Re: Reducing Friction in Shooter
 

The main difference is you anchor it to the frame rather than the catapult arm. This allows you use one set of spring force to overcome the intertia of the shooting arm, and another set of spring force to overcome the intertia of the winch being wound back.

All in all, this is fairly useless unless you can move to a larger winch spool diameter, 1/2" is not enough you should go to at least 1", ideally 2"

Re: Reducing Friction in Shooter
 

Ok, I understand what you're saying but assuming your overall "load" on the motor/gearbox is limited to some maximum, wouldn't you be better off attaching ALL of the springs directly to the launcher so that every bit of energy not needed to overcome the inertia of the winch would be available to put into the shooting arm (instead of being wasted pulling on a frame member)?

Re: Reducing Friction in Shooter
 

This is probably obvious, but I just wanted to make clear to the OP - increasing the winch drum diameter will increase your speed at the expense of torque. Think of it like the opposite of a gear reduction. That said, the greater diameter the winch drum is, the greater torque your spring force will put on the output shaft upon release.

A quick and dirty way to make a bigger winch is to throw some hex hubs on the shaft, the kind normally used for sprockets and wheels.

Re: Reducing Friction in Shooter
 

Does your spool have sides on it that rotate with the shaft to contain the cable/strap/cord?