[Pneumatic] Straight Through Valve STV

Just build a cannon and want to show it off? Post it in here.

Postby clide » Fri Apr 14, 2006 11:03 pm

Not exactly an entire gun, but it has 2" threads for the chamber and barrel so I can hook up a variety of barrels and chambers depending on what I am shooting for.

Basically it works like a normal tee piston valve, but the sealing face of the piston and the sealing port are angled so the piston can come down 90 degrees from the air flow path.

It's not really very complicated to make, you just have to be very careful to make sure you are lining everything up right. The sealing face has to be at both the right rotation and distance into the tee.

<img src="http://gbcannon.com/pics/stv/right.jpg">
<a href="http://gbcannon.com/pics/stv/left.jpg">left side</a>
<a href="http://gbcannon.com/pics/stv/bottom.jpg">bottom</a>
<a href="http://gbcannon.com/pics/stv/insides.jpg">piston against sealing port</a>
<a href="http://gbcannon.com/pics/stv/piston.jpg">another view of piston and sealing port</a>
<a href="http://gbcannon.com/pics/stv/closed.jpg">view down the barrel port</a>
<a href="http://gbcannon.com/pics/stv/open.jpg">again after firing</a>

Initially I was trying to get it to work using a blowgun for the pilot valve, but I could never get it working well. Since the valve is built for performance anyway, I figured the added bulk of the sprinkler valve would be worth it I this case.

It took quite a bit of tinkering to get it sealing right. I ended up sanding down the rubber face to fine tune the angle for it to seal properly. I've also removed the lower o-ring because it was too low and causing the piston to get stuck.

The screw sticking out the back of the piston in one of the pictures is to remove the piston. You can't push the piston out by sticking something through a port like other piston valves, so to remove it I put the screw in and pull with pliers.

I haven't had a chance to chrony it shooting anything yet, but it does seem like it will perform pretty well. I'll try to post some numbers once I get them.
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Postby SpudMonster » Fri Apr 14, 2006 11:16 pm

It took me a while to figure out the way it worked. That is a very clever design to say the least! It seems that you drew inspiration for the valve design from the pl3x valve concept. I love the flush fittings. Once again, your latest cannon is amazing, clever, and unique.
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Postby clide » Fri Apr 14, 2006 11:30 pm

The pl3x valve thread inspired me to build it, but the design of the valve was inspired by a high flow sprinkler valve that someone posted awhile back.
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Postby Bone-23 » Fri Apr 14, 2006 11:47 pm

Where do you get the rubber to make these? Also how hard is to get the valve sealing?
Btw i have the same blowgun =)
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Postby Freefall » Sat Apr 15, 2006 12:27 am

I've thought about this exact concept about since the time I built my first piston valve. I didn't build it because:

1: I don't have the proper equipment
2: I couldn't quite figure out how to keep the piston lined up without a guide rod.

So: How do you get the piston to stay lined up without a guide rod?

Congrats on yet another great design!
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Postby TalonXxX » Sat Apr 15, 2006 12:42 am

I love ALL of your cannons clide, especially the whole minipump series! This cannon is another awesome piece of work and I am so glad you are still making new, innovative cannons. I think it's safe to say that you are the pneumatic king around here. Congrats :)
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Postby saladtossser » Sat Apr 15, 2006 12:59 am

wth? it worked! YAY

put felt behind the rubber so it seals at inaccurate angles
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Postby clide » Sat Apr 15, 2006 1:05 am

The piston does try to slide down the slope so it is crooked back towards the chamber. To stop it I have that oval shaped washer I made out of PVC on the face of the piston. You can see in the down the barrel view that it is resting against the bottom of the sealing port. I made one a bit longer on the top than in the picture after I realized it was sliding down.

If you mean lined up as far as the piston turned at the right angle, then as long as it isn't significantly rotated from where it should be, the downward force of filling the gun will naturally rotate the piston into the proper orientation when the sealing face contacts the port.

Bone: I ordered the rubber from http://www.mcmaster.com
It was pretty difficult to get this particular valve to seal, but it was also complicated by several other issues I had with the valve.

While it isn't a lot different from a standard valve I certainly wouldn't recommend it for a first.

Thanks for the compliments.
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Postby Velocity » Sat Apr 15, 2006 8:42 am

that is awesome!! I can see though it would be very difficult to construct, because it looks as though it requires much more precise cutting and lining up.

its hard to determine whether the flow of this valve would be greater than the flow of a regular piston valve, but it sure looks cooler!

once again, awesome [:p]
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Postby utcpyro » Sat Apr 15, 2006 4:56 pm

Wow! Nice work there. If you happened to build inline cannon using this babe I think you'd have the best performance/valve seat area cannon out there. I wouldn’t be surprised if this thing came out near burst disk level of power.

When crono it, do you have anything else that you can compare it to in order to see how much better it is then more traditional design?
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