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Truck tubes as toroids fail

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LAN_403

Tesladownunder

Wed May 09 2007, 02:53AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

For my 18 inch coil I used a truck tube and a car tube with an aluminum plate between and all covered with chicken wire. It met my requirements for being light, resistant to damage and with a solid center for rotating breakout point stuff.
I did have one mishap when I was showing off and threw it in the air. The edge of the disc cut through the tube but it was easily repaired with another $15 second hand tube (1000x20 size).
It did survive a fall from the top of the TC without problem though.

So I thought I had a winner.

Alas after a full power run it appears that corona had eaten into the tube and created numerous holes (although the wire framework was intact).

TDU

1178679166 10 FT0 Tesla18toroidconstruction

1178679166 10 FT0 Tesla18toroidholescorona

teravolt

Wed May 09 2007, 03:48AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

nice idia, iner tubes have carbon in them maby aluminuim foil under the chicken wire would help

Coronafix

Wed May 09 2007, 03:58AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Why not just the chicken wire with a plywood frame
like Syd Klinge did? Then you're not limited to the
size of the truck tyre that you can get.

Tesladownunder

Wed May 09 2007, 08:36AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Syd has about 16 plywood circles for each toroid but I have a double toroid so I would need perhaps 32. I could have made the inner tube toroid up in the time it would take me to cut out a couple of plywood donuts. Also plywood won't bounce.
I was not expecting corona to be going backward into the Faraday cage of the chicken wire.
I guess it needs some sort of coating such as Al tape but it is a little hard to stretch the wire over the tape. It is probably the simplest way to modify it but adds a fair bit of cost in the tape.

TDU

1178699249 10 FT25027 Bdostreamersbesttoroidply

Coronafix

Wed May 09 2007, 10:54AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Well technically, you don't have a double toroid, you just have a funny shaped toroid
made up of two inner tubes. (As the chicken wire is spread over both at once)
You would only need 16 if you used a toroid size that added up to the two toroid capacitances
you are using into one. Does that make sense?
Bigger toroid = 2 current toroids.

GreySoul

Wed May 09 2007, 03:37PM

Registered Member #546 Joined: Fri Feb 23 2007, 11:43PM
Location: Albuquerque, NM
Posts: 239

Just another thought... have you tried insulation foam? There's stuff sold in big 8x10 sheets about 1.5" thick, blue and pink usually (not Styrofoam)... it's very easy to cut with a hot wire tool, and stacks up, glues, and sands like a charm.

Donuts made from foam might be light enough and strong enough when wrapped in wire to bounce a few times.

I'm planning to use this stuff wrapped in foil to make my next toroid, I'll let ya know how it goes.

-Doug

Marko

Thu May 10 2007, 10:55AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

The wire eating into rubber thing is wierd if you are using breakout point.
Plating the entire toroid in foil would probably stop that problem, but that's probably too much work.

To fix the tire you can simply fill it with self-expanding foam.
The toroid will be a bit heavier, but not too much if foam is good.

There are foams made particulary for tha tpurpose but I thing anything will work in your case.

Finn Hammer

Thu May 10 2007, 11:15AM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Tesladownunder wrote ...

Syd has about 16 plywood circles for each toroid
snip
Also plywood won't bounce.

Chicken wire toroids are cool, and I am sure the frame can be refined. Making the rings out of split cane or laminated fiberglass should produce a light and "springy" structure that might survive a fall.
Speculation based on related experience.

Cheers, Finn Hammer

Tesladownunder

Sat May 26 2007, 01:03PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I have wrapped the upper inner tube in aluminium tape. This should be secure and safer.
So far a run has been fine and I would not expect a problem now. Except that the inflation pressure is a bit high to fill the chicken wire.

TDU

Marko

Sat May 26 2007, 11:25PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hm, very nice and elegant! If you could wrap the smaller one you could maybe get rid of the chicken wire for looks.

Good luck with it!

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