Here are a few pictures of my piston for the upcoming valve that I am about to build. It is made from 3" of 1 7/8" PVC stock, along with neoprene disks, a spring, and assorted screws and bolts.
The back end is the one with the spring. As you can see, I added a neoprene disk there. This is not to seal anything; rather, it aids in holding the spring tightly against the piston.
The front sealing face is made up of two layer. The outer layer is a tough neoprene, which actually does all of the sealing. The inner layer is soft foam rubber, which provides some shock absorption and may aid a small amount in sealing.
Just tonight, I added a few layers of duct tape to the outside, giving a much better fit inside of the 2" sch. 40 it will be sliding in.
My question is, are there any factors/parts of this piston that will hinder performance? I used a very similar piston in my Plinker, and it yielded weak results. But in that particular cannon, other factors such as low chamber volume and too big of an equalization passageway on the piston may have contributed to this problem as well.
Does anyone see any obvious problems? Or does it look ok?