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spring loded bv

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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spring loded bv

Unread postAuthor: dudeman508 » Mon Jul 14, 2008 10:39 am

how well do those spring loaded bv work
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Unread postAuthor: pizlo » Mon Jul 14, 2008 10:49 am

Well I've heard it said that a burstdisk is open in 1 milisecond. A piston valve opens in 5, and a sprinkler between 6 and 10. Depending on your spring it could be between 20 and 10 milliseconds. Of course if you can see it opening its far too slow, and a light spring isn't going to cut it. I would say save yourself the time and effort and buy a sprinkler from www.bcarms.com or from home depot and mod it yourself.
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Unread postAuthor: pocket » Mon Jul 14, 2008 10:53 am

not true pizlo if u want to have a realistic look to it i would do the bv i did it to mine worked fantastic and keeps the realistic look besides how do u fit a sprinkler valve onto a stock
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Unread postAuthor: Hotwired » Mon Jul 14, 2008 11:00 am

How long is a piece of string?

It will work as well as you can construct it as with any other homemade valve.

There's more mass to shift for it to open which makes it milliseconds slower than an air piloted valve and possibly more cannon jolt on firing.

It also has external rather than internal mechanics which may or may not be a good thing.

On the definite upside it is possible to have full bore and low turbulence flow once it gets fully open.

Air piloted valves need at least one 90* bend for the air to escape with a full 180* bend being more common for compactness.

There's nothing wrong with using them in short :)
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Unread postAuthor: pizlo » Mon Jul 14, 2008 11:01 am

pocket wrote:not true pizlo if u want to have a realistic look to it i would do the bv i did it to mine worked fantastic and keeps the realistic look besides how do u fit a sprinkler valve onto a stock


I never said the BV did not have the advantages of being more inline and small... I'm actually almost done with my realistic gun (with a BV) And save that last question for about two weeks and then you'll see.
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Unread postAuthor: THUNDERLORD » Mon Jul 14, 2008 12:14 pm

pocket wrote:...besides how do u fit a sprinkler valve onto a stock


http://www.spudfiles.com/forums/silenced-erg-ssb-t14438.html

*cOUGH* CouGH*
I was thinking of extending the handle on a BV and making a new one with a rat trap spring for the spring. (I have lots of BV's).

But it would be so much better to use them to pilot pistons.
Or for BBMG trigger valves. :roll: 8)
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Unread postAuthor: trollhameran » Mon Jul 14, 2008 12:20 pm

the hardest part is getting the spring setup just right because with the kinda spring you need to open it fast you really dont want it to be going off with your fingers in the way, they are really cool though plus as long as your bv seals then there is no other parts that you have to get to seal unlike pistons and sprinklers which can be hard to get to seal properly
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Unread postAuthor: psycix » Mon Jul 14, 2008 4:35 pm

The BV stays slow no matter if you spring load it or not, but one thing that the spring does improve, is your acuraccy. Slapping open a ballvalve as fast as you can, throws off you acuraccy completely. A spring loaded valve with a trigger, allows you to hold your aim while firing.
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Unread postAuthor: SpudFarm » Mon Jul 14, 2008 4:41 pm

my marble gun hits my mailbox at 30 yards. i slap the pilot ball valve open and it really does not do anything to acuraccy, however i think a ball valve as mail valve would
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Unread postAuthor: dudeman508 » Tue Jul 15, 2008 9:33 am

[quote="pizlo"]Well I've heard it said that a burstdisk is open in 1 millisecond[quote] How do burst disks work, because im still in the desining stage of a piston cannon and now i might want to use a burst disk
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Unread postAuthor: Ragnarok » Tue Jul 15, 2008 10:18 am

pizlo wrote:Well I've heard it said that a burstdisk is open in 1 milisecond. A piston valve opens in 5, and a sprinkler between 6 and 10. Depending on your spring it could be between 20 and 10 milliseconds. Of course if you can see it opening its far too slow, and a light spring isn't going to cut it.

That's not actually right. Burst discs are into fractions of milliseconds, a good piston is between 1 and 2 milliseconds, and a modded sprinkler is about 5 or 6 ms - unmodded, it's closer to 20 or 30.
A hand opened ball valve - between 150 and 250 milliseconds, far too slow to be effective, as usually the projectile is gone before the valve is even a quarter open.

As an example of how much a hand ball valve damps performance, if I were to take HEAL and fit it with a ball valve instead, changing nothing else, the muzzle energy would be slashed by a factor of ~8.
A good, fast, high flow valve is the make or break on a cannon, closely followed by the pressure.

Spring loaded ball valves can come down to 20 to 50 milliseconds opening time - depending on the strength of the spring - so they can be reasonably respectable, and will probably boost a cannon's muzzle energy to maybe twice what a hand opened ball valve would give.

As a general rule however, the only thing a spring loaded BV is going to beat is a regular ball valve, or maybe an unmodded sprinkler.

@dudeman508:
Usually if you're below about 2 milliseconds, the faster opening time becomes fairly irrelevant to performance, generally earning only a couple of fps at most unless it's an infeasibly light projectile, and nothing that light would survive in the barrel.

The opening time of a burst disk doesn't help it much over a piston valve - the extra flow will, but in my opinion, the performance gains from a burst disc aren't worth the extra time it takes to work them, so I stick with piston valves.
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Unread postAuthor: dudeman508 » Tue Jul 15, 2008 11:59 am

ok I will and thanks for the info, but how do burst disks work
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Unread postAuthor: biggsauce » Tue Jul 15, 2008 12:44 pm

A burst disk is... well a disk that bursts.

You'll see them mentioned frequently in hybrid discussion. A burst disk can be made of whatever material you choose. Aluminum foil, coke and milk bottle plastic, neoprene, etc. are a few materials to name. They are held in place between the chamber and barrel, commonly by a union. The burst disk acts as your valve and "opens" when the pressure in the chamber increases to the point at which the burst disk material ruptures. Spudwiki should have some good info also.

EDIT: @starman. The score is 1:1 my man :P :lol:
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Last edited by biggsauce on Tue Jul 15, 2008 2:49 pm, edited 1 time in total.
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Unread postAuthor: starman » Tue Jul 15, 2008 1:05 pm

Think of having a pressurized chamber with a balloon wall sealing the breech behind the projectile. Now pop the balloon with a sharp instrument or too high pressure.

A burst disk offers a much more relevant performance upgrade for a combustion gun. Burst disks are designed to break at a pre-determined pressure so that break point needs to be somewhere less than the peak pressure that will be created during combustion. As you move into higher X hybrid combustion guns, the burst disk break point can and should be higher to extract the full potential from the shot.

A pneumatic gun burst disk can be broken by either just adding pressure until it breaks or by piercing it with a sharp object, and as Rag said offers only small performace improvement over a well designed piston.

Davidvaini has been developing a pneumatic burst disk cartridge system here if you're interested.

Edit: Beaten by the Biggsauce man.... :wink:
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