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Solving pump-pistol issues

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: jean » Tue Jan 15, 2013 4:27 pm

to precharge the pump tube high pressure isnt need only 1 or2 may3 bar to precharge the tube and for high pressure than the thinner diameter pump
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Unread postAuthor: jean » Wed Jan 16, 2013 12:25 pm

here
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 17, 2013 2:02 am

It would work as drawn, certainly - but in terms of complexity, you're not really gaining anything by having two pumps in my view.
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Unread postAuthor: jean » Thu Jan 17, 2013 6:37 am

@jsr can you please ggdt it for me?
100cm barrel 8mm
chamber 3ml @100bar

and the same with hgdt.

jean

@ brian sorry for the highjacking ;-)
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 17, 2013 6:53 am

jean wrote:@jsr can you please ggdt it for me?
100cm barrel 8mm
chamber 3ml @100bar


Sure, not just yet though as I'm at work and don't have access to GGDT. What projectile weight?

and the same with hgdt.


HGDT is for combustions and hybrids... actually, the single stroke mechanism is very interesting for a portable hybrid!

Let's say you 50cm long chamber tube, and a barrel/pump filler with a stroke of 45cm - that would take you to enough pressure for a 10x hybrid

I was thinking along these lines here.

By having a 1x mix in a syringe and using that to pressurise a cartridge, any pressure you reach would technically be at the right ratio. Using it manually would naturally limit you to the pressures you can achieve through the pressure you can exert, so a possible solution to this would be modifying the syringe to enable the plunger to be pushed by air pressure


Image

Coupled with Brian's concept here, hmmm...

Image

Replace the burst disk pilot with a check valve, add some ignition points and a quick syringe squirt of butane/propane before inserting the pump head... profit!

brian sorry for the highjacking ;-)


I'm sure this is exactly the sort of brainstorming he intended to happen ;)
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Unread postAuthor: POLAND_SPUD » Thu Jan 17, 2013 7:51 am

Replace the burst disk pilot with a check valve, add some ignition points and a quick syringe squirt of butane/propane before inserting the pump head... profit!
heh not a bad idea - sounds worth trying

ohh and a metal on metal detent mechanims would be ideal for this application

edit
now I am wondering... it would make more sense to reach higher pressures right? why choose 10x when you can 30x...
but then again isn't it possible to get the mix to auto ignite?
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 17, 2013 8:44 am

POLAND_SPUD wrote:ohh and a metal on metal detent mechanims would be ideal for this application


I've been thinking a lot about that lately, it seems that with pellets it's the best solution. O-ring detents are a dead end because of the head and skirt, works for BBs but not for pellets.

Jamming a 0.22" pellet into a 5mm hole on the other hand, that holds some promise...

now I am wondering... it would make more sense to reach higher pressures right? why choose 10x when you can 30x...


Say you have a 1 metre long pump tube, and a 5cm long cartridge, that's 20x easily...

but then again isn't it possible to get the mix to auto ignite?


I don't think so, propane has an autoignition temperature of 470ºC, you're not going to reach those levels unless you drop an anvil on the pump plunger from a great height...
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Unread postAuthor: jean » Fri Jan 18, 2013 5:48 am

@jsr
s i know that hgdt hybrid why not as a piston hybrid projectile weight say 3g
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 18, 2013 11:31 am

Here it is in GGDT assuming an 8mm steel bearing projectile and you can get to a pressure of 750 psi / 50 bar.

Note that at that pressure and using a 20mm ID chamber you would have to push down with around 125kg of force... so start eating :D
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Unread postAuthor: jean » Sat Jan 19, 2013 10:01 am

hi
im back at home now

ok i see the problems...

see my new thread at the hybrid discussions

jean
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 27, 2013 10:22 am

Just thinking aloud here, hmmm...
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Unread postAuthor: Labtecpower » Sun Jan 27, 2013 11:49 am

Should work I think, however the opening speed of your valve will be hugely limited by being fixed to the pulling rod..
you aren't going to manage a 1 ms. opening time on this one :D
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 27, 2013 11:50 am

Labtecpower wrote:you aren't going to manage a 1 ms. opening time on this one :D


With 1000 psi in the chamber giving a hand, I think it would ;)
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Unread postAuthor: Brian the brain » Mon Jan 28, 2013 4:18 pm

Looks like that thing would pop as soon as the balance is broken... :D
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 29, 2013 1:42 am

Brian the brain wrote:Looks like that thing would pop as soon as the balance is broken... :D


My thoughts exactly :) might be worth building but lots of other projects on the table at the moment.
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