Re: Bulk Buy Toroids (also selecting sync motors, and phase shiftquestion) (fwd)

["Tesla list" <tesla-at-xxxxxxxxxx>]

Original poster: Tesla List Moderator <mod1-at-poodle.pupman-dot-com>



---------- Forwarded message ----------
Date: Wed, 6 Dec 2000 09:05:22 EST
From: FutureT-at-aol-dot-com
To: tesla-at-pupman-dot-com
Subject: Re: Bulk Buy Toroids (also selecting sync motors,
     and phase shift question)

In a message dated 12/5/00 8:35:39 PM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

> 
>  . My only beef is that since I paid so much
>  > for this thing they could have at least put a dimple in the center where 
I
>  > would want to drill a hole.

Jim, Sue, all,

I received my toroids yesterday also, and they are BEAUTIFUL!!!!!!
The shape is excellent, the finish is excellent, nice and heavy and
strong, etc.  I bought the softer 1100 metal, but it seems plenty
strong to me since it's 1/8" thick.  I think the price was fantastic,
Some places charge $250 for a 14" toroid.  I've seen professional
spun welded toroids where the shape of the edge is not quite right
and is a little pointy.... but these are perfect !!  I'm happy to drill a
hole for that price.  I plan to just place a ruler across the center
part and mark the center, then turn the ruler 90 degrees, and make
another mark.  Where the two mark intersect.... that's where to 
drill.  Thanks so much Jim for offering, arranging, and handling this
bulk purchase !!

To reduce bandwidth, I'll talk about sync motors in this same posting.
There are basically 3 types of sync motors for sync rotary gaps; 
Hysteresis, Salient pole, and home modified induction motors.

Avoid the hysteresis motors like the ebola virus!!  They are NG for
our use.  I had tested one in the past, and I thought it locked
in the same position all the time, but I retested it, and it does not.
Fortunately, these motors usually are marked as hysteresis types.
The armature is a special metal that has a large hysteresis 
characteristic, and so it can lock in any random position.  If you
use this type of motor, you'll have to re-adjust the sync phase 
every time you run the coil... not fun at all.  I wonder if grinding
flats on these motors would make them lock in the same position,
I wonder if anyone has tried that?  Somehow I suspect it won't 
work well.  My hysteresis motor required the use of an 8uF capacitor,
and I was surprised that it worked poorly with a 15uF cap, I don't 
know if the cap size is critical on all hysteresis sync motors.  

The salient pole type is what we want.  These motors often don't
even say sync on them.  The clue is the rpm of 1800 or 3600, or
1500 or 3000 for 50Hz locations of the world.

Lastly are the modified induction motors.  Just take any 1725 or
1750, or 3450 rpm induction motor from a washing machine, clothes
dryer, etc, and file, grind, or machine flats on the armature, and this
will make the motor synchronous.  1725 gets 4 flats about 1/3 the
dia of the armature, 3450 gets 2 flats about 1/2 the diameter of the 
armature.  The width of the flats is not real critical but should be the
same for balance.  You'll lose some power when it's modified, and
the motor will run hotter.  But many folks have used this method
and it works perfectly.  There's a method of using the dead poles
to decide the width of the flats, but many small motors don't have
dead poles, so I just ignore this dead pole method.  The 1725 rpm
motor will jump up to 1800 when it's modified, and the 3450 motor
will jump up to 3600 rpm.

I'm presently building a new sync rotary using a 1/20 HP teletype
salient pole sync motor, and a 3/8" x 6.5" G-10 rotor.  3600 rpm.
This motor has plenty of torque for that rotor size and weight.

Can anyone suggest a way to shift the incoming ac phase to the
motor?  I know about the variac method which gives a small phase
shift, but I want a very large (full range) phase shift capability.
Usually I rotate the motor in the cradle to adjust the phase, but it
would be nice to simply shift the incoming ac phase which which
automatically give remote phase adjustment capability.

I still see some one-liner postings from folks such as, "Great coil",
or "thanks for the photos", etc.  I certainly hope that folks will
send these comments directly to the person involved instead of
to the entire list.  I hope Terry will begin to reject such one-liner
postings to reduce bandwidth and excessive numbers of postings.
Thanks.

John Freau