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Re: Rotary SG Safety

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 

A good safety lesson here.

Why not use a 1725 or 3450 fixed RPM motor to start with?  A 1/2 hp motor
with a 1/2 thick G-10 rotor and 10 electrodes will get the job done.  Never
use Lexan and never run a rotor at 6,000 RPM!

Many experimenters, on a budget, use a small cheap motor and handcraft their
own RSG without the aid of an experienced machine shop.

A typical visit to a US hospital small town emergency room is around
$3,000.00 and that's only the beginning.  A machine shop might charge you
$500-$600 for a high quality RSG but that's a bargain compared to the
$3,000.00 that starts when you walk or are carried in the ER.

Oh, and that's only the ER fee to enter the ER.  A doctor/surgeon will
charge you another $3,000 to remove the embedded tungsten from your head, or
worse, eye socket --- the one where your eye was.

A high quality rotor made by an experienced machinist usually does not
require a shield.   We've made them for over 35 years and never had one
explode yet.  Even though we have a good lathe and mill, I always farm out
the rotors to a competent machinist who has been doing this part of our work
for over 2 decades.  His quality is unmatched.

To new coilers:  Use caution and common sense.  Have an accident with your
coil and your parents won't be so understanding the next time around.  Do it
right the first time.  Let a professional make your RSG rotors.
If you're on a tight budget, tell them.  Most small shops are willing to
work with you especially if you show them photos of your "neat project".

I've seen so many coilers that skimp in this area that it's truly scarry we
haven't, as a collective community, had more accidents.

Safety first --- always!   It's certainly not unbalanced rotors of Lexan
(softens with heat) and unbalanced acorn nuts running at 6,000 RPM.  You're
lucky.  This was an accident waiting for a place to happen.

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913
 > Tesla List readers,
 > Recently a friend of mine who has been building Tesla coil projects for
 > over 20 yrs, built a small asychronous rotary gap. He wanted it for use on
 > small coils so it has only a 6" rotor disk. He used a small universal
 > from a vacuum cleaner. The rotor is 6" by 1/8" Lexan and the rotating
 > hardware was #8 brass acorns and all thread.
 > The rotor and motor were fully enclosed in plastic. The rotor case was
 > Lexan. The motor case was acrylic. The overall appearance is like an
 > fan but made of plastic. The finished project was a work of art with
 > everything carefully balanced so that it ran with no noticable vibration.
 > When I was over to see the progress on the rotary,  he had not installed
 > the stationary electrodes which were to be tungsten. We spun up the unit
 > and made speed measurements with a strobe tach. At 60 VAC the little motor
 > was turning over 6000 rpm and the unit had somewhat of a siren quality to
 > it. We stopped at 70 VAC as this speed was more than would be needed. I am
 > always a little wary when near rotating equipment that is in the whine to
 > siren mode.
 > A few days later, my friend was not in a great mood. He had installed the
 > stationary electrodes and gapped them at around 0.040". He decided to run
 > more safety checks and cranked it up to 80 VAC. At this point there was a
 > loud bang and shrapnel proceeded to eject through the 1/4" Lexan and some
 > small threaded parts left an indent in the shelves across the room. He
 > stated there were parts 30 ft from ground zero. Fortunately nothing hit
 > him. The probable cause was that the 1/8" rotor flexed enough due to air
 > pressure being ported through special holes for that purpose so that it
 > caused the flying electrodes to be sheared off. The Lexan disk did not
 > Fast forward. Due to his experience, I decided to rework my tungsten rod
 > propeller gap as used by some folks on this bulletin board. I had a 4"
 > fiberglass shield around it but it was fairly flimsy. So I replaced it
 > a "firewall" of 1/4" masonite I had around. The masonite has bricks
 > embossed on one side - thus the term firewall.  The shield was much deeper
 > (rotary is horizontal) so that flying parts have to bounce around a
 > while  before leaving the area. Today when I was running this rotary, I
 > heard a moderate "bang". The system shutdown on its own so I figured on a
 > blown cap. Instead, the tungsten propeller rod had turned into three
 > and hit the firewall without too much ado. I was glad for the added safety
 > of the masonite.
 > I will forward photos of the Lexan rotary to Terry  for possible inclusion
 > in his hotstreamer site.
 > Keep your coiling safe. Assume your rotary will fail so provide shielding.
 > Jim