Which ones better for this year?
Depends on what you want to do with them.#303
I’ve always used dual acting since they’re more versatile because you can use them as single acting or as double acting. (Also, double acting pistons are slightly smaller than single acting pistons).
Honestly, for us… We’re planning on not using any pneumatics at all… It adds a lot of weight to our robot and can make our lift system not be able to lift.
If you are just looking for raw force then i believe (correct me if I’m wrong) that dual action would be better. The single and the dual should output the same amount of force in one direction, but the single have to have a return spring which deducts from the force that they output. The dual action pistons also have the return direction (retraction), so for a quick re-set of a mechanism they would be better. Keep in mind that the retraction of dual action pistons is weaker than the forward direction. If i was using pneumatics this year, i would use dual action. 
Same, and good point!
I’ve used both before, but I’ve never found a situation where the backstroke needed to be powered. I would recomend the double acting because they are smaller, though.
Good to mention!
Thanks
This might be a misunderstanding on my part, but don’t double acting pistons consume more psi per actuation since it has a powered backstroke?
If you are planning on using these pistons a lot, I would recommend first testing if the number of actuations will be enough to work for your robot.
As for the argument that pistons are not useful, I can think of a lot of ways that they might be useful in the early season, but I personally think that teams will learn to use motors to do everything they need, and then simply ratchet off a lift by the time we’re headed to Worlds.
Come on… Discuss things related to the question and not something that deserves another forum post because answering like that doesn’t move the discussion forward and just spams up chat.
@TeraForce Well said
We are using them to off set weight so we don’t tip as easily.
I don’t mean to get this thread off topic, but…
@985C_Robohawks I would strongly recommend rebalancing your weight and centralizing the stuff you already have, rather than add more weight just to balance the robot… Unless, of course, you have an actual use for the pneumatics 
But im stuck between using a pneumatic catapult or a slip gear one, but if I only use one resevoir, does that still deduct from my 2 motors, otherwise, I would need to do pneumatics for the sake of motors (I predict 4 for drive, 2 for intake and 2 for lift. I would use pneumatics for a catapult and assist my lift.
Well this is clearly a different game than NbN @985C_Robohawks , I think it’s time to revisit some of the older brainstorming ideas the forums had then. Some of our inspirations for this year came from FRC robots, lots of cool mechanisms, like
You can use them as single action if you cover a solenoid output and only use the other output. This way the piston won’t consume air both ways and you could use a rubber band or any other force to retract/push them.
Using even 1 pneumatic reservior will deduct your 2 motors.