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Insulating the motor in a spark gap

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Jrz126

Fri Mar 10 2006, 12:48AM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

I'm working on the spark gap for my TC right now. (its going to be async. since I dont have a sync. motor).

Me thinks I need to isolate the motor from the electrodes. My dad will be able to machine some parts for me at work.

This was the first design I came up with, just using some rubber between the motor and the disk. I think home depot has some large nylon bolts that I can use to hold them together.

How thick should I make the insulation?

I'll post more on this later...the girlfriend is getting angry

[Edit: Fixed oversized picture.]

Desmogod

Fri Mar 10 2006, 12:52AM

Registered Member #139 Joined: Sat Feb 11 2006, 11:01AM
Location: Perth, Western Australia
Posts: 358

Be careful of the shear strength of the nylon bolts.
Could be quite interesting if it came apart

HV Enthusiast

Fri Mar 10 2006, 01:23AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Just a few things . . .

1. You need to make the rotor out of a non-conductive material such as G10, Phenolic, etc... A conductive rotor as you propose is just askng for problems. You are already going to machine a rotor, so why not do it right and use the right material.

2. You should never use Nylon bolts for an application like this. They will shear off and have the possibility to cause great injury should the rotor fly off. You should only use normal bolts to attach the rotor (steel, etc...)

3. Rubber insulation will just cause the motor to wobble, and cause the nylon hardware to fail even sooner.

Hazmatt_(The Underdog)

Fri Mar 10 2006, 03:58AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Don't use that design!

That thing is going to wobble like mad! Any slight vibration inherent in the motor coming up to speed will get amplified in the disk, and if you hit resonance it will all explode!

You need a solid fixture for your terminals, even if its Lexan or whatever.

HV Enthusiast

Fri Mar 10 2006, 02:25PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

You could also try for a propellar design, although these are more dangerous. Here is my propellar design i made awhile ago and it worked quite well . . .

http://www.easternvoltageresearch.com/oldwebsite/teslacoil9.htm

Jrz126

Fri Mar 10 2006, 11:21PM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

Is that 1/8" tungsten in your propeller design? how did it work out? I was thinking about using that size.

My dad would be using the machines at work for this. (a very nice 5 or 6 axis lathe/mill cnc machine). I dont think he'd be able to get away with machining anything other than steel.
I've got another design that I'm working on. I'll post a couple of pics later tonight.

Also, I'm using the teslamap software for my calculations, and for the tank cap, it has a couple of different values. one for a static gap and another for sync. which would I use for an async gap?
and what would happen if I went slightly above that value. (11.6nF instead of 10.1nF)?

colin heath

Sat Mar 11 2006, 01:59PM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

Hi There,
make the propellor gap safe by using brass threaded rod for the flying electrode you then reduce risk of it slipping through centre housing. I did this and it worked great with no machine tools needed( although i have them)
Cheers
Colin

HV Enthusiast

Sat Mar 11 2006, 02:46PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Jrz126 wrote ...

Is that 1/8" tungsten in your propeller design? how did it work out? I was thinking about using that size.

Yes, this was 1/8" thick tungsten rod which was purchased at McMaster. Propellar gaps are very dangerous and should be completely shielded with an enclosed container. If the brass rod works, then this would be a good solution as well as a safer one.

Jrz126

Sat Mar 11 2006, 09:09PM

Registered Member #242 Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210

I was curious as to using that diameter of tungsten. 1/8" is pretty small.
Whats a good price for it too. the local welding supply place has 2 6" 1/8" rods for about $15. I also got a pretty weird look from the salesman when I told him what it was for.

HV Enthusiast

Sat Mar 11 2006, 09:46PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

i used 1/8" diameter for my prop gap.

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