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Unread postPosted: Tue Jan 20, 2009 11:48 pm
Author: jackssmirkingrevenge
POLAND_SPUD wrote:QEVs have significantly bigger piston than the seat... do you happen to have one already?

Sadly I don't, but I'm sure there's someone willing to give it a go - brian perhaps?

(and It was my idea to use a QEV not lentamentalisk - yes I want to get all credit for it - hell you can even call it poland valve :D )

Never said it wasn't your idea to use a QEV, what I meant was it was his idea to reverse the piston ;)

Unread postPosted: Tue Jan 20, 2009 11:53 pm
Author: Lentamentalisk
Ok, here is a photo of my 3/4" McMaster QEV

The seat diameter is 2.5cm (1"), and the total piston area is 4.5cm (1 9/16")
That is not a major difference.

With some mods, I will give this a try this weekend though, and tell you how it works.

Unread postPosted: Wed Jan 21, 2009 12:30 pm
Author: jackssmirkingrevenge
It looks like it has a lot of promise, looking forward to your results :)

As to my own power tests, you're going to have to wait a bit longer as the air spring has (unsurprisingly, given it's just a syringe tube) sprung a leak and in the process of sealing it I too the opportunity to reinforce the whole section. Sadly this means that the piston will no longer be visible but at least I'll be able to test it without fear of breaking it. Also, the fact that the syringe tube sides will be supported means they can't bulge out under pressure and therefore the seal will be less likely to leak.

Unread postPosted: Wed Jan 21, 2009 2:40 pm
Author: MrCrowley
Instead of using a syringe tube, what about getting a cheap 120PSI bike stirrup pump, and hack a small section off the metal tube and use the piston from the pump for the piston in this? Then you just need to epoxy it to whatever.

Just means it could take a few hundred PSI no problem. I'm not sure about the size ratio between a piece of that tube and the syringe you're using, the bike pump tube might give you more volume then you want.

Unread postPosted: Wed Jan 21, 2009 5:23 pm
Author: jackssmirkingrevenge
A valid suggestion, in that case however you'd have to use a coil spring, as the pump piston will only seal one way. As an air spring my prototype only needs around 15 psi of pre-pressurisation, I doubt it rises much more than that when the piston actuates. In any case, it's got a layer epoxy around it now, plus PVC pipe which can take at least 400 psi, so in around 24 hours we should be good for testing ;)

Unread postPosted: Wed Jan 21, 2009 5:31 pm
Author: MrCrowley
Couldn't you replace the floating o-ring with a normal o-ring that is tight so it would seal both ways?

Edit: And looking forward to the next testing least we know it works this time and can't be disappointed too much :)

Unread postPosted: Wed Jan 21, 2009 5:37 pm
Author: jackssmirkingrevenge
Or simply invert the piston...

Unread postPosted: Wed Jan 21, 2009 5:39 pm
Author: MrCrowley
jackssmirkingrevenge wrote:Or simply invert the piston...

That too :)

They're a [female doggy] getting back in the tube, those bike pump pistons with the floating o-rings. If only I had some epoxy i'd give this a go.

Unread postPosted: Wed Jan 21, 2009 7:31 pm
Author: psycix

I just love it how it goes daka-daka-daka instead of braaaap. I'd send you a cookie if I knew where you live. ;)

Once you're done with playing with epoxy and finish tweaking n experimenting with full auto valves so that you have researched all the aspects of it; I think I'll build myself a machined one out of steel or aluminum running at about 30 bar. :D

BTW, where did your laz0r soundz go? xD

Unread postPosted: Thu Jan 22, 2009 12:30 am
Author: jackssmirkingrevenge
MrCrowley wrote:If only I had some epoxy i'd give this a go.

Join la revolucion ;)

I'd send you a cookie if I knew where you live

Address it to the "Epoxy Batcave" and it's bound to find its way here ;)

where did your laz0r soundz go? xD

Interesting that you should mention that - I think it's an indicator of the high flow, in that the air is not as restricted. I can get the sound by putting my finger over the port.

Still a lot of tweaking to find the ideal pressure in the air spring and flow from the compressor but we'll get there, what's more important though right now to get me to finish it is MOAR POWER!. I'll hook up a barrel this evening and try single shots to get an idea.

With this oneI had got a maximum of 2 ft/lbs with lead pellets for a single shot, this is about similar for the maximum I got for an individual shot with my ball-valve BBMG so not really very inspirational. If it can put a lead pellet through the bottom of a soup tin though, I'll be a happy man :) watch this space.

Unread postPosted: Thu Jan 22, 2009 1:45 pm
Author: jackssmirkingrevenge
Had a play with the reinforced prototype fixed to a 36 inch long 6mm barrel firing single shots and here are some average velocity results:

0.25g airsoft BBs: around 460 feet per second

Standard 16 grain 0.22 airgun pellets: around 280 feet per second

Modified16 grain 0.22 airgun pellets: around 330 feet per second

That's just under 4 ft/lbs for the last projectile, not out of this world it will be impressive on full auto and in the meantime, enough to give you a decent damage video with single shots through the bottom of a soup tin:


Here's the unit in operation, note how the pressure on the shock-pump gauge (attached to the air spring) peaks with each shot as the piston compresses the air behind it.


Out of interest, I tried a couple of shots with the modded pellets but filling the air spring to 30 psi and opening the schrader to fire, velocity was around 345 feet per second so I know the setup is tweaked reasonably well.

Now for a properly made reloading system :)

Unread postPosted: Thu Jan 22, 2009 1:59 pm
Author: Ragnarok
Very nice.
It sounds a little slower than the other prototype though - and measuring it, it is, it's ~180 rpm.

However, it seems like finally your quest for a full auto is moving towards an answer.
No doubt you'll want a better one soon after. :roll:

Unread postPosted: Thu Jan 22, 2009 2:15 pm
Author: jackssmirkingrevenge
The rate of fire is easily controlled simply by regulating the amount of flow from the compressor, it shouldn't be much of an issue.

As to a reloading system, I'm inclined to ditch blow-forward for now and give blow-back a go, alongthese lines.


Unread postPosted: Thu Jan 22, 2009 3:02 pm
Author: maggotman
im dreeming of waht i could do with this what yah think ????
is is a bit heavy but i think it wud make nice fully auto marble gun ????

Unread postPosted: Thu Jan 22, 2009 4:42 pm
Author: Brian the brain
Basically, it's a Snapvalve without the resetting problem.
Now turn up the pressure ( both sides) and up the ROF about 2x.

and your done.