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Plasma Lover

Wed Apr 15 2009, 12:41AM

Registered Member #1911 Joined: Mon Jan 05 2009, 06:30PM
Location: Salem, Oregon, USA
Posts: 165

I've been bitten by a MOT that had five 940C20P33K capacitors in parallel used for near-resonant arcs. The MOT was off, and the caps discharged partially through one hand, since I had a large potential difference. I've been caught with arm-to-arm 4.25KV peak voltage .02ÂµF cap discharges from pulling resonant arcs on a 3KV 15mA RMS bug zapper transformer. I've gotten zapped by an NST pulling 120 and putting out 7,500 on either leg, shocked on one leg.

I've never shocked myself on purpose, but you can bet that I'm going to be EXTREMELY safe, now. I know and my dad has shown me pictures of what can happen when HV strikes you and grounds through your body. Pig-like stuff where it comes in your hand and there's no mark, but when the doctors take off your left shoe there's a giant black hole where the center of your foot used to be and where the electricity formed a capacitor to ground. Be careful.

Anyways, more on-topic, the tungsten electrodes wouldn't be 'over-kill', but they may be over-kill for a safety gap, at least at first. With a safety gap, if it takes a little chunk out of the safety gap, it will destroy the usefulness of said gap. Without proper spacing, a safety gap is useless.

Anyways, it's your coil. If you want it to last and not need much adjustment or replacement of electrodes, then make it with tungsten; if you want it to be pretty, make it pretty.

=)

Ryan Parle

Wed Apr 15 2009, 11:59AM

Registered Member #2038 Joined: Fri Mar 20 2009, 03:39PM
Location: Bristol Uk
Posts: 60

Plasma Lover wrote ...

Anyways, more on-topic, the tungsten electrodes wouldn't be 'over-kill', but they may be over-kill for a safety gap, at least at first. With a safety gap, if it takes a little chunk out of the safety gap, it will destroy the usefulness of said gap. Without proper spacing, a safety gap is useless.

Anyways, it's your coil. If you want it to last and not need much adjustment or replacement of electrodes, then make it with tungsten; if you want it to be pretty, make it pretty.

=)

Fair point Plasma Lover maybe tungsten is a good way forward, it will certainly last a lot longer than most metals.

I'm not so much trying to make my tesla coil pretty, more so use materials that i already have at my disposal... unfortunatly i dont have any tungsten and i dont have a job to pay for any either.

As much as i would like to make my coil look as attractive as possible, i definitely prefer function over apearence, I am a person who finds beauty in thngs that are well engineered, so i guess that i will also find the tungsten electrodes a good point in both aspects... now i wonder if i can find some nice tungsten spheres for the best of both worlds... :D

Looking at the specs for a lot of ball bearings many of them are actually hard chrome plated tungsten, so it may be possible to use them after all!

i'll set a couple bearings up in a spark gap situation and see how well they put up with the arcs.

it maybe that using ball bearings is a slightly cheaper alternative to normal tungsten electrodes.

Plasma Lover

Wed Apr 15 2009, 05:14PM

Registered Member #1911 Joined: Mon Jan 05 2009, 06:30PM
Location: Salem, Oregon, USA
Posts: 165

Ryan Parle wrote ...

Looking at the specs for a lot of ball bearings many of them are actually hard chrome plated tungsten, so it may be possible to use them after all!

Well, that is surprising. I suppose I'll have to research that myself. Thank you.

Ryan Parle

Wed Apr 15 2009, 05:26PM

Registered Member #2038 Joined: Fri Mar 20 2009, 03:39PM
Location: Bristol Uk
Posts: 60

Ok, i've been doing a little more research, it seems that most of the "standard" ball bearings are actually hard chrome plated steel or hardened stainless steel. But there are some hard chrome plated tungsten ones on the market, but i cant find anywhere that sells them by small quantity. it looks like the tungsten bearings are for serious bulk orders only. DOH!!

even though the cheaper ones arent actually tungsten, they may be tough enough to do the job.

Ryan Parle

Sun May 17 2009, 08:46PM

Registered Member #2038 Joined: Fri Mar 20 2009, 03:39PM
Location: Bristol Uk
Posts: 60

Well things have been a little quiet on the TC front for me of late, i've been totaly skint for a couple of months as i was out of work since mid febuary, but i've been working for the last 3 weeks and have work booked for another 2 months and money has once again started to flow. So now i can start to think about making a few improvements to my TC.

Firstly the safety gap, i'm still going to give the ball bearings a try, but if they seem to wear quickly i'll change to Tungsten electrodes from TeslaStuff on ebay. I was talking to a friend who is rather handy with a TIG welder and he is going to weld a steel rod to each bearing, this saves the hassle of drilling them.

I'm also going to replace my spark gap, but i'm unsure of which design to use. i dont really want to use a rotary spark gap, so it will be a static design, But i want good quenching and a design that will last.

I managed to salvage a Vacuum cleaner motor, fan and adjustable speed controller last week which i would like to use to provide airflow around the spark gap. The options i am considering are.

Sucker gap similar to Gary Laus one here:
A pair of tungsten electrodes inside an enclosure (probably a piece of PVC tube) with air being drawn through the tube.
A tubular multi gap with air being drawn through the tube.

Apart from functionality my main concern is size. i dont really want to make the TC any larger and would like to keep everything within the wooden framework, there is enough room for the vacuum motor to fit inside the framework and about 6-8" to spare on the end for the actual spark gap.

Anyone got any recomendations? any other designs i have missed?

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