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hybrid mini question

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hybrid mini question

Unread postAuthor: b-nice » Sat Sep 03, 2005 10:13 am

im building a hybrid mini that is a 1.5'' sch80 chamber 12'' long sleeved with 2'' sch80 and 2.5'' sch40. this should be safe shouldn't it for shoulder and hand-held firing applications. all fittings a sch80 CPVC instead of regular PVC. I also would like to know if anyone has a idea of the expected fps.


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Unread postAuthor: spudshot » Sat Sep 03, 2005 10:47 am

what mix will you be firing it at? i would only hand hold it up to 1.5x or 2x MAX after alot of remote testing. 3x and 4x have the potential to blow unions and such, if you end up with DDT you're done for, i would NEVER hand hold a hybrid just because of the chance of DDT
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Unread postAuthor: b-nice » Sat Sep 03, 2005 12:43 pm

its design is similar to a ak-47 and will be filled gas and air through a scharader valve. no gas will be connected to the gun and the remote setup is for a 2x mix with a connection for a remote 3x mix. the rear stock of the gun will detach to attach a rear stand and the front stand will clamp to the barrel completely adjustable. i would like to add a scope and lazer beam also.

EDIT:
what exactly is DDT. sounds like ive heard it before.

EDIT2:
i plan to use around 3% propane mix also. i figured it would be a little safer. i expect it to shoot about 600+ fps but i have no clue of how to caculate the potential power.

im a comercial electrician and found the 1.5'' and 2'' sch80 along with 2.5'' and a 10' peice of the rarest size ive seen 3.5''!!! perfect sleeve for 3'' sch80. i had the 1.5'' and 2'' sch80 on a hybrid i built a year ago I didn't feel safe shooting it too many more times. plus the barrel was the newest one i had and had only been shot out of 3 times. the gun has so far only costed 60 buck and is 75% complete. will definatly post pics when finished.

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Last edited by b-nice on Sat Sep 03, 2005 4:58 pm, edited 1 time in total.

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Unread postAuthor: CS » Sat Sep 03, 2005 1:23 pm

EDIT button. Stop double and triple posting. Sound cool and also expensive. I dont remeber what DDT stands for but its when you get a perfect mixture and your combustion is alot more powerful than your typical shot. If your gun isnt built good you usally find the problem when you have DDT (dont want to find out a problem this way BOOM!) Thats why alot of these older spudgunners stress the point of making hybrids out of Sch 80 parts and to know what your doing before you do it. It can be deadly and can injure you. I definetly am looking forward to a AK potato gun so far all that Ive seen have miserably failed.
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Unread postAuthor: boilingleadbath » Sat Sep 03, 2005 1:35 pm

Acctualy, If I remember right, DDT (detonation-deflagulation transition) occurs more often with a leanmix (not enough fule). Don't quote me there, though. Basicaly, the flame front - the area where the burning is acctualy occuring - "accelerates" to a supersonic speed. This gets you a huge pressure spike - you might think of it as hitting your chamber with a hammer. If DDT acctualy occurs, even a steel chamber might not prevent a failure.

Secondly, the fittings are typicaly the weak points in a design - making multi-layer chambers is expensive and counter productive; bigger fittings are rated to lower pressures.

Thirdly, CPVC is different (chemicaly and dimentionaly) than pvc. That is, if you can acctualy glue the fittings together, the joint will be weak. Not good in a hybrid.
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