[RRLedford]

It is better, when possible, to use cylinders-pistons in TENSION than in COMPRESSION, but if this requires cables, then it becomes nore complicated
Tension loading tends to keep the forces aligned along axis of rod, which is where cylinder has most strength. Compression force tends to initiate torque and bending forces at an angle to the piston as objects try to "roll" around and past each other.

Since a hinged kicker rotates and moves away from cylinder, angle of force on kicker changes. Max acceleration happens, with a hinged kicker, with cylinder's force applied at 90 degrees to a line out from kicker pivot point to where cylinder is attached during the arc of the kick. As kicker moves away, this change the 90 degrees force angle, and applied force drops off. So, the cylinder should be oriented such that the force applied stays close to 90 degrees during critical acceleratiom range of the kick arc. This is easier to achieve when the piston's attach point stays closer to the pivot point -- but. this also reduces the leverage of the cylinder for accelerating kicker, so a larger bore is needed to gain more force.

There is also the issue of rate of pressure build up inside cylinder. Since the energy delivered to the kicker (then to ball) is the force times the distance over which it gets applied, reaching maximum force early in the stroke is important, since there are only so many inches of travel in which to apply it.
Having piston connect nearer to pivot point (low leverage) means force builds up faster in the cylinder. So having a stronger cylinder that pushes a shorter stroke on a spot nearer the pivot point can deliver more energy early in the stroke than a weaker cylinder attached further away from pivot having better leverage, but also building up force more slowly.
Finding the sweet spot between these two extremes is the key to a good kicker design.

-RRLedford


stance traveled during by point that piston connects to kicker is short.