12 replies to this topic

[Spider-Waffle]

I was looking at the plans for the Semi-automatic Homemade Valve in the homemade section. What concerns me most with the design is that with the hole that slides from one side of the O-ring to the other in the brass pipe being so small wouldn't it be hard for the air to escape out to the barrel rapidly?

Has anyone made this, or what do you all think?

I was thinking maybe make this hole bigger and require it slide by two O-rings spaced apart a bit.

[Paloose]

EDIT: Never mind.

Edited by Paloose, 18 February 2006 - 07:15 AM.

[Dr Nerf]

What concerns me most with the design is that with the hole that slides from one side of the O-ring to the other in the brass pipe being so small wouldn't it be hard for the air to escape out to the barrel rapidly?

It is true that smaller internal diameters of pipe have lower outputs. This is because there is less space for the air to escape out of. The 1/4" brass pipe that leads to the barrel in their valve probably has a terrible output rate because it is just so small.

Internal diameter was one of the considerations that I made when I was build my bolt action homemade. When I originally looked at semi-auto valve in the homemade section, I though that they really overcomplicated it and lowered the internal diameter too much. Their design turned a simple idea into a fabricating nightmare for me. So I designed my own semi-automatic valve system for use in my homemade. My valve is surprisingly simple in design and has a massive 1" internal pipe diameter (going to the barrel).

I don't know any people that have build the semi-automatic valve in the homemades section. The design seems too overly complicated to me.

I was thinking maybe make this hole bigger and require it slide by two O-rings spaced apart a bit.

The O-rings may help the valve seal better. I always like redundancies in my designs, and they can't hurt. Making the pipe that goes to the barrel larger in diameter should help to create higher output too.

[m15399]

Sorry, Dr. Nerf, didn't see you posted in this topic...
For future reference, you don't need to start two topics on the same thing Spider.

[ompa]

Dr. Nerf, you mind posting pictures of the valve itself? Or at least describe it? I was just kind of curious about how it worked and didn't see any pictures/descriptions of it on the link.

~ompa

[Dr Nerf]

Dr. Nerf, you mind posting pictures of the valve itself? Or at least describe it? I was just kind of curious about how it worked and didn't see any pictures/descriptions of it on the link.

I don't have any pictures of the valve itself but the valve can not truly be pictured. This is really the only picture of the valve that I have. The PVC end cap is the front of the valve. The reason the valve can't be pictured is because it is completely inline. The piston (which basically is the valve) is completely inside the PVC section of the gun. The valve is more or less a system of O-rings that seal at different places. The piston has all of the O-rings mounted on it. The PVC parts of the gun hold the piston.

The piston is pushed forward by a spring so that it seals inside of the piece of 1" PVC at the end of PVC section of the gun. When the trigger is pulled, the bell cranks pull the piston back, allowing the air to escape from the front. But because the piston has a set of O-rings in the middle, those O-rings seal inside of the 1" PVC at the end of the pressure chamber. This makes it so that only the air in the pressure chamber escapes.

The piston system allows for easy repairs. If you think that an O-ring is broken or something, you only need to take out the piston and replace the O-ring.

[Spider-Waffle]

I think I understand how your system works now, though a diagram would have been most helpfull :\ It seems pretty good to me, that's like the most direct chamber to barrel connection I can think of. As I understand the pressure from the air tank would move the plunger forward after firing eventually allowing air into the chamber, then I assume there's some sort block to prevent the plunger from getting pushed all the way into the barrel.

How would you incorperate a regulator to the airtank?

If you bull-puped it (I hope I'm using this made up term ok) would the 180 degree bend reduce the rate the air can escape much? This seems like a good system to bull-pup, then you would only need 1 lever for the triger system.

Edited by Spider-Waffle, 19 February 2006 - 09:58 AM.

[m15399]

I'm not him, but he sent me these in a PM.

Hope you don't mind me posting these Dr. Nerf.

Closed:


Open:


Those don't appear to be semi-auto, but the only difference would be an extra set of o-rings to keep the air in the tank (hooked up to the bottom pipe) from coming out the barrel (only the air from the PC should come out).

[Dr Nerf]

This diagram should do well (though I think I need to redo the transparency in it). I also made stills of the valve closed and open.

I assume there's some sort block to prevent the plunger from getting pushed all the way into the barrel.

Actually, when I build my gun I didn't have something to block it. You can add something but I wanted to be able to pull the whole piston through the gun in both directions if necessary (it makes it easier for repairs). If you just put a bolt through the pipe it should prevent it from coming out too far.

How would you incorperate a regulator to the airtank?

I don't think that you would need a regulator. Though the pressure will drop at an exponential rate, if you have a large enough "pressure reservior" the drop should be negligible. If you wanted to put in a regulator, put it in before the T. I designed my bolt action homemade to use a pressurized packback, so it you attach a regulator to the T and attach another pressure chamber ("pressure reservior") to the regulator, it should keep the pressure very constant.

If you bull-puped it (I hope I'm using this made up term ok) would the 180 degree bend reduce the rate the air can escape much? This seems like a good system to bull-pup, then you would only need 1 lever for the triger system.

A 180 bend is straight. This is the optimal angle for the air to escape at. So it won't reduce the rate of the air. It don't really know too much about bull-pup guns, but it seems to me that the system should work good with it.

[WratH]

So are these O-rings available at basicly any hardware store?

[m15399]

Yes. Look near the faucet repair.

[Spider-Waffle]

so it you attach a regulator to the T and attach another pressure chamber ("pressure reservior") to the regulator, it should keep the pressure very constant.

What's the purpose of the reservior? Why not just do: air tank > regulator > T

[m15399]

The PC (the part in the GUN) supplies power to the barrel. The air tank (probably in a backpack) refills the PC after each shot.