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Topic: Total weight a hobbico cs-60 Servo motor can handle? (Read 2617 times) previous topic - next topic

alexandros301

Hi,
I'm helping a friend with a project where she wants a small sculpture to move. She's got a hobbico cs-60 servo motor http://www.hobbico.com/radioaccys/hcam1000.html and I tried it with my Arduino and it works. I'd like to know though if it would be able to move a half a kilo heavy sculpture. The sculpture is gonna be made out of carton, based on half a meter long plexiglass column. Do you guys think this motor will do the job? Hope I'm clear enough...

PaulS

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Hope I'm clear enough...

Not even close. How the statue is to be moved has a lot to do with the torque required of the servo. You have said nothing about that.
The art of getting good answers lies in asking good questions.

alexandros301

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Not even close. How the statue is to be moved has a lot to do with the torque required of the servo. You have said nothing about that.


You're right, sorry. The sculpture is supposed to be swinging in a reverse pendulum fashion. It will be based on the floor, singing from left to right and back, rather slow. Say cover a distance of +/- 90 degrees in 5 seconds. The column will be approximately half a meter long (not sure about thickness), and the whole sculpture will weight around half a kilo.
Dunno if more details are necessary...
Thanks

Stingray

If it's a 0.5 meter long rod with a uniformly-distributed weight of 0.5 kg being rotated from horizontal, you need (0.5)*(0.5/2) = 0.125 kgf-m of torque. That servo is listed as being able to provide 3.5 kgf-cm = 0.035 kgf-m of torque. So you're nowhere close to what's required if I'm interpreting the setup correctly. Unless you buy a very expensive servo, you're going to have trouble connecting it directly to the pivot of an inverted pendulum which is that large. You might also burn out a servo by running it almost at its torque limit for extended periods of time.

Your power requirement is low [(pi/5 rad/s)*(0.13 kg-m)*(10 m/s^2) = 0.8 Watts], so a properly-designed lever/pushrod system could probably be used to make this work even with the servo you already have.


alexandros301

Plus, I've just been notified that the whole sculpture will weight approximately 200gr. Maybe the servo motor can handle that? If the equation for a half a kilo sculpture is 0.5*(0.5/2) = 0.125, is the equation for a 200gr sculpture 0.2*(0.2/2) = 0.02?

Stingray


Do you think something like this could work? http://www.robives.com/mechanisms/crank#.UlHF9iRPr0G


Yes, something like that is roughly what I had in mind.


Plus, I've just been notified that the whole sculpture will weight approximately 200gr. Maybe the servo motor can handle that? If the equation for a half a kilo sculpture is 0.5*(0.5/2) = 0.125, is the equation for a 200gr sculpture 0.2*(0.2/2) = 0.02?


The first 0.5 was for the mass of 0.5 kg. The factor of 0.5/2 was for the distance in meters to the center of mass. If you want 200 grams distributed uniformly over 0.5 meters, the max required torque is 0.2*(0.5/2) = 0.05 kgf-m. More torque is needed if most of the mass is at the end of the rod. Much less is needed if the sculpture isn't rotated all the way to the floor (which is how I've understood your description). Much less torque can also be required if you use something similar to the crank above.

If you just want a continuous back-and-forth motion, it would be better to buy an ordinary continuous-rotation motor that already has a gear mechanism attached. Then you can use a crank mechanism like what you linked to. You can find versions that develop much more torque than cheap servos and that stay put when you remove power (which a servo won't do).

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