RE: Balancing an RSG rotor

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "terry oxandale by way of Terry Fritz <twftesla-at-qwest-dot-net>" <toxandale-at-cei-dot-net>

I drilled several 1/8" holes between each contact, spaced about 1/2" apart.
Placing an 8-32 screw (1") into these holes at various places as I used the
trial and error method, quickly showed me where the counterweight needed to
be. Next I would add another screw next to the first one (or add a nut). If
it helped, I added a third one, if it made the vibrations worse again, I
moved the second screw to a point 90 degrees away from the first one, and
then added a 3rd screw to a point 180 degrees to the second screw (opposite
side of wheel for balance). with these two opposing screws (2nd and 3rd
screws) you can fine tune the vibrations by moving both of them (together in
unison) either toward the 1st screw originally used (to add effective mass
to the 1st screw), or away from the 1st screw (to reduce the effective mass
of the 1st screw). This way the 2nd and 3rd screw will always balance on an
line between the axle and the 1st screw, thus effectively adding mass or
reducing the mass of the 1st screw.

I have found that even with a well indexed and machined piece of G11, that
these wheels do not balance out perfectly (perhaps resin distribution
differences) and that I've had some pieces that had minor variations in
thickness from one side of the wheel to the other. If the arbor is a cheaply
made unit, this can also contribute to the problem. With all these
possibilities, It is important to only start the counterbalancing procedure
only after the wheel is firmly chucked up onto the arbor/shaft and at least
indexed so that if it must be removed, that it can be re-installed in the
exact same position. With about 30 minutes of time involved, I finally
achieved a vibration free (at rated motor speed) RSG that was a bit scary
before doing this.

Good luck,

(un) Terry

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, October 28, 2002 12:50 PM
To: tesla-at-pupman-dot-com
Subject: Re: Balancing an RSG rotor


Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Parpp807-at-aol-dot-com>

In a message dated 10/28/02 9:24:39 AM Central Standard Time,
tesla-at-pupman-dot-com writes:

 > What are good techniques for balancing the rotor?
 >
Aric,
I have a 10 inch disk of G-11 on a 1/2 inch arbor.
All bets are off if you didn't lay out all the holes B4 cutting the disc.
I first drill a very small (1/16) hole for the leg of the dividers. I make
all the layout
and do all the geometry from that point before I cut the disc. That small
hole
becomes the center which fits directly over the 1/2 inch shaft arbor. I cut
the circle on a band saw and faced-off the disc on a lathe.

Cheers,
Ralph Zekelman