Calculating Max Torque on a Ø140mm x 936mm Shaft

In summary: Check your math. The equation for Z is Z=J/c and c=outer diameter/2.The figure i have for the material is 77,000N/mm^2Ok now you can run the equation. Do you know how to calculate J?Sorry no i don't know how to calculate J.Do you have a book on strenght of materials?I don't have a strength of material book.In summary, to calculate the maximum torque that can be applied to a stainless steel shaft, you need to use the formulas T=Z*(allowable stress) and J=PI/2(r^4). If the shaft is solid, you also need to calculate r. The allowable stress
  • #1
pegghead
8
0
I have a stainless steel shaft that is Ø140mm x 936mm long.

I need to calculate what the maximum torque is that I can apply to this shaft. I have looked around for formulas and have just got myself confused. Could someone tell me what the formula is that i need to work this out.
 
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  • #2
What is the maximum torsional stress allowed for the shaft material? You will need this for the equation. Also, you need to calculate the polar moment of inertia, J, of the shaft and calculate the shafts section modulus, Z. The equation for Z is Z=J/c and c=outer diameter/2.
 
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  • #3
The figure i have for the material is 77,000N/mm^2
 
  • #4
Ok now you can run the equation. Do you know how to calculate J?
 
  • #5
Sorry no i don't know how to calculate J.
 
  • #6
Do you have a book on strenght of materials?
 
  • #7
I don't have a strength of material book.

Could yoou tell me the equations that i need.

Like T = ? ? ? ? ?

and

J = ? ? ? ? ?
 
  • #8
Well,

T = Z*(allowable stress) where Z = J/c

J = PI/2(r^4) if the shaft is solid. Is the shaft solid?

r = c = Outside Diameter/2

Think you can handle the rest?
 
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  • #9
Lastly, be sure to check and make sure all of the units are correct. You should end up with N-mm

Thanks
 
  • #10
I have calculated the torque using the formulas given and i get 3.5E-5 Nmm of torque that a Ø140mm shaft can transmit when material allowable stress is 77,000N/mm^2.

I think somewhere i have miscaculated, i have checked a couple of times and got the same result.

O/D = 140mm
R = 70mm
Allowable stress = 77,000N/mm^2

The amount of Torque transmittable seems very low.
 
  • #11
Check your math.

I have 4.15x10^7 N-m

That is a lot of torque.
 
  • #12
the figure i am getting for J is around 6.5E-8
 
  • #13
Check the allowable stress. It's about 2 orders of magnitude higher than a strong grade of steel.
 
  • #14
The allowable stress figure that i have is 77KN/mm^2.
 
  • #15
For J,

J = PI/2(r^4) = 3.141592/2*(70^4) = 1.570796*(24010000)=37714811.96 mm^4
 
  • #16
Are you using all the correct units?
 
  • #17
I know where i was having problems it was in the formula, i was dividing Pi by 2x(r^4) and not Pi/2 x (r^4).

I get a result of 26534.37mm^3 for Z.

However when i now multiply this by the 77,000N/mm^2 i get 2043146490Nmm. Not the 4.15x10^7 that you got.
 

1. How do you calculate the maximum torque on a Ø140mm x 936mm shaft?

To calculate the maximum torque on a shaft, you need to know the material properties of the shaft, such as its diameter, length, and material strength. You also need to know the applied load and the distance from the center of the shaft to where the load is applied. From these values, you can use the formula T = F x d/2 to calculate the maximum torque, where T is the torque, F is the applied force, and d is the distance from the center of the shaft to the applied force.

2. What units are used to measure torque?

Torque is typically measured in units of newton-meters (N·m) or foot-pounds (ft·lb). These units represent the amount of rotational force applied to an object. In the context of calculating maximum torque on a shaft, the units would be N·m or ft·lb depending on the units used for the applied force and distance.

3. How does the material of the shaft affect the maximum torque?

The material of the shaft is an important factor in calculating maximum torque because it determines the strength and stiffness of the shaft. A stronger and stiffer material will be able to withstand higher torque loads without experiencing failure or deformation. So, the material of the shaft directly affects the maximum torque that it can handle.

4. Can the maximum torque on a shaft change over time?

Yes, the maximum torque on a shaft can change over time due to factors such as wear and tear, corrosion, and changes in the environmental conditions. As the material properties of the shaft change, its ability to withstand torque loads may also change. It is important to regularly inspect and maintain the shaft to ensure it can handle the maximum torque required for its intended use.

5. Is there a limit to the maximum torque that a shaft can handle?

Yes, there is a limit to the maximum torque that a shaft can handle. This limit is determined by the material properties of the shaft and the design specifications of the shaft. If the applied torque exceeds this limit, the shaft may experience failure or deformation. It is important to calculate the maximum torque and ensure it stays within the limit to prevent damage or malfunction of the shaft.

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