SpudFiles

look what I've got for 10PLN (~3.6$)

bought off a site similar to ebay

lighter is for scale

POLAND_SPUD wrote:lighter is for scale

Weird. We use it for cigarettes

Good buy

So sharp is our Jack

there are several things I like about them...First off all, they are really really small but offer quite a lot of flow... they would make great triggers

now I can put the trigger anywhere I want to and use 4mm tubing and a small QEV to pilot the main valve


I've just tested a simple circuit with one of them and a single acting air cylinder...

[youtube][/youtube]

here is how it works->
the rod of the cylinder triggers the valve when its retracted... as it extends the air source is shut off and the cylinder is vented... spring returns it back to the starting position and the whole cycle continues

it's interesting to see how fast an air cylinder can cycle with one of them...

(you can also see push-to-connect fitting and tubing there ( 4mm OD X 2mm ID polyamide tube, rated to 50 bar ) ...they are really useful - you can assemble a circuit with them in a couple of seconds...


that got me thinking that the circuit could be used to mod a QDV (as iknowmy3tables suggested here ) to operate as a full auto gun... I am pretty confident that an air cylinder can open it fast enough (and probably operate the bolt at the same time)

the idea has some obvious advantages...
first of all, since there is no reason to pressurise the circuit to the same pressure as the main chamber the gun could safely use extremely high pressures


alternatively, the same circuit could be used to open a hammer valve

EDIT
video FINALLY added

nahh I don't plan to test the idea... at least not yet...
I still haven't finished my semiauto MKIII

but probably I'll first test this idea
well, actually there isn't much to test there as it's a proven design so it will work

Sounds like a plan I got mine for free, courtesy of my show-stuff-to-jack-before-throwing-it-out policy at work

jackssmirkingrevenge wrote:Sounds like a plan I got mine for free, courtesy of my show-stuff-to-jack-before-throwing-it-out policy at work

THAT'S A FANFRIGGINTATSTIC POLICY
I used to be a teacher's assistant for the tech ed department head, I was helping to clean out one of the closets since the curriculum was changing to a kit based (i.e. like legos or knex) and computer based curriculum so I pretty much was allowed to take any of it home to bad there wasn't much for pneumatics

anyways that's an excellent buy, however I'll have to stick to my blow gun mod, though I'm not very satisfied with the flow

uhmm wait a second... well I've just realized that a spool valve is almost like a QDV...
so I could use the setup presented in my video post but with a different valve (this one has only two usable ports.. the third one is just an exhaust port with an inbuilt muffler) to build a really simple full auto gun

this would be essentially the same as teh QDV idea but simpler as it wouldn't need a QDV as the 3 way valve would act as the QDV

sorry no diagram now I am too tired... but it's a fairly simple design so I'll just describe it the best I can...

build an almost exactly the same setup but use a valve with all 3 ports... the air cylinder is the chamber, 'exhaust' port is the barrel port

and voila... you've got a full auto gun...
no air is wasted as the only exhausted gas goes through the barrel... so it will be better than a pop-off QEV combo


what do you think??

@iknowmy3tables

my blow gun mod

have you posted it ??

@JSR
is it blood ??

show-stuff-to-jack-before-throwing-it-out policy at work

let me guess... he forgot to show it to you, right ? oh well... he deserved it

POLAND_SPUD wrote:is it blood ?

It could be mine, I usually dismantle such goodies with disproportionate enthusiam and there are typically lots of sharp edges

Neat. Could you introduce a flow restriction or add mass to make it cycle slower?


I'm still waiting for the taps so I can machine the block for your MKIII.
I expect em next week or so.

POLAND_SPUD wrote:first of all, since there is no reason to pressurise the circuit to the same pressure as the main chamber the gun could safely use extremely high pressures

Exactly what I did in my new cannon. My new creation has a working pressure of 1000psi. I use a regulator to reduce to 100psi for the low pressure functions. I also installed an adjustable flow control valve (clippard, about $14) to slow the speed in which low pressure components react.

@psycix
I've just tried adding mass but it didn't help much to slow down the rof... I would introduce a flow restriction but I don't have a needle valve

besides I don't think it's needed.. the ROF of the setup used in the video was only about 5 cycles per second, which seems to be an optimal value...

notice that the air cylinder retracts using a spring return... so the moment the air enters the air cylinder and causes it to extend rapidly the rod gains momentum. The spring is relatively weak so even though the valve vents it it takes a while for the rod to stop and retract (and start a new cycle)... it's the spring 9that fact that it's weak) that brings ROF to an acceptable level


It's interesting to note that air consumption was fairly low. t run directly on air pumped by the fridge compressor (no tank used) yet the pressure stayed above 250 psi (but the tubing was attached to the QC on the compressor via a blowgun connected the other way round so it was probably about 180- 200 psi)


this might be a feasible idea but one would have to use a larger valve (1/4" or larger) to fire stuff such as BBs

@velocity
wow any chance to see this gun or is it still under construction ??

Imagine a hammer that strikes the valve and the cilinder coming back to recock the hammer.

It would mean that if you pul the trigger it would keep going untill you released it.

This is PERFECT full auto material..

What is the rating and to what pressure can it actually be used?

( wait..I could also use a QEV and hammervalve like that... )

POLAND_SPUD wrote:
@velocity
wow any chance to see this gun or is it still under construction ??

I'd love to show it right now but, I'm waiting for a return letter (ruling) from NFA. It's best to get their ruling before I claim any ownership. You're on the right track with your valve idea.

You're on the right track with your valve idea

well, that seems like the simplest and cheapest way to build a semi auto gun running on HPA.
I can't wait to see that gun... Is it a semi auto ? if so how reliable it is?

What is the rating and to what pressure can it actually be used

I don't know really I haven't tested that yet
but I've used the metal ones at about 350psi and they worked fine
but the two with plastic bodies are rated to 8 bar... they can handle more because they are really small but I wouldn't like to have them close to my face when pressurised to 400 psi

This is PERFECT full auto material

it might be useful... I like its simplicity...
if you need it only to get full auto you might try it but but it might be tricky to get the air cylinder to load ammo reliably...
not that I am saying it won't work but it probably won't be as reliable as
this design

you see, the biggest advantage of the design mentioned in my post there is the fact that you can adjust the time delay between each cycle and also the fact that it's a proven design that's commonly used in pneumatics...

ohh well just watch this and enjoy (it's not mine)
[youtube][/youtube]

I thought I had the monopoly on fart machines

Looks like a fair complicated way of pulsing the ait though...