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Made the holes too big!

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Made the holes too big!

Unread postAuthor: jimmy163 » Wed Jan 28, 2009 12:57 pm

Right so I am using a lighter sparker for ignition. It is fairly weak but can create sparks around 1.5cm long which works well.

The bolts I originally was using are too thick for the electricity to go through and as such only make sparks 1mm long!

I have some thinner screws I would like to use however I already have 2 bolt size holes in my combustion chamber.

How do I go about making these smaller? I am guessing hot glue and then screwing them through will not be strong enough and will pop out upon combustion?

Any ideas?
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Unread postAuthor: SpudsMcGee » Wed Jan 28, 2009 1:07 pm

Epoxy putty... It seals great and won't pop out.
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Re: Made the holes too big!

Unread postAuthor: jackssmirkingrevenge » Wed Jan 28, 2009 1:22 pm

jimmy163 wrote:The bolts I originally was using are too thick for the electricity to go through


As far as I know, the thicker they are, the easier the electricity can pass through it...
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Re: Made the holes too big!

Unread postAuthor: starman » Wed Jan 28, 2009 1:49 pm

jackssmirkingrevenge wrote:
jimmy163 wrote:The bolts I originally was using are too thick for the electricity to go through


As far as I know, the thicker they are, the easier the electricity can pass through it...


Exactly, you can't get too large when it comes to conductors....your large screws aren't your problem.

Take a photo of your setup and post it. Make sure your HV wires are well separated and not criss crossing. Chances are you are arcing outside of you chamber somewhere.
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Re: Made the holes too big!

Unread postAuthor: Ragnarok » Wed Jan 28, 2009 2:46 pm

starman wrote:Exactly, you can't get too large when it comes to conductors....your large screws aren't your problem.

Unfortunately, that's not the case.

The natural capacitance of the conductors can affect the situation, particularly given the high voltages and limited energies. In fact, over generosity on cabling and electrodes can actually be a big issue as to why sparks are rather small.

It's a possibility that he's right about them being too large. For those exact reasons, it's actually better to have modest cables for a sparker than beefy ones - remember, the resistance of the wires is insignificant next to the resistance of the air gap.
Small wires won't affect the resistance notably (but they should still be kept short), but it will cut the wire capacitance, so a lot of cannons could probably be getting more spectacular sparks if they had lesser wiring.

Another reason screws will work better is that electrical arcs jump better from points (like screw-tips) than the blunter ends of bolts.

EDIT: Spielung.
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Last edited by Ragnarok on Wed Jan 28, 2009 2:57 pm, edited 1 time in total.
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Unread postAuthor: psycix » Wed Jan 28, 2009 2:50 pm

Some bolts have a coating or some other treatment and they do not conduct well. But usually any bolt will do.

Note that the gap in your chamber should be 1mm or less.
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Unread postAuthor: jimmy163 » Wed Jan 28, 2009 2:56 pm

Never mind. Fixed it. I think the distance was a bit off.

Anyway I soldered on some wire to the bottom of one of the bolts and freyed it out. Now it will zap one on every click.

Hopefully it will be enough to ignite.

By the way, anyone wanting to test a sparker already installed, I hooked up my DV cam to the TV and pointed it down the gap.

My trigger is too far away to click and look down the tube, so the DV cam came in handy. :D
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Re: Made the holes too big!

Unread postAuthor: starman » Wed Jan 28, 2009 4:06 pm

Ragnarok wrote:
starman wrote:Exactly, you can't get too large when it comes to conductors....your large screws aren't your problem.

Unfortunately, that's not the case.

The natural capacitance of the conductors can affect the situation, particularly given the high voltages and limited energies. In fact, over generosity on cabling and electrodes can actually be a big issue as to why sparks are rather small.


I doubt greatly that capacitance is a significant problem for him in this install. I would tend to go with psycix assertion that screw coatings could have limited solid conductivity and my original wiring issues.

In any case, it looks like he's figured out his problem.
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Re: Made the holes too big!

Unread postAuthor: Ragnarok » Wed Jan 28, 2009 4:53 pm

starman wrote:I doubt greatly that capacitance is a significant problem for him in this install.

At the 30 to 50 kV of a typical sparker, even the tiniest capacitance starts to eat energy fast. No, it's probably not a critical issue, but that doesn't mean that it's a good thing.

Most likely, simply having pointed electrodes will be a much bigger advantage.
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Unread postAuthor: Combustion Monkey » Wed Jan 28, 2009 6:09 pm

And again, a noobs two cents. You can never throw too much power at your spark.
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Unread postAuthor: Ragnarok » Wed Jan 28, 2009 6:15 pm

Combustion Monkey wrote:You can never throw too much power at your spark.

I would have it that you certainly can...

[youtube]http://www.youtube.com/watch?v=PXiOQCRiSp0[/youtube]

Actually though, that reminds me of a plan I had to use a Marx generator to generate a chamber length spark to basically ignite the chamber almost instantly.
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Unread postAuthor: Combustion Monkey » Wed Jan 28, 2009 6:22 pm

Ok Rag, you got me on that one but how many of us have access to such technology on a practical level :wink:
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Unread postAuthor: Ragnarok » Wed Jan 28, 2009 7:17 pm

Combustion Monkey wrote:but how many of us have access to such technology on a practical level

Not many perhaps, but you will note that your statement was entirely without any ceiling to it, but beyond a certain point, more spark is unnecessary. If you've run a spark along the entire chamber, that is probably more than enough.
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Unread postAuthor: inonickname » Wed Jan 28, 2009 7:45 pm

Good to see you have it sorted, but still take to those bolts with a dremel, file or bench grinder and maker them into sharp points (consider you still need to get your hands in the occasionally). Up to you, but it will work better. Theres much less resistance jumping from a pointed to a pointed gap, rather than a blunt to blunt.

Good work on using your head and fixing it, most newer members would just wait to be spoonfed information.
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