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| jackssmirkingrevenge |
 Posted: 09/08/2007 1:20 AM Post subject: high velocity burst disc 6mm pneumatic |
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space monkey
Joined: 15 Mar 2007
Posts: 6676
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Not sure if this should be in the hybrid section, as that's what I intended this project to be - here's the original design idea, but I was doing some routine air testing and this was the velocity (according to my Combro CB-625 that has been tested against other chronies at over 1300 fps so I have no reason to doubt the result) I got for a 0.12 gram BB 
I was trying to see at what sort of pressure different discs would burst, and quickly discovered that across a 6mm diameter area, it's pretty high. With a single layer of ordinary transparent tape, it held right up to the maximum pressure I could give it with my shock pump (around 400 psi) and only burst when I unscrewed the fitting slightly. I ran a BB through the chrony and got 1032 feet per second, so I tried again, hence the above result 
I was going to try it as a hybrid but to be honest I think I'd rather do some more high pressure air tests for now. Here's the completed breech with an inch tape for scale:
It's interesting that in spite of the smaller chamber than the final version of my HVBB project, the velocity with 0.12 gram BBs is much higher - clearly some sort of valve bounce is the problem. Enough of that, I have more holes to make
As always, for more detailed information on using epoxy, check out the how-tos here and here.
Last edited by jackssmirkingrevenge on 09/08/2007 13:31 PM; edited 1 time in total |
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| hi |
| Posted: 09/08/2007 1:23 AM Post subject: |
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Major General
Joined: 01 Feb 2007
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i wonder if that would hurt...
thats very cool. i think making it a hybrid would be very hard. |
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| jackssmirkingrevenge |
| Posted: 09/08/2007 1:50 AM Post subject: |
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space monkey
Joined: 15 Mar 2007
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| hi wrote: | | i wonder if that would hurt... |
I don't think you'd be very popular on your local skirmishing ground
I just tried with a 16 grain 0.22 airgun pellet and got 720 feet per second - that's a very healthy 18.4 ft/lbs  |
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| wannabie |
| Posted: 09/08/2007 1:52 AM Post subject: |
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Captain
Joined: 15 Apr 2007
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wow thats really fast lol.
yeah i think it would be hard to make into a hybrid but if you could get it to work it would be worth it. |
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| jackssmirkingrevenge |
| Posted: 09/08/2007 2:21 AM Post subject: |
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space monkey
Joined: 15 Mar 2007
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| As usual (honestly, when will I ever learn?) I've put it under too much strain and it's sprung a leak. I've removed the rear section, screw the hybrid, I'm rebuilding it as a pure pneumatic for high speed testing. |
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| wannabie |
| Posted: 09/08/2007 2:26 AM Post subject: |
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Captain
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OH NOES mabye ill just have to make a 6mm hybrid... hmmm mabye...
Oh well i look forward to seeing the result of you rebuilding
BTW how long is your barrel? |
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| jackssmirkingrevenge |
| Posted: 09/08/2007 2:34 AM Post subject: |
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space monkey
Joined: 15 Mar 2007
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| wannabie wrote: | | OH NOES mabye ill just have to make a 6mm hybrid... hmmm mabye... |
If you can get your hands on the right materials, I don't see why that should be a complex undertaking.
| Quote: | | BTW how long is your barrel? |
37 inches |
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| wannabie |
| Posted: 09/08/2007 3:07 AM Post subject: |
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Captain
Joined: 15 Apr 2007
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37 inches... thats like nearly a meter right?
is your barrel 9/32's or somthing? |
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| jackssmirkingrevenge |
| Posted: 09/08/2007 3:09 AM Post subject: |
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space monkey
Joined: 15 Mar 2007
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| 94 centimetres, my barrel is 7mm O/D 6mm I/D brass tube. |
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| spud yeti |
| Posted: 09/08/2007 3:10 AM Post subject: |
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can i change this name
Joined: 08 May 2007
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| wow, nice speeds! I agree that you should just screw the hybrid and make a pneumatic |
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| experament-u2 |
| Posted: 09/08/2007 3:24 AM Post subject: |
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Lieutenant Colonel
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| jackssmirkingrevenge wrote: | | As usual (honestly, when will I ever learn?) I've put it under too much strain and it's sprung a leak. I've removed the rear section, screw the hybrid, I'm rebuilding it as a pure pneumatic for high speed testing. |
oh well its very impressive for a pneumatic and i would love to see a video of it shooting
good luck with fixing it and getting it to shoot faster and better |
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| jackssmirkingrevenge |
| Posted: 09/08/2007 3:30 AM Post subject: |
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space monkey
Joined: 15 Mar 2007
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| experament-u2 wrote: | oh well its very impressive for a pneumatic and i would love to see a video of it shooting
good luck with fixing it and getting it to shoot faster and better |
It's already curing, I'm going to leave it till Monday to make sure it's completely cured, I'll definitely make a few videos afer that |
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| wannabie |
| Posted: 09/08/2007 3:30 AM Post subject: |
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Captain
Joined: 15 Apr 2007
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| jackssmirkingrevenge wrote: | | my barrel is 7mm O/D 6mm I/D brass tube. |
Hmm thats odd, when I went to my local hobby shop to see if they sold brass tubing they did, but it was all mesured in imperial... |
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| jackssmirkingrevenge |
| Posted: 09/08/2007 3:40 AM Post subject: |
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space monkey
Joined: 15 Mar 2007
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| Joys of living in Europe 9/32" is around 7mm, so it could be close. Best thing is to take a vernier caliper or actual BB with you to the shop to see what fits well. |
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| wannabie |
| Posted: 09/08/2007 4:49 AM Post subject: |
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Captain
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Mabye ill just take a BB and see which one it fits best in  |
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