help in robocon 2012 manual robot

[free_matrex2010]

hi all
i found this site useful to type my question.
can u plz help me to find suitable motor for  manual robot.
the specification of robot :
weight is 110 kg.
have four mecanum wheels.so i need four motor.
the motor speed is 400 to be good.
what is the motor torque can i get to do this robot.
is 25kg.cm stall torque is good for that???
i dont know how can i choose motor torque.
thx in advance

[Soeren]

Hi,

is 25kg.cm stall torque is good for that???

Each motor, assuming a perfectly balanced load, will need to haul away 27.5kg.
If your wheels are 1 cm in radius (2cm in diameter), you'll need more than 27.5kgf-cm of stall - around double that, say 50kgf-cm of stall, would be good. Stall is when it can just hold the force, but cannot move.
If your wheels are 5cm in radius (10cm in diameter) you'll need 5 times that, or around 250kgf-cm.
3 times larger wheels equal 3 times more torque needed and so forth.

i dont know how can i choose motor torque.

Reading a few tutorials (link on top of the page, right side or Google the subject) on the subject might be a good start.

[free_matrex2010]

oh thx for u reply
the wheels that i will use :http://www.andymark.com/product-p/am-0137.htm
this is the motor i will get four for 4 mecanum wheels :http://www.robotmarketplace.com/products/0-BHG31.html

what is ur opinion

[Soeren]

Hi,

the wheels that i will use :http://www.andymark.com/product-p/am-0137.htm
this is the motor i will get four for 4 mecanum wheels :http://www.robotmarketplace.com/products/0-BHG31.html

what is ur opinion

Are you serious?

With a wheel radius of 7.5cm, you need motors with a torque of 7.5 x 50 = 375 kgf-cm
375 kgf-cm equals 5208 ozf-inch - these motors have 395 ozf-inch and as such is less than 1/13 the needed power (and at a no load speed of 360 RPM, much slower than what you wanted.

Either get motors thirteen times as powerful and at a higher speed, or lessen the load. These motors (with 15 cm wheels) are good for a total weight of around 8.5 kg (evenly shared) running the wheels at (guesstimate) 200 RPM.