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New Toy

Built a hybrid cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Re: New Toy

Unread postAuthor: PeteS » Wed Jan 22, 2014 6:17 pm

Also be sure the spark gap isn't gunked up with something. I have had to clean mine before, even when it didn't look like it needed it. Not sure what was the offending substance.
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Re: New Toy

Unread postAuthor: noname » Wed Jan 22, 2014 7:00 pm

I'm just crossing my fingers and hoping it's the battery since fixing anything spark plug related is going to require actual tools. I'll test it tonight and then hopefully shoot later this week!
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Re: New Toy

Unread postAuthor: jackssmirkingrevenge » Wed Jan 22, 2014 7:18 pm

Booooo sorry to hear that.

In a pinch, an ordinary cigarette lighter piezo should do the trick for sub 16x mixes. Just make sure the spark gap is around 0.5mm
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Re: New Toy

Unread postAuthor: noname » Wed Jan 22, 2014 11:01 pm

Well, as an update, I think I have a spark plug problem. I took all the wiring and the circuit apart from the gun and tried it with the old battery and the spark was weak, so I put in the new battery and tried again. A much stronger (louder/scarier) spark jumped across the same gap, which got me excited and optimistic. But when I tried the circuit again attached to my spark plug, I got the same weak, squealy spark.
So now I have to take apart the spark plug and do something with it; I can't even tell what exactly is wrong. All I know is that it's gonna be a pain to redo since there's probably 15 mL of JB Weld holding the wire in place. Maybe I just need to use something else for the electrode, like a bent screw or a paperclip?
Time to find someone who has tools...
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Re: New Toy

Unread postAuthor: PeteS » Thu Jan 23, 2014 6:46 am

Before completely redoing the spark plug, I would take some very fine sand paper to both sides of the spark gap. Also check that the connection to the ground pipe (and any other connections) is (are) good. Are any of the pipe joints the current passes through taped with teflon tape or pipe dope? How big is the spark gap? Smaller is often better.
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Re: New Toy

Unread postAuthor: noname » Thu Jan 23, 2014 11:57 am

The problem is that I can't diagnose the problem without taking the spark plug out. The problem with taking the spark plug out is I don't have any tools. The fix itself honestly shouldn't be too hard, I can always throw something together as a short term solution until I have access to my bench at home.
I have a bad feeling that my copper wire electrode might have been burnt off by excessive amounts of stun gun zapping. I'm glad the circuit is fine though; that was my biggest worry until I replaced the battery.
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I feel like having a more solid steel electrode might be better than copper wire...
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Re: New Toy

Unread postAuthor: PeteS » Thu Jan 23, 2014 1:38 pm

In the pictures it looks like the wire is probably not high voltage insulated. Could the charge voltage be bleeding off through the insulation especially since it is in contact with metal much of it's rather long length? At least that is something you can check without taking much apart.
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Re: New Toy

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Re: New Toy

Unread postAuthor: sw5amped » Thu Jan 23, 2014 7:37 pm

What exactly are using for the ignition. And obviously I'm sure u know that less than a millimetre is sufficient
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Re: New Toy

Unread postAuthor: noname » Fri Jan 24, 2014 1:16 am

The insulation is stripped off the part of the wire that's submerged in epoxy.
I really don't think that's the problem though. I'm positive it is something electrode-related just because the gun was firing perfectly every single time at home, at my friend's house when I came back to school. The gun sparked perfectly, I put it in his trunk, and when we took it out the next day, it had the spark problem. Therefore the problem must have occurred in the trunk! And since the circuit works fine by itself, not attached to the spark plug, but fails when attached to the spark plug, I'm positive it's something to do with the electrode.

I'll update this topic when I get the spark working again. Worst case scenario it'll be around 2/15, since that's the next time I'm going home. Until then, it's not worth speculating about.
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Re: New Toy

Unread postAuthor: jackssmirkingrevenge » Fri Jan 24, 2014 5:36 am

oh... when you said "spark plug" I assumed you meant an automotive spark plug.

This is definitely far from ideal.
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Re: New Toy

Unread postAuthor: PeteS » Fri Jan 24, 2014 7:23 am

noname wrote:Worst case scenario it'll be around 2/15, since that's the next time I'm going home.


Bummer that you have to wait that long but I am sure you will get it sorted out. It is a shame to have a nice cannon sitting around and not be able to use it.

A lot of the following is just my preference, presented as food for thought.

I like to use automotive type spark plugs. I found that you can get a 'VA21140 Vermont American 21140 Metric Plug Tap, Sparkplug, 10mm - 1.00mm' from autotoolworld.com for $5 plus shipping and then use a 10 mm threaded spark plug. I have been using NGK 4628 (C7HSA) spark plugs that a local auto parts place stocks.

Oh and I usually would have put the spark plug where your fill fittings are and vice versa. If you later convert to a piston valve, which I think you mentioned earlier, the plug would have to move from where it is now anyway.

As I mentioned, most wire insulation is not meant for the kind of voltage your stun gun puts out, not even close. Even the high voltage stuff I have found is technically not rated for that. I use high performance copper spark plug wire, but it is kind of expensive and I had to buy a full set of wires. A cheaper work around might be to sleeve your wires with silicone or rubber tubing.

Probably not a big deal and I may be wrong but I think it is better for the flame to burn toward the barrel. Someone did some tests and I think they said that with a single gap the best performance they found was with ignition a bit farther away from the barrel than the mid point. I don't like to drill the pipe so I just drill and tap the end cap and that puts it all the way away from the barrel.

Again, that is all personal preference so it may not be the optimum setup. I just present it as food for thought.
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Re: New Toy

Unread postAuthor: sw5amped » Fri Jan 24, 2014 7:39 am

Well of course i gotta throw my 2 cents in now!!! Just like a typical spark the spark gap should be just barely open. You could use a feeler gauge to set it to just a few thousandths. Also the gap, electrode, must be super clean from debris. If that don't work change the plug.
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Re: New Toy

Unread postAuthor: sw5amped » Fri Jan 24, 2014 8:16 am

Yo noname!!! One more thing.... i wouldn't worry about it being a wire insulation problem. If ur using a tazer for a source, and ur wire had real basic insulation on it, it would still produce plenty of voltage for ignition. U would have to have a dead short or a break in the circuit to not get spark. It is agood idea to get the hi current insulation wire just so u get all your supply to ur electrode s. Being a commercial electrician i deal with similar things.
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Re: New Toy

Unread postAuthor: noname » Fri Jan 24, 2014 1:15 pm

Thanks everyone, I'm fully aware my setup is not optimal! :D

I'm on a college student budget here, it's not my first hybrid, and it was working fine for my purposes before it decided to stop working. It'll end up being fine once I get my hands on some wrenches.
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Re: New Toy

Unread postAuthor: PeteS » Fri Jan 24, 2014 3:50 pm

Yes understood. Just to be clear I didn't mean anything I said as a put down of your gun. If it sounded that way I apologize. It looks like a nice setup and a lot of fun. I look forward to more pictures and reports when it is working again.
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