Re: Towards the autonomous lifter - electrostatic voltage generators.

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Robert Clark <bobbygc2001@xxxxxxxxx>

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: Robert Clark
> <bobbygc2001@xxxxxxxxx>
>
> --- Tesla list <tesla@xxxxxxxxxx> wrote:
>
>  > Original poster: "Antonio Carlos M. de Queiroz"
>  > <acmdq@xxxxxxxxxx>
>  >
>  > Tesla list wrote:
>  >
>  > >Original poster: Ed Phillips <evp@xxxxxxxxxxx>
>  > >"Especially useful for our methods might be the
>  > >Wimhurst, Wehrsen,
>  > >Holtz, or Bonetti machines. I believe these
> devices
>  > >would be able to
>  > >deliver more current and therefore greater
> wattage
>  > for
>  > >our
>  > >application than a Van de Graaff generator."
>  > >     Not sure about it, but I think that ES
> motors
>  > have a very poor
>  > >power/weight ratio, and are probably quite
>  > inefficient.  Antonio would
>  > >know about that.  Has anyone calculated the
> power
>  > required to operate a
>  > >lifter of useful size?
>  >
>  > Apparently, the required voltage is not so high,
>  > maybe less than 20 kV,
>  > but the current is high, more than 1 mA for a
> small
>  > device.
>  > It's not simple to build an electrostatic
> generator
>  > that can produce
>  > 1 mA, operating in normal air. My most powerful
>  > machines produce
>  > just 100 uA, and I can't power a lifter with just
>  > this. I tried,
>  > a significant "wind" is produced, but not enough
> to
>  > lift the device.
>  > Maybe if I manage to build a very light one. An
>  > electronic power
>  > supply, maybe using a Tesla-coil transformer (air
>  > core) and a suitable
>  > rectifier may be more practical than an
>  > electrostatic generator,
>  > when weight is the critical factor. A 1 mA
>  > electrostatic machine
>  > would weight many kilograms, not counting the
> motor
>  > to power it.
>  >
>  > Antonio Carlos M. de Queiroz
>  >
>
>
>   Thanks for the responses. There have been lifters
> made that have a thrust to power ratio of about 1 to
> 1
> measured in grams lifted, to power required in
> watts.
> In particular a lifter created by Blaze Labs
> produced
> a lifter weighing about 200 grams powered by a 200
> watt power supply.
>   Antonio, it looks like the thickness of the rotor
> should have no effect on the production of the
> charge,
> what's important is the surface area and the speed
> of
> rotation. So instead of being millimeters thick, you
> could make it microns thick. In fact you might be
> able
> to make the rotor 1/100th as thick so 1/100th as
> heavy. Since the rotor would be 1/100th as heavy the
> support structure would probably also have to be
> only
> 1/100th as heavy.
>   But the rotor has to rotate at high speed to
> generate
> sufficient current; so this very thin rotor has to
> be
> very stiff. One way would to have strong stiff rods
> inserted radially into the rotor material to
> maintain
> its stiffness. You probably wouldn't need many of
> these to keep it stiff so the weight would stay low.
> Also, on your page you mentioned a rotation speed of
> about only 40 rotations per sec. I want to use at
> least 10 times that high. You might want to use an
> electrical motor to get it up to this speed, for
> example a vacuum machine motor.
>   Speaking of vacuum, electrical breakdown requires
> the
> medium to become a conductor, like a metal. Since
> there is no "medium" in a vacuum I was assuming this
> would require some immensely high voltage to where
> bizarre quantum mechanical effects come into play
> like
> "virtual particles".
> However, I am informed that in practice what happens
> is that at moderately high voltages emitted
> electrons
> from the electrodes and even trapped gases in the
> electrodes can cause currents to flow across the
> vacuum gap.
> This voltage depends on alot of factors with the
> electrodes: smoothness, trapped gas content,
> cleanliness, etc. Some high voltages I've seen for
> this were in the range of 150 MV/m, which explains
> why
> in the example the voltage given was 100 MV/m and
> not
> some immeasurably high voltage.
>   Since the breakdown in air is only at about 3
> MV/m,
> in a vacuum you could go 30 to 50 times higher
> thereby
> generating that much more power.
>
>
>    Bob Clark
>


 On the Powerlabs.com page I saw discussed use of a
Dremel grinding tool to generate high revolutions per
second:

PowerLabs High Speed CD-Rom Experiments.
http://www.powerlabs.org/cdexplode.htm

 This tool can generate 35,000 RPM or nearly 600
revolutions per second. Perhaps this can be used to
increase the current generated by an electrostatic
generator by increasing the rotation speed. See the
formula on Antonio's page for the current generated:

Maximum electric field.
http://www.coe.ufrj.br/~acmq/efield.html

 Antonio gives an example here of a rotor with 13 cm,
5", outer diameter with a rotation speed of 40
revolutions per second generating 36 microamps. So at
600 turns/sec using the formula there should be 15
times the current or 540 microamps. Note too that in
the example there is a 9 cm inner diameter which
reduces the surface area by about 1/2. So for a solid
disk at 13 cm diameter there would be about 1000
microamps, 1 milliamp.
 Dremel grinding tools are available for reasonably
low prices. Here's one for $29.00 US:

Wholesale Dremel Type Rotary Electric Grinder kit NEW.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=29528&item=4389954711

 You could also increase the current by increasing the
number of rotors (but see the caution below.)
 Note that the idea is to see if these electrostatic
generators could provide a self-contained power unit
for a lifter. But at first we want to see if they can
supply sufficient power/current to raise just the
lifter. So in the first experiments you just use
already existing electrostatic generators on the
ground, which are not optimized to be lightweight.
 Then we also want to see how the energy of rotation
is stored and converted into electrostatic energy. So
once it is confirmed the generators can provide
sufficient power, you disconnect the Dremel to see how
long the rotor can spin fast enough to provide
sufficient power to raise the lifter.
 Note that these first experiments are done in air so
the air friction will significantly reduce the
rotation time once the Dremel is disconnected. Later
the idea would be to contain the rotor in vacuum. This
will increase the rotation time and at the same time
increase the voltage possible 30 to 50 times. (Note
that to get this voltage increase, it has to be a very
high vacuum, since reducing the pressure can actually
decrease the breakdown voltage until a very high
vacuum is reached.)

CAUTIONS!
Note that on the Powerlabs page they were attempting
to cause a CD disk to disintegrate by spinning at the
highest speed of the Dremel. In *this* experiment they
had to additionally strike the spinning CD with
another CD to get the spinning CD to shatter. But
there have been cases where CD's have shattered at
lower speeds than 35,000 RPM. Acrylic if that is used
for the rotor probably would have comparable tensile
strength as a CD. It is *strongly* advised that the
rotor be gradually brought up to higher speeds
stepwise. And it is *strongly* advised that the rotor
be behind a protective wall during these experiments.
You can view the experiment by video camera or by
mirrors (metal so as not to shatter.) In the Powerlabs
experiments the experimenter held the Dremel with the
spinning CD out in front of him. This is strongly
disadvised.
 Note also if you use more than one rotor on a single
Dremel this could cause wobbling which could put more
stress on the rotors increasing the chance of shatter
and also making the directions the shards would go
more unpredictable.
 Also, if you increase the diameter of the rotors the
speed at the edge of the rotor is also increased
thereby increasing the chance of shattering. Moreover,
the Dremels are actually designed for rather small
diameter grinding attachments. Large diameter rotors
could damage the Dremel motor.


   Bob Clark