Re: SRSG motor modification

["Garth van Sittert" <garth-at-mediasupplies.co.za> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Thanks for replying.

The motor is 1/4 HP or 180W
2850 rpm 50Hz

My armature measures: 4" long,  2" diameter.

The 2 flats I have made are 1" wide.

I have pictures of it at http://teslacoil.8k-dot-com/spark_gap.htm


----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, August 07, 2000 7:44 PM
Subject: RE: SRSG motor modification


> Original poster: "Colin Dancer" <CMD-at-datcon.co.uk>
>
> Hi Garth,
>
> Could you give a bit more detail about your setup?  The key factors are
the
> width of your flats, the diameter of the rotor, the motor's speed and
power,
> and the dimensions of your disc.
>
> I've modified a couple of bench grinder motors which sound like they have
a
> similar winding pattern, and found that I needed 2 x 15mm flats on an
~40mm
> dia rotor. In terms of power, my 1/4HP motor will easily lock a 5 1/2"dia
x
> 1/16" disc at 3000RPM with 4 x 4mm bolts as flying electrodes.  For a
> thicker 6" x 1/2" disk it will only lock if I initially boost the voltage
to
> 260V using a variac and increase the capacitor to 4uF from 2uF.  I've
tried
> making the flats a bit wider (I've gone up to 22mm in 2mm increments) but
> the torque is if anything slightly lower.
>
> Last week I modified a 1/2HP 3000RPM bench grinder, again with 15mm flats,
> and this locks with no problem on a 6" x 1/2" disk including 4 rather
hefty
> 6mm bolt flying electrodes.
>
> It's amazing how much extra drag the 1/2" increase in diameter and
thickness
> generates, but I guess it makes sense as the formula for drag is ^2 for
RPM
> and ^3 for d.
>
> I know running reducing RPM isn't an option with this motor, but have you
> tried a smaller disk or even running the motor without a disk and looking
> for lock using a mark on the shaft?
>
> Hope this helps,
>
> Colin.
>
> P.S. There's a good photo of my altered rotor at
> http://www.pyrochrome-dot-net/tesla/
>
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: 06 August 2000 21:57
> To: tesla-at-pupman-dot-com
> Subject: SRSG motor modification
>
>
> Original poster: "Garth van Sittert" <garth-at-mediasupplies.co.za>
>
> I recently modified a 1/4 HP capacitor start; approx. 2800 rpm motor to
make
> it
> synchronous.  I ground two flats across the 'dead poles' on the armature
> according to motor1.gif etc...  However I must have done something wrong
as
> it
> is not synchronous.  Using a neon as a timing light the blur only comes
into
> focus a couple of seconds after power off when it is coasting down.
>
> The motor only has 16 poles so I was't 100% sure on the modification
> compared
> to the instructions referenced above which I have seen mentioned a couple
of
> times before on this list.  The starter windings seemed to ocupy much more
> pole
> space than the ones shown in the diagrams and are interwoven with run
> windings
> as well, so I thought rather than grind too much.....
>
>
>
>
>