True Semi
Posted: Sat Feb 05, 2005 6:28 pm
<div align="center">TRUE SEMI
Provided By Mr.Plow - <a href="http://www.geocities.com/boomstick989"> ... tick989</a>
T he first development of my semi-auto idea was completed weeks ago. It consisted of a tri-chambered design with three independently operated blowgun-modded sprinkler valves linked to a 1" diameter barrel by means of a 1" cross. A tee and small section of pipe just before the barrel acted as the hopper, with a 15 round capacity. Although a complex system of smaller electronically actuated valves connected to a timer relay circuit was devised to make the gun essentially fire full automatic, it never got past the initial phases using 3 plain ol' blowguns. Ammunition was at first a limited number of round wooden balls I found in my basement that loosely fitted the barrel. While the initial design worked, it was extremely unreliable. One test would work perfectly, shooting all 15 balls without jams or other problems, and right after that the next test would go FUBAR in every possible manner! Obviously, it was flawed in several ways. I scrapped the tri-chambered design, for now focusing on resolving the problems encountered with just one chamber. Perhaps sometime soon I'll rebuild the original with all the bugs worked out...
Working out the magazine jamming issues was easy; a little dremeling the inside of the barrel plus plastic balls for ammo that actually fit the barrel did the trick. The most difficult problem was getting the valve to re-seat the diaphragm quickly enough. Since air was continually flowing into the chamber, the valves had the tendency to "honk" after each shot for 4-10 seconds as the diaphragm vibrated quickly. To fix this problem, I removed the inner spring and essentially made a bigger equalization port by adding an air-in line to the top of the valve. Of course, I had to limit the amount of air going to the top of the diaphragm (or else it wouldn't fire), so I added the needle valve with gauge. With the chamber at 40psi and the top restricted to a little less than 10psi, it works like a dream! I can get about 3 shots per 2 seconds, and I estimate the ammo is getting more that 150fps (although I dont have a chrony...so a real number will have to wait)
Provided By Mr.Plow - <a href="http://www.geocities.com/boomstick989"> ... 9</a></div>
Provided By Mr.Plow - <a href="http://www.geocities.com/boomstick989"> ... tick989</a>
T he first development of my semi-auto idea was completed weeks ago. It consisted of a tri-chambered design with three independently operated blowgun-modded sprinkler valves linked to a 1" diameter barrel by means of a 1" cross. A tee and small section of pipe just before the barrel acted as the hopper, with a 15 round capacity. Although a complex system of smaller electronically actuated valves connected to a timer relay circuit was devised to make the gun essentially fire full automatic, it never got past the initial phases using 3 plain ol' blowguns. Ammunition was at first a limited number of round wooden balls I found in my basement that loosely fitted the barrel. While the initial design worked, it was extremely unreliable. One test would work perfectly, shooting all 15 balls without jams or other problems, and right after that the next test would go FUBAR in every possible manner! Obviously, it was flawed in several ways. I scrapped the tri-chambered design, for now focusing on resolving the problems encountered with just one chamber. Perhaps sometime soon I'll rebuild the original with all the bugs worked out...
Working out the magazine jamming issues was easy; a little dremeling the inside of the barrel plus plastic balls for ammo that actually fit the barrel did the trick. The most difficult problem was getting the valve to re-seat the diaphragm quickly enough. Since air was continually flowing into the chamber, the valves had the tendency to "honk" after each shot for 4-10 seconds as the diaphragm vibrated quickly. To fix this problem, I removed the inner spring and essentially made a bigger equalization port by adding an air-in line to the top of the valve. Of course, I had to limit the amount of air going to the top of the diaphragm (or else it wouldn't fire), so I added the needle valve with gauge. With the chamber at 40psi and the top restricted to a little less than 10psi, it works like a dream! I can get about 3 shots per 2 seconds, and I estimate the ammo is getting more that 150fps (although I dont have a chrony...so a real number will have to wait)
Provided By Mr.Plow - <a href="http://www.geocities.com/boomstick989"> ... 9</a></div>
. Good work though. I reckon i will make soon a 3-5 chambered, single barreled cannon. The only thing i can find that wold be dodgey would be the size of the chamberes, as the gun needs to be portable. I hope to have this built within the next... 
year. 
It will take a while and must be a 