What is this strange encoder motor?

Lots of new pictures here.
http://igor.chudov.com/projects/Bridgeport-Series-II-Interact-2-CNC-Mill/24-Troyke-Rotary-Table-U12PNC/
This is a servo motor driven rotary table Troyke U12PNC.
I thought that it was a simple servo motor with a tachometer and encoder on the back. Nothing could be further from the truth. When I opened it up, the tach was on the back alright, but no encoder.
I took off a box hanging on the front of this contraption and I think this is where the encoder is. There are two cylinders.
One is called "Electro-craft moving coil tach generator". Part 0100-00-022.
The other is "Summit engineering, Boseman MT. Model 573-211-10, 2500 Hz, rotor 1 phase, stator 2 ph, spec code H.S.C.T., 11BRW-300-70/10."
Does anyone have AN idea just what are they and whether I can use it as a quadrature encoder.
On the rear of the motor, there is not enoug free hanging shaft to mount a modern encoder.
My uneducated guess is that it is a "resolver".
Thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 08/02/2010 04:50 PM, Ignoramus18921 wrote:

http://igor.chudov.com/projects/Bridgeport-Series-II-Interact-2-CNC-Mill/24-Troyke-Rotary-Table-U12PNC/
My educated guess is that it is a resolver. The frequency is right, the labels on the rotor and stator are right.
Do you have a signal generator and an O-scope? Feed it with 2500Hz to the rotor, and see if you get 2500Hz out the two stator windings, with a coupling that depends on the shaft position.
There may be industrial resolver to encoder converters out there -- it would be something that a machine designer or retrofitter might need.
--

Tim Wescott
Wescott Design Services
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

There are some converters out there, Jon has one for sale too.
Tim, how much angular accuracy could I get from this resolver, in pulses per revolution?
If this is too complicated, I may just look for the right sized modern servo motor on ebay.
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I forgot to add, or make a shaft adaptor if it is at all possible, and mount an encoder.
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 08/02/2010 06:48 PM, Ignoramus18921 wrote:

Um -- pretty damn good?
It's hard to say, because it varies with the resolver. But I'd expect anywhere between one and ten minutes of an arc (no, you don't get dimensions in degrees, or counts, when you're dealing with resolvers). Resolvers that do better than that generally go to "multi-speed" units, with a "high-speed" resolver that repeats itself 8, 16, or 32 times around the circle, and a "low-speed" (1x) resolver to tell you what quadrant of the high-speed resolver you're looking at.

Aw, what's the fun in that?
--

Tim Wescott
Wescott Design Services
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Say, ten minutes of arc, gives you 360*6 = 2160 units of resolution per circle. Very good in my view. Certainly enough in a geared way down rotary table.

I am having enough fun as it goes. I want some uncomplicated solutions.
I have seen people having too much fun with unfinished machines sitting for years. The second addiction is being too cheap. $30 servo drives are not cheap enough for them, so they sit and wait until they can find $5 servo drives or "make their own" from stuff they find in dumpsters.
The first approach (too much fun) has some advantages, but disadvantages are big enough, in my view, to not go there.
The second approach is uneconomical, if you are smart to make your own servo drives it is better to buy one and make money doing something more economically valuable.
i milling out a bigger mold than yesterday and standing in front of EMC
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

[much snipping]

Iggy has a resolver, is it safe to say that an Inductosyn linear scale is the same type of device? I'm curious since I have a sick id od grinder at work that still has some issues after replacing the sliding head for the scale.
Wes -- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 03 Aug 2010 17:59:44 -0400, Wes

It's the same thing, just laid out flat.
db
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Jon might know, I have no clue. Who made that Inductosyn?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus30076 wrote:

An Inductosyn is similar in concept to a resolver, where a coil is energized with an AC field, and by varying magnetic coupling to other coils the position is detected. Inductosyn is a registered trademark of Farrand Controls, but their patent has run out. The classic Inductosyn has an exciting winding consisting of a serpentine trace on a PC board like material. Very close to this is another short piece with two serpentine traces of the same pitch a the spar. The two traces are offset by 1/4 of a pitch, to provide the quadrature relationship.
The problem with the Inductosyn is that it takes a LOT of drive current to provide a useful signal from the sense windings, often several amps of drive.
Jon
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus18921 wrote:

