We have worked with double-acting pneumatics, but not single-acting. Are there significant performance differences between the two, or is the only difference the ability to pull back in?
Also, what is the spring return on single-acting pistons? Can the spring return move a small amount of weight?
We happen to have a single acting piston in our little collection, but I haven’t personally used it myself yet.
The spring return just pulls the rod back into the rest of the piston (so it is air pushing out, spring pulling in). The spring is strong (from what I can remember), so it should be able to pull some weight.
Although I’m sure the single acting pistons are great, I think the double acting ones are even better. Just because they have 2 directions available which can be powered by air, doesn’t mean you have to use both ends to be powered by air. I just put the tube into the end I want and then add a sufficient amount of rubber bands to pull it back in. And whats better with using the double acting pistons is if you only use one air input, you can change the strength of the “spring” and also change which direction is powered by air, and which is powered by rubber bands (or latex tubing).
~George
Thanks! The reason I ask is because I’m considering adding a third pneumatic piston to our design, and Pneumatics Kit 1A is less expensive than Pneumatics Kit 2A.
Ah, I see. That’s also a huge difference in price! :eek:
I guess it’s one of those cases of “Is it worth the extra cost” to buy the double acting piston. I personally would pay the extra money, as then you have more freedom with the pistons and you are also future-proofing, but the single acting ones may be alright and then that’s an extra 2 393 motors you have saved in money.
Good luck with the pneumatics though, they are fabulous to work with and add so much to your robots capabilities.
~George
So, I cant seem to find my extra single acting piston right now maybe someone can do this for me?
Anyway take the the piston and mount it into a vice or something stationary, don’t do this to tightly as it can break the piston.
Take a fish scale and attach it to the rod end of the piston, then pull. This will give you the force provided by the spring at a constant tension.
Here is the funny thing, its a common misconception with double acting and single acting, sometimes the single acting could be longer in the long run.
Here is why the pressure you have drops correct? Well What happens is the pushing force on the rod end of the piston is already signicficantly lower than that of the clevis end. This is because of the change in surface area on the piston itself. This causes the pushing power to drop slightly or significantly depending on your piston and applications.
So I propose that someone run that test that I mentioned if I can’t find my fish scale and piston as there will be a point where the single acting piston could be consistently better than the double acting.