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Author Topic: will this motor work  (Read 679 times)

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Offline sohailsamejaTopic starter

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will this motor work
« on: March 06, 2013, 09:49:32 AM »
I obtained this motor from a cd-drive and i identified it as a brushless motor funny thing is that it has 2 contact points that one touched with a 9.v battery it spins happily it does not have 3 contacts as most brushless have.Question is am i mistaking it for a brushed motor because of its shape
2)is it a good substitute for a 9v battery that can run in the $40 Robot by pratheek.
MODEL NUMBER

RF-300EH-1D390
SD36404
D/V5.9
« Last Edit: March 07, 2013, 12:51:58 PM by sohailsameja »
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Offline newInRobotics

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Re: WILL THIS MOTOR WORK
« Reply #1 on: March 06, 2013, 09:59:39 AM »
If it has only 2 wires, it's a brushed motor (we are talking about DC motors only, some AC motors have 2 wires and they are brushless), which You proved by plugging it to 9V battery and seeing it spin. Brushless motors have more than 2 wires and would not spin when plugged directly to power source.
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Offline sohailsamejaTopic starter

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Re: WILL THIS MOTOR WORK
« Reply #2 on: March 06, 2013, 10:14:23 AM »
PLEASE CHECK THIS IMAGES OUT.AND TELL ME THE MOST APPROPRIATE ONE THANK YOU($40 dollar ROBOT)
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Offline sohailsamejaTopic starter

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Re: WILL THIS MOTOR WORK
« Reply #3 on: March 06, 2013, 10:15:18 AM »
THE 2nd PIC
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Offline newInRobotics

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Re: WILL THIS MOTOR WORK
« Reply #4 on: March 06, 2013, 10:25:26 AM »
Pictures do not show motor specs, plus, all these motors, as far as I can tell, are plain (without gearbox), hence won't be able to run robot as they are (not enough torque).
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Offline sohailsamejaTopic starter

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Re: WILL THIS MOTOR WORK
« Reply #5 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)

P.S You are very helpful thanks.
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Offline sohailsamejaTopic starter

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Re: WILL THIS MOTOR WORK
« Reply #6 on: March 06, 2013, 10:33:26 AM »
by the way can increasing the weight of the tires or bodies increase torque.

BTW: is this true:

velocity=2*pi*r*rpm
torque=d*f
f=m*a
a=change in velocity/time

so if i calculate a using anything even a ticker timer
and i have the mass of robot and rpm of motor.Can i be able to calculate the torque?
« Last Edit: March 06, 2013, 10:54:39 AM by sohailsameja »
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Offline drinu

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Re: WILL THIS MOTOR WORK
« Reply #7 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.

Offline newInRobotics

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Re: WILL THIS MOTOR WORK
« Reply #8 on: March 06, 2013, 11:22:18 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)
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.

by the way can increasing the weight of the tires or bodies increase torque.
Increasing weight of the robot will increase torque required to move it.

BTW: is this true:

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

[...] i have the mass of robot and rpm of motor.Can i be able to calculate the torque?
To calculate required torque You have to know desired acceleration, mass of the robot and wheel radius.

so if i calculate a using anything even a ticker timer
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;
« Last Edit: March 06, 2013, 11:51:55 AM by newInRobotics »
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Offline jwatte

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Re: WILL THIS MOTOR WORK
« Reply #9 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.

Offline sohailsamejaTopic starter

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Re: WILL THIS MOTOR WORK
« Reply #10 on: March 06, 2013, 12:38:41 PM »
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.
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
is there a way of modding it so it can be geared,but according to you which is the best choice(regardless of anything)
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.

by the way can increasing the weight of the tires or bodies increase torque.
Increasing weight of the robot will increase torque required to move it.

BTW: is this true:

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

[...] i have the mass of robot and rpm of motor.Can i be able to calculate the torque?
To calculate required torque You have to know desired acceleration, mass of the robot and wheel radius.

so if i calculate a using anything even a ticker timer
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;

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
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.
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.

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Offline waltr

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Re: WILL THIS MOTOR WORK
« Reply #11 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.

Offline sohailsamejaTopic starter

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Re: will this motor work
« Reply #12 on: March 09, 2013, 12:12:56 AM »
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.
Do you have a diagram representation or a tutorial.
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Offline voodoo

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Re: will this motor work
« Reply #13 on: March 09, 2013, 08:14:12 AM »
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

Offline waltr

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Re: will this motor work
« Reply #14 on: March 09, 2013, 09:53:41 AM »
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/

 


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