Electronics > Electronics

will this motor work

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sohailsameja:

--- Quote from: drinu on March 06, 2013, 11:19:07 AM ---Hi,

It depends on the size of the robot. Do you have a photo?

Are you going to use gears with the motor's output shaft to increasing torque?

On ebay you will find many inexpensive motors with gears :

http://www.ebay.co.uk/sch/i.html?_nkw=gear+motor+kg&_sacat=0&_odkw=gear+motor&_osacat=0&_from=R40

and BTW I would guess the top motor is the best. The ones at the bottom, as far as I know have very low torque.

--- End quote ---
Well thanks for the reply i do not have any gears(cant obtain them) and e-bay does not ship to my area.well i tried all the motors in the picture directly with a 9v and they did not show any burning signs so i guess they go well with 9v.The weight is around half KG

--- Quote from: newInRobotics on March 06, 2013, 11:22:18 AM ---
--- Quote from: sohailsameja on March 06, 2013, 10:30:10 AM ---is there a way of modding it so it can be geared,but according to you which is the best choice(regardless of anything)
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Gearing is the only way to reduce angular velocity (RPM) and increase torque of the motor. You can buy required ratio gearbox separately and plug to Your motor.

--- Quote from: sohailsameja on March 06, 2013, 10:33:26 AM ---by the way can increasing the weight of the tires or bodies increase torque.
--- End quote ---
Increasing weight of the robot will increase torque required to move it.

--- Quote from: sohailsameja on March 06, 2013, 10:33:26 AM ---BTW: is this true:

velocity=2*pi*r*rpm
torque=d*f
f=m*a
a=change in velocity/time
--- End quote ---
Velocity formula is correct.
Torque formula is not, it should be T = F * r (Torque = Force * radius).
Force formula is correct.

--- Quote from: sohailsameja on March 06, 2013, 10:33:26 AM ---[...] i have the mass of robot and rpm of motor.Can i be able to calculate the torque?
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To calculate required torque You have to know desired acceleration, mass of the robot and wheel radius.

--- Quote from: sohailsameja on March 06, 2013, 10:33:26 AM ---so if i calculate a using anything even a ticker timer
--- End quote ---
To get acceleration simply think this way - decide on the max speed You want your robot to go, and then think of how long You wouldn't mind to wait for robot to reach that speed.

Example:

I want my robot to go at 5km/h (1.39m/s) max and I'm prepared to wait no more than 2.5s for it to reach that speed;
a = 1.39m/s / 2.5s = 0.556m/s2;

Now, my robot's mass is 1.6kg, so force required to achieve required acceleration is F = 1.6kg * 0.556m/s2 = 0.8896N (Newton);

Say my robot has wheels of 2.5cm radius (0.025m), this tells us that motor should output at least T = 0.025m * 0.8896N = 0.02224N*m (Newton meters) of torque, but we don't want motor to run at 100%, so lets do this NewTorque = 0.02224N*m / 0.75 = 0.03N*m;

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Thanks you have been helping me all way.since i cannot have a gearing system i will use rubberbands or anything stronger and see what happens.I think the gears are originally 6v but im pushing them at 9v.hence higher velocity.but hopefully i shall try to contain them.(please give any other ideas apart from gearing)Thanks

--- Quote from: jwatte on March 06, 2013, 11:47:47 AM ---The easiest way to increase torque is to use a rubber band across the output shaft of the motor (small diameter) and then across a large wheel/cup/plate/disc on your actual wheel shaft. Maybe even directly around the wheels. Getting the rubber band to stay on and not jump off is tricky; you may need to build some rims with glue or epoxy or plastic or something.

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I shall try that method as the wheels have to 7.5 cm or 8cm cd's i will see how to do it(if you have a tutorial just tell me.

:'( :(I JUST LOST MY L293D CHIP SHOPS ARE CLOSED AND DEADLINE IN 5 DAYS. :'( :(

waltr:
Another cheap method to reduce RPM and increase torque:
Mount the motor so that it shaft is parallel to the wheel's axle and the motor's shaft contact the outer edge of the wheel. The reduction ratio is the wheel's diameter divider by the motor's shaft diameter. The torque is increase by the inverse of the speed reduction ratio minus some frictional looses.
The trickiest part is adjusting the motor shaft pressure on the wheel. Too little and the shaft slips, too much and the motor won't turn.

I've built a couple of robots using this method and they did run well. Best was that the cost was very low.

sohailsameja:

--- Quote from: waltr on March 06, 2013, 05:54:10 PM ---Another cheap method to reduce RPM and increase torque:
Mount the motor so that it shaft is parallel to the wheel's axle and the motor's shaft contact the outer edge of the wheel. The reduction ratio is the wheel's diameter divider by the motor's shaft diameter. The torque is increase by the inverse of the speed reduction ratio minus some frictional looses.
The trickiest part is adjusting the motor shaft pressure on the wheel. Too little and the shaft slips, too much and the motor won't turn.

I've built a couple of robots using this method and they did run well. Best was that the cost was very low.

--- End quote ---
Do you have a diagram representation or a tutorial.

voodoo:
Its a brushed motor, use transmission to make for a better torque.  Also it will not strain the motor as much with gears. Worm drives are amazing for torque

waltr:
Here is an examples of the motor shaft to wheel I described above and is shown in the first picture:
http://www.wired.com/design/2012/09/afron-winners/