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series circuit or spark gap ignition

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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series circuit or spark gap ignition

Unread postAuthor: jct0064 » Thu May 28, 2009 2:16 pm

I wanted to know if it is just opinion or if one is superior (series circuit or spark gap ignition).
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Unread postAuthor: dewey-1 » Thu May 28, 2009 2:26 pm

You may want to rephrase your question so that is understandable.

It is rather difficult to read your mind. :D


Edit; it must be in reference to this posting!

http://www.spudfiles.com/forums/viewtop ... tml#244834
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Last edited by dewey-1 on Thu May 28, 2009 2:52 pm, edited 1 time in total.
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Unread postAuthor: Moonbogg » Thu May 28, 2009 2:29 pm

Whats a series circuit?
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Unread postAuthor: Hotwired » Thu May 28, 2009 2:36 pm

Hmmm?

Spark gaps in series or parallel?

Doesn't really matter except that in parallel you need more wire.
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Unread postAuthor: Moonbogg » Thu May 28, 2009 2:46 pm

Man I still don't get it. You have a stun gun with wires attached and the electricity jumps gaps. How can it be series or parallel? No matter what the wires connect the positive and negative with spaced between. I must say...double yew tee eff.
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Unread postAuthor: Biopyro » Thu May 28, 2009 3:02 pm

Hotwired - Won't the spark only jump the shortest gap if they aren't all the same length? Because that is like giving it the choice between travelling trough 3cm of air or 1cm...

Series is better if you mean several spark gaps in series.
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Unread postAuthor: Moonbogg » Thu May 28, 2009 3:14 pm

Biopyro wrote:Hotwired - Won't the spark only jump the shortest gap if they aren't all the same length? Because that is like giving it the choice between travelling trough 3cm of air or 1cm...

Series is better if you mean several spark gaps in series.


I know you were talking to hotwired, but I get it now. It just doesn't make any sense and I think maybe thats why I didn't get it. I think you are right. It won't jump across all of them at all, it will have to make a choice lol. Of course in series, it doesn't have the luxury of choosing, it only has one place to go.
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Unread postAuthor: Biopyro » Thu May 28, 2009 3:23 pm

Yeah, I'm still not sure if that's what jct was asking!
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Unread postAuthor: jct0064 » Thu May 28, 2009 5:04 pm

Sorry, I guess I do not make sense sometimes. What I meant was- would you ignite a combustion cannon with multiple electrodes (screws close enough together for a spark to jump the gap) or would you use a spark strip. Also I should have added that I plan on putting in 5 spark gaps.
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Unread postAuthor: jimmy101 » Thu May 28, 2009 6:17 pm

I doubt you could tell the difference between say three gaps made with screws and the same number of gaps made with a spark strip.

The screw setup will usually put less material in the chamber, which will reduce the amount of heat loss. That is probably such a minor affect that you wouldn't be able to measure it without a chrony.

A spark gap will cause a "shadow" in the flame front unless it is made in such a way that the flame front can propagate in all directions from the spark. Even with a significant "shadow" you would probably be hard pressed to actually measure the affect on performance.

The spark strip is sometimes a bit easier since you only have to drill two holes in the chamber regardless of how many spark gaps you have. With screws you need two holes per gap. And, with screws you need to get the pairs of holes lined up pretty well, which isn't always as easy as it sounds.
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Unread postAuthor: Hotwired » Fri May 29, 2009 2:25 pm

Biopyro wrote:Hotwired - Won't the spark only jump the shortest gap if they aren't all the same length?


Nope.

Common sense can't win all the time :)

If it's something like a piezo then you'd probably never notice.

But if you use higher energy rapid sparking ignition like a stungun then you can see something else, yes there will still only be one spark at a time BUT every now and again the spark will quite perversely take the longer path. Not talking centimetres here, one or two mm in spark gaps of 2cm might be all the difference.

Just weird little variables that suddenly make the longer route the easiest option.

Anyway, not important, no one sane would bother doing parallel gaps including the thread starter since he actually meant something else :)
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Unread postAuthor: Moonbogg » Fri May 29, 2009 2:40 pm

jimmy101 wrote: With screws you need two holes per gap. And, with screws you need to get the pairs of holes lined up pretty well, which isn't always as easy as it sounds.


My first cannon was all glued together and as a last step I drill the holes for the spark screws. I spent the next 2 hours in bed crying and sucking my thumb.
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