I want an old tape drive motor

From: Carlos Murillo <carlos_murillo_at_epm.net.co>
Date: Wed Oct 30 07:08:11 2002

At 11:33 PM 10/29/02 -0800, you wrote:
>...I am wondering if anybody knows where I can find a couple super low
>inertia motors like some older tape drives and other very rapid
>positioning equipment used
-snip-
>Motor Moment of Inertia (Jm) = 0.0007 to 0.0009 oz/inch sec^2
>Torque constant (Kt) = 9 oz/inch per Ampere (for 1 Ohm motor, ie. Rdc = 1
Ohm)
>Torque constant (Kt) = 14 oz/inch per Ampere (for 2 Ohm motor, ie. Rdc = 2
Ohm)
>Drive shaft = 3/8 in. (diameter)
>"Figure of Merit" (FoM) = Kt/(Square root of Rdc) = 9.9 oz-in of
>torque per watt disipation

So you want to build a contrabass? I have never heard one...
but I have always been skeptical about its ability to put out HiFi.
The reason is that people use DC servomotors with *brushes*, and
believe, the behavior of these things at low speeds is very nasty
in terms of nonlinearity: static friction, nonlinear torque(i,theta);
so until someone proves me wrong I think that they are just
huge rumble-makers without any HiFi attributes.

Now, if they used a high-grade brushless servo with special
feedback control algorithmics and sensors... and a more reversible,
static friction-less kind of transmission... I might buy the idea.

carlos.

--------------------------------------------------------------
Carlos E. Murillo-Sanchez carlos_murillo_at_nospammers.ieee.org
Received on Wed Oct 30 2002 - 07:08:11 GMT