# Torque estimate ?

1. Feb 16, 2008

### rngd

Guys, I have a solar panel screwed onto a shaft which connects directly to a servo motor shaft. How much should the torque rating of the servo be to be able to rotate it ? I mean an estimate of the minimum torque required. The panel weighs 0.8kg plus a few grams for the solar panel holder (made of perspex). No gears are used.

Thank you.

2. Feb 16, 2008

### FredGarvin

You'll need an estimate of either the radius of gyration or the moment of inertia about the rotating axis. You will also have to either assume or specify a rate of angular acceleration about that axis.

3. Feb 17, 2008

### rngd

I would need the servo shaft to rotate a total of 135 degrees, rotating a few degrees every half an hour for eight hours (It will operate like a stepper, stepping during each hour). The speed of rotation is not important, as long as it rotates. The panel's length is 32cm and height is 18 cm. It is a sun tracker.

There will also be another servo to rotate the round base.

Pls see diagram attached below.

Does this help ?

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4. Feb 17, 2008

### Staff: Mentor

If the collector is balanced, and with the angular velocity being small, the torque required from the motor is tiny. I'd look into a telescope clock drive (if they still make them). Otherwise, you can get a stepper-motor upgrade kit, but they are more expensive than one that just plugs in and runs at the clock rate.

5. Feb 17, 2008

### rngd

How tiny ? The panel weighs 0.8kg. Is this servo sufficient (3.40 kg-cm torque) ?

http://www.databitz.com/Resources/crservo.pdf

What about the servo at the bottom (there will be some bearings below the base) ? It seems like the top would be a bit heavy. The whole frame will be made of perspex.

Last edited by a moderator: Apr 23, 2017