View Full Version : load bearing capacity of a 150 rpm dc motor

02-08-2007, 06:27 PM
how much wt of a robot can four motors of 150 rpm sustain. we are using the robot for racing so will it provide sufficient speed if the wt of the robot is approx 3.5-4 kg. what is the torque provided by the motor.

02-11-2007, 01:56 PM
u first decide how much speed it requires and what is the max acceleration req. then calculate the torque req for the motor.



04-12-2007, 10:50 AM
For any moving object (may be car) force (F) can be calculated as

F= FF + FA + FG + FW + FR

FF=frictional force= u * Rn
FA = acceleration force = m * a
FG = Gradient Force = m * tan theta
FW = Wind force = 0.5 *cd * den * v^2
FR = Inertia force of Rotating component = I * alpha (don't consider if
you have already considered wt of rotating elements in "m")

u = coefficient of friction
Rn = Normal reaction
m = Mass of car
a = acceleration rate
theta = Inclination angle with resp. to ground.
cd= drag coefficient ~ 0.3 to 0.5
den = density of air = 1.5 kg / m^3
v = velocity of car
I= Moment of inertia of wheel , gears etc about rotational axis
alpha = angular acceleration = r * (w1-w2)/t
r = radius of wheel

power of motor =motor voltage * current = (2 *3.14 *N*T) /60

Torque =T= F * r

you know Motor torque, normally all this gear motor can take current up to 250 mA,

T / r = F

substitute the every thing in F, except "m" , you will get answer of your question.

Note : - 1. your motor is atlest provide torque to overcome FF else your
car will say i am happy here and don't interested in going
anywhere so go ,take tea and don't disturb me again.
2. You can neglect FW,FR as there constribution is small.
3. Let me know if i am wrong anywhere.