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Wye piston valve - good idea?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Wye piston valve - good idea?

Unread postAuthor: dongfang » Wed Jul 11, 2007 5:16 pm

Hi,

I have played around with the idea of a piston valve without the 90 degree bend: Put it in a wye.

The barrel and the piston each need to be cut at 90 degrees - half the angle of the wye (so 90-22.5 degrees for the wyes I can find).

I know there are some details missing in my plan, such as how to get the thing to open at all, but that should be no easier and no harder than with tee piston valves.

The idea is that should have a better flow coefficient because there is no bend. Of course the piston gets in the way pretty badly, until it has moved far enough back.

What do you think?

Regards
Soren
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Wye barrel sealing valve
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Unread postAuthor: noname » Wed Jul 11, 2007 5:22 pm

The main reason why you don't see piston valves in a Wye configuration is that Wye fittings aren't pressure rated here in the US. Clide made one in a T which is the same as your diagram, you could probably find it in the SpudTech Archive.
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Unread postAuthor: dongfang » Wed Jul 11, 2007 5:28 pm

Hi,

http://koi-breeder.wyssnet.ch/shop/

Expand PVC in the tree; choose T-stueck45.

I think these are OK for pressure. Anyway those were what I thought of using.

Regards
Soren
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Unread postAuthor: noname » Wed Jul 11, 2007 5:34 pm

Hmmm, they might be. I have no idea where to get them or what language that site is or anything though. :lol:
I clicked on a regular T and they look pretty thick, like Sch 80, and they're PVC. The depth of the sockets also looks pretty good, so I think they would hold pressure.
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Unread postAuthor: Gepard » Wed Jul 11, 2007 5:40 pm

They look identical to the 16bar rated fittings I use.....

<disclaimer>

Michael

EDIT: There's only a 0.30 GBP price difference....
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Unread postAuthor: dongfang » Wed Jul 11, 2007 5:55 pm

Hi,

The language is German, the place is 20 km from where I live, and whatever the price difference is, one be be damn sure it´s more expensive here.

An 1 inch Rain Bird jartop -- ta-daa, 82 CHF gone :x

Regards
Soren
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Unread postAuthor: Gepard » Wed Jul 11, 2007 6:08 pm

lol the prices are about the same....your 110mm pipe is cheaper than the UK by 30p :D

Michael
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Unread postAuthor: Modderxtrordanare » Wed Jul 11, 2007 6:29 pm

Why put the piston in the bottom pipe that splits off? Why not assemble it like a regular piston valve, with the pilot being parallel with the barrel, and the chamber coming (45* instead with the Wye) off the bottom?

I suppose you were trying to eliminate the bend all-together, but the way I suggested would atleast make construction easier (the same as normal) and still reduce the bend by 45*.

I suppose you could special order a pressure rated Wye off McMaster though.
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Unread postAuthor: MrCrowley » Wed Jul 11, 2007 6:41 pm

Well the piston wouldn't work anyway in that diagram as the seat diameter = the sealing face diameter, so make the seat have a smaller diameter compared to the sealing face and then you practically have got what clide made.
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Unread postAuthor: VH_man » Wed Jul 11, 2007 7:09 pm

has anyone made an inline piston valve? im pretty sure you could make one out of pressure rated fittings. it would reduce flow slighly, but its as ergonomic as a sprinkler, but 100's of times more powerful.
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Unread postAuthor: Modderxtrordanare » Wed Jul 11, 2007 7:15 pm

VH_man wrote:has anyone made an inline piston valve? im pretty sure you could make one out of pressure rated fittings. it would reduce flow slighly, but its as ergonomic as a sprinkler, but 100's of times more powerful.


A coaxial piston is inline. Maybe not what you meant, since technically the air does do a 180, but still.. :lol:
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Unread postAuthor: noname » Wed Jul 11, 2007 7:15 pm

I've made a few. Check out the beautiful one in my avatar! :lol:
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Unread postAuthor: clide » Wed Jul 11, 2007 7:40 pm

As others have said, I made a valve with a similar idea in a regular tee. Unfortunately I never quite got the performance I was expecting out of it. This was actually what I was planning to do to as a next step to try and get it working better.

Some sources for pressure rated wyes in US
http://www.plumbingsupply.com/pvc.html
http://pvcfittings.com/ (cheaper for the wye)

Although I would suggest that you make the piston a normal one with a 90° face and use a 45° sealing face in the wye. That way you wont have to worry about the piston trying to slide off the sealing face, which was one of my problems in the regular tee.
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Unread postAuthor: Acdcmonkey1991 » Wed Jul 11, 2007 8:08 pm

I'm not sure if this a good idea or not??? I just stumbled upon this design when I was looking at a squirt gun valve. Funny eh?? I made a VERY, small model and tested it at about 60 psi no leaks at all. I was hesitant to post this here because I wasn't sure if anyone had done anything like this valve design before. It can be fired as a semi-auto valve if the chamber is large enough, and under enough pressure.
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This is it, it's actually pretty simple. I think it's similar to Clide's idea.
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Unread postAuthor: dongfang » Thu Jul 12, 2007 2:21 am

Hi,

Thanks for all the responses. That's where inspiration comes from...

Why put the piston in the bottom pipe that splits off? Why not assemble it like a regular piston valve, with the pilot being parallel with the barrel, and the chamber coming (45* instead with the Wye) off the bottom?


Mostly to avoid a big fat pipe coming off to the chamber at an odd angle. I can't find any 45 deg bends to straighten it up. Of course one could use another wye ...

Although I would suggest that you make the piston a normal one with a 90° face and use a 45° sealing face in the wye. That way you wont have to worry about the piston trying to slide off the sealing face, which was one of my problems in the regular tee.


Wait wait that's actually a good idea. I did design like that originally. The problem is that the 45 deg barrel cut becomes sqrt(2) times longer than it is wide.
With a 67.5 degree cut, the length:width of the piston and the barrel end becomes the same ---> better fit, smaller piston.
With a 45 degrees barrel cut, one will then need a piston diameter quite a lot larger than the barrel diameter - but ok that brings us back to:

Well the piston wouldn't work anyway in that diagram as the seat diameter = the sealing face diameter, so make the seat have a smaller diameter compared to the sealing face and then you practically have got what clide made.


I drew up the situation. Maybe there is a single solution for both problems.

But ok it WILL be a somewhat large piston for the barrel. Something like 71 mm piston OD for a 50 mm barrel OD. On the other hand, construction is simple (90 degrees piston end).

What is a good piston surface area : sealed face area for barrel sealers?

Maybe the best cut is somewhere in between 67.5 degrees and 45 degrees.

noname, have you revealed somewhere what is inside that valve of yours?

Regards
Soren
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