Re: Rotary gap nearly done...

To: tesla-at-pupman-dot-com
Subject: Re: Rotary gap nearly done...
From: Chuck Curran <ccurran-at-execpc-dot-com>
Date: Sun, 20 Oct 1996 19:12:30 -0500
Tesla List wrote:
> 
> >From chip-at-poodle.pupman-dot-comSat Oct 19 21:30:48 1996
> Date: Sat, 19 Oct 1996 21:21:12 -0600 (MDT)
> From: Chip Atkinson <chip-at-poodle.pupman-dot-com>
> To: Tesla List <tesla-at-poodle.pupman-dot-com>
> Subject: Rotary gap nearly done...
> 
> Greetings,
> 
> First, we now have over 250 subscribers!  What have I gotten myself into? :-)
> 
> Anyway, I got the rotary gap virtually done today.  I was going to use a
> totally wimpy vacuum cleaner beater bar electric motor to turn it, but
> there was far too much friction in the new ball bearings (!) for that
> motor to overcome.  The vacuum motor's smoke tried to make a break for it,
> but I only let a little escape.
> I then went to our local HVAC (sorry, that's Heating,
> Ventilation..., not High Voltage) shop and got an old furnace and
> salvaged the motor.  It's turning out fall is the time to scrounge
> furnace motors and blowers -- good for ventilating ozone.
> 
> I reversed the pulleys from the blower and motor, so the RPM of the
> rotary gap is about 3450 (~2*1750).  Unfortunately, this arrangement is
> hard on the motor as it takes several seconds for the whole thing to come
> up to speed.  During that time, the starting windings are energized and
> the motor gets pretty warm.  The other problem is that the motor, being
> induction, is pretty much a fixed speed.
> 
> Since I have 12 studs on the rotor, I get about 690 breaks per second
> with this arrangement.  The rotor is about 12" in diameter, so the dwell
> time is "short".  The question that I have is "Is the 690 bps too high
> for starting out?"  I ordered one of those Carter motors from C&H Sales,
> but I'm wondering if It would be OK to start using the gap as is, or will
> I likely blow a cap?
> 
> I took a fair amount of time and care in building the thing, and it looks
> pretty nice.  The other thing that's kind of amazing is how smoothly it
> runs.  I made sure everything was true on the lathe, and used uniform
> parts.  Still, I expected some sort of vibration, but get little if any.
> I'm totally psyched about the whole thing.  I also took some pictures,
> and will try to get them scanned and posted sometime in the coming week.
> 
> Chip
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>  Chip Atkinson
>  http://bhs.broo.k12.wv.us/homepage/chip/info.htm
>  --- Everyone is someone else's weirdo. ---
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-


Hi Chip:

	It sounds like our rotaries might have certain similar
characteristics.  I also used 12 moving electrodes on the G-10 rotor and
I decided to limit the RPM to 2500, or as close as I could get it using
an old Tach originally designed for propellor RPM on small glow plug R/C
plane engines.  Two reasons for this: First, I had read where very good
results had been realized at around 400-500 bps on two coil systems.  I
had nothing else to go on, so that information was a starting point for
me.  Another item posted was in regards to the CP .025 mfd at 20,000 VAC
cap I have.  Someone had listed some of the data that I believe they
said was from the factory.  This is a guess, but the item that caught my
attention was the factory rating on the cap was a max of either 100 0r
150 bps.  I really don't know if this is a real number, but it made me
not want to exceed that 400-500 bps that others had been running with
apparent success (on intermitant duty cycles).
	I've found the Carter motor to be very handy but it really appears to
have more than enough speed at 10,000 RPM.  Glad I had that old Ohmite
autotransformer for speed control laying around.  I set mine system for
the 450 bps as a target and after getting things resonated the arcs to
ground got to 75"-85" without retouching the gap speed.  I got some on
video.  Good Luck with your tests.

Chuck