Semi-automatic Homemade Valve
This is an adaption of the Advanced Pull Valve, with inspiration from Cadmond. Originally, this was made with two valves, the air-management one of which was called the "Goliath valve," in honour of nerfer Lemmypoo's idea of manual air regulation. However, Cadmond took this design and built it into one package, involving multiple chambers. Thus, I owe him some credit for this valve, though it's now been redesigned since then from a 4 O-ring design to a 3 O-ring design. He did, however, inspire progress in that direction with his horrible Paint diagrams. Either way, this valve basically allows air into the firing valve when it is at rest, and seals off the firing valve's connection to the main air tank, before opening the firing valve, when the trigger is pulled. So, pending the air source, PSI, and storage type, this valve allows for crudely regulated Semi-automatic fire. It's the best you can get for under $5!
So, onto construction:
- 5/8"OD, 1/2"ID Vinyl Tubing
- 1/2"OD, 3/8"ID Vinyl Tubing
- 1/4"OD Brass tubing
- 3/4" PVC (~2cm ID)
- 3 x 1/2" CPVC Endcaps
- 3 x 1/2"OD, 1/4"ID Rubber O-rings
- Plumber's Goop
- White Grease or Petroleum Jelly
- Stationary Clamp (or Hammer, and Patience)
- 1/4" or larger Drill Bit (At least < 12/32")
- Small drill bit (Smallest you can find)
- Sandpaper, file, Dremel, or knife
- Rod, Nail, or Dowel that fits inside 1/4"OD Brass tubing
So, take some kind of punch, like a nail or some sharp spike, and mark the EXACT center of the endcap's circular end with it. Drill a hole through with the drill bit, and test to make sure the 1/4" Brass piping can slide through it easily.
Cut off a piece of the 5/8"OD Vinyl tubing, about 2-3cm. Apply a very small lining of Plumber's Goop around the inside of the endcap. Apply a tiny bit around the vinyl tubing stub, and push it into the endcap, all the way. Now, push the O-ring into the tubing, all the way, so you can see through the hole in the center of both the O-ring and endcap. Now, apply a bit of a lining of glue on the inside of the 5/8"OD Vinyl tubing, cut a 2-3cm piece of the 1/2"OD Vinyl tubing, and push that into the 5/8" Tubing, all the way, until it hits the O-ring. You should have a bit of Plumber's goop between the O-ring and the 1/2"OD tubing; This is a good thing. Repeat the above process for two more Endcap Plugs.
If your Endcap has some side lines protruding from the outside, you may want to eliminate those with the knife/sandpaper/dremel/file. Also, you will definitely want to round the inside end of the piece of 3/4" PVC you're using for the valve. I'd recommend doing this with a hobby knife with a curved-blade, or the Dremel. Just make sure you clear any bits of plastic cut or ground off.
Let the Endcap Plugs dry a day, and apply some White grease or Petroleum Jelly to the inside of the O-rings, before proceeding.
Now, apply a bit of Plumber's Goop or PVC Glue all the way around the outside of the CPVC endcap, as well as one of the inside ends of the 3/4" PVC. Push the endcap in, O-ring side out, with either the clamp or the hammer.
Do the same for the other side, but push it to about the middle of the pipe, by hammering it in farther with a piece of CPVC, or using the clamp to do the same, also with a piece of CPVC. Then, push in the third like the last, though push it just a bit in. When you're done pushing and gluing in all the plugs, cap the open end with the 3/4" PVC endcap, using some PVC glue or Plumber's Goop.
Now, grab your 1/4" Brass tube. Grab the smallest drill bit you can find, and drill one or two holes in the side of the tubing, making a sort of ring, just before where, the tubing in rest position, the hole will rest behind the middle plug's O-ring. Basically, you want it so when you push the tubing in, the hole will hop from one side of the O-ring to the other, allowing air from the Temporary Air Resevoir into the Barrel Chamber, and from there, out the barrel. Just look at the diag. Make sure the hole is smooth with some filing or very fine sanding.
Now, to crimp the Brass piping. Hold the non-hole end of the Tubing to the Plumber's Goop tube, so it squeezes goop directly into the tube, and use the rod/dowel/nail to push it to wherever you intend on kinking or crimping the Brass. Crimp, kink, or bend, whatever style of language you want to use.
Let this dry two days or so (The Brass is cold metal, so it'll take a bit). Lube with White Grease, and push the Brass piping into one end of the Valve, through all 3 O-rings. Poof. You have a valve.
Now, to get the air in. You can either drill a 3/16" hole in the side of the valve, and with a little patience, twist in, then Plumber's Goop in, a piece of 1/4"OD Vinyl Tubing, or do something similar with brass tubing or a piece of 1/4" PVC Rod. Either way, anything that will allow you to hook one tank to a pump or seperate air tank, and the other to your barrel. You could even have a 3/4" PVC Tee between two parts of the valve! Anything that will work. Just remember that the less cubic area the air has to expand across to get to the barrel, the better.
So, you now have a valve that cost you very little to make, and will fire a burst of air on every trigger pull, until the air has run out. Congratulations!
Also, you can adapt this technology to larger valves, though I recommend one keeps the valve pin at a 1/4"OD, as the less inner surface area you expose to possible leakage, the better. But it's all up to you. Remember the principles of this valve next time you're thinking of a valve system for a gun, as it can be applied for push or pull activation, or different orientations, even designs with less O-rings, with easy modification. Either way, enjoy!
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