Efficient! Very few post throw wobbles.

Thanks, guys.

David, usually when you see the arm oscillating a lot it means there is some lack of "harmony". Usually too heavy an arm or too light a payload. Plus I try to keep the counterweight as close to the vertical plane of the axle as possible (for boring technical reasons of CW drop geometry). I once had a setup that had the arm stop almost dead at the vertical, with sling release occurring at that point. Really neat, no visible motion once the ball went flying.

Thom

Considering that all the wood was fished out of trash bins it came out pretty nicely. 

I may have a pic of the trigger (or another just like it) somewhere, but not on this hard drive where I can get at it right away. It's a primitive but effective setup made from a length of nylon twine, a nail, and two screw eyes. A sort of captive loop goes over the "release pin" (the pin the free end of the sling hooks onto) and holds the arm down. It's simple in action but difficult to put into words. And it's not really more than adequately strong, though it's simple, cheap, and within its limits reliable. If I happen to run across a photo I'll post it.

Thom