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Gun made of Plasson pipe and fittings vs MAPP gas?

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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Gun made of Plasson pipe and fittings vs MAPP gas?

Unread postAuthor: ozoncqp » Fri Jul 23, 2010 2:10 pm

Ok hey again, it's been a while.

Right so I upgraded my guns a bit and made a new light weight version with the stuff thats avail in denmark.

at the mo I'm currently running with a golfball system, well almost.
Gun is made of 4" chamber and 2" barrel
Chamber is running a near 4.2liter and the barrel is specced for a 1.5:1 as I like that the most.

Running with a single spark unmodded flyswatter ignition as running 6 or 9 volts fried 6 of em' already.
Metered propane system inspired by tripplethunder (cheers)
and a small but crazy turbine'ish 40mm fan.

Right well heres my question, as I finally came across some MAPP gas in my local DIY shop i went bonanza, I was all LIEK GIEF! Tho my wife who I guess finally showed some interest in my "work/art" asked, "Myah, but are you sure your gun is fit for MAPP and wont go gigantic boom in yer face?"
me ;"??, Myah but it's MAPP!!"

So here I am.
The make and pressure ratings of my pipe and fittings is Plasson. All the fittings is rated PN12 that should be aproved for 12 bar.
Barrel is PN10 and chamber 7.5.
Now to translate my metrical to imperial 7.5 bar is 109 PSI and I recon reading somewhere that the highest explosion measured was around 89PSI i woulnd't have any problems would I?

When I find my card reader again I'll toss up the pictures with the gun, the golfballs, my whacked neighbourg shouting FORE! and my old satellite dish being molested.

Anyways, I guess I could just jump into it with both legs, but then again I just wanna make sure before I blowup stuff ;)
Oh and would I have to adjust my metering system? As I run 3 bar worth of 30/70 butane/propane gas in my pipe. I'm just thinking if it's that much more powerful the amount needed might need to be rescaled.

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Unread postAuthor: SpudBlaster15 » Fri Jul 23, 2010 3:04 pm

A launcher built to safely withstand propane combustion (Or the propane/butane mixture you've been using) will also handle MAPP gas without issue. MAPP is slightly more energetic, and will burn faster and produce a higher peak pressure, but the difference isn't mind blowing. It works out to a ~10PSIG increase in peak chamber pressure, and a ~3ft/s (IIRC) increase in burn rate. You will be safe to use atmospheric pressure air/MAPP with 12 bar rated pipe; the only thing you have to ask yourself is if it's worth paying 3x the price for your fuel. For me, it always has been. :D

Oh and would I have to adjust my metering system?

Yes. The stoichiometric ratio is 95.4% air to 4.6% MAPP.
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Unread postAuthor: ozoncqp » Fri Jul 23, 2010 3:29 pm

Cheers man, yeah I run with mixture on the propane/butane right now. And all I could read from the bottle is the burn temp, goes from 1800 to 2400 celcius and I found on the wiki I think that it burns about 30% faster.

Well It's time to meet up with Mr MAPP then :P
And the tripple price doesnt matter really, I havent used my first can yet and I've shot a ton already, and compared to the guns overall cost it deserves the best;)

Now you said 12bar rated pipe, thats only the fittings, the chamber pipe is only 7.5-
I still think I'm on the safe side tho, I'll grab a bottle, add 4 meter to the cable and shoot it around the house :)
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