Re: RSG unbalance

["Tesla list" <tesla@xxxxxxxxxx>]

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


Remove the rotor from the drive motor.

Make up a shaft that extends thru the RSG hub and sticks out 3-4 inches on
each side.

Mount 2 razor blades on portable vises or some other type of support.  Place
the rotor shaft across these razor blades.  Rotate the rotor slowly by hand
and note "how it stops".  If it seeks a point, repeatedly, that is low, then
you've just found the heaviest portion of the rotor.

Use small 1/8th or 1/4 oz lead fishing weights --- stick them on with small
pieces of tape.  When you find a smooth balance, and the rotor doesn't hunt
for a stop point, then weigh up the balancing weights.

Now, the hard part.  You drill out a hole in the rotor to balance it.  Save
all the drilled out particles and carefully weigh them on an accurate postal
scale.  Match the taped on weight with the drilled out particles and you
should have a good balance.

Do it very slowly and carefully because if you drill out a hole too large
you could ruin the rotor.

Next, spin it up fast in a lathe or on your motor and look for smoother
operation.  Unwanted resonances can be a nightmare.  The only usual solution
is to use a high HP motor (we use 3/4 HP on all of our rotors in medium and
large coils) so it spins up fast past any resonance points and operates
smoothly at the desired speed.  Usually only 1 or 2 holes are required.
Drill excessive holes and you end up with a siren.  We did that once.  After
we all stopped laughing real hard, we scrapped out the rotor and started
over.

It can be a lot of work and requires great patience but the result is worth
the effort.

Dr. Resonance


>
> I am in the process of building an RSG. The disk spins at
> 2950 rpm (the motor is asynchronous, mains frequency is 50 Hz).
> The first trial run indicates a slight unbalance. It is
> probably OK, but if possible I like to improve the balance of
> the disk. Is there a systematic method to do this 'on line',
> i.e. with the disk mounted on the motor shaft?
>
> In a garage they use equipment to balance wheels: after a short
> spin the apparatus spits out what balance weight should be
> placed where on the rim to balance the wheel: anybody knows what
> the principle of operation is here?
>
> thanks in advance,   Rob
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