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Re: Rotary gap nearly done...



At 04:25 AM 10/20/96 +0000, you 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. ---
>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>
Chip -

Congratulations on your success with the Tesla List. It not only is growing
but contains a wealth of Tesla coil information for coilers. We all
appreciate what you are doing.

The number of breaks for your coil depends on on the following:
          Breaks = 2*watts input* eff/(CpVp^2)
Example - If your coil has a 12000 volt, 5000 watt input, .06 uf primary
capacitor, and the overall efficiency is 30% the breaks should be about 347.
For 690 breaks you would need about 10000 watts input to properly charge the
primary capacitor. The overall efficiency can be estimated according to my
10/9/96 post "Power and Efficiency". The capacitor charging time is so short
it is not a factor.

Good luck with your coil

Jack C.