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# To much torque robotic arm

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#### moh

##### New Member
Hi,

I was trying to calculate the torque for my robotic arm from this website calculator

Here is the spec

motor Hitec ,Torque 10 kg/cm

L1 (Length from shoulder to elbow) 7 inches weight W1 steel frame about 5 g
L2 (Length from elbow to wrist) 5 inches weight W2 steel frame about 4 g
L3 (Length from elbow to gripper) 3 inches weight W3 steel frame about 2 g

W4 object to lift 1kg

M1 (Shoulder 1 motor ) 25g
M2 (Elbow 2 motors) 50g
M3 (gripper 2 motors) 50g

I want to lift 1kg object

I left the Joint Rotational Acceleration blank 0

It is showing about 40kg/cm torque ,Is it correct?

If it is true ,is there any way around it?.

I am using arduino board

You must insure that your units are consistent.
It looks like your motor is capable of producing about 1 N-m of static torque ....
So, you need to get the calculator motor torque results to be less than what the motor will generate.

By the way .... kg/cm is not correct, but kg-cm would be correct for a unit of torque.

Thanks for the correction.So I have to lighten the load.Is there any way (pulley,gears), I can increase the torque.

I could not find any servo motor with 40kg-cm torque.Even if I do find, I have a feeling it will be very expensive.

... Can't make any specific recommendations.
A gear head ....
would provide an increase in available torque, at the expense of slowing down the acceleration/movement.
Also, consider the added mass/weight of the gearhead in the calculator.
I think you are on/track about the expense involved. Surplus is usually a good place to start looking for motors/gearheads.

The image here gives a generalized picture of the torque/power vs. rpm of a servomotor. A gear ratio of something greater than 1:1 would slide the green line up on the vertical axis, and inwards on the horizontal axis.

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