Posted: Mon Apr 26, 2010 11:50 am
The technique of cutting pipe and putting o rings in the resulting gap does work. My ABS Cellular Core test cannon used that technique to make the piston. The piston is 2 pipe caps shoved inside a piece of pipe. Rings were cut from the pipe and glued onto the pipe caps first, the o rings were added, then the caps with o rings and pvc rings were glued into each end of the pipe. To get the pipe and pvc rings to fit the caps, the pipe was heated to soften it to fit the parts together. Lesson learned, use sandpaper on a sheet of flat wood to polish all the flat surfaces that touch the o rings. I didn't sand this after cutting it with a saw. The o rings against the rough plastic leaks a little.
Notice that this piston is smaller in the middle than at the ends. The pipe was heated and shoved onto the PVC pipe caps so the rings and pipe expanded to fit. The pipe caps are facing each other top to top.
If memory hold true, the piston is made from a pair of 1 inch pipe caps inside 1-1/2 pipe to make a piston that fits inside the 2 inch ABS barrel in a QDV style valve. The valve is opened by pulling the rope. It is closed by pushing it into place with a rod. For safety at the church camp the rod becomes a safety. Without it, the valve can not be properly closed.
This early QDV cannon does not use floating o rings. It can be hard to pull.
The full thread on this ABS test cannon cannon is here;
http://www.spudfiles.com/forums/abs-cel ... 17968.html
The cannon is still functional after all those years. It has not failed.
Notice that this piston is smaller in the middle than at the ends. The pipe was heated and shoved onto the PVC pipe caps so the rings and pipe expanded to fit. The pipe caps are facing each other top to top.
If memory hold true, the piston is made from a pair of 1 inch pipe caps inside 1-1/2 pipe to make a piston that fits inside the 2 inch ABS barrel in a QDV style valve. The valve is opened by pulling the rope. It is closed by pushing it into place with a rod. For safety at the church camp the rod becomes a safety. Without it, the valve can not be properly closed.
This early QDV cannon does not use floating o rings. It can be hard to pull.
The full thread on this ABS test cannon cannon is here;
http://www.spudfiles.com/forums/abs-cel ... 17968.html
The cannon is still functional after all those years. It has not failed.