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Hammer Valve Vs Piston?

Unread postPosted: Wed Jun 27, 2007 6:55 am
Author: chaos
Well i have been having thoughts... 8)

but im just not sure?

Im gonna make a bb gun this year sometime, a nice accurate tight fitting barrel bb gun.
Now i just cant figure it out, would a piston valve have better flow therefore performance compared to a hammer valve, such as ones found on commercial market PCP air guns?

im stumped on this one cause i know if i put my mind to it i could make a hammer valve, but would it overall be better power wise if i made a Very Nice piston that could cope with the high pressures?

your thoughts on this would be greatly appreciated :D


Unread postPosted: Wed Jun 27, 2007 6:58 am
Author: spud yeti
Yeah, I know what youre saying about it. You already have experience in piston valves, so you could make a really nice one. If you made a hammer valve it might not be as smooth and perfected.
I say you should use a piston valve and also make a "prototype" hammer valve for future use! :D

Unread postPosted: Wed Jun 27, 2007 6:59 am
Author: mark0491
well i think That if you made a high quality Piston that it should out perform a hammer valve But in the long run the hammer valve might last longer :?

Unread postPosted: Wed Jun 27, 2007 7:07 am
Author: chaos
Thanks guys the feedback is great so far.

yer im also thinking about the strength factor in all this, pistons do have the heavy hitting exhaust movement, but this could be possibly be overcome with a decent bumper and/or good choice of materials used on the valve and housing.

Unread postPosted: Wed Jun 27, 2007 7:13 am
Author: mark0491
im sure if you had a decent bumber that it would last longer i have no clue on you other question though lol

Unread postPosted: Wed Jun 27, 2007 7:28 am
Author: iPaintball
It would be very hard to make a hammer valve similar to those in PCPs, mainly because PCPs are charged up to thousands of psi. You would have to make a quite large valve to overcome the lower pressure. A piston would probably your best bet.

Unread postPosted: Wed Jun 27, 2007 7:29 am
Author: chaos
yer well i supose hammer valves do involve a more mechanical look towards actuation but yer i guess they might last longer, but involving more moving parts may have a better chance at breaking tho.

i know how they work, i could possibly get the parts machined, but if i made a piston out of say 6061 grade aluminum with o-rings and a nice way of attaching the sealing face, it could possibly outlast a hammer tho may need servicing more regular due to the wear on the sealing face

Edit for Pneu Kid: i know i have the machinery and materials available to make a valve either: hammer or piston capable of withstanding say 2500psi+

Unread postPosted: Wed Jun 27, 2007 7:53 am
Author: mark0491
i say you go with the piston 1 because youve beuilt them befor +10 Experience and because you can bak it really good with aluminum +7 for Construction LOL sorry thier but yeah deffinatly go with the piston

Unread postPosted: Wed Jun 27, 2007 7:58 am
Author: chaos
but i have a piston gun i could put it in that,

im thinking making a first hammer valve* (if thats true) on spudfiles.

but this is early stages i may change my mind, and knowing me like i do, i probably will :lol:

Unread postPosted: Wed Jun 27, 2007 8:05 am
Author: demilus
I think that a hammer valve would be way cooler. Granted, a piston design would probably enhance performance, a hammer hasn't been made before (to my knowledge). Also, the hammer valve gives the option of blowback also.

Unread postPosted: Wed Jun 27, 2007 8:15 am
Author: jackssmirkingrevenge
Definitely go for the piston valve, no doubt about it.

Commercial PCPs can afford to use hammer valves because they operate at pressures in excess of 3,000 psi, but piston valves are much more efficient and a better idea for a high-performance single shot gun.

Hammer valves are more convenient for semi-auto though, it depends what you have in mind, but for a near supersonic sniper go for the piston valve.

Edit - food for thought: a blowgun can easily be adapted as a suitable valve, all you have to do is add a hammer ;)

Unread postPosted: Wed Jun 27, 2007 8:26 am
Author: chaos
ahhh the great mind of Jack :D thank you for your input mate.

yer i was contemplating for the blowgun but i rely want a high powered (2000psi+) rifle im sure i can do it, ill just have to think over the design a little but what accuracy could i expect from a 6mm barrel with metal bb's? im thinking a 8mmO-D copper lining in the barrel (6.02 or sumthing i-d) i will have a 2x-4x scope it will be for short distance (30m) but i really need it accurate and powerful.

so far im thinking:

6mm I-D barrel of some kind
25mm chamber (length yet to be decided)
possibly a bull pup design.
magnified scope (2x or 4x)
backup open sights
stock n all

im gonna put a lot of work into this one, maybe even figure out a way for a rifled barrel with copper

Unread postPosted: Wed Jun 27, 2007 8:41 am
Author: turbohacker
I hope you dont plan on taking copper to 2000psi. Do you have acess to a TIG welder? You could probobly achive those lofty goals if you made it out of aluminum or steel, providing that the chainber was thick enough.

Id also make a piston valve, mainly because the are easyer t construct, and you plan on doing single shots. Good Luck!

Unread postPosted: Wed Jun 27, 2007 8:49 am
Author: chaos
turbodude wrote:Do you have acess to a TIG welder?

yer i do, i actually use one most of the time at work for purging pressured water lines.

turbodude wrote:I hope you dont plan on taking copper to 2000psi.

i do know my pressure ratings and i assure you i am not using copper for any main load bearing parts ie. only using copper for its I-D, sleeved inside 12mmO-D annealed stainless tube with an I-D of 8mm*.

most of it will be made of..yep u guessed it stainless! 3mm walled 304 stainless pipe will hold the pressure.

and yer i am starting to lean towards a piston valve on this :D

feedback is great guys thanks!

Unread postPosted: Wed Jun 27, 2007 8:53 am
Author: jackssmirkingrevenge
a 2000 psi piston gun would *REALLY* be something :shock:

The thing with commercial PCPs is that hammer valves are more convenient to use, but less efficient, so to still get worthwhile power, they up the pressure - it's the age old "American" way of thinking - screw efficiency, just add more power. I say maximise efficiency *then* add power.

For 30 metres range, a 6mm smoothbore barrel for BBs should yield satisfactory results (in spudgun terms of course though really it's impossible to tell before you actually test it) - longest barrel you can afford to make, put the parameters into GGDT and vary the chamber volume until you get the optimum performance.

If you care for your ears, plan on an integral suppressor - why not go for a full length shrouded barrel, like this: