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auto-piston prototype

Built a BB Machine Gun? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: Sticky_Tape » Wed Mar 12, 2008 7:25 pm

Why didn't you make somthing like this it would be alot simpler and you could hook up your blow forward brech if you make another one :P
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Attachments
untitled.JPG
it uses a pop-off safety valve as the pilot.
untitled.JPG (15.6 KiB) Viewed 1387 times
untitled.JPG
This is the revised edition it has a larger chamber to make up for dead space throught the system if linked with a blow forward brech and it also has a weak spring to help push the piston back.
A side note that the constant flow of air into the pilot chamber may slow the piston down a bit it wont stop it completly due to the restrcted flow into the pilot chamberand the fact that the pop off would have a higher flow.
untitled.JPG (10.52 KiB) Viewed 1364 times
Last edited by Sticky_Tape on Wed Mar 12, 2008 9:06 pm, edited 1 time in total.
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Unread postAuthor: keep_it_real » Wed Mar 12, 2008 7:31 pm

a blow forward breech connected to the piston is generally more reliable. The opening time (if there is one) in the valve above would be slower because it's refilling while the pop off is open.
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Unread postAuthor: Sticky_Tape » Wed Mar 12, 2008 7:51 pm

keep_it_real wrote:a blow forward breech connected to the piston is generally more reliable. The opening time (if there is one) in the valve above would be slower because it's refilling while the pop off is open.
The pop off would be open so the air would exit out the pop off and when the pressure gets low enough the pop off closes and there is also restricted flow. And JSR s attempt on the blow forward bolt was to get full auto but couldn't because the flow wasn't pulsed and this little device provides pulsed air and I think Jsr is also after slower rof that would sort of sound like pop... pop... pop... pop... pop... pop... pop... pop... pop... pop... as you see there wouldnt be too much ammo wasted un like a cloud that is like hiss bruuuuuuuuuup!!!
EDIT: I was thinking that there could also be a regulator to control the pressure into the pilot chamber and a valve after it the regulator would be to somewhat control the rate of fire that's probably be somthing that jsr fancys.
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Last edited by Sticky_Tape on Wed Mar 12, 2008 10:13 pm, edited 1 time in total.
You can tell how awesome a cannon is by the pressure used.
http://www.spudfiles.com/forums/high-pr ... 12803.html
xnt rnm ne z ahtbg
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Unread postAuthor: Sticky_Tape » Wed Mar 12, 2008 8:47 pm

I was thinking that there could also be a regulator to control the pressure into the pilot chamber and a valve after it the regulator would be to somewhat control the rate of fire that's probably be somthing that jsr fancys. sorry forgot not to dubble post I tried to delette this and edit the other post but this post wouldn't delette.
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You can tell how awesome a cannon is by the pressure used.
http://www.spudfiles.com/forums/high-pr ... 12803.html
xnt rnm ne z ahtbg
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 14, 2009 5:09 am

Just a heads up, I'm giving this concept another go, this time with an adjustable pop-off valve as a pilot. I found a female threaded section that fits the valve perfect, so it will be removable and allow me to adjust piston spring tension. The vertical brass tube will be connected to an air chamber (which in turn will be connected to an air supply) while the horizontal tube will feed into an as yet undecided reloading mechanism.

You also might recognise the breech and piston as being recycled from the failed marker project - to avoid the same fate as the latter, all will be comprehensively encased in epoxy ;)
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all lovingly encased in epoxy, waiting for it to cure :)
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Unread postAuthor: ALIHISGREAT » Wed Jan 14, 2009 12:19 pm

i hope it works, you deserve some sucess from your many efforts :D
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 14, 2009 12:28 pm

ALIHISGREAT wrote:i hope it works, you deserve some sucess from your many efforts :D


I'm quite confident it will, the pop-off pilot formula is a proven one, indeed my first prototype functioned in this manner. The advantage here is that not only do I have fine control over the pop-off pressure, but also I can make sure there's enough tension in the piston spring for the chamber to fill without exhausting through the "barrel" while also allowing the piston move when the pop-off actuates.

I'm hoping for a much more powerful blast of air that will give me the confidence to turn it into a properly completed mag-fed auto launcher, and a more relibable firing cycle than I got using just the pop-off.
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Unread postAuthor: Brian the brain » Wed Jan 14, 2009 5:17 pm

It's all starting to look familiar now..THe set up that is..not the actual parts.

This sleak design looks to be quite effective at high pressures.
THe pop-off is quite big compared to the main valve, wich should give you very good results...


Now finish the damn design buddy!
It looks to be a winner this time!
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 15, 2009 2:29 am

Brian the brain wrote:It's all starting to look familiar now..THe set up that is..not the actual parts.


Nothing original, I know, but I had to give it a go.

The pop-off is quite big compared to the main valve, wich should give you very good results...


This is one of the reasons why I'm confident, 1/4" pop-off pilot when I usually get great results with just a schrader :) testing in a couple of hours, fingers crossed ;)

I gave it a quick go and it sounded extremely angry and promising, but started to leak so there'll be a bit longer to wait for full test results I'm afraid.
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 16, 2009 12:20 pm

Update - no luck :? tweak as I might I just couldn't get the valve to pop. It either leaks slowly or seals completely. I'm guessing it's because a valve this size needs a bit of volume to force it open and in this case, the tiny pilot volume worked against me.

Bach to the drawing board, bigger piston this time.
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Unread postAuthor: Brian the brain » Mon Jan 19, 2009 4:12 pm

Darn-it!

Seems there is just no way of by-passing the hunger for gas of a full auto rig.

So maybe an autococker design ís the best way...

But that is not what we're after...
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 20, 2009 1:37 pm

Brian the brain wrote:Seems there is just no way of by-passing the hunger for gas of a full auto rig.


We could always try a more efficient pop-off,take a look;)
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