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Aluminium Chamber(Ignition Ideas????)

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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Aluminium Chamber(Ignition Ideas????)

Unread postAuthor: SPUD-U-LIKE » Sat Jan 03, 2009 5:51 am

hi all, noobies here,a few colleagues and i are in the middle of designing an aluminium spud launcher,the question we pose is How to attatch the BBQ igniter electrodes the the ali chamber without stray arc to the body,all sensible help fully appreciated
regards the SPUD-U-LIKE boys :D
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Last edited by SPUD-U-LIKE on Sat Jan 03, 2009 2:05 pm, edited 1 time in total.
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Unread postAuthor: iemand » Sat Jan 03, 2009 6:16 am

Use glue(epoxy). Just glue an insulated wire in there...
(unless you're building a hybrid)
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Unread postAuthor: Pookydarts » Sat Jan 03, 2009 8:26 am

Hang on! It IS a trick question! It was a few years ago now but the biggest problem I had with BBQ grill igniters was that they require the thing that they're screwed through to conduct part of the circuit. (As per what a cast iron or steel BBQ would do.)
Just drill and tap the fibre reinforced plastic bit through (or just drill a hole and use the lock nut) and reassemble the shroud on the inside.
Add some wires to make it remote if you want. (I can't quite remember if you have to or not...)
Then, throw the whole lot in the bin and build a pneumatic! :P
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Unread postAuthor: FishBoy » Sat Jan 03, 2009 2:20 pm

just hook 1 wire up to the chamber as a ground, then drill a holw in the chamber and put the second wire through it (insulated) until it's about 1/8" away from the chamber wall or less. I'll make a pic in a sec...

edit pic up
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Unread postAuthor: psycix » Sat Jan 03, 2009 3:22 pm

Make a threaded hole or reduce the end of the chamber to a small diameter. Or use a T piece.
Then make a plastic plug which screws in, and then have a metal rod going through the center of that.

Use the metal rod and the chamber wall as electrode points, just like the wiring in the above post of Fishboy
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Unread postAuthor: Pookydarts » Sat Jan 03, 2009 5:10 pm

For an alternate insulated grommet (is that the right word?) go to your nearest tyre sales and repair shop, and ask for a rubber tyre valve for a tubeless wheel.
Measure the bit that will end up in the hole, and drill the hole 3-4mm undersize. (Clean up the burrs)
Unscrew the valve assembly, whack your wire through it and throw in some epoxy to seal it.
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Unread postAuthor: Radiation » Sun Jan 04, 2009 1:02 pm

Question, to what ends are you using aluminum? Do you just have it lying around? Is it pressure rated? Generally speaking it's a very poor idea to just make a spudgun out of this or that. Pressure rated PVC is pretty much the best way to go in a standard combustion. Is this something you are milling yourself? More details please.
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Unread postAuthor: SPUD-U-LIKE » Sun Jan 04, 2009 5:30 pm

hi radiation,yep were machining all parts ourselves,using T6 aluminium as we believe that it has a far higher pressure rating than P.V.C (330 psi)were still at the design stage at the mo so any input would be spot on,were going along the lines of twin 4" combustion chambers 12" long with a single 2" barrel 50" long to give a 1.5:1 C.B ratio, 80mm chamber fan controlled by simple push button and release switch,4 way spark ignition system undecided as yet as we cant seem to purchase stun guns over here in good old blighty,6 line rifled barrel for greater accuracy,using fixed underslung propane with metered regulator twin ISO valves for greater fuel air mixture ratio and compressed air injection any comments welcome
regards wayne :) :)
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Unread postAuthor: SpudBlaster15 » Sun Jan 04, 2009 6:05 pm

T6 is not an aluminum alloy, it is a temper designation. Means that whatever alloy you have has been solution treated and artificially age hardened. The alloy is probably 6061, as it is the most common. 6061-T6 has roughly 15 times the tensile strength of PVC, so you're good to go.
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Unread postAuthor: sputnick » Sun Jan 04, 2009 6:37 pm

Does it have to be completely aluminum? why not just build an apparatus out of plastic tube that could be secured to the wall of the chamber, and have a spark gap made of 2 screws on either thick rigid wire or bent strip of metal, that would be my approach...
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Just a section of threaded pipe secured by plastic rings on each side, with a spark gap suspended inside.
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Unread postAuthor: starman » Sun Jan 04, 2009 7:43 pm

How about a regular everyday automotive spark plug. It's insulation properties are designed for a metalic "chamber". Just "ground" one side of your spark source like Fishboy suggested and feed the other side to the anode of the plug.

The spark positioning in the chamber won't be ideal but it should get the job done, especially if you have a chamber fan running.
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Unread postAuthor: SPUD-U-LIKE » Mon Jan 05, 2009 1:35 pm

yep 6063 T-6 aluminium,thought about a traditional spark plug from a vehicle but wouldn't that mean having a coil to produce a high tension spark then a motor to drive a magneto of some description,maybe someone could put me in touch with a supplier of stun guns over there(i presume this is an american forum as it was an american company that put me intouch) that would be willing to ship to great britain
wayne :?:
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Unread postAuthor: john bunsenburner » Mon Jan 05, 2009 2:21 pm

This is an international forum, and i am sure you will find something in GB, maybe ask ragnarok i think he lives in GB to, he might be able to help you out.
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Unread postAuthor: starman » Mon Jan 05, 2009 2:48 pm

BCarms will sell you a stun gun that is striped of its case. You'll receive it marked as a "high voltage circuit" and will make it through customs easily. A stun gun will very easily work with an auto spark plug...as would a BBQ ignitor and anything else involving an electrical arc.

Also, unless you are planning to hybridize this cannon, using aluminum is vast overkill, unless you are just going for the cool factor of course.
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Last edited by starman on Mon Jan 05, 2009 2:55 pm, edited 1 time in total.
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Unread postAuthor: Radiation » Mon Jan 05, 2009 2:51 pm

ok another question, if you are making a standard combustion spudgun why use/make a chamber that is rated for 300+ Psi? Any standard combustion is only capable of 100-120psi max. The rest is just unnecessary and quite honestly pointless ovrerkill. Perhpas if you were making a hybrid I'd would make more sense...

Edit: Statman beat me to the punch! I'm slow typing on this iPhone. :p
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