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Rotating seal?

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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Rotating seal?

Unread postAuthor: )DEMON( » Mon Apr 14, 2008 12:00 pm

Hi guys. I know I have not been on in a while but I hope everyone is still good. I had to go though 10 000 new posts recently and I can see this forum is getting very big.

I am not sure what sort of component I am looking for but it needs to fill a certain purpose. It needs to have a ridged input and a rotating output, something like a rotating coupling of some sort AND it needs to seal at about 1000psi and be able to rotate at around 900 rpm.

I know it is a tall order but I have found something that might do, its called a rotating onion and can be seen here: http://www.dynamicsealing.com/gp_2-passage_unions.html

I need to know what sort of component will suit my needs, not where to get it (unless it is in South Africa).

Thanks in advance :)
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Unread postAuthor: jrrdw » Mon Apr 14, 2008 1:35 pm

"Max. Rotational Speed: up to 850 RPM* " Theres a link to request information, but it looks like you found what your looking for.

What are you working on/building this time?

Welcome back!
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Unread postAuthor: )DEMON( » Mon Apr 14, 2008 2:04 pm

The only problem is finding the bugger, I hope I can get them here, no dought that they are around though.

What am I planning to build you say, well it everything is just a concept right now, I don't know if I am going to go ahead with it but it is paintball related and it has multiple barrels. I am not going to attempt anything until I have it nailed down. And I am busy with my last year of highschool, I wish I had more time, at least I have a job now.
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Unread postAuthor: judgment_arms » Mon Apr 14, 2008 2:10 pm

Let me guess, Gatling gun or a Minigun. :D
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Unread postAuthor: )DEMON( » Mon Apr 14, 2008 2:17 pm

Maybe :D

A portable one too.
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Unread postAuthor: jrrdw » Mon Apr 14, 2008 2:29 pm

" it is paintball related and it has multiple barrels" Geeeee, I wonder what gave it away hehehe. <a href="http://plugin.smileycentral.com/http%253A%252F%252Fwww.smileycentral.com%252F%253Fpartner%253DZSzeb008%255FZR%2526i%253D14%252F14%255F6%255F12%2526feat%253Dprof/page.html" target="_blank"><img src="http://smileys.smileycentral.com/cat/14/14_6_12.gif" alt="SmileyCentral.com" border="0"><img border="0" src="http://plugin.smileycentral.com/http%253A%252F%252Fimgfarm%252Ecom%252Fimages%252Fnocache%252Ftr%252Ffw%252Fsmiley%252Fsocial%252Egif%253Fi%253D14%252F14_6_12/image.gif"></a>
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Unread postAuthor: )DEMON( » Tue Apr 15, 2008 11:31 am

I might have found a source for the parts I need, I am waiting for their responce.

I think the most important aspect for a paintball style minigun to function properly is the barrel must pause while the paintball is moving down it.
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Unread postAuthor: jrrdw » Tue Apr 15, 2008 11:33 am

It's delivered through the mail if ordered off the internet, why not just order it for yourself?
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Unread postAuthor: )DEMON( » Tue Apr 15, 2008 12:19 pm

I have had post stolen before, if I can go out of my way to collect it in person I will.
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Unread postAuthor: THUNDERLORD » Tue Apr 15, 2008 1:25 pm

1000 psi is a lot of pressure.
With pressure that high designing seems to be much more difficult.
I would suggest some kind of seamless hydraulic pipe.
Then you'd probably have to have the end cap welded on.

But I was thinking for the spin part, you could mount a ball bearing sleave like for skate boards or rollerblades on the inside and drill the hole in the end cap the same diameter as the axle bolt hole and epoxy the bolt head to the inner ring of the bearing.

Since the hole in the end cap will be the same diameter as the bolt passing through it I think it will hold pressure, spin and not leak air.

BTW I wouldn't try 1000 psi in a standard threaded pipe since the threads go about halfway into the metal that's the point they will usualy fail.

