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2" T Piston Valve

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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2" T Piston Valve

Unread postAuthor: airpress » Sun Jul 15, 2012 12:34 pm

Hi all.

I got some time to do something else than working on my hybrid.
I decided to make a steel 2" piston valve.

Something to know:
- everything is made out steel (except the piston)
- piston is made of ACULON (i don't know the exact name for America)
- the metal fittings are sealed with an special thread sealant, i can hold pressure upto 17bars
- piston seat is a piece of 5/4" pipe, pipe sits in a 2" to 5/4" bushing

Here a some pics:
Image
Image
Image
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Image

More testing this week.
I ordered some pvc pipe and fittings. The pvc is PN16.

Airpress
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Last edited by airpress on Sun Jul 15, 2012 1:07 pm, edited 1 time in total.
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Unread postAuthor: mattyzip77 » Sun Jul 15, 2012 12:42 pm

Very nice. Must weigh a ton!!! cant wait to see it in action!!
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Unread postAuthor: airpress » Sun Jul 15, 2012 12:44 pm

Indeed, it's not light at all. :p
That's why I bought some pressure rated pvc pipe.
After much searching I found a dealer in the little country Belgium!
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Unread postAuthor: acs2997 » Sun Jul 15, 2012 12:59 pm

if you want to be able to use your gun to its full potential, use more metal instead of pvc. unless the pvc is different elsewhere, it wont hold 17 bars. im from the US and the pvc here cant nearly withstand that much pressure. just a suggestion. If you dont have a heavy duty compresser, maybe pvc would be the best choice
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Unread postAuthor: airpress » Sun Jul 15, 2012 1:02 pm

The pvc is pressure rated for 16bars of waterpressure, not air.
I won't go any higher than 7 to 8 bar. When I want to get more power, I can easliy replace it with a steel chamber.

Some more details:
airchamber: 75mm 90cm long
barrel: 50mm 1,5m long

I will use this cannon where I haven't acces (field) to an aircompressor. That's why I will stuck to a pvc chamber. I will use a bicycle pump.
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Unread postAuthor: acs2997 » Sun Jul 15, 2012 1:08 pm

oh sorry, i accidently typed in 61 bar into my converter:p yeah, pvc would be fine for those pressures as long as the size isn't too big.
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Unread postAuthor: MrCrowley » Sun Jul 15, 2012 1:18 pm

Looking good but I reckon the barrel seat might extend too far in to the tee and reduce flow.
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Unread postAuthor: airpress » Sun Jul 15, 2012 2:09 pm

@ Mr Crowley,

Indeed, the seat is yet too long. I will test it when I have my chamber.
When I need to shorten it, I can. When it is too short, that would be a different problem. Then I need to buy a new 2" bushing and weld a new the pipe in it.

Something else, the gap between the fitting and piston is 0.5mm.
I might think this is to small, or not?
I've made a piston valve before but it was only 1"piston with 1/2" seat with the same gap as now. It worked great!
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Unread postAuthor: jackssmirkingrevenge » Sun Jul 15, 2012 4:13 pm

http://www.aculon.com/technology.php

Not sure if it's a material or a coating....
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Unread postAuthor: mattyzip77 » Sun Jul 15, 2012 6:03 pm

MrCrowley wrote:Looking good but I reckon the barrel seat might extend too far in to the tee and reduce flow.


If need be he could just cut off a inch or whatever needs, to be cut off. Not a big deal and smooth down rhe edge of course.
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Unread postAuthor: MrCrowley » Sun Jul 15, 2012 8:46 pm

mattyzip77 wrote:If need be he could just cut off a inch or whatever needs, to be cut off. Not a big deal and smooth down rhe edge of course.

I figured as much, thought that would be assumed :wink:

airpress wrote:Something else, the gap between the fitting and piston is 0.5mm.
I might think this is to small, or not?
I've made a piston valve before but it was only 1"piston with 1/2" seat with the same gap as now. It worked great!
I believe you can (IIRC) calculate the area between the piston and then piston housing (cross-sectional area of the piston housing minus the cross-sectional area of the piston) and then compared that to the cross-sectional area of the flow through the pilot valve. I'm not sure how much larger the pilot valve cross-section should be though.
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Unread postAuthor: airpress » Tue Jul 17, 2012 12:09 pm

Today the pipes arrived.
I cutted them and glued the needed fittings to the pipes.
Image

Here a close up of the pvc markings.
The pipe is rated for 16bars(PN16). (waterpressure)
Image

I also screwed the pilot area together.
Image
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Unread postAuthor: mattyzip77 » Tue Jul 17, 2012 12:37 pm

Very nice but why did you use sch 80 for the barrel? Also wait the full 24 hours for the glue to dry. This thing will have some serious power..
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Unread postAuthor: airpress » Tue Jul 17, 2012 12:45 pm

All those pressure rated pvc pipes here have the same color.

Yep, I will wait 24 hours. It said on the glue container. :)
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Unread postAuthor: airpress » Tue Jul 17, 2012 1:30 pm

A little preview.

Just slight screwed the airchamber and barrel to the valve.

Image

Image

Tomorrow I will make 2 support for between the barrel and chamber.
I will make it the same roundness of the airchamber and barrel.
The material used will be 1cm thick black pvc sheets.

Just to make it clear, the valve weighes more than the chamber and barrel. :P
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