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View Full Version : TORQUE-RPM??? HOW ARE THEY RELATED???

shash_v_s
02-04-2005, 11:01 AM
Hi guys,
Just kidding!! Make a lot of sense,torque and rpm.
I have a query on these, though.
My problem is-
How do u calculate the TORQUE of a motor if rpm is the only spec given and vice-versa??
Besides, if a motor of 30rpm has a torque of 2kgcm, does that mean all motors of 30rpm have the same torque of 2kgcm?
When u say torque of 2kgcm or 0.5Nm, whats d max load the motor can move without stalling?
Also, how do u decide the torque if u have a rough estimate of the robot the motor is supposed to drive?
I am planning a Mobile Robotic Arm with 4 degrees of Freedom. Its a Tank Tracked robot. Now, the overall weight including the arm is abt 10kgs. So how much do u thnk shld be the Torque of the motor? We are planning to use geared DC motors.
Also, please tell me abt the CHASSIS BUILDING aspects of robots. Any links will help.
The arm chassis is another problem.
Theres no problem at all with the electronics and programming part.
MOTORS AND CHASSIS HOLD THE KEY.
I would appreciate any help.
See ya,
Shashank :)

technojunk
02-04-2005, 05:48 PM
hi shashank

Taking power of motor as constant (in general it is)..torque and rpm of a particular motor are inversely related..its is well known that
Power=TorquexR.P.M

Hence for the given motor it holds good...but it is not true that all the motors having same rpm ( say 30 rpm in ur case) have same torque...it depends on motor.Further u may refer to torque speed characterictics of motor.

And coming to the torue of motor it is generally specified with motor. Measuring torque is sort of difficult..u may use a dynamometer type of arrangement for that!!

And for calculating the torue required...first u need to know the rolling and static friction coeff between the suface and the wheels of ur robo....u may do approximations here! And then follows the simple calculations of the force ....

Hope this helps.Do tell me abt ur project.

All the best

praveen

shash_v_s
02-05-2005, 11:02 AM
Thanx Praveen,
That really helped!!
However, I have another query. When u say torque of 2kgcm or 0.5Nm, whats d max load the motor can move without stalling?
Its an All-terrain robot we are building. And, we are complete novices when it comes to the mechanical aspect. However, one of the members is prepared to do the chassis design. The prob is that we have no idea where to start. As I said the Electronics and Pgming part pose no problem. Its the Mechanical aspect viz the motors, chassis and the drives.
Heres abt out project:

All-Terrain Robotic Vehicle for Multiple Applications
(ATRVMA)
Sounds cool,isn't it??

Well, Its a Tank-tracked robot with a robotic Pick and Place arm with 4 degrees of freedom. Its controlled via RF by a PC running the VB control software. The movement will be controlled by either the keyboard or the Joysticks. Its a Duplex RF module wew are using. So, the onboard PIC will be transmitting viatal parameters back to the HOST. The parameters include
Velocity(rpm of motor)
Distance travelled from the last reset position
Battery Levels
Status of the various modules -- SONAR, Metal Detector etc
etcetera.

Well, all this is still on paper, though. Its the mechanics thats troubling us a great deal.
We could do with all the help we can get.

Also, do u know where we can get Cheap Stepper motors. Anywhere in Pune, Mumbai or Bangalore??

Regards,
Shashank

ice
02-05-2005, 01:05 PM
Also, do u know where we can get Cheap Stepper motors. Anywhere in Pune, Mumbai or Bangalore??

Lamington Rd,Chor Bazaar :: Mumbai..
Go on a friday.U get 5 quarter disk drives with a "1/8 step" stepper.

Its a Duplex RF module wew are using
can i know which one.

technojunk
02-06-2005, 04:19 PM
hi shashank

its really a cool project man.....looks like a simulatory model of extra terrestial space vehicle :)

When u say torque of 2kgcm or 0.5Nm, whats d max load the motor can move without stalling?

With regards to ur project u have to maintain enough "tractive effort" i.e the effort which wheels can apply on ground (terrain) in order to move the vehicle forward. Hence all these depends upon the size of the wheels , teh coeff of friction between wheels and ground ( to consider slippage too!!).

I recommend gear motors for the motion of the robo as they can give higher torque .. ( as u are goin for all terrain )and for the same torque from steppers u may need to switch to steppers with gear boxes which are costlier ....and where precision is required u may use stepper motors (for arm movement and feedback etc). well but u may find difficulty in judging the distance (acculately) travelled from previous position if u use gear motors!

do tell me abt duplex rf modules....and how u are decoding the data etc

02-09-2005, 10:37 AM
Thanx again Man,
About the RF modules, we are using the ones marketed by a Chennai company. Or atleast we are planning to. Heres their site:
www.mdclrf.com

They have all the information on their website.

surephenomenon
02-20-2005, 04:51 PM
Dude,hi,
As far as the mechanical aspect of the robot is concerned are u having trouble putting down a design or in getting the parts manufactured...neways where u guys located?i mean i could help u with the mechanical aspect of things and in return u could tech me about the electronics aspects...eh?sounds like a good arrangement what say...get back to me at sureshkool@yahoo.com or sureshkool@hotmail.com...try to help u guys to the max....

Vishy
02-21-2005, 09:24 AM
Hi shash,

for info on mechanics, torque etc. chk out the mechanics of my robot FIRE in http://beamindia.solarbotics.net and for improvisation on the mechanics check out Scamvee.

vishy