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"In the world of spuds today"

A place to ask general spud cannon related questions.
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Unread postAuthor: mark.f » Sat Mar 05, 2011 5:55 pm

Double post.

I think I need a check valve. :lol:

[youtube]http://www.youtube.com/watch?v=Q-Ii8VHj3Ls[/youtube]
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Unread postAuthor: Gun Freak » Sat Mar 05, 2011 5:59 pm

lol fail :lol:
Is that a schrader or a presta? Is the problem in your pump head?
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Unread postAuthor: Lockednloaded » Sat Mar 05, 2011 6:08 pm

More like win! A what looks to be 3/4 piston valve that can be piltoted by a schrader valve
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Unread postAuthor: Gun Freak » Sat Mar 05, 2011 6:10 pm

Yeah I guess you're right... :lol:
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Unread postAuthor: POLAND_SPUD » Sat Mar 05, 2011 6:22 pm

More like win
more like -> you is not has a 3 way valve.... you is need one :D
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Unread postAuthor: mark.f » Sat Mar 05, 2011 7:33 pm

Yup, 3/4" porting valve, 1" tee. :D Props to Gippeto for the one-way o-ring idea.

I just slapped a ball valve on there for now and have resumed work on the rest of the launcher.
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Unread postAuthor: Gippeto » Sat Mar 05, 2011 7:35 pm

Nice stuff Mark! :D

Edit: Aww shucks. :lol:
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Unread postAuthor: mark.f » Sat Mar 05, 2011 8:53 pm

Still can't call it complete until I'm filling to 450 PSI, though. :D

(Plus some minor cosmetic improvements)
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Unread postAuthor: jackssmirkingrevenge » Sat Mar 05, 2011 11:21 pm

Lockednloaded wrote:More like win! A what looks to be 3/4 piston valve that can be piltoted by a schrader valve


I told you it was possible :) nice work Mark, looking forward to the finished item and damage pics/vids :D
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Unread postAuthor: mark.f » Sat Mar 05, 2011 11:59 pm

Well, don't worry, I'm not posting it until I have plenty of the above items. :wink:
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Unread postAuthor: saefroch » Sun Mar 06, 2011 3:08 pm

Does the one-way o-ring idea allow the compressed pilot volume to flow back to the chamber side of the valve when the valve opens?
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Unread postAuthor: Gippeto » Sun Mar 06, 2011 3:19 pm

saefroch wrote:Does the one-way o-ring idea allow the compressed pilot volume to flow back to the chamber side of the valve when the valve opens?


Good question...I don't know for certain.

It (the o-ring check) opens/closes in response to differential pressure, so I would THINK it should allow for decompressing the pilot if the chamber pressure was lower than pilot volume pressure.

But...

A decent sized pilot valve should not allow the recompression in the first place.
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Unread postAuthor: mark.f » Sun Mar 06, 2011 9:01 pm

I guess the point here would also be the amount of flow around the piston with the o-ring in the "open" position. It's not much, so I doubt the flow of air required for the trapped pilot volume to have no effect on the opening of the piston would far exceed the amount of air able to get through the "o-ring check".

Another way to negate this (besides a larger pilot valve) is to have a smaller difference in piston OD and barrel seat OD, requiring a lower pilot pressure before the piston begins to open in the first place.

So like Gippeto said, I wouldn't rely on the tiny notch in your o-ring groove to prevent piston bounce.
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Unread postAuthor: saefroch » Sun Mar 06, 2011 9:14 pm

I was just interested, because I know that I've piloted my special piston with an internal check valve (shameless self-promotion :roll:) by just cracking open the pilot valve and letting the pressure drop slooowwwwwllllllyyyyyyyyyy, which is quite scary because it's hard to know when it's going to go off. But my point is that while I have no doubt you could do that with any really good piston valve, one with a low-cracking pressure check valve has very little likelihood of bouncing, because it vents the compressed pilot volume to the chamber.
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Unread postAuthor: mark.f » Tue Mar 08, 2011 12:02 am

"Low" pressure testing video. :D

[youtube]http://www.youtube.com/watch?v=bHC1802JgHE[/youtube]

It's coming along. My pump and revised piston parts are arriving tomorrow.
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