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Pneumatic aided catapult
I admit, it was more challenging to find them.
Likely because the design isn’t the most efficient
I wouldn’t recommend using Pneumatics solely for the catapult.
I believe they could be used for a PTO, to aid the catapult, while being used as a tensioner, and to change the direction of a flywheel.
I do not think it will be as good for a catapult.