A Few Advanced Combustion Questions

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
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clemsonguy1125
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Fri Aug 13, 2010 6:15 pm

I finally got the hang of piston valves and decided it was time to try something new. I decided on a Advanced Combustion with a 3 inch by 20 inch chamber and a 5 foot 1.5 inch barrel. Ive got a few questions though.
1-I plan to use and piezo grill ignitor, Ive been seeing a bunch of cheap 1 lead ignitors, is it possible to use one of these or do I need a dual lead ignitor?

2.For the spark strip to bolt on the strip do I need to add extra couplers to put the bolt through 2 layers.

3- I have not decided on a a material yet, for a combustion I know I want pressure rated pipe, but as for the fittings, is it ok to use DWV if I use screws to re-enforce the bond? If not is www.plumbingsupply.com a good place to order from.

4-At my lowes all 3in 2 foot sections are cell core, and at my plumbing supplier they sell the pipe in 20 foot lengths, sometimes they have scraps but not always. Do any Home Depots or Lowes have pressure Rated 3 inch pipe?
Thanks Clemsonguy1125
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Gaderelguitarist
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Fri Aug 13, 2010 7:24 pm

1. Piezo grill ignitors are fine, if you're into that sort of thing...

2. Couldn't hurt to do so.

3. I've always used UHMW pipe, as it is nearly 1/2" thick. It's difficult to find, unless you live in a community where cable companies are constantly running their wires. They use the stuff as conduit.

4. It's completely possible.
so many muchness
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c11man
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Fri Aug 13, 2010 10:59 pm

for pressure rated pvc i go to true value. the prices kinda suck there on everything else but they do have solid core pvc up to 4inch. and you can get 5 or 10ft sections

for the fittings i go through www.savko.com. great prices and if you cant find the right fitting on the site just call em up. he will call manufactures and find the part for you.

and always drill through double layers
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Moonbogg
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Sat Aug 14, 2010 2:05 am

Cellcore ABS SCH40 is starting to look like the better way to go for advanced combustions. Super tough, widely available, cheap, and LIGHT WEIGHT! Plus, it doesn't shatter like PVC does. Consider it. I've used it and loved it.
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clemsonguy1125
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Sat Aug 14, 2010 10:17 am

I had considered it for the reason of it doesn't shatter but are dwv abs fittings ok to use to
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Gun Freak
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Sat Aug 14, 2010 10:42 am

I've seen advanced combustions with dwv fittings, but I'd go with pressure rated because advanced combustions can generate over 100 psi. I'm pretty sure the 3-6 inch pvc they carry at homedepot is all solid core so you should be fine.
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clemsonguy1125
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Sat Aug 14, 2010 10:58 am

If I go with abs they don't carry pressed rated fittings, but if I use PVC I will use pressure rated parts, but abs doesn't shatter if it fails so....
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c11man
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Sat Aug 14, 2010 11:11 am

if you build it right, you dont have to worry about how the material fails becuase it wont

@gunfreak. i doubt it is solid core, all big home improvment stores ive gone to have cellular core. they useualy lable it on the price tag as dwv and on the pipe is says cellular core
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clemsonguy1125
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Sat Aug 14, 2010 11:14 am

But I have to think about failure since its cellulor core, its beter to worry about failure before it happens, because its to late afterwords, Tech test it up to 100 PSI but Advanced Combustions can reach 120 PSI.
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Gun Freak
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Sat Aug 14, 2010 11:18 am

Dude, get a stick of it, and pump it up as high as you can with that bike pump of yours, and see if it bursts. Give it like 30 minutes full, and it if passes, then you can't go wrong with it in a combustion.
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clemsonguy1125
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Sat Aug 14, 2010 11:21 am

Thats the worst idea, Ive heard in a while(No Offense), what if it blows while Im pumping.
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c11man
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Sat Aug 14, 2010 11:26 am

clemsonguy1125 wrote:But I have to think about failure since its cellulor core, its beter to worry about failure before it happens, because its to late afterwords, Tech test it up to 100 PSI but Advanced Combustions can reach 120 PSI.
thats why you get solid core pvc, can more that handle the pressure
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clemsonguy1125
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Sat Aug 14, 2010 11:44 am

I may us ABS because to mant PVC combustions have failed, id much rather a ABS cannon explode than a PVC fail, I know you said if built properly it wont fail, but there have been way to many pvc guns that have exploded.
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Gun Freak
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Sat Aug 14, 2010 1:11 pm

clemsonguy1125 wrote:Thats the worst idea, Ive heard in a while(No Offense), what if it blows while Im pumping.
Dude I didn't mean stand on top of it while you pump, put it behind a corner and a big thing over it so if it DOES blow, then you're safe and nothing gets damaged except the thing over it.
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clemsonguy1125
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Sat Aug 14, 2010 2:05 pm

Yeah but i still dont like that idea, the only SAFE way to test it is hydrotest which I dont have acess to the equipment
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