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Ignition again

Posted: Sat Feb 25, 2006 6:13 am
by FiveseveN
Nothing n00bish, don't worry :D , just some numbers that don't add up. As mentioned some time before, I've been working on a cannon for quite some time, not because it'a very complex system, but because I just can't seem to find a good ignition source.
I've tried the usual lighter piezo, but it's not reliable enough (the chamber is pretty big for it's spark)
I've spent two weeks making an induction electrostatic generator, but that one has to be portable, precise, efficient, and run far from humidity. Those factors just cancel themselves out. I am finishing it, though, as a side-project.
I bought a portable neon lamp, thinking - hey - this one has an inverter. I'm sure it uses high frequency high voltage. Wrong. It only puts out like 200 V. I'd step it up, but I don't have a transformer (although I hope to get a hold of one soon). I'd build a tesla coil, but I don't know it's frequency. I can barely find a transformer here; where am I gonna find an oscilloscope?!
A car ignition coil is half a month's pay, so that's out of the question. No one has even heard of a BBQ ingniter. Stun guns are probably illegal, as I've never seen one over here, so, as you can see, my options are pretty limited.

I've recently tried Rambo's idea of using capacitor discharge. I have a bank of 3 caps, 4200 uF total at 25V. The discharge is quite powerful, enough to weld the electrodes together when I touch them. Yet it can't seem to light up the damn fuel mix. And, I assure you, the mix is not the problem - it lit up with the piezo and the old fashion "hold a flame to the end of it" way.

So these are my adventures: trapped in this God forsaken country with no good source of ignition. I'll try to get a hold of a transformer, still try out some options, add another cap to the bank... I dunno. I'll ask Rambo to throw one over the border :D Keep you posted. If you can think of anything, based on my options (perhaps some new ideas), I'd appreciate the help.

Posted: Sat Feb 25, 2006 9:11 am
by Rambo
My gun have two ignitions. One is a lighter piezo sparker and the other is a capasitor.The gun didn't even fire once with the piezo and with the capasitor it didn't misfire.(well there was one but with small curent)It gives a huge spark.You better use a bigger capacitor with at least 50v.The elektrodes are imprtant too.

Posted: Sat Feb 25, 2006 10:34 am
by FiveseveN
Yes, I'd better... if only it were raining caps :lol:
You said you use a 650000 millifarad cap. That's 154762 times more than what I use :lol: I've personally never heard of such capacitance, but -hey- I'm obly 20. Plenty of time to learn. What do you use to charge it and what electrodes do you use? That kind of discharge should turn a TV on 6 feet away :D
I'll try thinner, more fusible electrodes (which should mean more sparks). Get back to you with results.

Posted: Sat Feb 25, 2006 12:11 pm
by Rambo
650000mf=0,65f The elektrodes are from some irom(I don't know what but it is soft)Better if the elektrodes are from tick, soft, easy to melt steel.In that case they give a lot of hot metal pieses flynig around.

Posted: Sat Feb 25, 2006 3:19 pm
by Atlantis
You guys are over-complicating it. Just mod a disp[osable camera and attach it to the cannon.

Posted: Sat Feb 25, 2006 3:57 pm
by FiveseveN
Atlantis, perhaps I wasn't clear enough, or maybe some people think I have the twisted pleasure of overlooking the obvious. In a nutshell: THERE ARE NO DISPOSABLE CAMERAS IN ROMANIA. The cheapest camera with a flash is around 10$. That's like half the total budget I had planned for this cannon. It may not seems like much to you, but 10$ is quite a lot over here.
Sorry for the short temper, it's just that it's been quite a frustrating search.
Rambo: do you think you can post a picture of the capacitor(s)? Maybe frame it with a ruler or some well-known object, so we can figure out it's size.