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Old 06-03-2010, 09:08 PM   #1 (permalink)
y0da900's Avatar
Join Date: Oct 2007
Location: Plattsburgh, NY

MCB community project 1- Closed Bolt Spool Valve

Work in Progress R1_5 prints and CAD files now available
Or here

It was decided rather resoundingly in the previous thread that the most desired aspects of the first open source community project would be an efficient gun that was completely unique (not a retrofit, not a rehash of an existing commercially available gun). There was a lot of interest in the project, but not a lot of design choices put forward, let alone choices that met the decided on criteria. Based on numerous requests for it (and lack of choices), the first (of hopefully many) open source community project will be based on a closed bolt spool valve, similar to one that I have designed (and built) as an Ion retrofit.

The valve shares some similarities to the unreleased Legion Shocker (prototype closed bolt 03 Shocker) and to the Nova family of guns. The main firing valve is actuated in a manner almost exactly the opposite of those guns though. In this design (anyone want to think of some good names?), the firing plunger is held forward with pressure supplied from the output of a normally open valve, and the chamber is filled through the side with the rear of the firing piston acting as a spooling shutoff mechanism. When the chamber is pressurized, a net rearward force is created on the piston due to the rear seal being of a larger diameter than the seal in the power tube (main firing valve seal). As air of an equal pressure is supplied to the back of the piston to push it forward, the total net force is pushing the piston forward despite chamber pressure biasing it rearwards. A hole or series of holes in the power tube pushes the bolt forward to chamber the ball once chamber pressure has climbed to a point where the forces acting on the bolt bias it forwards, against the constant air pressure supplied to the front of the bolt (this gas never vents). To fire, the gas at the rear of the piston is vented, altering the bias on the piston so that the chamber pressure forces it backwards, both sealing the chamber from the air supply and opening the main firing valve. Once adequate air pressure has been vented, the air at the front of the bolt becomes the biasing driving force, and the bolt retracts allowing the next ball to fall into the breech. As air from the normally open valve is re-applied to the rear of the piston, the cycle starts over.

The only air vented (not for projectile acceleration) in this cycle is the tiny amount used to drive the piston forward. All other air is recycled in the system. That the piston creates a chamber seal on its rearward stroke allows the valve to be operated either mechanically or electronically. I tested my first prototype with a modified Cocker 4-way valve and a pair of pliers to move the shaft.

I have gotten very promising efficiency numbers from early testing with CO2. Leafy will be receiving an Ion conversion kit based on this in the near future (waiting on some back ordered tubing to come in) for beta testing, and will be doing some more testing than I have done thus far. I never got a chance to do an efficiency test after verifying velocities, but I was getting just short of 2,300 shots from a 20 ounce CO2 tank at playable velocities (as in reliably breaking paint and having a comfortable trajectory), so I have rather high hopes.

Here is the image of the gun that I posted in the previous thread.

An animation I did of the first generation prototype Ion conversion kit.

A video of some shooting of the prototype.

I have models of the design in the body shown with the rotating breech and variations that fit into a more traditional body style. I'm not sure which variation would be less expensive, or if price will even be the driving factor in our decision. The rotating breech, while having an entirely additional component, does not require boring a hole ~6 inches deep, which may be prohibitively difficult for some people to do. That's a decision that may be influenced rather strongly by the community machinists who will be working on the project. Other aspects of the design, such as the seemingly worthless change of inner diameter in the rear piece is to accommodate the other valve systems that I have designed to fit into the body trying to reuse as many of the components as possible to keep price down for future projects that use the body.

For the things we need:
  • Constructive criticism for the design posted (both in function and machinability)
  • Any other accompanying designs to complete this (frame for instance)
  • A list of what people are able to provide for the project (machine time, anodizing, metal discounts, control boards, fittings, etc...)
  • Price estimates for the different aspects of the gun
  • A list of people interested in owning a unique MCB generated gun
  • File hosting, possibly through here if Carter would be interested

Let the project begin!!

Original Thread
Second thread
Rat's Nest (lots of paintball patents within)
Marker animations

Last edited by y0da900; 07-14-2012 at 04:11 PM.
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