Valve - modified pressure washer valve
Chamber - ~.25" x 3.5"
Barrel - 6mm x 3.5"
Ignition - lighter piezo
Mix - 1-4x
Ammo - 6mm .12gm bb's
The valve is run backward from its normal application. The spring and sealing face I replaced. The rubber ball is from a check valve in a bike pump.
The small size and low pressure is because I am testing this inside. I built it as a prototype to test the valve. And it works!
Damage sucks because of the huge dead space relative to the chamber and barrel, as well as the opening pressure. It opens at around 50 psi. But I can't crank that up because I don't have an appropriate place to test it at the moment.
Hopefully that will change soon and we can see what it'll do at 25x . (Will upgrade brass tee to steel and point spark plug in other direction first)
Edit: Tried to see what pressure the original spring would open at with a shock pump and the valve seat popped out at 200 psi. I didn't realize it was a separate peice . Back to the drawing board.
Posted: Sun Mar 22, 2009 7:10 pm
by JDP12
hm interesting. I Like it!
Posted: Sun Mar 22, 2009 7:56 pm
by psycix
Awesome! A micro-hybrid! Its so tiny.
Great job converting the pressure washer valve into a piston hybrid.
I'm sure you can fix the current issues. And when you do, I'd love to see this cute yet beastly cannon in a video.
Posted: Mon Mar 23, 2009 1:23 am
by daccel
Thanks guys.
I solved the problem of the seat coming out by making a sleeve that presses it in when the plug is screwed in. Took some trial and error to get the length right. The upper o-ring acts as a tensioner.
However, this creates a new problem of not enough flow around the ball. So I have to find something smaller about the size of the original ball, as pictured. Tried one of the airsoft bb's, but it wouldn't seal.
Also made a pill bottle suppressor which will hopefully bring the noise level down to an acceptable level. So far I've only fired it with a bundle of rags wrapped around the cannon and target. It's filled with a spiral steel dish scrubber, which may be too coarse to suck the heat out fast enough. But the only other thing I have is extra fine steel wool which would just light on fire I think.
Should be able to get a video up tomorrow, stay tuned.
Posted: Mon Mar 23, 2009 2:19 am
by starman
Really impressive work daccel...ground-breaking sizewise as far as I know. I'll be curious to know how effective your suppressor is.
Very interested to see this thing in action.
Posted: Mon Mar 23, 2009 4:04 am
by Carlman
starman wrote:Really impressive work daccel...ground-breaking sizewise as far as I know. I'll be curious to know how effective your suppressor is.
Very interested to see this thing in action.
not quite spudfarm made a 1/4" T hybrid
nice work mate!
Posted: Mon Mar 23, 2009 5:40 am
by jonnyboy
Carlman wrote:
starman wrote:Really impressive work daccel...ground-breaking sizewise as far as I know. I'll be curious to know how effective your suppressor is.
Very interested to see this thing in action.
not quite spudfarm made a 1/4" T hybrid
nice work mate!
Sticky_tape also made a pen gun hybrid I'm not sure if it was bigger than this though.
Nice mini a little messy though.
This uses your shock pump metering thing doesn't it?
Posted: Mon Mar 23, 2009 8:39 pm
by daccel
I think those were bigger if I was looking at the right threads, but who's counting. The pressure washer piston I will take credit for though .
jonnyboy wrote:
Nice mini a little messy though.
This uses your shock pump metering thing doesn't it?
And here I thought I'd slipped one by the anti-ghettoers . Yes it uses the venturi/pump system for metering.
Decided to go ahead and take some video without resolving the flow around the ball, to see what it could do.
4x into the bottom of a can:
[youtube][/youtube]
4x into soft target to isolate combustion sound:
[youtube][/youtube]
And damage pics below. The shot in the side of the can wasn't on film, but you can see the entry and exit holes. The shot in the bottom was the one in the first clip. It almost penetrated, leaving a flap bent in a bit.
Anyone know what that means approximately for velocity from airsoft experience? I don't know how to model this thing in HGDT.
I don't know how much effect the suppressor is having, because I haven't actually fired it without or without a suppressor made of a pile of rags. The videos don't do the volume justice and I don't want to take off the suppressor to find out it was actually working quite well! As I am at the limit of what I can test inside.
Posted: Mon Mar 23, 2009 11:27 pm
by Ragnarok
daccel wrote:Anyone know what that means approximately for velocity from airsoft experience?
Unfortunately, the "Poor Man's chrono" as it is known depends on the use of 0.2g BBs, not 0.12 g BBs, which will give entirely different velocity results.
There might be people out there who do know it for .12g BBs, but if the results do exist, they're going to be hard to find.
I would guestimate somewhere a little over 400 fps though, from what experience I do have with shooting cans with various low powered gubbins. That's not a guarantee though.
Posted: Mon Mar 23, 2009 11:34 pm
by jook13
Those damage shots seem to be somwhere near equal with my red ryder bb gun. I chronied it at 190 fps. Of course I am talking about .177 copper bb's. Not sure how that would translate into your setup. I would figure in the 250-350 fps range.
Posted: Mon Aug 03, 2009 2:44 am
by wannabie
Oh wow. Very nice. I didn't think you meant THAT mini.
. (Will upgrade brass tee to steel and point spark plug in other direction first)
. Back to the drawing board.
.
. Yes it uses the venturi/pump system for metering.