Well you should definitely look for leaks, since one problem we experienced was that the tiny black rubber washer between the fitting and the cylinder was missing, and so we were only getting ~10 actuations when we should’ve been getting closer to 70. One test you can do to try to determine if there’s a leak is to pump up the system to 100 PSI, let it sit overnight, and check the pressure the next day. If it’s considerably less than 100 PSI, you definitely have a leak, though it will probably take a little bit of troubleshooting and close listening to determine where exactly it is.
Using CODE tags won’t hide the spaces (but each space character ends up bigger which messes with the formatting again):
Reservoir --> T fitting<-- Reservoir
Manual on/off and pressure regulator --> T Fitting --> Single Acting solenoid --> T --> 2 Single acting pistons
Double acting solenoid and double acting piston
In addition to leaks, it could also just be how much air is being used in each shot, and how much friction there is in the system that is being moved. Have you tried tuning the pressure regulators to the optimal adjustment?
If you think there is a leak, try filling it, and then doing the same test after 20 minutes of waiting. If the results are the same, you probably don’t have a leak, because a leak would be constantly letting air out, regardless of if you are firing the pistons or not.
Then again, I suck with pneumatics, so maybe there is something that would cause the system to lose more air than it should when it is active, but not while resting? If that’s the case, someone should definitely correct me.
In theory it would seem that you should get double the actuation with single acting, but maybe there is some extraneous variable that applies in practice that messes everything up? Maybe only getting 20% more is normal? I haven’t used both so I can’t confirm this, but maybe someone who has used both can.
Turn left on the pressure regulator knob will let less air into the piston which means you will have more air for future activations but that also means you will have less force for each stroke. Just don’t turn it too much or you’ll close the circut.
A quick side note: The amount of friction in the system the pneumatic is trying to move won’t have any impact on how much air is used, assuming everything else is the same (pressure the pneumatic is regulated to, etc). If you need to increase the pressure to overcome friction, that’s another thing entirely, but pneumatics fill the same volume with air at the same pressure every time you fire them, assuming an ample supply of pressurized air is available.