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ideas for multiple spark points

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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ideas for multiple spark points

Unread postAuthor: rdunajek » Wed Jun 05, 2013 3:37 am

I am building another cannon and I am moving up from the "spray and pray " style to a metered direct propane injection. I have seen some people use screws but I want some ideas on other ways. I am looking to try and have 3 spark points inside the combustion chamber. I am using a 12kv electric BBQ spark source. Any ideas?
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Unread postAuthor: jackssmirkingrevenge » Wed Jun 05, 2013 3:41 am

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Unread postAuthor: rdunajek » Wed Jun 05, 2013 6:57 am

I like that but it is less effective than say screws. What I am really wanting to know is if screws in the chamber the best way for the most power?
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Unread postAuthor: jackssmirkingrevenge » Wed Jun 05, 2013 8:19 am

rdunajek wrote:I like that but it is less effective than say screws. What I am really wanting to know is if screws in the chamber the best way for the most power?


How do you know, what did you do exactly?

It's not really about what you use as electrodes, rather the power of your ignition source and the number and position of your spark gaps.

For example, three small spark gaps in the front, middle and rear of the chamber will be more effective than a single large spark in the middle of the chamber. If you had three spark gaps but still kept them clustered together, you're not going to see much difference in power.
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Unread postAuthor: rdunajek » Wed Jun 05, 2013 3:00 pm

That's what I needed to know. I am trying to make this cannon my best one yet. Learning from my past projects, I am making this one flawless. I do appreciate your help.
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Unread postAuthor: jimmy101 » Wed Jun 05, 2013 10:54 pm

Where the sparks are probably does matter. The spark strip in Jack's link puts the sparks up against the wall and the resulting flame front is less than a hemisphere. If the spark gaps are out near the central axis of the chamber you can get spherical flame fronts for part of the combustion process. Seems to me that the optimum multigap setup would have the gaps near the chamber's axis and there would be a spark gap every chamber diameter. A 3" diameter change would have spark gaps at 1.5, 4.5, 7.5, ...

Here are a couple ways to do the wiring (and some wrong ways).
Image

you can put the wires between the electrodes inside the chamber.
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Unread postAuthor: rdunajek » Thu Jun 06, 2013 1:45 am

OK that's what I was looking for. I am not wild about drilling a bunch of screw in my chamber but what you are showing just 2 holes and multiple sparks in the center throughout the chamber. I bought everything for the propane meter today and going to sch 80 PVC tomorrow. After I get it built I will be posting pics.
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Unread postAuthor: Hubb » Thu Jun 06, 2013 5:45 pm

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Unread postAuthor: dart guy » Fri Jun 07, 2013 8:36 pm

i think that u should use 2 wires in a taser placing about 1-3 mm apart
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