# Too Complex for me - multiple torques on rotating disc

1. Sep 22, 2011

### pron

Hi all... my first time here... I hope someone can help.

I'm toying with a home project (in the early conceptual stage), and the attached picture shows "in general terms" what I'm trying to figure out.

The outer 'wheel' rotates about its central axis, driven at that axis by a small motor.

Near the outer rim of that wheel is a through-hole, with a ball bearing, and an axle going through to a 'hanging-weight' (for this example anyway).

On the back-side of that 'hanging weight' axle, a rotational load-torque is placed, that is relative to the main wheel center axis.

As the outer wheel is turned, how much of the "load torque" (percentage or formula) would be reflected back to the main wheel drive motor?

Assume the load is light enough that the weight does not significantly swing... and just hangs straight down... just looking for what I'd call "inferred counter-torque".

(BTW... I have had ZERO mechanical physics training/classes, so please excuse any obvious stupidity in my question or the way I'm asking... ask me about Electronics though, and I'm quite capable there)

Am I missing anything needed to make this calculation?
(Is this even possible to calculate, since gravity seems to play part of it?)

The "load" can be envisioned as an "adjustable slip-collar" fastened around the "hanging weight axle", with an arm extending from this collar back to the 'main wheel' axis point, with a frictionless bearing so no drag is incurred. This "slip-collar" is adjusted loose enough that the axle will turn, but will also present a rotating torque against that axle.

The only unknown reference point is for the drive motor (which is the same as the main wheel mounting/supporting structure), but that should not affect the calculation, since the load torque refers back to the 'main wheel' axis, and not the main wheel mounting point.

Assume: the main wheel is balanced by an additional identical weight, exactly opposite the one shown.

Weird problem... I know... I keep thinking there will be no effect... no additional torque reflected back to the main wheel drive motor.

I'm hoping for someone to just show me the math on how to calculate this, since these "example" values are drastically off from my real values.

[PLAIN]http://home.comcast.net/~rchinnery3/miscpix/physics_question_sml.jpg [Broken]

Last edited by a moderator: May 5, 2017
2. Sep 24, 2011

### Naty1

I could not open the picture to view it.

3. Sep 24, 2011

### pron

Try again... picture fixed