I just had this idea for a simple semi/full auto gun. The mechanism is very similar to one used by a person on spudfiles, and uses many of the same ideas as Captain Slug's Arr and ABP5K on nerfhaven. Basically, it consists of a short PVC tube w/ an endcap on one side. There is a hose barb mounted in the endcap, which goes to the trigger valve. A piston with a sliding o-ring mechanism is connected to a piece of 1/2 inch brass which slides over a piece of 15/32 inch brass that is connected firmly to the endcap's inside face. The 1/2 inch brass slides inside of the barrel (17/32" or 9/16" brass) and doubles as the bolt. A spring holds the piston in an open position. When air is allowed into the tube, the piston goes forward, stripping a dart out of the magazine, until it slides off of the 15/32" brass and air is allowed into the bolt. The air is channeled behind the dart, shooting it out of the barrel. When the trigger valve is closed, the return spring pushes back the piston, causing the o-ring to uncover the vent hole and allow unused air to escape. The gun will have a selector switch to choose between semi/full auto, and the valve will be activated by a solenoid. The solenoid will be triggered by either a 555 timer circuit configured as a monostable multivibrator or another 555 circuit configured as an astable multivibrator. Both circuits are adjustable by independent trimpots for precise ROFs. The trigger will be a simple snap-action switch that activates the oscillators. The trigger itself is a basic pushbutton valve that opens when pushed, and closes when released. A small LPA tank will be the stock, and will be able to be charged by a small double-acting pump. The solenoid will use two 9v batteries in parallel, to allow longer run times before a battery change is necessary. The rifle will be configured as a bullpup, and will have a 10-round removable box magazine in front of the stock that is expandable to a larger drum magazine.
Does anyone forsee any problems?
(Yes, I know that I forgot to show the oscillators, and they go in between the snap-action switch and the solenoid, with a DPDT slide switch for a selector.)
Yes, I am new to this forum, and I am only 13, but I can be an asset to this board if you guys give me a chance.
Edited by roboman, 19 August 2008 - 06:21 PM.