The AD2S1200 converter chip I use in my converter board gives 4096 quadrature counts/rev, with an index pulse.
Jon
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Sounds like a luxury item.
I already bought this converter from you. Things seemingly are going well.
Igor
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I had a second look at the motor.
http://tinyurl.com/2vagsc7
You can see the rear end (ODE) of the motor shaft. It is kind of roughly machined, as if cut off with a hacksaw or something.
If a recolver converter is not practical here for any reason, I think that simply mounting a US digital E5 encoder on the back may be the best option of all.
I think that it is a simple machining exercise to flatten that side, locate a center and precisely drill a hole in the shaft (precisely, here, means under 0.005" error) along the axis of rotation. Then I would tap it and use a shoulder bolt with the head cut off, to mount the encoder wheel.
If it does not fit under the cover, I will make a bigger cover from aluminum.
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 08/02/2010 08:09 PM, Ignoramus18921 wrote:

Threads don't make a good center reference, in my limited experience.
I would bore the hole for the threads, then counter-bore and ream to a light press fit of some handy drill rod. Then I'd make a bushing out of the handy drill rod and press it (lightly) into the hole. Then I'd say "whoa, look! a stepped shaft!" and I'd bolt an encoder disk to it.
--

Tim Wescott
Wescott Design Services
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
...

This is the best route to go. I did this to a 7.5 hp lathe spindle motor.
Karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Should be one evening's job with this little servo motor.
How would I pick a drill and reamer to make a press fit hole for, say, a 1/4" shaft?
Say, McMaster has two reamers, 0.248" and 0.2495", for a 1/4" dowel pin. Which one should I use?
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If you use the small one, at only 1/4", it'll take a lot of heat to get the hole to expand that one thou or so you'll have left to go. You'll also have to work with confidence and speed when you press it on.
Some guys would use the larger one, and a drop of Loctite to secure the joint. It won't be under any significant load.
Just for G.P.s, I'd figure getting a .250+ hole out of the .2495 reamer unless _everything_ in the setup was spot-on.
One trick is to heat the work before reaming with the optimum-size reamer (and keep it hot during reaming, so it doesn't seize up on the tool). When the piece cools, it will be exactly the amount undersized to fit up the way you want.
LLoyd
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2010-08-03, Lloyd E. Sponenburgh <lloydspinsidemindspring.com> wrote:

Lloyd, I cannot heat it, it is a motor shaft mounted in the motor.
I think that .2495 and loctite would be perfect.
So, .2495 reamer, 1/4" dowel pin, and what drill should I use for initial drilling of the hole?
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Unless that's a really short-shafted "pancake" motor, you're going to play hell setting it up to run true for the initial spotting, unless you've got enough shaft sticking out to mount the outboard end in a steady rest.
For that purpose, you should use a short, stiff "spotting drill". A center drill will work. But if you want the hole not only true in size, but also perfectly centered in the work, you should bore it to reaming size, not drill it. (pre-drill, of course...) That's a teensy boring tool.
Somehow, I envisioned turning a "hub" type shaft extension, and pressing it ONTO rather than INTO the motor shaft. That would be a lot more accurate to set up and make, and wouln't involve modifying the motor itself (along with the concomittant problems of getting a heavy weight on a relatively long spindle to run true in total overhang.
If you did it the way I envisioned, then you could even mount the whole affair between centers after joining, to true everything up and finish the stub shaft to size.
LLoyd
LLoyd
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2010-08-03, Lloyd E. Sponenburgh <lloydspinsidemindspring.com> wrote:

I can have up to 0.01" shaft error.

I cannot do it, the shaft sticks out only by 1 mm or so.

I would do it on a mill, not on a lathe. 0.01" is not space age accuracy, I think that I can do it.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.