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What kind of fuel should i use ?

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: jimmy101 » Wed Dec 17, 2008 11:58 am

Xxplosive42o wrote:But he said spray and pray and keep price in mind; therefore, running a metered propane system is out of question.

Keeping price in mind the best fuel system (heck it's one of the best even if money isn't an issue) is a $0.99 disposable butane lighter with a $2 syringe and a hunk of insulation from a piece of wire.
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Cheap (<$5), accurate, easy to use. The 2cc syringe shown is good for a mini. For a more typical size gun you need a 60cc syringe. The needle shown is helpful but not required. Needles typically cost about $1.

A full blown meter system with propane tank, regulator, valves, meter pipe etc. only beats the syringe in "bling factor" and fueling speed.

Heck, omit the syringe and just use the lighter plus wire insulation. You still get a fuel system that is much easier to control then any aerosol can.

dudeman508 wrote:I tryed using some anti static spray, that i know for a fact is very flamamble, my chambre is about a foot and a half of 1in pipe and i spent about 10 minutes today trying to get the fule mix right .Is it that exact or am i doing somthing wron

Yes, fueling has to be fairly precise. The combustion limit for propane in air is about 3% to 8% (by volume). Less than 3% or more the 8% propane won't ignite.

In addition, even if the amount is fuel is correct if it is poorly mixed it still won't ignite. Gases diffuse (mix) fairly slowly and it might take anywhere from a couple seconds to a couple minutes for the fuel to fully mix in the chamber. That's why a chamber fan is often included. The fan will mix the fuel consistently and quickly. (The fan also increases the burn rate of the fuel and helps to vent the chamber between shots).

A long skiny chamber (like your 18" x 1") will mix very slowly, a short fat chamber mixes quicker.

For your gun you'll need to wait a minute or more after fueling and closing the chamber. Invert the gun slowly a few times to help mixing (propane, butane etc are denser than air). Pull the trigger. If the gun doesn't fire you need to open up the chamber and ventilate it well before trying to refuel. Adding fuel to an already fueled gun that you have attempted to fire is not recommended. The unsucessful firing will have consumed some of the fuel and oygen in the chamber.

For your chamber I would start with the shortest burst of fuel I could get my finger to do. If it doesn't fire then vent and try two of those short bursts. Keep doubling the number of short bursts until the gun fires. Once the gun fires you can fine tune the fueling by small amounts.
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Unread postAuthor: SP00K » Wed Dec 17, 2008 5:07 pm

Hairspray will eventually gum up in your chamber


Which reminds me. I need to go and clean out my gun. Sometimes I can't even get the end cap on or off it's so gunky. Yeah, I totally forgot about that. What does everyone else think of spray deodorant when it comes to cannons? *goes to try*
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Unread postAuthor: CasinoVanart » Wed Dec 17, 2008 7:15 pm

Xxplosive42o wrote:explosive ingredients.


Ermm, the word is Combustible not explosive :) As in burn, not blow-up.
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Unread postAuthor: Radiation » Wed Dec 17, 2008 7:32 pm

Another fan for carb cleaner. BUT only if you have a really big chamber. I find small chambers are just to tough to get the ultra rich mixture of carb cleaner right. Honestly it takes a very small spray to make my almost 650 cu in. chamber. If you use a small chamber it'd be very tough.

That said, quit wasting your time with Spray and pray. Build a propane metered setup.
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Unread postAuthor: jimmy101 » Thu Dec 18, 2008 12:43 pm

CasinoVanart wrote:
Xxplosive42o wrote:explosive ingredients.


Ermm, the word is Combustible not explosive :) As in burn, not blow-up.

Ermm, no, the term is explosive. Combustable gases are explosive when ignited in a confined volume.

Someone had a sig along the lines of "an explosion can be defined as a loud noise followed by the displacemnt of objects at high speed".

There are two basic "explosion" domains; deflagration (rapid burning as in a spudgun) and detonation (which hopefully a typical spudgun isn't doing). Most high speed combustions in air are deflagrations. There are realitively few fuels that will detonate in air. Usually, detonations occur only with high powered explosives specifically designed to detonate. Many explosives are deflagarants though.
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