How to Calculate the Force Required to Lift an Arm

[kgp43]

Hi,

Hope one of you might be able to help me with some calculations :)
I'm trying to calculate the amount of force required to lift an arm, based on weight, distances and angles.

I made a sketch to illustrate my problem.

where:

Lac = Length of arm
Lab = Distance from "anker-point" to mounting point for cylinder/aktuator.
Lad = Distance from "anker-point" to mounting point for cylinder/aktuator.
F1 = Force in Kg.
Da = Angle #1
Db = angle #2
Dd = Angle #3

Is there a formula to calculate the force required to lift the arm? Not sure where to look.Thanks,

Kenneth

 

[BvU]

Hello kgp, !

You can write balances for the forces and for the torques. Both should be zero (otherwise the lot will start to accelerate or to rotate). Be sure to include ALL the forces and torques.

You will also want to make some sensible approximations in order to get started: you have drawn the cylinder in great detail, but the arm is a single line. Is it massless ?

$F_1$ is unclear to me. What does it represent ?

Not sure where to look

Seems to me an introductory textbook on mechanics should be helpful. Look under torque, lever and such things.

 

[jrmichler]

The first step is to make a free body diagram (search the term) from your sketch. The second step is to use the free body diagram to calculate the sum of moments about the pivot. Search that term also, but only AFTER you have a complete and correct free body diagram.