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Hammer Valve Vs Piston?

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Piston Vs Hammer

Piston
12
80%
Hammer
3
20%
 
Total votes : 15
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Unread postAuthor: Modderxtrordanare » Wed Jun 27, 2007 9:04 am

I ran it through GGDT with some rough values, 3 foot barrel and 2 foot chamber.

I don't know if I inputed everything correctly though, but it looks like it will turn out nice.



(*GGDT isn't very accurate with high velocities or high pressures, so this is probably over/under-estimating it's power. All depends on if I put everything in properly. :oops: )

It would help if I posted it.
Image


But I forgot to change the projectiles weight, I put it back in as .5 grams and the velocity is 1189ft/sec*.
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Unread postAuthor: jackssmirkingrevenge » Wed Jun 27, 2007 9:15 am

A 6mm steel ball is closer to 1 gram, and why so much dead space? also the chamber seems a little big - chaos, how do you intend to achieve this pressure, regulated SCUBA tank?

edit: 3.5 cubic inches of pilot area?! The gods of efficiency, they hurtle swiftly from the heavens and smite you! :shock:

:D :D :D

The piston only needs to move back 0.0575 inches, for a 1 inch diameter piston housing this means a pilot area of a mere 0.045 cubic inches ;)
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Last edited by jackssmirkingrevenge on Wed Jun 27, 2007 9:22 am, edited 1 time in total.
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Unread postAuthor: TwitchTheAussie » Wed Jun 27, 2007 9:16 am

I wouldnt put it past him Jack :lol:
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Unread postAuthor: Modderxtrordanare » Wed Jun 27, 2007 9:25 am

jackssmirkingrevenge wrote:A 6mm steel ball is closer to 1 gram, and why so much dead space? also the chamber seems a little big - chaos, how do you intend to achieve this pressure, regulated SCUBA tank?

edit: 3.5 cubic inches of pilot area?! The gods of efficiency, they hurtle swiftly from the heavens and smite you! :shock:

:D :D :D

The piston only needs to move back 0.0575 inches, for a 1 inch diameter piston housing this means a pilot area of a mere 0.045 cubic inches ;)


I wanted to see what you would do, and as I expected, the effieciency nazi returned. :wink:

Not really, it was like that as a default, and I never bothered changing it.

Image

Much better. :wink:
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Unread postAuthor: jackssmirkingrevenge » Wed Jun 27, 2007 10:04 am

no no, dead volume should be zero, pilot volume should be 0.045 cubic inches.

Sieg Heil! :D
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Unread postAuthor: Modderxtrordanare » Wed Jun 27, 2007 10:32 am

jackssmirkingrevenge wrote:no no, dead volume should be zero, pilot volume should be 0.045 cubic inches.

Sieg Heil! :D


Type 71349315 into a calculator. It's the most efficient number ever.

Anyways...


It's not my gun, I'm too lazy to model it and re-host it again.
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Unread postAuthor: jackssmirkingrevenge » Wed Jun 27, 2007 11:52 am

lol all I ever did at school was 5318008 , cheers for that :)
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Unread postAuthor: boilingleadbath » Wed Jun 27, 2007 12:14 pm

At pressures such as this, it may be best to forget the 'gasket type' seals we typically use on our piston valves and use O-rings on the piston-barrel seal.
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Unread postAuthor: jackssmirkingrevenge » Wed Jun 27, 2007 12:18 pm

boilingleadbath wrote:At pressures such as this, it may be best to forget the 'gasket type' seals we typically use on our piston valves and use O-rings on the piston-barrel seal.


Good point to mention if you're planning a co-axial - I had changed the design of my mini-pistons after I found that the thin walls (7mm o/d, 6mm i/d) of the airsoft barrel on one of my early prototypes had actually cut into the face of the piston seal over time.
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Unread postAuthor: Modderxtrordanare » Wed Jun 27, 2007 1:00 pm

jackssmirkingrevenge wrote:lol all I ever did at school was 5318008 , cheers for that :)


We typed 71349315 onto a calculator and hung it upside down on our school's German teacher's door. Man did that piss him off. :lol:
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Unread postAuthor: chaos » Wed Jun 27, 2007 7:39 pm

OK FORGET THE EFFICIENCY NUMBERS!!


now i remodeled it,

i think ill be right with the seal/gasket i use a large surface area sealing face that will be honed. i don't actually use the barrel as the sealing face

ok screen shots of what i obtained please correct me if i made a mistake somewhere (im tired theres more than likely one mistake)

Image

Image

so i think i may have went wrong somewhere in the calculations but then again i dont think my chamber needs to be that big.
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Unread postAuthor: VH_man » Wed Jun 27, 2007 7:52 pm

hmm. i contemplated a hammer valve once, but it was for a select fire blowback gun, not for a single shot.

the nice thing aobut hammer valves is they can be used to release tiny amounts of air very quickly, and only let out that tiny amount. if you look at most PCP's, youll notice that after every shot the projectile velocity drops. thats because the hammer valve is releasing small amounts of air out of the chamber, lowering the pressure in small increments.

basically, go piston for a single shot gun, and just highly polish the barrel face and the piston face, and make brass seals...... i know its possible....... i think BTB did it for his sawed-off riot gun.

im sitting here with my GBB airsoft gun, and if i fill the mag up wiht some gas, and press the hammer down fast, i get a FSSSTT not the POP youd be looking for. go piston. nuff said. mabey use a hammer to actuate a burst disk :)
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Unread postAuthor: chaos » Wed Jun 27, 2007 7:57 pm

hmmm yer... i think a hammer valve would be a bit of a disappointment power wise but multiple shots. i think ill go for power.

brass seals? please more info, does that mean you dont use a rubber for the seal?
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Unread postAuthor: Kenny_McCormic » Wed Jun 27, 2007 8:52 pm

Modderxtrordanare wrote:
jackssmirkingrevenge wrote:lol all I ever did at school was 5318008 , cheers for that :)


We typed 71349315 onto a calculator and hung it upside down on our school's German teacher's door. Man did that piss him off. :lol:
what does SIEBHEIL mean in german?
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Unread postAuthor: chaos » Wed Jun 27, 2007 9:38 pm

seriously there is a thing called google for you translations, stop hijacking this is a serious thred
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