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Do I have this right?

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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Do I have this right?

Unread postAuthor: dapallox1 » Thu Oct 18, 2007 1:52 pm

This is how I'm going to make my piston... do it have it right? oh, I forgot to show that it is in a 4" tee. And is there a 3 1/2" to 2" coupling like that?
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Piston Layout - 4" Tee | Click to enlarge
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Unread postAuthor: pvcmaster » Thu Oct 18, 2007 2:24 pm

Looks good so far, dont forget the pilot valve! Also, I think the "coupler" you are looking for is called a reducing bushing, But I have never seen 3 1/2" pipe, i assume you mean 4" because that is your tee size.

Your barrel port is bigger than shown in the picture right? because the way you have it will restrict flow.

Good luck with 4" fittings on price, cant wait to see this valve!

Part number 4880K614 on http://www.mcmaster.com
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Unread postAuthor: dapallox1 » Thu Oct 18, 2007 2:28 pm

The pilot will be where the Pink thing is. And what could I do to get it down to 2", thats how big my barrel is.. how would i do that if I can't get a 3 1/2" to 2". Because I cant' use a 4" to 2" reducer because it would make the tee even longer... would that be a problem though? Now that I think about it, I don't think it would be.
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Unread postAuthor: williamfeldmann » Thu Oct 18, 2007 2:50 pm

I agree that the blue part that is being sealed should be 3 inches. If you have the money to buy a 4 inch tee you can afford the parts to make this as good as it can be. Port it 3 inches. You can always put a smaller barrel on it via the threaded barrel adapter you talk about (green part).

A 4 inch to anything bushing will fit in the tee as shown. GO THREE!!!

I am not sure you want to use a cleanout cap. If we are talking the threaded cleanout caps like you use on a combustion they won't hold pressure. I don't think they even make pressure rated cleanout parts. Depending on what you are piloting with I would use another reducing bushing back there, probably a 4 inch to 2 inch or 1 inch and then a big ball valve or big sprinkler if you got the cashes. A blow gun won't work, not big enough for this size of valve.

Port it three inches, you know you want to....
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Unread postAuthor: dapallox1 » Thu Oct 18, 2007 3:44 pm

I have a 1" sprinkler valve that i was going to use. Thanks for clearing up all of that about the barrel part. I'll port to 3". I've seen a few people that have used cleanout caps, but those were for 2 inch piston valves.. I just need someway to get in there and get the piston out if I have too.
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Unread postAuthor: ShowNoMercy » Thu Oct 18, 2007 3:49 pm

Buy a piece of PVC sheet and cut out a circle and then with a few self tapping screws put it in the back as a bulkhead. Maybe O ring it, but if the fit is good and maybe use some caulk you don't need one.
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Unread postAuthor: dapallox1 » Thu Oct 18, 2007 3:54 pm

okay, I just called Home Depot and Lowes, and neither have a pressure rated 4" tee. They have non-pressure rated (DWV), what's a website I could order some from?
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Unread postAuthor: williamfeldmann » Thu Oct 18, 2007 4:22 pm

Check out McMaster-Carr. They have basically anything you want in pressure rated. You will be able to get the part cheaper if you have a professional plumbing shop around you. Hit up the yellow pages and look for stores that cater to contractors.

The sheet PVC idea is a good one and has been used. However most people have better luck with an actual bushing that they drill or rout a channel in for an oring and then attach to the tee with screws. I would say check out these valves to see what I am talking about.
Original Unknownss Slayer Valve
PVCmaster's new barrel sealer

Both of these are good examples and have decent photos. You can see how they screwed the back end in. You will need to do the same but on a much bigger scale, meaning more screws). Also search through the pneumatic showcase, there are many other good examples.[/url]

EDIT: Sorry Original Unknown, I mixed up two links from my favorites lists and combined them. Fixed now. Give credit where credit is due.
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Last edited by williamfeldmann on Fri Oct 19, 2007 10:02 am, edited 1 time in total.
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Unread postAuthor: HaiThar » Thu Oct 18, 2007 4:33 pm

williamfeldmann wrote:Check out McMaster-Carr. They have basically anything you want in pressure rated. You will be able to get the part cheaper if you have a professional plumbing shop around you. Hit up the yellow pages and look for stores that cater to contractors.

