Generating Sparks

[dknguyen]

If I wanted to generate a spark to ignite the fuel mist in my potato cannon, could I just hook up a 9V battery to a step-up transformer where the secondary coils have 2 wires running out of them where the exposed ends are very close together but not touching? The change from 0 to 9V would generate a momentary AC voltage to produce a momentary spark across the air gap between the output leads?

What about the resistance for transformer coils? Is it be low enough to cause a DC short down the primary coils if the 9V battery was left connected?

 

[Oznog]

It'll arc over the insulation in a normal transformer in a flash. It needs much more than the 120v * 1.414 those windings were designed for to make an arc. You need several kV here to make a spark plug spark.

A BBQ grill ignitor, or ignition coil (and preferrably with its electronic ignition box) off a lawn mower/scooter/whatever. Yes the primary can easily overheat. You really want an electronic circuit that pulses the transformer primary, not rely on the button to only be pressed really really briefly. It only takes like a millisecond to charge up that transformer primary, something beyond human speed. Anything more is not helpful and may cause burnout.

 

[mramos1]

Nigel is freaking out now.. So this is what they do in there spare time!

Hey, on the good side, my 16F628A chips showed up today, and I am about to go back to assembler (3 weeks of compilers, and I give up). And 12F509 came in too. I should have gotten 12F629, but too late now. And lots of 15-22pf caps and 32K xtals (man are they small)...

Anyway, the BBQ piezo will work great. The push button kind, not the spin with you fingers type.

Also, Aqua-net hair spray, misted in the tube is the best brand... But hair spray works well as a fuel. And people put that in their hair???

Mind you it was years ago, and I did it for "my kids".. That is how I know this.

 

[dknguyen]

Asd

My friends wants to use a gasoline spray...because he says it's more effective and cheaper than hairspray...probably won't do that until the ABS pipe is switched to aluminum.

You did it for your kids? DOes that make it better? Or worse...?

 

[mramos1]

Did it for my kids

hahahaha.. Not sure, no one was hurt and we had a great time. They will always remember those days. And I never said how old they were.. hehe.

Not sure I would have used gas mist though.. Engine starter fluid is cheap too if you are looking to blow something up. We just wanted to lanch spuds and did (into the Ocean).

Also, if you file the tip (bevel it inward like a spear) you can stab the spud, and use a mop handle to shove them down. We had a good system.

Oh shoot.. Tomorrow is 6-6-06 I better get to bed or hide or something...

 

[dknguyen]

Ours is supposed to more of a mortar type than a gun because I don't want to be anywhere near the thing, let alone holding it when it goes off. SO my theory is, if you aren't going to be holding it, perhaps you should give it a big enough kick so that you can't hold it and make it worthwhile.

 

[Oznog]

My friends wants to use a gasoline spray...because he says it's more effective and cheaper than hairspray...probably won't do that until the ABS pipe is switched to aluminum.

Sounds like a TERRIBLE idea.
Let me count the ways:
1. Gasoline must be in vapor form to ignite explosively. Unless you have a pressurized fuel injector, that's not going to happen.
2. Gasoline in the LIQUID state, due to imperfect injector spray or waiting too long, will spray out and set things on fire.
3. Gasoline is way messier. You're likely to get some on your hands or leaking somewhere. Yeah, about the same time you're igniting the other gasoline in the tube.
4. Bet aluminum is more likely to break than the PVC (and do you even have access to a TIG welder??)... and it's going to be really, really damaging to you if it does.

Tell your friend to lay off the crack pipe. The plans out there are dangerous enough without making insane modifications to them. They can throw a potato a good portion of a mile on a spritz of hairspray... and you think that's not enough?

Slightly less insane would be a propane system, which should not be in a liquid state so it's considerably safer. Yet completely unnecessary. In fact I think the combustible component of hairspray is propane or a close relative thereof.

 

[dknguyen]

hmmm

I see. Noted.

 

[HarveyH42]

Sounds like a TERRIBLE idea.
Let me count the ways:
1. Gasoline must be in vapor form to ignite explosively. Unless you have a pressurized fuel injector, that's not going to happen.
2. Gasoline in the LIQUID state, due to imperfect injector spray or waiting too long, will spray out and set things on fire.

Wow, flames! That would be really cool for night time launches, especially with Fourth of July coming up...

 

[Hero999]

If I wanted to generate a spark to ignite the fuel mist in my potato cannon, could I just hook up a 9V battery to a step-up transformer where the secondary coils have 2 wires running out of them where the exposed ends are very close together but not touching?

That will work with an ordinary mains transformer, a 9V battery and a capacitor, but it's true be careful as there is a risk of damaging the insulation. I recommend a 12V to 240V 1A mains transformer a 1000uF capacitor and a 9V battery connected as a pulse voltage doubler which can be made in a number of ways.

A piezo will work also, but I've been told that they're not that reliable and you can't have a long cable as the short weak pulse they produce quickly gets absorbed by the capacitances in the cable.

 

[RODALCO]

Back in The Netherlands we blew up Calcium Carbide, from a 30 litre steel milk tank with jammed lid during New Years day.
It gave an enormous bang.
I made one with a welded sparkplug in the back, used a 12 volts car coil and 12 volts car battery with a 12 volts relay + push button.
It worked great. When the Calcium Carbide got wet acythelen gas was created which was explosive and gave a hughe bang.
Also a 240 / 12 volts ac transformer can be used to trigger lots of sparks at the same time.
Some trial and error are required for the best output sparks.
Be cautious when working with 240 Volts mains and put everything in a insulated controlbox, so BE SAFE here.

 

[HarveyH42]

I think an unpleasant shock off the mains is the least of this guys worries...

 

[Nigel Goodwin]

I think an unpleasant shock off the mains is the least of this guys worries...

Notice he used to be in the Netherlands?, and he's now in New Zealand - Britain used to use Australia as a penal colony, perhaps the Dutch still use New Zealand for the same purpose?

 

[RODALCO]

You could say so, Some Dutch names here too like Cape Maria van Diemen up north of the North Island.

This is a great country to live in and lots of space and nice beaches.

Raymond