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New 12V ignition idea

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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New 12V ignition idea

Unread postAuthor: Insomniac » Sun Jul 15, 2007 11:00 pm

I thought of this a while ago, and finally decided to post it.
I have figured a way to make lots of sparks continuously with a 12V motor. Basically what you do is wire a motor up so that the electricity flows through a wire, onto a bit of metal resting on the shaft of the moter, flows through the bearing and into the moters frame, through a wire and into the motor, then out and back to the power source. This means that when you turn on the power, the spindle moves and the bit of metal resting on it bounces on and off, making one tiny blue spark and lots of orange ones. The pictures of the one I made wouldn't work in a cannon because its too delicate and fiddly, but I'm sure somone on this forum would be able to make a better version to put in a cannon. One way to improve it would be to flatten the shaft slightly, and put a spring on the metal, pusing it against the shaft. This would make it bounce on the shaft much better, and still be strong enough to mount in a cannon. The one I made is bad because the shaft is too smooth to make the bit of metal (the bolt) bounce if it has any force applied to it, so it relys on gravity to hold it against the shaft.

Here are pics
Image

These are a couple of 2 second exposures while it was running.
Image
Image
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I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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Unread postAuthor: spudbud101 » Sun Jul 15, 2007 11:07 pm

Very interesting... Where did you get the motor? I'm building a combustion cannon and was looking for ignition sources, and this looks promising. Delicate, yes, but I'm sure some different materials could solve that.
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Unread postAuthor: Marco321 » Sun Jul 15, 2007 11:22 pm

We had to make a motor for school, and some of them sparked like that. You can make a very robust motor using your idea, but removing the wires and metal which you added, it can be done inside the motor itself.

For the people who understand a basic DC motor, you make the commutator uneven, and the brushes can be made out of semi-rigid copper wire. So as the motor makes a revolution, the brushes bounce of the commutator and hit it again, making a spark like was described. My method could prove to make a slightly better spark because of the resistance of the screws and motor body which the current goes through.

For those who want an explanation of a DC motor's commutator can read here Commutator and brushes You can also look on how stuff works and wikipedia for the info on the whole motor.
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Unread postAuthor: Insomniac » Sun Jul 15, 2007 11:29 pm

Marco, I like your idea, but I wouldn't make the brushes out of copper. When I was experimenting with my method copper wire hardly sparked at all, and other types like stainless steel did. Also, cutting a big hole in the side of the case would probably make ignition more likely. Adding a load to the shaft of the motor (like a fan) would probably help too.
I can see your method having a few different problems that my method doesn't have though. While the unit would be stronger and smaller, the motor would probably run faster. When I was trying my way if the motor spun too fast hardly any sparks were made. Also, the commuter would slowly wear away and bits of metal that had come off would get in it, which may stop the motor from running (I kept having to reposition the bolt because it slowly wore it away in places it had been running for a while). Although even if it did break you could just replace the motor.

And spudbud, the motor is just a $5 12V motor from an electronics store.
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I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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Unread postAuthor: Marco321 » Sun Jul 15, 2007 11:40 pm

Yeah i see what you are saying Insomniac, i didn't think of those things.
If you spring loaded the bolt it would always push against the shaft, this would allow the motor to spark at any angle and not rely on gravity. But the spring would have to be weak so the shaft can push the bolt down
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Unread postAuthor: Insomniac » Sun Jul 15, 2007 11:56 pm

I think the best way would be to put a fairly strong spring on the bolt, but flatten the motor shaft into an '0' shape. This would put a load on the moter, slow it down and make the bolt bounce more, which are all good things.
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I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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Unread postAuthor: Marco321 » Mon Jul 16, 2007 12:21 am

Thats a good idea, good luck with it, if i make a combustion I'm going to use this method
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Unread postAuthor: Insomniac » Mon Jul 16, 2007 12:29 am

Marco321 wrote:good luck with it


I have no intention of building a better one, I just wanted to throw the idea out and see what people made of it. Combustions are way too noisy for the city, and I doubt my dad would let me build a big one.
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I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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Unread postAuthor: Marco321 » Mon Jul 16, 2007 1:27 am

Lol ok, its a good idea though.
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Unread postAuthor: jimmy101 » Mon Jul 16, 2007 11:23 am

I kind of doubt that the sparks you are creating will actually ignite a propane + air mixture.

Any small commutated DC motor will create sparks at the commutator brushes. Usually, you can see the sparks if you look into the motor in a darkened room. People have tried to get those sparks to ignite a gun but nobody has ever reported getting it to work. The sparks are just too small and are not plasma sparks, they appear to be small bits of hot metal knocked off the commutator.

If I understand your wiring description, you are running the same current though both the motor and the "sparker". The impedance (resistance) of the motor limits the total amount of current (hence power) you can draw through the sparker. If you separated the two power supply lines, and switched to a kick-ass 12V power source like a car battery, you might get sparks hot enough to ignite a gun. Of course with 12V at a couple hundred amps across the sparker it is going to get fried pretty quickly.

Put it in a gun (or a zip-lock bag with propane+air) and see if it works.

I would love to be proven wrong since this would be a simple and cheap ignition system.
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Unread postAuthor: Marco321 » Mon Jul 16, 2007 11:44 pm

I kind of doubt that the sparks you are creating will actually ignite a propane + air mixture.

Any small commutated DC motor will create sparks at the commutator brushes. Usually, you can see the sparks if you look into the motor in a darkened room. People have tried to get those sparks to ignite a gun but nobody has ever reported getting it to work. The sparks are just too small and are not plasma sparks, they appear to be small bits of hot metal knocked off the commutator.

If I understand your wiring description, you are running the same current though both the motor and the "sparker". The impedance (resistance) of the motor limits the total amount of current (hence power) you can draw through the sparker. If you separated the two power supply lines, and switched to a kick-ass 12V power source like a car battery, you might get sparks hot enough to ignite a gun. Of course with 12V at a couple hundred amps across the sparker it is going to get fried pretty quickly.

Put it in a gun (or a zip-lock bag with propane+air) and see if it works.

I would love to be proven wrong since this would be a simple and cheap ignition system.


Yeah i see what you are saying, they might not be hot enough to ignite a mixture. But someone should try it.
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Unread postAuthor: Insomniac » Tue Jul 17, 2007 1:07 am

I might try lighting a butane torch with it if I get the time. I think that it would ignite, but it may be a bit hit-and-miss.
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I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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