EDIT:At the outer ring of the bearing, gas would be blocked by a rubber washer between the plate steel end cap piece and the bearing.

At the inside of the bearing, gas would be blocked by the bolt passing through by the bolt head to the inner ring of the bearing.

The hole in the end cap will only be the diameter as the axle bolt to hold the bearing inside.
It should work. And It should still spin and hold pressure.
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Last edited by THUNDERLORD on Tue Apr 15, 2008 1:39 pm, edited 1 time in total.

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Unread postAuthor: )DEMON( » Tue Apr 15, 2008 1:37 pm

Sounds interesting.

I am using paintball parts though and high pressure fittings and hose, 1000psi is not a problem. Essentually the minigun will have the same number of valves as barrels and I am designing it around the Tippmann 98c valve set up, because it has a threaded hole in the valve instead of a tombstone. This is being designed to be used in paintball so it has to be safe. Parts will have to be machined and the cost could come to hundreds of dollars. Its a big project.

You can source high pressure parts from hydraulics shops that are rated to thousands of PSI, it would be silly to put such high pressure in normal pipe. The trick to using high pressure is to have low volume.
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Unread postAuthor: THUNDERLORD » Tue Apr 15, 2008 1:51 pm

If it has a seperate valve and seperate hose for each barrel I am confused why the cylinder will need to contain pressure?

I don't understand,Why can't the whole set-up be mounted to aluminum rotating on a bearing?

I understand the safety thing, that's why I suggested using materials with specifications to those levels.

Maybe you could show a diagram.
BTW Looks like interesting parts on the link.
Also I had edited my last reply at the end with more description.

EDIT: Perhaps you could mount everything to an aluminum plate rotating on a bearing with the air tank in the center of the barrels spinning right along with them.
For loading either each barrel could have it's own hopper spinning w/it or one singl hopper.
I'm not fimiliar with how the hammer strikes the valve to link them all to one trigger though.

DOUBLE EDIT: I was thinking about it and if the barrels have seperate hoppers the centrifugal force will throw the PB's outward .
That may cause feeding problems so I think one large magazine should be mounted on the inside w/ a hole for each barrel(so the PB's move outward into each feed tube).

Like an original Gatling, notches or"cams" on the rotating alum. piece could drive the hammer back and release it to strike the valves.
Hope you show us pics when you get done!!!!!
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Last edited by THUNDERLORD on Tue Apr 15, 2008 2:51 pm, edited 2 times in total.

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Unread postAuthor: Hotwired » Tue Apr 15, 2008 2:25 pm

its called a rotating onion


:D
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Unread postAuthor: )DEMON( » Tue Apr 15, 2008 2:41 pm

Thunderlord, I think I know what you are saying (man, I need some sleep), it would make the whole marker way too bulky to mount the air cylinder inside the barrels, sure it would be easyer though.

The marker will be belt fed, it won't have any hoppers obscuring the looks, that also saves up some space on the design and simplifies it slightly. The forward action of the bolt in each marker assembly will seal between the valve and the barrel on each shot, also pushing the paintball out of the belt.

I know it is difficult to describe but I will try get some pics up when I have time. It would make it easyer to understand if you familiarize yourself with the Tippmann valve platform.
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Unread postAuthor: THUNDERLORD » Tue Apr 15, 2008 3:04 pm

Yes, I should read up on the Tippman valves.
Btw, I went back to edit my last reply so I wouldn't double post and I added an idea for having one magazine with a seperate tube going into each feed for each barrel.

As far as the idea for sealing a spinning container it would go like this:
1)Into the pipe put a washer same inside diameter as outside of ring of bearing.
2)Put the bearing.
3)Put some epoxy onto bolt(to keep it from falling out) with head diameter same size as outer diameter of the inner ring of the bearing

The bearing should still spin because of the gap between the inner ring of it and the end cap piece.
I wish I could post a diagram. I think it would hold pressure and spin.
Sounds like it won't be useful but I wanted to clarify that :roll:
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