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Variable Cyclic Rate Full Auto BB Gun

A place to ask general spud cannon related questions.
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Use your knowledge of physics and airflow, and tell me if you think this SHOULD work.

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Variable Cyclic Rate Full Auto BB Gun

Unread postAuthor: Darkerweb12 » Mon Jul 17, 2006 4:51 pm

The idea here is the air source is to be a CO2 tank with a 100 psi regulator. When the trigger is pulled and held the area infront of the piston fills with air, gradually pushing the piston back against the spring. Eventually, the piston breaks the seal between the barrel and the chamber and all the pressure is dumped immediatly. Sort of like a exhaust gun but made simpler. When their is little or no pressure left in the chamber, the spring pushes the piston back into its original position.

In order to have a variable Cyclic Rate, this gun can be taken apart easily to put a different strength spring in. A weaker spring would increase the Cyclic rate, but also theoreticly diminish end velocity. A stronger spring would slow the Cyclic rate, but theoreticly give a higher end velocity.

Also, this idea can be scaled up or down for any caliber. So it can be .177 BB, Airsoft BB, or even paintball. And if a large enough air source can be obtained, who can say, "Fully automatic golf balls!"

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Also, the shaft from the piston may come back very fast, so if anybody builds this, you may want to shroud the shaft.

I plan to make mine out of copper, and chamber it for Airsoft. Now peter can't whore his CO2 powered fully automatic Desert Eagle.
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Last edited by Darkerweb12 on Mon Jul 17, 2006 5:03 pm, edited 1 time in total.

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Unread postAuthor: SpudStuff » Mon Jul 17, 2006 5:00 pm

dude the piston would go back almost instantly so you should be very careful with the shaft from the piston
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Unread postAuthor: carlbelcher » Mon Jul 17, 2006 7:07 pm

It couldn't be full-auto, you would have to stop the flow of co2 into the chamber in order for the piston to move back to the forward position. It might work as a semi-auto design.
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Unread postAuthor: SpudStuff » Mon Jul 17, 2006 7:34 pm

you could put the co2 through a push valve that is located behind the piston shaft to turn off the co2 when the piston is all the way back
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Unread postAuthor: carlbelcher » Mon Jul 17, 2006 7:44 pm

But you would still have to turn the co2 back on somehow when the piston reaches the front of the chamber.
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Unread postAuthor: boilingleadbath » Mon Jul 17, 2006 7:59 pm

I think your piston will probably end up sitting at the half-open-flow-to-barrel position.
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Unread postAuthor: Darkerweb12 » Mon Jul 17, 2006 8:54 pm

No, look, the tube that the CO2 flows into the chamber is a small diameter compared to the chamber itself, which means it has little pushing power until it can build up in the chamber. So the spring would have time to push itself back to the original position
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Unread postAuthor: carlbelcher » Mon Jul 17, 2006 9:36 pm

I don't think you understand what you are saying here.

If the piston is say 1" in diameter pi x .5 = 1.57 sq inches x 100psi = 157lbs of force on the piston not matter where it is in the chamber.

Even if the flow has low enough that the piston could move forward before the chamber filled, filling the chamber would take an excessively long time, there for I would hardly call the rate of fire "full-auto".

Good idea, just not well thought out.
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Unread postAuthor: Darkerweb12 » Tue Jul 18, 2006 12:33 am

Well, I may be right, I may be wrong. I was just throwing my idea out there to see what people think. I am going to attempt to build it within the next week, and if it doesn't work, it should cost less than 20 bucks, so I'm not worried about price.

Anyways, I have wanted a regulator for a long time...
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