Re: Wimhurst powered TC?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Beans45601-at-aol-dot-com>
> 
> Could you use a Wimhurst (i think that is what it is, it is the thing
that has
> the 2 glass plates with hetal strips on it and they both spin in a diffrent
> direction) to power a tesla coil. Of cource, you would have to run it with a
> motor of some sort, would this work?

Wimshurst.

Possible, yes, but these machines (with reasonable size) don't produce
a lot of current, so your break rate will be low. A Wimshurst machine
with 31 cm disks turning at 20 turns per second produces about 20 uA
of current only, and a maximum voltage of ~50 kV. It could drive a 
strange Tesla coil with a quite low primary capacitance operating at
high
voltage. A practical connection would be to attach two Leyden jar-type
capacitors to the terminals of the machine, connecting the primary
coil between the outer plates of the capacitors. The gap would be
the normal spark gap of the machine, set at a small distance.
To charge 1 nF of capacitance to 30 kV with 20 uA takes:
t = 30000*1e-9/20e-6 = 1.5 seconds
Each bang would discharge 0.45 Joules of energy.
Turning the machine faster increases the current in proportion, and
it's also possible to connect multiple pairs of disks in parallel.
Using larger disks also increases the current, in proportion to the
square of the diameter for the same speed, and also increases the
maximum output voltage in proportion (not very useful for a Tesla coil 
driver).
A sectorless machine produces about twice more current. 
A monster machine with 10 pairs of 62 cm sectorless disks turning at
20 turns/second would then produce 20 uA x 10 x 4 x 2 = 1.6 mA 
Keeping the 30 kV and 1 nF primary, this would produce 53 bangs
per second, corresponding to (quite low) 24 Watts of output power.
You can use John Freau's formula to predice spark length.
(The machine itself could produce 35 cm sparks)

Antonio Carlos M. de Queiroz

(electrostatic machines:
http://www.coe.ufrj.br/~acmq/electrostatic.html)