will not share our exact designs because I think it is good for you to come up with them on your own (and record the results in your EDN). Although, as a pointer, both of our designs used only one cylinder, so that should not be your limiting factor.
Sorry if this response is not helpful because I totally misunderstood your question.
They’re not necessarily better, but they don’t need as much air since the piston releases using a spring.
This was indeed helpful I created this thread due to the fact our mentor ordered single acting cylinders (thanks for correcting me by the way) since the double acting cylinders were back ordered/ out of stock so we had to resort to single acting ones. Our plan was to use one cylinder for the clamp for our mogo lift to put on to the platform and two cylinders for a mogo lift like the one that is used in this video https://youtu.be/35HMOQGIZHc but now since we are using single acting we might have to change that mogo lift design
It can be both a blessing and a curse that the air cylinder is retracted by an internal spring. It reduces the plumbing required, but it also reduces the extending force of the pneumatic cylinder by the strength of the spring. So instead of a maximum 12 lb of force from a double acting cylinder, you probably get only about 10 lb of force maximum.
While you won’t see this problem in robotics, industrially, single acting cylinders are obnoxious because the spring will break after a certain number of cycles, while a double acting cylinder doesn’t suffer such fate. I learned this the hard way when I used a single acting cylinder as part of a chair mechanism tester while I was working for La-Z-Boy. The spring broke at a million cycles, which is only ten chair durability tests of 100,000 cycles each, less than two weeks of chair tests!
Noted, kmmohn knows his pneumatics and used to work for La-Z-Boy
I was able to get a single piston clamp like stated above by Quejty. With some tuning I got it to actuate 16 times on 1 gas tank. If you had two, you could so even more.
Wait but would it be strong enough to clamp on to a mogo and put it on to the platform?
Wait another thing we’re trying to experiment is to make a mogo lift using single acting cylinders but we wouldn’t know if it work
Yes, it is. Only a direct clamp on the goal from another robot is enough to pry it out
It might, it might not. You’ll probably have to use multiple cylinders at max power, which will drain your air pretty fast. You also cant raise the lift partially so you’re either full up or full down. Overall, I recommend motors instead.