The impact mechanism strewn out across the table. On the right side you can see the cam mechanism. The roller slips over the pin, and the pin goes in the small hole in the side of the flywheel. The piece to the left is the actual cam, it's splined to the output shaft and rides against the clutch piece. There's a small dowel pin inside of the output shaft to hold the long splined shaft in place. When assembled the spring is almost completely inside of the output shaft.