The sheet PVC idea is a good one and has been used. However most people have better luck with an actual bushing that they drill or rout a channel in for an oring and then attach to the tee with screws. I would say check out these valves to see what I am talking about.
Sgort's Slayer Valve
PVCmaster's new barrel sealer

Both of these are good examples and have decent photos. You can see how they screwed the back end in. You will need to do the same but on a much bigger scale, meaning more screws). Also search through the pneumatic showcase, there are many other good examples.[/url]


Actually I had a question on MC-Master...

With the steel pipe, there are never any pressure ratings...Does that mean that there is no pressure rated steel pipe that they sell?
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Unread postAuthor: dapallox1 » Thu Oct 18, 2007 4:38 pm

Okay, I better understand it now. I called around and the only place I could find only sell 2" pressure rated, I really wanted to do a 4" though. I guess I'll do a 2" first, then move onto a 4" after I have experience doing it. Oh, and williamfeldmann, tell me when you have that 6" tee barrel sealing piston done, my eyes widened when I saw it in your signature. :D
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Unread postAuthor: DYI » Thu Oct 18, 2007 4:54 pm

Steel pipe has no pressure ratings, just like PVC fittings. Like PW-PVC fittings, the SCH determines the safe working pressure. There are tables available that list the working and burst pressures of various schedules of steel pipe in different sizes however.

This is also the reason that none of Mcmaster's plastic fittings are pressure rated. Mcmaster doesn't sell "pressure rated steel pipe" because such a thing does not exist, at least not by your definitions.
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Unread postAuthor: dapallox1 » Thu Oct 18, 2007 5:03 pm

I can only find non-pressure rated 4" Tee's on McMaster's, and only 2" pressure rated... Should I just do the 2" piston valve?
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Unread postAuthor: HaiThar » Thu Oct 18, 2007 5:27 pm

DYI wrote:Steel pipe has no pressure ratings, just like PVC fittings. Like PW-PVC fittings, the SCH determines the safe working pressure. There are tables available that list the working and burst pressures of various schedules of steel pipe in different sizes however.

This is also the reason that none of Mcmaster's plastic fittings are pressure rated. Mcmaster doesn't sell "pressure rated steel pipe" because such a thing does not exist, at least not by your definitions.


Oh, thanks for helping me understand....

Last question...

Where can you find these tables? Are the on MC-Master, or on an external site? :?
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Unread postAuthor: iknowmy3tables » Thu Oct 18, 2007 5:30 pm

you really need to understand pvc fittings cause this shows you don't know very well

brushings = adapter fittings with a larger male side and a smaller female side,
couplers= fittings with 2 female sides can have 2 same sizes or 2 diffrent sizes however most of these 2 size adapters are non rated DWV

this is your first so go with a simple threaded port no bolts and orings
on the barrel side of the tee have
2 inch pipe--cleaned out 4" pipe to 2" brushing-- opening in tee
and on the actuator side
opening in tee--4" inch pipe--4"to 4" threaded female NPT coupler-- (4" threaded NPT to 1" female socket) or if no avalible (4" male threaded NPT to 4" female socket--any rated brushing(s) to convert 4" to 1")--1" pipe--1" male threaded adapter

by the way with the single spring in the center may just go into the hole of the actuation valve and not press against the wall to cushion anything
plus the sealing face must be larger than the barrel
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Unread postAuthor: dapallox1 » Thu Oct 18, 2007 5:31 pm

I just noticed on a lot of the pvc pipe i have, it says NSF-dwv AND NSF-pw ... some have a psi rating, and others don't... so... What are safe to use?
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