Easy formula for figuring this?

[ray1377]

Hi Ray, Everything on the gun is custom made except the barrels which are 2260 and 1760 barrels cut down to 19.250". The pump lever is 19.250" long from the pivot pin to the end of the lever. It takes 64 pounds of force to close the lever. The valve being opened faced with the piston closing off the front of the valve I allowed .070 for the valve head travel, there's nothing to prevent the valve head from striking the piston on opening other than the pressure, so I don't know if the valve head contacts the piston or not. Since the piston diameter and stroke length are fixed, I had to make six valves before I had the firing chamber volume small enough to make the most power I could out of the gun. The firing chamber volume with the valve stem and head in place, is only .028 cubic inches/twenty eight thousands of a cubic inch,if my math is correct. The valve is the same diameter as the piston, it's a knock open valve with a 1/16" valve stem, the head of the valve is .223 in diameter x .170 long. The valve is 1.031" in diameter and the firing chamber is placed up near the top edge of the valve to keep the transfer port short, the valve throat is off set in the firing chamber high enough so that the 1/16" valve stem almost touches the inside wall of the compression tube. It's all very nit picky , but that's what it took to get it done. James

Fantastic work Mr. James.
Thank you so much for the information

Thanks
Ray

[ray1377]

I wonder if it would be beneficial to use a spring on the outside of the valve stem with a keeper to close the valve instead of an internal spring pushing against it to close it? It would make building a smaller volume valve more simple I would think. Thoughts guys??

Thanks
Ray

[Blutroop]

Check out the crosman a.i.r.177. It’s a ssp valve is open to piston and is plastic.. Fortitude valve opens to gauge and could be a good donor for a disco tube sized ssp if you wanted to use oem parts for simplicity.

Bobs millennium pumper is the reason I joined gta! I spent/spend a lot of time thinking about a acp once reading bobs work showed me the inefficiency of a dump valve.

There were others that have attached co2 cartridges into the valve on 1377 to make a acp with relative ease? It’s a option with caveman tools and skills.