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Author Topic: Torque  (Read 2958 times)

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Offline omee66Topic starter

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Torque
« on: March 13, 2007, 07:02:17 AM »
Hello everyone!
I've been a frequent visitor and have been reading the wonderful tutorials on this site-- they are very helpful.
I have recently started to work on my first robot, hopefully a line following robot. I constructed my motor drivers and it seems the small vibrating motors will not do. It is probably a torque issue, so I am wondering what is the best method to increase the power of my robot?
I was thinking this, but I am not sure how good it is:
http://elm-chan.org/works/ltc/ltc02.jpeg

Thank you!
Omar

Offline JonHylands

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Re: Torque
« Reply #1 on: March 13, 2007, 07:41:20 AM »
Omar,

If you're building a pager motor-sized robot, you need to gear it way down.

Two easy ways to do this:

http://www.robotshop.ca/home/products/robot-parts/motors/gear-motors/low-cost-gears-motors/solarbotics-gm10-geared-pager-motor.html

http://www.robotshop.ca/home/products/robot-parts/motors/gear-motors/low-cost-gears-motors/solarbotics-gm15-gear-motor.html

Note that the second gearmotor is 4x faster than the first, so it will only work with small wheels - if you want to use larger wheels (say, larger than 1/2" diameter), go with the first option...

- Jon

Offline omee66Topic starter

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Re: Torque
« Reply #2 on: March 13, 2007, 08:05:55 AM »
Thank you very much, Jon. I actually got these motors from those tiny R/C cars, so each has a very tiny gear and the wheels have a larger gear included. I suppose I can use those?

I was just a little confused, because that site I showed you used a tiny motor as well, without much gearing. Am I overlooking something?

Thank you very much!
Omar

Offline Admin

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Re: Torque
« Reply #3 on: March 16, 2007, 05:27:47 PM »
because of volumetric scaling laws, motor torque decreases by the cube as size decreases linearly.

simply put, by laws of electromagnetics, tiny motors have almost no torque. :P

even worse, if you put gears (high precision gears required) on them, the weight of the gears plus efficiency losses kills what little torque they do have . . .

if you are trying to build a really small robot, you may want to consider using linear piezoelectric actuators and piezoelectric motors instead.

this tutorial might also help you calculate what torque you require from your motors for your robot to work:
http://www.societyofrobots.com/mechanics_dynamics.shtml

Offline omee66Topic starter

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Re: Torque
« Reply #4 on: March 16, 2007, 07:03:36 PM »
Thanks a lot :).
It seems that using a small motor might just be a drag. I'll stick to bigger motors, I suppose.

I guess my next question is-- how good are elastic bands for torquing?
I am thinking of making a large engraved slit in the middle of my wheels, and get rubber band to spin around them. This way, more torque and more power. I don't need to get up slopes or anything, just as long as my robot moves I'll be happy at this point :P.
So rubber bands, are they a no no?

By the way, Admin, you're like my biggest hero. So the fact that you replied, I feel special :P.

Thanks,
Omar

Offline Admin

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Re: Torque
« Reply #5 on: March 17, 2007, 04:51:05 PM »
Quote
I guess my next question is-- how good are elastic bands for torquing?
I am thinking of making a large engraved slit in the middle of my wheels, and get rubber band to spin around them. This way, more torque and more power. I don't need to get up slopes or anything, just as long as my robot moves I'll be happy at this point .
So rubber bands, are they a no no?


took me a bit to figure out what you meant . . . good thick rubber bands might work but since they are elastic they are hence a bit unpredictable. have you considered the mouse trap car idea? i made one many years ago and it was really reliable - just make sure you do the gearing calculations/guessing properly (wheel diameter vs spool diameter ratio). :P

Offline omee66Topic starter

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Re: Torque
« Reply #6 on: March 17, 2007, 09:14:13 PM »
Actually, I am making a line following robot using a 16F684 microcontroller (due to its A/D conversation for the sensor)-- so I am using motors and wheels. That is why this dilemma started.

Any tips?

 


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