# Society of Robots - Robot Forum

## Mechanics and Construction => Mechanics and Construction => Topic started by: JoePatrick1 on October 08, 2015, 08:03:35 AM

Title: Need help calculating the torque required by each servo
Post by: JoePatrick1 on October 08, 2015, 08:03:35 AM
So I am building a Hexapod and want to use SG90 servos. They are rated up to 1.8 kg/cm but if possible I want to keep it under 1.5 kg/cm.
I would like to know how to calculate the torque of each servo at a time.
Here is a diagram of my design, assume that 3 (2&1) out of 6 legs are in contact with the ground at a time and assume for simplicity that the total weight is 10N - I am not sure what the final weight will be yet
Each leg has 2DoF, and therefore 2 servos as shown in the diagram below
(http://i.imgur.com/wSDebpx.png)
Title: Re: Need help calculating the torque required by each servo
Post by: cyberjeff on October 08, 2015, 11:48:17 AM
Be aware that  the 1.8kg cm is the stall torque, where it isn't moving at all. Half of stall torque is where servos put out the most power.

Torque is nothing more than weight times the lever arm length (along the direction of force). You can make assumptions about how the force is distributed, but I would be very generous in those.