Re: RSG Treadmill Motor and precision rotors

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>


It's always best to take your rotor to a local machine shop.  Let them cut
the rotor round and precision mount all the electrodes.  They usually hit
1/2 of one mil (.0005) accuracy and this translates into a very smooth
running rotor after balancing.

A good machine shop will use a high precision turntable on a milling machine
to get everything as accurate as possible.  They will locate and bore all
holes with excellent accuracy.  They can also balance the rotor for you.

Costs a few bucks but, as you found out, it saves time and trouble later.

Dr. Resonance



> Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>
> Steve, all,
>
> I, too am in love with treadmill type DC motors for ASRSG drive
> purposes ;^) Mine that I am using in my large coil that I am in the
> process of building is a 2.5 HP, 130 VDC, 3500 RPM motor. It
> cost me considerably more than $10 but then again, it's a little fan-
> cier than this one, too :^) The motor body is over 11" long and
> has a built-on mounting foot. There is also no perceptable end
> play on the shaft of mine and the biggest problem was getting the
> GPO-3 disc balanced and the electrodes positioned properly
> (and perpendicullar) along the same axial position of the disc.
> Actually, I didn't get them quite prefect, but was able to get
> them pretty close. Darn, it's hard to machine nice looking stuff
> w/out a lathe and a drill press, minimum. I did end up finding
> a local fellow hobbiest who had a nice acoutrement of machine
> shop tools in his garage and I got him to put a few of the finishing
> touches on my gap. I should have let him do all of the drilling from
> the beginning and that would've saved me a lot of headache and
> I would have ended up with a "perfect" looking RSG ;^) But
> all in all, it's definitely the best and nicest looking ASRSG that I
> have built to date (not that that's saying much) ;^)
>
> BTW, 1000 uFd seems kind of "overkill" on the fitering to me.
> I use 200 uFd and it seems to work fine for me. I get similar
> current readings on mine with the 200 uFd cap for filtering.
>
> David Rieben
>
> ----- Original Message -----
> From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Saturday, January 01, 2005 12:25 PM
> Subject: RSG Treadmill Motor
>
>
>  > Original poster: "S&JY" <youngsters@xxxxxxxxxxxxxxx>
>  >
>  > Happy New Year,
>  >
>  > For those contemplating building an asynchronous rotary spark gap, the
>  > following may be useful:
>  >
>  > I bought one of the new $10 surplus treadmill motors from Surplus
Center
>  > (www.surpluscenter.com), Item # 10-2167, and I am most pleased with it.
> It
>  > is a permanent magnet DC motor rated at 2.25 HP at 260 volts and 5
amps.
>  > The bearings are tight with inperceptable end play.  It comes with a 6
> inch
>  > diameter combination flywheel, cooling impeller and pulley that is
> perfectly
>  > balanced.  The temptation to use it as-is as an arbor for the RSG rotor
> was
>  > too much, so that is what I am using.  As there are 11 impeller blades,
I
>  > had to drill 11 mounting holes between the blades through the rim to
> attach
>  > the rotor.  Any other number of bolts would result in imbalance.
>  >
>  > With the hub at 6 inches, the rotor must be 12 inches in diameter to
allow
>  > enough space between the electrodes (mounted at 11 inch diameter) and
the
>  > "arbor" rim.  This is not a problem - there is power to spare to turn
this
>  > relatively large rotor, a 12 inch x 3/8 inch piece of GP03 (electrical
> grade
>  > fiberglass) from McMaster Carr (8549 K47), cost about $13.
>  >
>  > A small 0 - 120 VAC variac powers a full wave bridge rectifier with a
> 1,000
>  > uF filter capacitor.  Here are some test results:
>  >
>  > Rotor RPM    AC Volts   AC Amps
>  > 1000                       30          0.6
>  > 2000                       56          1.1
>  > 3000                       82          1.9
>  > 4000                      106         2.8
>  >
>  > At 4,000 RPM, the motor power needed is only about 0.4 HP, and it runs
> cold
>  > and is very quiet.  I will be using 12 rotor electrodes, so at 4000
RPM,
> the
>  > break rate will be 800 which is more than adequate for most purposes.
>  >
>  > Bottom line - this is a winning combination, and I commend it to
anyone.
>  >
>  > --Steve Y.
>  >
>  >
>  >
>
>
>