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hybrid questions...

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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hybrid questions...

Unread postAuthor: spudthug » Thu May 31, 2007 7:57 pm

ok well i am building my first hybrid (yay! :D ) andmy freind and i *found* a huge fire extinguisher in his basement... we are using it for my hybrid...i do not completly understand hybrids though...

things i need to know:

1. how do i get the ci (cubic inches) of my chamber?

2. can i fill my gun with air through my propane metere if it has a ball valve on it and i shut the ball valve going to the propane?

3. i do not really understand mixes and i need some help from all u hybrid experts out there...

for example in a 1x mix how much psi is put in and how much propane...

and in a 2x mix all the way to 6x mix if u could...


do not yell at me but i am a noob with hybrids and i want expert advice before i die with mine...
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Last edited by spudthug on Sat Jun 02, 2007 9:51 pm, edited 2 times in total.
4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: hi » Thu May 31, 2007 8:05 pm

for the area take the area of the bottom of that tank and multiply it by the hight of the tank

you need to add one atmosphere of pressure for every time you want to go up a mix. for example, for a 3x mix you need three atmospheres of pressure.

one Atmosphere = about 14.7 psi. so 2x mix= 29.4 psi of air + propane.

make sence?
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Unread postAuthor: spudthug » Thu May 31, 2007 8:10 pm

yes thats what i was looking for hi..thank you so much...now i understand mixes yay!! but could it be like 15 psi+propane for 1x,30psi+ double propane for 2x,45psi+tripple propane for 3x, and so on? or do u jsut fill it to the normal propane pressure in the metering pipe?

any more help appreciated
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: spudthug » Thu May 31, 2007 8:23 pm

oh and btw some other things...

how high of a mix can a 28.5"x7" Fire extinguisher take that said tested to 585 psi on it go??

if my chamber is 129.5 cubic inches (18.5x7), and my meter pipe is 1/2x10", would 25 psi be the right pressure to put into it??

and i have this brass pipe that is 1/2"x10" with 2 nobs sticking out in the middle that are 1/4 female adapters (molded that way i found it in my basement) can i use one 1/4 adapter for the psi guage and another for the air input? or can i not fill it through my propane meter also...?
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Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: hi » Thu May 31, 2007 8:25 pm

you can fill through the meter, but you have to have some way to shut it completly off from everything else because you dont want extra propane in it.
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Unread postAuthor: mark.f » Thu May 31, 2007 8:29 pm

hi wrote:you need to add one atmosphere of pressure for every time you want to go up a mix. for example, for a 3x mix you need three atmospheres of pressure.

one Atmosphere = about 14.7 psi. so 2x mix= 29.4 psi of air + propane.

make sence?


One atmosphere is 14.7 PSI<B>A</B>, meaning it would read 0 PSI on a pressure gauge. For a 2x mix, he would add 8.4% the chamber volume of propane, and then 14.7 PSI of air off his pressure gauge.
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Unread postAuthor: spudthug » Thu May 31, 2007 8:30 pm

yea like have two ball valves on the end of the brass and one on teh quick connect..shut the one off leading to propane source and leave the one leading into the chamber open....


One atmosphere is 14.7 PSIA, meaning it would read 0 PSI on a pressure gauge. For a 2x mix, he would add 8.4% the chamber volume of propane, and then 14.7 PSI of air off his pressure gauge.


mark im not good with this stuff...so i have no clue what u are talking about... for a 1x mix how much propane and how much psi would i need... for a 2x mix how much psi and how much psi and propane would i need, and so on...
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: noname » Thu May 31, 2007 10:29 pm

1x, 1 propane injection, 0 psi
2x, 2 propane injections, 14.7 psi
3x, 3 propane injections, 29.4 psi
4x, 4 propane injections, 44.1 psi
5x, 5 propane injections, 58.8 psi
6x, 6 propane injections, 73.5 psi

Hope that helps.
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Unread postAuthor: spudthug » Fri Jun 01, 2007 5:37 am

oo so there really isnt a 1x mix??

thanks no name that clears it up...

any other help appreciated.

how high of a mix can a 28.5"x7" Fire extinguisher take that said tested to 585 psi on it go??
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: Velocity » Fri Jun 01, 2007 9:23 am

Depending on the pressure of your other materials (lets say the fire extinguisher has the lowest pressure rating of all your parts), then I think it should be able to go up to a 4X mix. Many people would disagree with me, saying possibly a 5X or 6X mix (I'm usually pretty conservative in the pressures which I use in spudguns). Anyways, I heard that using about a 4X in ANY hybrid risks DDT (Deflagration to Detonation Transition). Maybe a fire extinguisher could hold the pressure spike created by DDT... but maybe not.
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Unread postAuthor: spudthug » Fri Jun 01, 2007 11:06 am

i was thinking my extinguihser could hold atleast a 5x mix maybe a 6x..but i was worried about ddt to...
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: spudthug » Fri Jun 01, 2007 2:38 pm

hey guys i was wondering what the best setup in a hybrid for ignition wqith a bbq ignitor? nails would leak, im not a big ignition expert im in to pneumatics...
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4" piston valved cannon-half done..( i spilt my cement...)

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Unread postAuthor: Fnord » Fri Jun 01, 2007 3:50 pm

For ignition I just drilled through the thickest fitting I could find and epoxied+superglued to seal it. Since you are using a FE I would attach a short piece of steel pipe between the union and the FE tank and make holes in it.
You could put lengths of coathanger back into the chamber to form a sparkgap after you run wire through holes you drilled.
you'll need a very small gap(1/8" or less) for a bbq ignitor to work with higher mixes.

(also, since you are using a chamber you are unsure of, remote firing is a must. You will probably save yourself time in the long run by using a stun gun or ignition coil).
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Unread postAuthor: noname » Fri Jun 01, 2007 7:32 pm

You can always put the wire through an aluminum rod....
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Unread postAuthor: spudthug » Fri Jun 01, 2007 8:35 pm

i think i am going to get a stungun...actualy i know i am..so i need some ideas for stun gun ignition...any help appreciated
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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