Stresses Acting on Pulley

(not verified)
Posted in: , on 17. Aug. 2012 - 22:32

I need to find stress acting in the belt pulley.

For this i formulated logic, From power transmission, Tensions are found out and further accounted centrifugal tension .

I have two doubts to calculate total tension in the belt pulley T1+T2+T(centrifugal) all that has to add.....?

From this tension force can divided by pulley section modulus ---?

Also unit of section modulus is mm^3

Final result is Force/mm^3--units miss match.

Polar section modulus to find?

Back To The Drawing Board

Posted on 20. Aug. 2012 - 03:55

Your problem is not uncommon. Read a text on structural analysis to try and understand what your task is all about. Your existing method is ignoring Bending Moment which is the basic reason for your inconsistent unit. There is disturbing ignorance of engineering units throughout modern heavy engineering activity. Call me old fashioned, because I am, but I remember times when mixed units was a scource of amusement. Your recognition of mixed units should give you encouragement to meet the challenge.

When you understand some circular bending theory you might be able to progress on to existing elementary pulley behaviour. Stress levels vary throughout the pulley assembly and you should read previous threads on these forums.

Good luck,


These forums are not just classrooms.

Re: Stresses Acting On Pulley

Posted on 20. Aug. 2012 - 05:05

Dear “old fashioned” louispanjang,

Indeed, “Force divided by a section modulus” is not the right way to derive a material stress.

That is probably the reason for the question mark. (?)

Luckily, we have now computers to do the “boring” work for our engineers.

No need to understand, as the programmers are to blame.

A manual, overall, rough, check is then a source of unnecessary worries.

(Although there are brilliant young engineers, who can do this, although not in a widespread number)

I can remember 3 occasions, where the computer calculation mistakes could have ended in a catastrophe. (Hoisting beam for 450 tons, 25 tons – 32m grab crane tower with a truss beam with 6000 kgf/cm2 # 600 N/mm2 and a link system of a hydraulic manipulator arm for a cement unloader)

Errors, detected by simple manual calculation and intuition.

Is it true that new engineers are under educated and not really motivated or are we just old grumpy men, who had their time and are not asked anymore?

A managers generation, who want to know everything by demand but not by themselves?

Nevertheless, we have computers, cell phones, the mars probe curiosity, discovered the Higg’s particle, can read DNA, discuss worldwide on a bulk online forum, make and solve economic crises, bomb targets with an astonishing precision at half globe distances, cool the room by heating up the world, propel 500.000 dwt ships with 40.000 kW diesel engines, fly through the air, sail under water powered by nuclear power, built the molecular gas theory, described evolution, developed mathematics, make music, built the Panama canal, protect endangered specious and have you noticed the cleverness of a sewing machine or a rear bicycle derailleur?

I am sure there is more to be proud of.

Cheer up