Capstan/Pulley Radial Load calcs
Capstan/Pulley Radial Load calcs
(OP)
Hi all
I have been trying to calculate radial loads on a capstan for a belt drive system. I have not been able to find much on this topic; or the ones I have found seem too complex as these methods uses Fourier series making things too complicated.
I found a research paper for this which has a simple equation to calculate the pressure acting radially upon the capstan/pulley.
pressure P(Θ) = T(Θ)/(R.b)
where T(Θ) is the Tension dependent upon Θ
and R is radius of capstan; b is width
As it is a driving pulley, the belt tension is different on either side. The tension profile can be seen below (image).

Based on the formula and after calculating the radial pressure load; I've found the radial pressure load profile to be the same as the belt tension profile; i.e. the load increases as you go along the circumference (where belt is wrapped) towards the high tension side. Hence the pressure peaks out on this side.
As this is a dynamics case, I didn't think using a static basic pulley force resolving would give accurate results. But I am not sure if this technique is correct or even close.
Can anyone please provide me guidance on this? Any help would be appreciated.
Regards
Kishore
Stress Engineer
I have been trying to calculate radial loads on a capstan for a belt drive system. I have not been able to find much on this topic; or the ones I have found seem too complex as these methods uses Fourier series making things too complicated.
I found a research paper for this which has a simple equation to calculate the pressure acting radially upon the capstan/pulley.
pressure P(Θ) = T(Θ)/(R.b)
where T(Θ) is the Tension dependent upon Θ
and R is radius of capstan; b is width
As it is a driving pulley, the belt tension is different on either side. The tension profile can be seen below (image).

Based on the formula and after calculating the radial pressure load; I've found the radial pressure load profile to be the same as the belt tension profile; i.e. the load increases as you go along the circumference (where belt is wrapped) towards the high tension side. Hence the pressure peaks out on this side.
As this is a dynamics case, I didn't think using a static basic pulley force resolving would give accurate results. But I am not sure if this technique is correct or even close.
Can anyone please provide me guidance on this? Any help would be appreciated.
Regards
Kishore
Stress Engineer





RE: Capstan/Pulley Radial Load calcs
If the pulley is turning at constant speed, then it is not a dynamic system.
A static sum of forces in the vertical and horizontal directions will give you a lot of information about the change in belt pressure applied to the pulley.
How perfect does you answer have to be?
(hint: if this is school homework, you need 3 decimal places accuracy, but if it's for a real-world problem, getting within 50% may be OK because you plan to multiply all loads by a safety factor)
STF
RE: Capstan/Pulley Radial Load calcs
This is one of the paper. I have taken the simplest route and used the formulas given in the beginning. I found the rest of the stuff abit too complicated for now.
Unfortunately this is not just a school homework. I am designing a capstan/pulley subjected to belt tension (case 1 is equal and case 2 is unequal tension). I am trying to find a profile of the radial load for FE Analysis. This is why I don't want to simply resolve forces at one point but rather find a profile to apply it along the wrap angle for accurate results.
Please have a read and see what you think.
Thanks.
RE: Capstan/Pulley Radial Load calcs
quote: ...I've found the radial pressure load profile to be the same as the belt tension profile...
Sounds good to me. Equation 4 from the paper would seem to agree with what you say, and hands you the answer you need, directly. Do you disagree?
STF
RE: Capstan/Pulley Radial Load calcs
Cheers
Greg Locock
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RE: Capstan/Pulley Radial Load calcs
I wouldn't say I disagree since I have consulted my senior engineers and few other ppl. But since this is based on a theoretical (ideal) method I wasn't sure how much of this would be relevant in the real world. Just need to make it a little more accurate.
GregLocock
I have attempted that method before but I doesn't seem realistic and haven't found anyone using that method.
p.s.
Yup first question (post) ever. Thanks for the tips
RE: Capstan/Pulley Radial Load calcs
Does this help?