Sorry for the DP, but I have made a change to the gun's firing mechanism, after realising that the original mech. was too inefficient (thanks CS). Instead of two separate 555 oscillators controlling the solenoid valve, I will end up using a Parallax Basic Stamp 2 microcontroller. Also, instead of the original breech actuator, I will implement an electromechanical actuator to close a simple breech, which has compressed air run straight through it.

this may be because i've only moded my scout

If you've only modded your Scout, then it probably isn't a good idea to jump in and mod your Vulcan.

I was hopeing to increase some range because im only getting some were around 15'' (eye balled it so it may be more or less) with stock.

15" doesn't sound right for a Vulcan. Mine gets around 35 ft right out of the box!

Basic NF AR removal.



Its airbrushed with Testor's paints.

EDIT: Picture resized.

Your system is actually more automatic than semi-automatic, but you don't have enough control over the timing of each part of the feed and firing cycle to be able to adjust the setup to increase reliability.

There are potentiometers on each of the circuits, which control the frequency of oscillation of the valve. A monostable multivibrator only pulses once for a set amount of time each time the input pin is pulled high (or low). An astable multivibrator oscillates continuously while the input pin is high (or low).

See below diagrams:



An astable multivibrator; R2 is swapped with a potentiometer, and the other component values are altered to achieve the desired frequency.



A monostable multivibrator; the resistor is swapped with a potentiometer, etc.

More complicated than it really needs to be. You can accomplish the same effect using only pneumatic components.
It would be more reliable to have the breech actuation speed controlled by a flow regulator.
And have the trigger valve(s) setup to simply empty the breech actuator into the barrel while closing off the supply line from the tank.

Unfortunately, I don't have the money/access to the tools for the construction of a full pneumatic system. Also, I am much more comfortable working with electronics.

They have a tendency to chew up darts.

That, or the air pressure will just compress the spring and release it all in one shot..

The oscillating solenoid valve should prevent that.

I build robots.



This one, Trilo-BOT, won 3rd place at Robogames in San Francisco.

Mine is 1/2 SCH40.

SCH 40 PVC isn't CPVC.

Is the 1/2 PVC supposed to move?

I play, but its pretty boring.

If you want multiple barrels, go to Home Depot or Lowes, pick up some PVC and Tees, and use that for your manifold.

Just drill the head off of the stripped screw with a regular drill bit. I did that on a NF once, and it worked perfectly.

(Also posted on NerfX)

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.)

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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.