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Topic: Torque needed for rotating a solar dryer (Read 247 times) previous topic - next topic


Sep 17, 2018, 10:20 pm Last Edit: Sep 17, 2018, 10:25 pm by Theta_Tau_Tau

I want to control the rotation of a solar dryer with an arduino and a motor.

I didn't build the solar drier, I'm still in the conception phase, but it will look like this (maybe a bit smaller) :

I have no experience in mechanics, so I have no idea of the order of magnitude of the torque required.

Slow rotation speed is not an issue. It have to turn ~180° in the day (in increments of ~10°) then go back to the starting position at sunset. Something like 1 or 2 RPM would be ideal but even 0.1RPM is ok.

I want to use a worm gear, because it will lock the thing in place when it is not powered (wind won't make it rotate).

Looking in the internet I found cheap 1RPM DC motors with worm gear inside and a torque of 100 to 150 N.cm but I have no idea if this is even close to what I need. Also the solidity of the small worm gear they are using worries me.

The other possibility is to use a simple DC motor and add reduction gears and a worm gear, but again, I have no idea of the torque required.

Do you have an idea about the torque needed or about the method to get it? It's my first time doing a thing like this, I understand the concept of torque but I have no idea of what can be done with 100 N.cm.


I assume you want to rotate the entire box in your diagram?

If so the important thing is to mount it on a bearing with mow friction. You can get things called "lazy susan" that may be suitable.

If the bearing has low friction it will not require much force to rotate the box.

Two or three hours spent thinking and reading documentation solves most programming problems.


Thank you, I didn't know about "lazy susan", I will consider it.

I will try one of those cheap motors.


When you've built it , you can measure the torque needed to rotate with a spring balance . If  you divide this value by your worm gear ratio you will get the torque required for the motor - I would always add a margin (30-50%?) to allow gear friction etc etc


Any situation where friction and wind forces are important is not going to be trivial to
estimate - best to build it and measure.
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