Spark Plugs

[Fnord]

yes a electric grill ignitor is a little less expensive, but its doesnt give you 100,000 volts or more like a stungun

You won't get 100,000 volts with a stungun either. Those numbers are taken from what the circuit can theoretically put out with no load applied. Add a spark gap and it'll go way down.
If you can't jump a 3.5 inch gap with your stungun, it's not putting out 100kv.

Grill igniters, seventeen dollars at walmart. Appears to be designed for two gaps and comes with a battery.
http://www.walmart.com/ip/Backyard-Gril ... t/19581268

[Bowman]

@Fnord Thanks for the link it's a great find. I just have one more question and if the answer is yes then I think I have some more designing and testing to do. Anyway, how could I get around shorting the circuit out. Because, if you just take an aluminum combustion chamber drill two holes in the side and attach two screws (spark gap) then the circuit will short out because the bolts in the spark gap will be touching the aluminum so the chamber itself will short out the circuit. I had an idea of just maybe wrapping some rubber tubing around the bolt or something that way it won't touch the aluminum. It looks like on that grill igniter they already have that so would it work?

[Fnord]

Notice the white cylindrical parts on the electrodes- it's a ceramic insulator similar to what is found in spark plugs. You could either drill a hole to epoxy them into, or go with sparkplugs as in your original idea

[Bowman]

Alright drill a hole and just insert them and they'll be fine. I know I said no more questions but are you sure epoxy will hold a seal. You see, the cannon will be powered by propane. So, it has to seal, I was thinking of attaching them with JB weld, plumbers goop, or epoxy putty. Or even all of them combined.

[Fnord]

JB weld will hold and seal fine for a normal 1x combustion. It's rated for temperatures of around 500F also. Don't try to mix different adhesives.

Spark plugs will be a little more durable, but take more work to install. It's a trade-off.

[Bowman]

By 1X combustion do you mean single shot? Because this design is semi automatic. Oh well, I guess I'll end up going with the grill ignitor because it's easier to install and the design has it to where the gun can be easily disasembled.

[jsefcik]

yes a electric grill ignitor is a little less expensive, but its doesnt give you 100,000 volts or more like a stungun

You won't get 100,000 volts with a stungun either. Those numbers are taken from what the circuit can theoretically put out with no load applied. Add a spark gap and it'll go way down.
If you can't jump a 3.5 inch gap with your stungun, it's not putting out 100kv.

Grill igniters, seventeen dollars at walmart. Appears to be designed for two gaps and comes with a battery.
http://www.walmart.com/ip/Backyard-Gril ... t/19581268

still junk in my eyes

[Bowman]

still junk in my eyes

Coming from the guy who said to hook up a stun gun to a pvc pipe.......

[mackconsult]

Built up an aluminum spud gun out of spare material. Tapped the end plate for 14 mm spark plug and wired a BBQ light to it.

It is sparking but no combustion for some reason.

Any thoughts .... the BBQ lighter was one of those cheap disposable ones ($1) at walmart.

[jimmy101]

mackconsult:
Most likely cause is a bad fuel mixture, usually too rich. For propane in air the volume of propane must be between about 3% and 8%. Percentages outside that range won't ignite regardless of the spark source.

[Fnord]

By 1X combustion do you mean single shot? Because this design is semi automatic.

1x, as in one chamber volume of air/fuel.
A 2x combustion would mean pumping in another volume of fuel and air, or adding additional oxygen. It would be considered a 'hybrid'.

Basically I was just saying it'll be fine for low pressures, but for anything else such as propane/pure oxygen, used threaded fittings.

[natas]

if u want easy to install. id say this one is really easy

http://ultimatespudgun.com/30kv-igniter-p-219.html

[Bowman]

if u want easy to install. id say this one is really easy

http://ultimatespudgun.com/30kv-igniter-p-219.html

There aren't any electrodes so I assume you use these: http://ultimatespudgun.com/electrodes-c ... p-273.html

Also, I found something even better (more expensive) but in my mind better.
http://ultimatespudgun.com/pistol-grip- ... p-274.html

I'll probably end up using these. I have no further questions. I guess this thread is done?