# Calculating torque from yield stress understanding

vitaljunk
Hello,
I'm new here and so if I've put this in the wrong section or anything, please let me know and I'll fix/change whatever needs to be done.

I just wanted to see if someone could help me understand something.

When choosing a torque value, is it just ~90% of the yield stress of the material of the torque rod? I have to design a torque arm that needs to withstand a certain volume before hitting a switch and need to decide where to put the force/hang the volume along the arm. I already know the force, and the material of the torque arm and rod, so need to chose a torque value so I can figure out the distance along the arm for the force. Sorry if I'm being a bit vague, I want to solve it myself, but am just having some trouble with understanding things. If you need more info, please let me know.

Anyway, I found the yield stress of the material of the torque rod, it was around 185MPA. I just plugged that straight into torque = force x distance. Is that right? Should I have converted that to Pa? Or because torque is in Newton meters and stress is in pascals and they're not the same right, so I need to do something else to it? I'm not sure what to do. By doing that (putting 185 into the equation as torque) I got a really small value, so I think I've done it wrong and am currently lost.

Could someone please point me in the right direction?

WillemBouwer
Vitaljunk;
You mast definitely can not input the yield stress as torque! Torque is measured in n.m whereas the yield stress is measured in Pa or N/mm^2.

If you could attach a picture of what you want to achieve I could try to help you a bit more, also include some of your equations and what you try to achieve.

As I understand you are trying to have a weight hang on a rod and let the rod release once a certain weight is reached? is this correct, from the weight and the distance to the centre of the arm around which it swings will give you a torque figure that you want.

For me to help you I would have to understand what you are on about a bit better

Try to explain...