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... I need serious help with a piston...

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Amos » Tue Nov 14, 2006 10:49 pm

Okay.. We used gasket rubber and bolted it on.. all we need now is an air compresser to test and we're peachy...

I don't understand equalization holes though...

If some one could post diagrams and pictures of the pistons.. that would be quite helpful...
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Unread postAuthor: Infernal2 » Sat Nov 18, 2006 7:14 pm

Unless you are planning to use O-rings don't even worry about equalisation. The point of the equalisation hole is to equalise pressure on both sides of the piston so that when you release your pilot (blowgun, sprinkler, ballvalve, QEV) a vacuum will be created because of the sudden pressure loss, dragging your piston backwards and firing your gun.

The reason you don't need one is that due to size differences between the piston and its medium (say 3" end cap and 4" pipe). The air will flow around the piston and that is your equalisation, unless of course your piston is a perfect fit.. If you still have trouble with your piston not sealing forward you can utilize a spring to hold it against the barrel, you can increase the piston surface area by bolting neoprene on the front and back of the the piston making it match the ID of the pipe, or you can use a very fast fill; such as a compressor.

Hope this helps.
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Unread postAuthor: alkalineall » Sat Nov 18, 2006 11:57 pm

Amos, most of my cannons use 3" endcaps as the piston body. The barrel seal that I use for 2" barrels is a thick gummy gasket that I think is used in sink basins. The best one that I've found is in the plumbing section @ Lowes. In the sink hardware and gasket section (the aisle next to the pvc parts). These work great if you have a Lowes in your area. I just find the center of my endcap and then draw a circle the size of the gasket with a compass so that the alignment is correct. I use Goop or hot glue to attach the gasket. These gaskets are the best that Ive found and can be stretched around something to seal larger barrels. They come in a mostly red package and I think the company is like Danco or something similar. Hope this helps.
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