Re: Re: Brushless Servo

PTENGIN@... wrote:

> From: PTENGIN@...
>
> In a message dated 10/09/1999 6:08:42 PM Hawaiian Standard Time,
> gregg@... writes:
>
> <<<snip> Another source is the range of ink jet and laser printers.<snip>
>
> Jim Gregg
> >>
>
> I remember seeing large servo's (or were they steppers?) driving the carriage
> of the old Qume daisy wheel printers.

Yup, those are VERY nice motors, enough torque to break your arm (or
fingers, anyway) and optimized for moderately low speeds. Very smooth,
too, and they have an optical encoder on the back.

> I think DEC writers and others may
> have had large motors too.

The motors in a DECwriter are not of the same quality, but they work. I think
they intentionally allow a GREAT deal of eddy losses in the armature iron
to help damp out a very unstable servo system. If you try to turn one of these
motors with nothing attached, you will find an awful lot of drag.

> Old IBM stuff had clutches and belt drives from
> constant running jack shafts. Some of the larger IBM line printers had very
> large steppers driving the paper through the machines.

An old Honeywell line printer I retired a few years ago had a big printed
motor (a method of making a servo motor with a round printed circuit
board as the armature and windings) in a servo loop for the paper feed.

> Older hard disk drives
> often had band drives or lead screws on steppers moving the head back and
> forth just like the old 8 inch floppy's. Some had voice coil style servos. (
> basically a linear motor) Large drum plotters often have servo's or steppers
> in them also. Hopefully others can add to the machines we can look through.

My big Calcomp pen plotter has some very nice servo motors with encoders -
but it is too useful as a plotter to take apart.

Jon