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Need Help!

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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Unread postAuthor: nickz » Wed Sep 24, 2008 1:38 pm

I just built a combustion gun with a bbq ignitor and a automotive sparkplug, the problem is the the plug only fire if I hold the metal part of it.

I need to know how to fix this.
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Unread postAuthor: jimmy101 » Wed Sep 24, 2008 1:55 pm

Electrical circuits always require two wires, or things equivalent to two wires. When you hold the metal part of the plug you are acting as one of the wires.

Do you have two wires? On the piezo there are two electrical contacts, one may be a metal tab, the other is usually neat the tip. The plug also has two, though one of them is the metal body of the plug itself.

Run wires from the two contacts on the piezo to the two contacts on the plug. For the plug end, you can just trap the wire between the plug body and the pvc of the chamber for one of the connections.
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Unread postAuthor: nickz » Wed Sep 24, 2008 2:11 pm

There is a wire from the end of the ignitor to the plug, and there is a small wire that runs down the side of the ignitor but bothe ends are hooked up internally.
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Unread postAuthor: stevenarroyo » Wed Sep 24, 2008 3:57 pm

u can make a piezo work with a automotive sparkplug???
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Unread postAuthor: TurboSuper » Wed Sep 24, 2008 4:36 pm

Disconnect the small wire running along the side and solder a wire between it and the plug (to it's chassis I think). Should work fine after that.

u can make a piezo work with a automotive sparkplug???


Sure, a spark plug is just a spark gap made to withstand high heat/pressure, and form an airtight seal. You can hook up any HV source you want.
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Unread postAuthor: Fnord » Wed Sep 24, 2008 7:34 pm

@Jimmy: In my honest opinion, if he doesn't know that by now, he really shouldn't be messing with anything more dangerous than a squirt gun.
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Unread postAuthor: stevenarroyo » Wed Sep 24, 2008 7:57 pm

fnord are you talking about me or nickz
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Unread postAuthor: Fnord » Wed Sep 24, 2008 8:04 pm

Nickz, aka the person Jimmy responded to.
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Unread postAuthor: stevenarroyo » Wed Sep 24, 2008 8:21 pm

o ok

and thanks TurboSuper for answering my question am going to use a spark plug on my new cannon am going to make soon
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Unread postAuthor: nickz » Thu Sep 25, 2008 6:07 am

_Fnord wrote:@Jimmy: In my honest opinion, if he doesn't know that by now, he really shouldn't be messing with anything more dangerous than a squirt gun.


it came off of a grill and that wire wasn't even hooked up to anything, in fact when I started to bend the wire the whole thing came out, it was press fit and it wasn't hooked up to anything, it was just there.
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Unread postAuthor: jimmy101 » Thu Sep 25, 2008 12:00 pm

There were two electrical connections between the piezo sparker and the gap in the BBG. One of the connections may well have been the entire metal body of the BBQ.

The sparker has two connections on it. You have to find them. The plug has two connections on it. One is the end where the spark plug wire attached. The other is the metal body of the plug. In an engine, the entire engine is one of the two "wires" required for a circuit.

_Fnord, I agree. It's one thing to not be able to locate the second contact on a piezo since it is often kind of hidden. It is really scary when someone is making a deadly weapon and they don't know that all electrical circuits must have at least two wires (or wire equivalents).
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Unread postAuthor: nickz » Fri Sep 26, 2008 6:31 am

jimmy101 wrote:There were two electrical connections between the piezo sparker and the gap in the BBG. One of the connections may well have been the entire metal body of the BBQ.

The sparker has two connections on it. You have to find them. The plug has two connections on it. One is the end where the spark plug wire attached. The other is the metal body of the plug. In an engine, the entire engine is one of the two "wires" required for a circuit.

_Fnord, I agree. It's one thing to not be able to locate the second contact on a piezo since it is often kind of hidden. It is really scary when someone is making a deadly weapon and they don't know that all electrical circuits must have at least two wires (or wire equivalents).


I Knew all of that, but I thought that I would only have the use one because it would ground through the gun or me.

Also I scrapped the spark plug ignition because it wasnt igniting the fuel, So I bought a new endcap and I did a more standard ignition with two screws, now it works fine.
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Unread postAuthor: jimmy101 » Fri Sep 26, 2008 2:01 pm

nickz wrote:I Knew all of that, but I thought that I would only have the use one because it would ground through the gun or me.

Uh, OK. Remind me to never fire one of your guns after you've upgraded to a stungun. :D

You might put the piezo sparker on your tongue then click it. Just to get an idea of what a couple KV might feel like.
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Unread postAuthor: nickz » Fri Sep 26, 2008 3:43 pm

jimmy101 wrote:
nickz wrote:I Knew all of that, but I thought that I would only have the use one because it would ground through the gun or me.

Uh, OK. Remind me to never fire one of your guns after you've upgraded to a stungun. :D

You might put the piezo sparker on your tongue then click it. Just to get an idea of what a couple KV might feel like.


If I use a stun gun I will hook it up like everyone else.
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Unread postAuthor: jimmy101 » Fri Sep 26, 2008 4:46 pm

nickz wrote:
jimmy101 wrote:
nickz wrote:I Knew all of that, but I thought that I would only have the use one because it would ground through the gun or me.

Uh, OK. Remind me to never fire one of your guns after you've upgraded to a stungun. :D

You might put the piezo sparker on your tongue then click it. Just to get an idea of what a couple KV might feel like.


If I use a stun gun I will hook it up like everyone else.

Then why didn't you hook up the piezo like everyone else? :evil:

EDIT: Added
The aligator clips make it easy to move the sparker between guns. The black thing on one of the wires is a piece of heat shring tubing that gets pushed up over the bottom of the sparker's body.
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