Low-friction/Specialty Ball Valves?

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Xamllew
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Tue Feb 11, 2020 9:08 pm

Just curious if any of you spudders have run across any ball valves that are in some aspect better for pneumatic spudguns than your typical hardware store plumbing ball valve. I'm looking for a full-port ball valve that requires very low effort to turn, at least 600psi max pressure. If anyone has run across something like this I'd greatly like to know. :twisted:
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Moonbogg
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Thu Feb 13, 2020 11:46 pm

What size? Also, I don't think low friction would increase performance much. What are your requirements for the cannon? Ammunition, barrel size, construction material etc.
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Thu Feb 13, 2020 11:59 pm

You're not going to get much lower friction than teflon seals, but they can still be a bear to turn. Ball valves simply aren't designed for quick/easy motion.
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Xamllew
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Fri Feb 14, 2020 2:49 am

Moonbogg wrote:
Thu Feb 13, 2020 11:46 pm
What size? Also, I don't think low friction would increase performance much. What are your requirements for the cannon? Ammunition, barrel size, construction material etc.
I'm looking for a replacement valve for my ball-valve musket. It's a 3/8" full port, standard plumbing valve with a modified turning handle. The handle is actuated by a spring loaded hammer. It seems to have good days and bad days, some days the valve is more stiff and has to be sorta warmed up by manually turning it for a few mins to get it turning smoothly. The performance difference between a stiff turn and a loose turn is noticable. Silicon grease doesn't have much effect.

Barrel is 36". Ammo is everything from .50 cal lead slugs to nerf darts.
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Anatine Duo
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Fri Feb 14, 2020 12:44 pm

I've noticed that variability also. I wonder what that is? Deformation of the seal that creates a detente? Temperature? I play with the valves at the building center and notice that new ones are often very stiff.

My 3/4" ball valve gun had a heavy hammer driven by bungees that easily overcame opening stiction. It was obnoxious to shoot as it knocked the gun all over when the hammer struck the valve handle.

I keep working on opening mechanisms because 600psi high flow valves are cheap at Home Depot!
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Xamllew
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Fri Feb 14, 2020 7:01 pm

Anatine Duo wrote:
Fri Feb 14, 2020 12:44 pm
I've noticed that variability also. I wonder what that is? Deformation of the seal that creates a detente? Temperature? I play with the valves at the building center and notice that new ones are often very stiff.

My 3/4" ball valve gun had a heavy hammer driven by bungees that easily overcame opening stiction. It was obnoxious to shoot as it knocked the gun all over when the hammer struck the valve handle.

I keep working on opening mechanisms because 600psi high flow valves are cheap at Home Depot!
Yes, i like them because they make simple cheap leak-free dump valves. I realize there are plenty of better performing valves, but I don't mind the performance hit for a compact rugged valve.

My valve opening mechanism is pretty low tension but manages to kick the valve hard enough to open it, but it will occasionally fail to open it more than half way resulting in a very weak shot. Due to some regrettable design decisions in my airgun I can't increase the spring tension so I'm left trying to come up with an alternative to make the valve want to turn.

If you know the Youtuber Joerg Sprave, he has made ball valve based airguns and has run into the issue of stiff valves, it seems he was able to solve the issue by removing the handle and spinning the valve core at a high rate with a drill, this probably heats up and wears down the teflon allowing the core to move more freely.
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mrfoo
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Sat Feb 15, 2020 1:43 am

The problem with teflon is that it's soft, it deforms. So although its coefficient of friction is low, it's on a relatively huge area, you're gonna get a lot of stiction as pressures increase. I believe the seals in high-pressure ball valves (400 bar and up) are made from POM rather than teflon.
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hectmarr
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Sat Feb 15, 2020 5:32 pm

You can try to lubricate the compressed air, and not the valve. While the lubricant added to the ball valve is not constant, at first it is a lot and then it disappears, the lubricated air is constant, and your valve will always have moderate lubrication. I have not tried but it is not much work to do the test.
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Xamllew
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Sat Feb 15, 2020 7:17 pm

hectmarr wrote:
Sat Feb 15, 2020 5:32 pm
You can try to lubricate the compressed air, and not the valve. While the lubricant added to the ball valve is not constant, at first it is a lot and then it disappears, the lubricated air is constant, and your valve will always have moderate lubrication. I have not tried but it is not much work to do the test.
Wouldn't this require oiling the schrader valve before each shot in order to keep the chamber oiled?
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hectmarr
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Sat Feb 15, 2020 10:05 pm

If you are using a manual air pump, the lubrication system goes into it. In the case you use a motocompressor, it is the same. Always the air that comes out will be lubricated.
Commercial devices are not very expensive. I suggest you study thoroughly, what kind of lubricant is a friend of the seal material of your valve.
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mrfoo
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Sun Feb 16, 2020 1:40 am

Here's one, for example : https://www.valvesonline.co.uk/manual-v ... l-bkh.html

Relatively cheap, pom / molybdenum disulphide seals, rated for 500 bar.
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jackssmirkingrevenge
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Fri Feb 21, 2020 8:06 am

hectmarr wrote:
Sat Feb 15, 2020 10:05 pm
If you are using a manual air pump, the lubrication system goes into it. In the case you use a motocompressor, it is the same. Always the air that comes out will be lubricated.
Commercial devices are not very expensive. I suggest you study thoroughly, what kind of lubricant is a friend of the seal material of your valve.
A good suggestion, you can get airline lubricators on amazon.
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