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My hyrbid will NOT fire

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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My hyrbid will NOT fire

Unread postAuthor: steven_main » Thu Oct 25, 2012 10:26 pm

Im absolutelly 100% positive Im fueling this thing correctly. I built a VERY large PVC hybrid.
I have a slightly odd shaped chamber (lots of steps) so I filled the cannon chamber with water all the way to the burst disk and it came out to be 408 cubic inches (6700CC/ML) I built a volumetric propane log with a matching pressure gauge to the one on the launcher. It happened to be 3.57 Cubic inch (58cc) from the first cutoff valve to the male air fitting. 100/95.8=1.0438 or 4.38 CC fuel per 100 CC chamber im told is optimal or stoich for propane. 67 (100)cc is my chamber so I need 67(4.38cc) fuel or 293.46 cc. Since my fuel meter came out to 58 CC I need 293.48/58=5.05 bar of propane in my meter. 5.05 * 14.7 = 74.235 PSI absolute or -14.7 to read ~ 60 psi on my gauge....

I finished these calculations, screwed the cap on my chamber, installed a burst disk of Nashua aluminum Foil Insulation tape. Put 60psi in my fuel meter and filled the cannon with the 1x charge... Boom ... 4 times with 100% reliability... Next I pressurized my log to 60 PSI fueled the cannon, repeated again for 2x. Charged the Cannon to 1 bar on the same brand/type of gauge I used on the meter.... Nothing. no light no anything. I tried pumping more air in up to 30 PSI with the same fuel and it still wouldnt light. I started letting air out and held down the trigger while doing so and One time as a fluke in lit, it was so spectacular to launch a 3 oz slug of potato at 500 Miles per hour into a tree! I didnt know a potato could cut wood like an axe!... However, the celebration didnt last... after a dozen attempts I can not get this thing to light. any ideas folks?
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Unread postAuthor: Zeus » Thu Oct 25, 2012 11:01 pm

Narrow your spark gap, as pressure increases, the distance a fixed voltage can arc drecreases. I'd use a 2-3mm gap.
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Unread postAuthor: steven_main » Thu Oct 25, 2012 11:12 pm

oh, makes sense, you do the same thing when you supercharge a car (I have a 1200 horsepower trans am drag car) Ill try it out thanks! :-)
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Unread postAuthor: Zeus » Thu Oct 25, 2012 11:15 pm

No worries mate. Good to see someone else who doesn't think turbos are the be all of performance addons.
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Re: My hyrbid will NOT fire

Unread postAuthor: jackssmirkingrevenge » Thu Oct 25, 2012 11:25 pm

steven_main wrote:I built a VERY large PVC hybrid.


What is the smallest pressure rating on your parts? On large diameter fittings I would not go beyond 2-3x.
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Unread postAuthor: Crna Legija » Fri Oct 26, 2012 3:03 am

Zeus wrote:No worries mate. Good to see someone else who doesn't think turbos are the be all of performance addons.


Turbos are for toddlers, bottles for babys, real men get BLOWN!
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Unread postAuthor: pneumaticcannons » Fri Oct 26, 2012 5:30 am

You aren't by any chance this guy, are you?
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Unread postAuthor: jrrdw » Fri Oct 26, 2012 6:09 am

pneumaticcannons wrote:You aren't by any chance this guy, are you?


No Trans Am or Hybrid so I doubt it...

Remember the smaller the gap the hotter the spark.

Is your electrodes on a strip on the chamber wall or centered in the chamber?

Did you think about using multiple spark gaps?
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Unread postAuthor: steven_main » Fri Oct 26, 2012 6:42 am

Actually I was just being vague didnt realize so many auto enthusiasts were here. From an Engineering standpoint my race car is what an engineer would refer to as Turbo-Supercharged. From an automotive standpoint its Just turbocharged baby.

402 LQ9 (LS type motor but an Iron block from a truck) LS3 Corvette heads flowing 330 CFM per port with 2.165" intake valves :-) Precision Turbo 101 MM Turbocharger and Air to water intercooler. Its a beast, and now its for sale I cant afford to run it no more.
http://www.cardomain.com/id/z28boysteve
http://www.youtube.com/watch?v=cNnjzNPE058
http://www.racingjunk.com/Outlaw-10-5/2 ... ns-am.html
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Unread postAuthor: jrrdw » Fri Oct 26, 2012 7:58 am

steven_main wrote:didn't realize so many auto enthusiasts were here.


We have everything from mechanics to rocket scientist here.....well...close to it, a rocket engine tester for sure. L0L :lol:
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Unread postAuthor: steven_main » Fri Oct 26, 2012 3:15 pm

OUCHHHHH It was spark gap, ... without a barrel or projectile it fired perfectly, I thought it was so loud like a .45 going off next to my ear... Until I tried to shoot it at 1bar indicated (2x)...... Pics to follow... PVC hybrid bad idea even at 2x.. I can't believe im alive but my arm feels broken.... CURSE WORDS !#(#*!*!)!#(#!)(#!)(!#)#!(
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