### Author Topic: Getting torque out of 3DCV  (Read 2098 times)

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##### Getting torque out of 3DCV
« on: September 14, 2007, 12:36:14 PM »
A school project limits my energy sources to 2x Duracell AA batteries(1.5V each). I need to pull a wheeled prototype weighting around 1kg. I'll need to get up a 15deg slope. Now the best stall torque i could find for 3V is 15cm-g which, unless my math is wrong, isnt enough. Anyone knows of a better motor or if there's a way to raise my voltage? Unless im mistaken, i cant use a transformer on DC...

Thanks

#### Rebelgium

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##### Re: Getting torque out of 3DCV
« Reply #1 on: September 14, 2007, 12:54:37 PM »
You can't use transformers on DC, but you can use DC-DC switching to make the voltage higher.
And you could also use those small 3VDC FA130 motors, use a motor (with gearbox ofcourse) for every wheel. So you can use four motors with gearboxes for your robot without having to make the voltage higher...
That should do it.
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#### hgordon

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##### Re: Getting torque out of 3DCV
« Reply #2 on: September 14, 2007, 02:13:29 PM »
Raising the voltage probably won't help you, since you're still limited by the output current of the AA's.  Look for the highest gear ratio you can find - that's the way to get more torque.

These motors should be adequate -
http://www.solarbotics.com/products/index.php?scdfa-250100084-viewDetail-productzq31047zq4categoryzq37=true

They should be able to run at 3V, and are rated at 30.7 oz-in at 5V, which would be equivalent to 2210 gm-cm at 5V or 1326 gm-cm at 3V (1 oz-in = 72 gm-cm).  Also, use the smallest drive wheels you can find to maximize your torque.
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#### Rebelgium

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##### Re: Getting torque out of 3DCV
« Reply #3 on: September 14, 2007, 02:27:23 PM »
Quote
Raising the voltage probably won't help you, since you're still limited by the output current of the AA's.
Unless he's at the maximum current of the AA's, that's not true.
Raising the voltage will help.

And yes ofcourse, how could I forget to mention the most obvious  , small wheels and high gear ratios.
The higher the gear ratio: more torque, less speed.
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#### paulstreats

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##### Re: Getting torque out of 3DCV
« Reply #4 on: September 14, 2007, 05:29:39 PM »
the tamiya twin motor gear box by pololu can gear down to 501:1 ratio, its cheap and includes motors which can operate at 3v, i have a spare one and ive just tested it at 3v. There are different sized wheels that you can buy at the same time, obviously the larger ones will reduce the effect of the gearing slightly but move faster.

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##### Re: Getting torque out of 3DCV
« Reply #5 on: September 15, 2007, 01:07:38 PM »
This is a tutorial I wrote with a calculator to answer this exact type of question . . .
http://www.societyofrobots.com/mechanics_dynamics.shtml

Just plug in your numbers and it will tell you if your motor is strong enough.

Now you didnt mention speed . . . so you could just gear down your motor a lot. Your robot will be very slow, but have high torque:
http://www.societyofrobots.com/mechanics_gears.shtml