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Fuels

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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Fuels

Unread postAuthor: Jared Haehnel » Mon Mar 24, 2008 1:28 pm

Ok we all know that different fuels give a better or worse performance in the spud gun. But how much does it effect the performance? Does a advance combustion using a propane metering system give 100fps increase over a regular spud gun using aqua-net?

For the poor guy who wants the most bang for his buck its it cheaper to buy cans of starting fluid then to build a metering system if it only give a few extra fps for the relative cost?

Does this make sense to anyone? Any thoughts?
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Unread postAuthor: SpudFarm » Mon Mar 24, 2008 2:48 pm

if I were a poor guy i would just pick a pc or somethig apart and take the fan out and use the power switch for spinning the fan. then i think you can get almost the same performance out of starting fluid.

and if you think of it, if you realy need a broken computer you can get it at a school or something for $0 and you have everything you need for an easy fan setup.

to answer your question: if you are poor you stay to the aersol. if you got those few $ needed for an simple propane metering system i would go for that since you can get those really cheap.
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Unread postAuthor: rcman50166 » Mon Mar 24, 2008 3:49 pm

Well I've been told and told again that gasoline and propane have very little difference when it comes to performance of a spudgun.

BTW I know someone is going to freak out about this topic. It's been done before. So I will deliver the message before someone says something that they'll regret later. There is a page in the wiki about fuel. http://www.spudfiles.com/spud_wiki/index.php?title=Common_Fuels_for_Combustion_Spudguns
I don't care enough about the fuel to learn what all the terms mean in the chart so a thread like this would be beneficial to those who just don't know there chemicals.
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Re: Fuels

Unread postAuthor: jimmy101 » Mon Mar 24, 2008 5:10 pm

Jared Haehnel wrote:Ok we all know that different fuels give a better or worse performance in the spud gun. But how much does it effect the performance? Does a advance combustion using a propane metering system give 100fps increase over a regular spud gun using aqua-net?

Probably something like that, but not for the reason you might think.

The "spray-n-pray" combustion will under perform the metered gun not because of the relatively minor differences in the energy content of the fuels. (Hairspray is probably more than 90% butane and iso-butane anyway.)

The "spray-n-pray" under performs because you can't reproducably inject the same amount of fuel for each shot. One shot you'll have 3% fuel and the performance will suck. Then you'll have 6.5% and the performance will suck. Then you'll get lucky and hit 4% and the performance will be as good as with metered propane.

So the differences isn't so much the fuel, it's the difficulty in geting the correct amount of fuel in the chamber.

I don't believe anyone has ever looked at how much the performance of a typical combustion spudgun drops off as the fuel ratio is moved away from the stoichiometric mixture. For ICEs, you can usually get slightly more energy per cycle with a slightly rich mixture. That is why many race cars can tweak their fuel mixtures up and down by a very small amount during a race. Lean mixture minizes fuel consumption but lowers power a bit. Rich mixtures boost power at the expense of inreased fuel consumption.
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Unread postAuthor: bluerussetboy » Mon Mar 24, 2008 9:33 pm

How would/could you accurately and consistently measure AquaNet or StaticGuard to compare it to metered propane/MAPP in a real spudgun enviroment?
You can't really. It really is 'hit or miss' with 'spray and prays'.

BTW: all my combustions with Tool stickers shoot farther than your combustions with Cindi Lauper stickers :o
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Unread postAuthor: Jared Haehnel » Tue Mar 25, 2008 6:11 am

Ok that helps a lot... I'm not the poor guy by the way I'm just trying to help out the new guys...

There a lot of improvements one can make to their spud gun and I was curious to seem how much on an increase of performance it really gives...if meter propane give 100fps increase then that would be significant enough in my book to go for it.
The easiest way to measure spray can fuel would be to get and average fps over say ten shots. If you used a spud gun with the same chamber volume, barrel length and just run some tests to be able to post the results.
That way we can say...if you use this fuel, or a chamber fan running during combustion...or a muti-point ignition do you get an increase of decrease in performance....
Do some spray fuels have a huge advantage over others?
I figure if some one has a chronograph a few hours worth of testing could produce some hard facts that would be very useful to new comers or even the seasoned....it would save use from a lot of speculation 8)
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Currently buying part for...
http://www.spudfiles.com/forums/my-new- ... rt,15.html
Still on the drawing board...
C02 tank hybrid
Screen doors for submarines...
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