Re: DC rotary gap?

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

Original poster: "Jason Johnson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <hvjjohnson13-at-hotmail-dot-com>

Whatever you can find that looks good to you will work. I would look for a
1/4+ horse 90vdc motor. They come in various RPMs, around 5000 would be
good. You can power it off a variac and full wave bridge rectifier. AC
motors will work too, but they're not as easy to vary RPMs from zero to max,
because they really need a variable frequncy drive, where DC motors vary
with input voltage. You may want to put a DC voltmeter in the circuit and/or
a tachometer. Your BPS will vary, depending on the size of your cap,
voltage, and power you want to be able to run. You can figure the approx.
BPS w/ the formula:

BPS= ((Vo*Io)-L)/(C*Vo^2)

where:
Vo is your transformers output voltage (after rectification to DC)
Io is your transformers output current
L is losses from filters etc.
C is capacitance in farads

You can build the gap for whatever BPS you want, around 700-1000 is a good
number, but you may want to be able to change the number of electrodes, so
you can go higher or lower at a given RPM.

Good luck on your coil!!

Jason Johnson

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, April 25, 2001 7:14 PM
Subject: DC rotary gap?


> Original poster: "G by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<nieporgo-at-email.uc.edu>
>
> >The best use of async rotaries IMHO is on DC coils. On a DC coil you can
get
> >really neat effects by varying the break rate from less than 100 to as
high
> >as your little motor will spin the electrodes, and the sparks changing
> >appearance all the while. On AC coils, such as NST powered coils they do
not
> >have much advantage, especially when you try to run a low break rate and
the
> >electrodes are not in the right place at the right time (especially with
a
> >close to resonant cap value), and your transformer and/or cap goes poof
and
> >lets the smoke out (all electronic equipment runs on smoke, let the smoke
> >out and it stops working ;-).
>
> Hi, I am going to be working on a DC mot-powered coil soon, what
> motor specs should i look for to power my rotary gap? I will be
> looking through a surplus shop for my motor. Do i just throttle the
> motor with a variac or dimmer, or is some electronic controller
> required? I am assuming many electrodes are also used on the disk to
> enable several thousands of bps. I seem to remember Kevin O. saying
> his rotary gap did a few bps to thousands of bps.
> Here's to keeping the smoke in,
> Greg
> --
>
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