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| noname |
 Posted: 07/19/2007 22:23 PM Post subject: |
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Mr Vortex
Joined: 10 Apr 2006
Posts: 2509
2698.56 Spud Bux
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| You should use a regular threaded fitting for that. Drilling holes in a pipe lowers its structural integrity. |
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| PVC Arsenal 17 |
| Posted: 07/19/2007 23:17 PM Post subject: |
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WITTY PHRASE
Joined: 27 Mar 2006
Posts: 1231
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Balls. All these additions take away the "compact".
How bout tapping a brass coupling? |
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| clide |
| Posted: 07/19/2007 23:52 PM Post subject: |
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Donating Member
Joined: 06 Mar 2005
Posts: 692
1998.70 Spud Bux
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The idea has come up at least a few times before. It is also the basic idea behind DR's first hybrid except he was using a sprinkler valve instead of a piston.
It should work fine, but a more ideal valve would be something like a DFTV, which is what galfisk used in his valved hybrid. |
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| chaos |
| Posted: 07/20/2007 1:10 AM Post subject: |
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Brigadier General
Joined: 17 Jan 2007
Posts: 1222
913.08 Spud Bux
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hmmm... wat if:
instead of having the as would be on a regular co-ax a pressurized pilot area..
with this idea takes out the danger of the pilot air locking the valve shut
ok here goes
you could make a realy nice piston that was "air tight" you would then not have to worry about the pilot locking up and turning it into a pipe bomb,
and to compensate put a spring that will hold the mix before it was combusted behind the valve,
and then "i think" it would work without having to worry about the pilot area locking.
did i make a mistake or would it work? im planning a hybrid soon too  |
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| PVC Arsenal 17 |
| Posted: 07/20/2007 16:35 PM Post subject: |
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WITTY PHRASE
Joined: 27 Mar 2006
Posts: 1231
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This is back end I hope to use:
The 3/4" copper coupling fits well into the brass 1" x 1/8" bushing and it will most likely be the are the piston travels in. I will be getting a micro ball valve to prevent the schrader from leaking when the air chuck is disconnected from it.
If I'm going to shoot 1/4" ball bearings, how long of a chamber should I use? I was thinking of using 2, 3" lengths of 1" pipe, connected in the center with a coupling. Since the coupling is thick I can thread another schrader into it for propane filling and also the two electrodes.
I could always use bell reducers and make a shorter but larger chamber. |
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| wannabie |
| Posted: 07/20/2007 16:44 PM Post subject: |
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Captain
Joined: 15 Apr 2007
Posts: 308
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| Awww man i was going to do the exact same thing but i was waiting for permition to make a hybrid from my mum..... damn i might still try it though |
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| noname |
| Posted: 07/20/2007 19:14 PM Post subject: |
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Mr Vortex
Joined: 10 Apr 2006
Posts: 2509
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I'd go with 8-12," so it's not huge, but it's also not seen as some little  y piece of pipe.
If you're using brakeline as a barrel (I'd use double layered brass), the front bushing will require almost no modification. I thought of this and am using it in making a 1/4" QEV for less that $5. It's simple, and I have no idea how I thought of it (oh, the suspense), but just use a compression fitting. |
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| PVC Arsenal 17 |
| Posted: 07/20/2007 20:34 PM Post subject: |
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WITTY PHRASE
Joined: 27 Mar 2006
Posts: 1231
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Brakeline is safe to use up to 1000psi I think.
I found that 5/16" sleeved in some hobby brass tube I got, fits well into 1/4" brass pipe, which fits well into 1/2" copper. So I'll have a lot of soldering to do but it should be decent. |
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| jackssmirkingrevenge |
| Posted: 09/05/2007 13:00 PM Post subject: |
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space monkey
Joined: 15 Mar 2007
Posts: 6475
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| goose_man |
| Posted: 09/05/2007 13:59 PM Post subject: |
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Sergeant First Class
Joined: 08 Apr 2007
Posts: 138
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| One problem: how does the mix get past the piston into the chamber. Normally you have an equalization hole, but you can't here. |
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| iknowmy3tables |
| Posted: 09/05/2007 15:18 PM Post subject: |
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Brigadier General
Joined: 15 Dec 2006
Posts: 1122
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I thought of the same thing too even the poprelif valve, in fact I heard on a diffrent forum a coaxile piston hybrid has been done before but i have never seen one nor do i know if it used a poprelif
for good results you really should inject the fuel from the chammber
and lower presure pop-relif valves can be found at mc masters |
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| dongfang |
| Posted: 09/05/2007 15:30 PM Post subject: |
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Lieutenant Colonel
Joined: 27 Aug 2006
Posts: 446
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Hi,
Great design; I think it will work just fine.
You could always just inject fuel and then air from behind the piston. When you finish with air, the fuel behind the piston will be diluted to eliminate any chance of explosion on the back side of it.
I think the pop off valve will have no effect. Its opening area is 100s of times smaller than the piston area. Suppose you have 3 bars of pressure on both sides of your piston. Suppose it rests 9 centimeters from the breech. At ignition, let´s just say the pressure in the combustion chamber triples. In a static situation and with a very heavy projectile, it would cause the piston to move so that the pressure on both of its sides is adain the same. That will be at 3 centimeters from the breech. That´s going to leave a 6 cm opening!
All this is to say, the piston is going to fly back even without the pop off valve. The compression behind it will even stop it softly again.
Anyway, stand back at a goood distance when testing the "theory".
Regards
Soren |
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| noname |
| Posted: 09/05/2007 21:05 PM Post subject: |
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Mr Vortex
Joined: 10 Apr 2006
Posts: 2509
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| Jack, I fire at 6x mixtures no problem with a BBQ igniter. Just make the spark gap literally as small as possible, as long as you can still see the spark. |
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| jackssmirkingrevenge |
| Posted: 09/05/2007 21:48 PM Post subject: |
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space monkey
Joined: 15 Mar 2007
Posts: 6475
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| noname wrote: | | Jack, I fire at 6x mixtures no problem with a BBQ igniter. Just make the spark gap literally as small as possible, as long as you can still see the spark. |
Interesting, thanks for the heads up. I'm tempted to make a 6mm hybrid, for the sake of something different. I would of course be sealed up in a epoxy sarcophogus but I could make the spark gap adjustable, hmmm... |
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| Novacastrian |
| Posted: 09/05/2007 21:55 PM Post subject: |
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Bloody Aussie
Joined: 11 Aug 2007
Posts: 1622
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I use a 2mm spark gap for up to 4x mixes with a piezo JSR  |
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