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main valve + loading mech. as one unit

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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Unread postAuthor: POLAND_SPUD » Mon Feb 15, 2010 4:18 am

o-rings are cheap (you could order 10 sets of spares for it) and AFAIK if the o-ring seals are properly designed there is very minimal wear

The fact that you need two air sources is also a little awkward
and so is using HPA pressures to pilot it. There are no ideal solutions here. With a regged down circuit you can use basically any easily available (meaning -> cheap) pneumatic valves to pilot it
(or use pop-off, fullauto valves, or solenoid valves)

Quite a lot of pb guns have separate LP circuits too. They wouldn't have them if it wasn't practical
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Unread postAuthor: velocity3x » Mon Feb 15, 2010 8:33 am

POLAND_SPUD wrote:ohh BTW I am not planning to machine it myslef... either I'll ask psycis if he could machine it for me or I'll contact local machine shops, which I suppose are quite cheap...

I am aiming at 50- 75$ for the prototype as that's what I can spend onmachinining it ATM....


Poland
Be prepared to exceed your budget by many times. Machine shops are not cheap.... neither is material.
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Unread postAuthor: POLAND_SPUD » Mon Feb 15, 2010 11:34 am

I know that your launcher was expensive but it is quite large when compared with this. Also, stuff is generally cheaper here and wages are lower so I assume that it won't cost me as much as I would have to pay for it in the US.

AFAIK wages and consulting the design constitutes most of the costs so I hope I can cut down the costs.


I found a site where I could post the CAD model of this valve and service providers (that is machinist in this case) would bid it ( tell me how much they'll charge me for it).
At least I would know if it makes sense or not.
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Unread postAuthor: jrrdw » Mon Feb 15, 2010 3:41 pm

Poland_Spud wrote:I found a site where I could post the CAD model of this valve and service providers (that is machinist in this case) would bid it ( tell me how much they'll charge me for it).
At least I would know if it makes sense or not.


Would that site be CNC-ZONE? They will also bid on work. The less sense it makes the more they want to make it, it's a challenge thing... :D
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Unread postAuthor: ALIHISGREAT » Mon Feb 15, 2010 3:50 pm

Maybe its worth mentioning that the Dump valve design used on the threshold and G3 is horribly inefficient?

The spool valve style in markers such as the ION, PMR and Dye matrix markers is far more effecient:

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Unread postAuthor: jrrdw » Mon Feb 15, 2010 3:58 pm

Where are all these nice animations coming from?
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Unread postAuthor: POLAND_SPUD » Mon Feb 15, 2010 4:16 pm

is horribly inefficient
In what way ?? I assumed that the one I chosen is better while the ION has lots of small holes etc. which reduce flow

Where are all these nice animations coming from

http://www.zdspb.com/tech/misc/animations.html
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Unread postAuthor: iknowmy3tables » Mon Feb 15, 2010 4:51 pm

are you really going to machine a high pressure pneumatic
couldn't you just buy an air cylinder and make something simpler like this
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Unread postAuthor: jackssmirkingrevenge » Mon Feb 15, 2010 5:00 pm

iknowmy3tables wrote:couldn't you just buy an air cylinder and make something simpler like this


I had a similar idea here but using an electric solenoid as opposed to an air cylinder, with properly sized seals it would certainly be feasible.

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Unread postAuthor: POLAND_SPUD » Mon Feb 15, 2010 6:13 pm

are you really going to machine a high pressure pneumatic
couldn't you just buy an air cylinder and make something simpler like this
lol that's why I wrote great minds think alike... lol I had been considering this but I abandoned this idea because I couldn't figure out how to close off HPA source when the valve fires... I guess that now I know... I've got to think about it now

probably if 'my' design proves to be too expensive I'll try this one

thx for drawing it
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Unread postAuthor: POLAND_SPUD » Thu Feb 18, 2010 8:47 pm

damn designing this is much more difficult than I thought

what should be the gap between the bolt and the housing ?? to me it seems that 0.2mm would be ok, but that's just a guesstimate

another question... how much larger the o-rings should be than the clearance + o-ring groove depth ?

and finally.. is it a good idea to use just 1 oring to form a seal between both the bolt (reciprocating) and the valve housing as well as between the main part of the valve housing and the loading T (which will probably be bolted to the main part)

I've added some pics of it (all of them are cross-sections... uhmm halves of cross-sections - I found it easier to design it in this way)
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Unread postAuthor: velocity3x » Thu Feb 18, 2010 11:09 pm

POLAND_SPUD wrote:what should be the gap between the bolt and the housing ?? to me it seems that 0.2mm would be ok, but that's just a guesstimate


Personally, I like to build with .127mm max clearance.

another question... how much larger the o-rings should be than the clearance + o-ring groove depth ?


In your design, you need select a bore size that's close to a standard o-ring.

http://www.marcorubber.com/sizingchart.htm

The Machinery Handbook contains more technical info than you could possibly need or want. All the info on sizing and machining of static and dynamic o-rings can be found there. You can't simply guess at dimensions and clearances. They're in the book.

http://www.amazon.com/Machinerys-Handbook-Toolbox-Franklin-Jones/dp/0831127007/ref=sr_1_4/184-9372436-2784367?ie=UTF8&s=books&qid=1266551425&sr=1-4
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Unread postAuthor: Gippeto » Fri Feb 19, 2010 12:42 am

Re: Machinery's Handbook

And a fine book it is! I have the 18th edition on my desk, and 27th on the computer.:D

Check ebay for a good used copy.You may be able to find a download-able copy as well. :wink:

There is a users guide book as well.

http://www.amazon.com/Machinerys-Handbo ... m_b_2#noop

Useful??? I don't have one, but am tempted to get one "just because". :)
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Unread postAuthor: POLAND_SPUD » Fri Feb 19, 2010 10:57 am

thx
the only problem is that AFAIK AS568 is used in the USA and it isn't popular here... I am in the process of obtaining the Machinery Handbook but again I am afraid it might be useless for me as it probably uses imperial units...

well at least now I know that there might be a similar polish book so I'll try to find one



anyway I think I'll follow this guy's advice clicky
and use it to design the seals 'around' metric o-rings

though there are still a couple of things I don't know...

like for example is height important (meaning cross-section of orings) ? I can get orings with 1mm or 1.5 mm CS but I don't know if they are not too thin
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Unread postAuthor: kenbo0422 » Fri Feb 19, 2010 2:25 pm

Well, will your oring meet the 30% criteria? I.E> with the o-ring groove in place, will the outside diameter allow it to be compressed 30%? (this is for moving parts, a 40% compression is recommended for static seals).

The o-ring in the groove should compress to 70% of its original thickness.
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