Re: Towards the autonomous lifter - electrostatic voltage generators.

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Robert Clark <bobbygc2001@xxxxxxxxx>

> This might be workable using Cockcroft-Walton
> voltage
> multipliers to get the high voltage required. This
> would eliminate the need for many batteries
> connected
> together and also the need for a transformer. The CW
> multiplier is also light-weight consisting just of
> diodes, capacitors and wires.
>  However, I estimated given the power and the weight
> of lithium polymer batteries and assuming a 1g/1
> watt
> lifting capability of a lifter, the batteries would
> only be able to lift their own weight for a few
> minutes before they became drained.
>  For instance using the TP4000-8S2P battery with the
> specifications below, at 29.6 volts and 4000 mAh,
> this
> gives a power rating of 29.6V x 4 Ah = 118.4
> watt-hours. But the battery itself weighs 656 grams,
> so assuming a 1 g/1 watt lifting capacity, it could
> lift its own weight for 118.4/656 = .18 h, or about
> 11
> minutes. This is not even considering the weight of
> the lifter. The CW multiplier would probably be only
> a
> small portion of this.
>  From Blaze Labs examples we might expect the lifter
> body to be about the same weight as the payload
> (which
> here includes the power supply), so about 656 g.
> Then
> the battery would be able to raise the lifter and
> battery for less than 5.5 minutes.
>  Nevertheless, it would be great if someone did this
> to prove a lifter could raise itself under it's own
> power if only for a few minutes.
>
>
>   Bob Clark
>
>
>  TP4000-8S2P	
>  Amp Hours: 4000 mAh
>  Voltage: 29.6V
>  Balancer connectors
>  Rating: 10-12C continuous, 20C (80A) burst
>  Output: 29.6V Nominal, 4000mAh
>  Dimension: 50mm x 245mm x 28mm
>  Weight: 656 grams	
>  Retail: $349.95
>
>

I wanted to save weight by eliminating the
transformer. But it may turn out the large number of
components for a kilovolt CW multiplier without
transformer would cancel out the weight savings. I
discussed this in a post to www.powerlabs.org copied
below. A question I would like to see answered is what
is the weight for a microfarad capacitor?
The post refers to the 555 oscillator IC. I needed
that because the CW requires AC while the lithium
batteries put out DC. The 555 provides a simple
lightweight method for converting DC to AC:

DC to AC Inverter with the 555.
http://www.uoguelph.ca/~antoon/circ/555dcac.html


  Bob Clark


Post to www.powerlabs.org:

*************************************************
RGClark
Joined: 11 May 2005
Posts: 20
Posted: Fri Jul 01, 2005 9:48 pm

...
You're right about the problem of getting up to
kilovolt ranges. I wasn't taking into account the size
increase of the CW circuit in relation to the voltage
multiplication. For instance this page shows you need
to increase the number of stages to increase the
voltage multiplication:

Cockroft Walton Voltage Multipliers.
http://home.earthlink.net/~jimlux/hv/cw1.htm

This also shows a transformer attached at the
beginning. I wanted to eliminate the transformer to
save weight. But this might result in an impractical
number of stages.
For instance, this lithium battery puts out about 30
V:

TP4000-8S2P
Amp Hours: 4000 mAh
Voltage: 29.6V
Balancer connectors
Rating: 10-12C continuous, 20C (80A) burst
Output: 29.6V Nominal, 4000mAh
Dimension: 50mm x 245mm x 28mm
Weight: 656 grams
Retail: $349.95
http://www.thunderpower-batteries.com/html/batteries.html


Let's say we use 100 CW stages to multiply this to
about 3,000V. How much would 100 diodes and capacitors
add to the weight? Would we be better off just using a
transformer?
Actually I'm not even sure 3000V would be enough
voltage to raise a lifter. You might actually need
1,000 stages(!) Also, the "Cockroft Walton Voltage
Multipliers" page mentions the voltage loss as the
number of stages increases.
However, the page also mentions you can reduce the
losses by using high frequency AC. So perhaps instead
of the standard 60 Hz AC, we could use an AC source in
the thousands of hertz range. This page shows the 555
IC can operate in the kilohertz range:

555 timer IC.
http://www.doctronics.co.uk/555.htm

And this page suggests the frequency for the 555 can
range into the megahertz:

555 Timer Tutorials.
http://www.williamson-labs.com/555-tmg-charts.htm

According to the diagrams on the first page, it's just
a matter of choosing the resistors and capacitors
attached to the timer to change the frequency.

This page by Blaze Labs discusses use of the CW
multiplier and calculates the voltage loss for an
example 3-stage CW multiplier:

Experiment 15 - Cockroft Walton Multiplier.
"The voltage drop under load can be calculated as:

VDROP = [Iload/(6fC)] * (4n^3 + 3n^2 - n)

where:
Iload is the load current (Amps)
C is the stage capacitance (Farads)
f is the AC frequency (Hz)
n is the number of stages.

Example: A 3 stage CW, driven by a 70kHz peak voltage
of 10kV, with capacitors value 390pF, and a load
current of 10mA:

VDROP = [Iload/(6fC)] * (4 n^3 + 3 n^2 - n)
VDROP = 8kV
Eout = 60kV - 8kV = 52kV"
http://www.blazelabs.com/e-exp15.asp

This loss of 8kV is only for 3-stages where I'm
envisioning hundreds of stages. For this to work, I
would need both much higher frequency and much higher
capacitance. Notice the capacitance in this example is
only 390 pF. But small capacitors exist at a million
times that, i.e., in the microfarad range. You could
also make the 555 run at say 1 megahertz instead of
the 70kHz in this example.
However, as shown on this page the larger microfarad
capacitors are the heavier tubular kind rather than
the lightweight flat kind:

Capacitors.
http://www.kpsec.freeuk.com/components/capac.htm

So you still have the question of the weight of the
hundreds of capacitors required.

In regards to the thrust to weight ratio, here are
some examples from Blaze Labs showing approximately 1
gm/1 watt thrust to power ratio:

Super V1.0 cell - 15/04/03
http://www.blazelabs.com/l-c-superv1.asp

Experiment 14 (21/03/03)- 100g payload lifter.
http://www.blazelabs.com/e-exp14.asp
*************************************************
http://www.power-labs.com/forum/viewtopic.php?p=3815


->Terry notes - If they are going to power their lifters with a Tesla coil, 
it is probably on topic... <-