Re: SRSG Alignment

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

Original poster: FutureT-at-aol-dot-com 

In a message dated 1/2/04 11:17:30 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

>About to start grinding my flats.  I do not have ready access to a vertical
>milling machine or a horizontal ramrod shaping machine, either of which
>would make this job sooo much easier, so the good old angle grinder is the
>go.  Any hints from anyone (Claude ?) on doing a good job of this before I
>start ?


Ian,

I often do the job first by drilling a bunch of holes to the correct depth
using a drill press, then finishing the job using a large hand file.  I used
the angle grinder method one time and it worked fine.  I first wrap a
metal tape measure around the armature to find the circumference.
Next I divide that number by four, and draw scribe lines on the armature
at the four equal spacings.  Then I made another set of scribe lines the proper
distance from the first set of scribe lines.  Finally I grind/drill/file the
metal away beween the proper sets of scribe lines so that the flat
areas extend between the sets of scribed lines.  When the flat just
touches the lines, then the flat is deep enough.  Make sure the
flats are truly flat, not crowned.  Actually crowned is OK, if they're
crowned to the same degree (which would be tricky to do, sort of).
If the flats are not exactly the same, or spaced the same, there will
be some vibration of the motor, but usually it is acceptable.


>Finally ... is there any way of knowing that the modification has worked
>without something to measure RPM on the motor ?


Yes, there are some ways.  One way is to tape a cardboard disc to
the motor shaft, and place a black or white line across the diameter
of the disc.  Observe this spinning disc under fluorescent light.  If
the motor mod is successful, a stationary pattern will be seen on
the disc.  If the mod was not successful, the pattern will appear
to rotate.  Some folks have a great deal of trouble learning to see
the pattern under fluorescent light.  It helps to slow down and
speed up the motor to learn to see the pattern.  Some folks like
to build a special stobe unit to see the pattern more easily.

In addition, the motor will sound very smooth when it's working
properly (at 1800 rpm, locked in to sync spinning operation).
If the motor can't quite lock up, it will produce a irregular hunting
sound.  You can experiment with all this by using a variac to
control the motor speed.  Usually the motors will lock up into
sync at about 50 volts with no load, or with a light load.  Of course
the motor will remain in sync as the voltage is raised.  The
phase will shift slightly as the voltage is raised.

Some folks have had to supply the motor with 140 volts from
a variac to get the motor to lock into sync operation.  This was
because their motor was marginally powerful for the heavy rotor
they were spinning.

John


>Rgs
>Ian
>