Torque calculation for a jaw coupling. 3

[pb10101]

Hello,

I'm trying to calculate the amount of torque that can be transmitted to a shaft through a jaw coupling. The coupling will be attached to a 2.5 inch drive shaft. The coulping has a 5 inch OD(with a 2.5in bore). The driven shaft has an OD of 1.25in.

What radius do I use to calculate the torque to the driven shaft? Is it the radius of the drive shaft, the radius of the coupling or the average of the bore and OD?

Thanks for your help.
pb

 

[dimjim]

Driven shaft OD. That is where the resistance is.

 

[MikeHalloran]

I'm sorry, I don't understand the question.

The coupling manufacturer can tell you the torque rating of the coupling. So, why do you need to calculate anything?



Mike Halloran
Pembroke Pines, FL, USA

 

[pb10101]

Mike,

I know the rating for the coupling, I'm just unsure if the diameter of the coupling will affect the force applied to the driven shaft.
(like with pulleys, the larger the radius of the drive pulley, the less force can be applied to the driven pulley)

pb

 

[MikeHalloran]

The coupling doesn't change the torque.

The radius of the driven shaft does affect how that torque produces shearing forces on the key between the shaft and the coupling.

The radius of the driven shaft also affects how a given torque produces shear stress in the driven shaft.

That should be covered in your machine design textbook, or in your Machinery's Handbook. This would be a good time to review at least one.






Mike Halloran
Pembroke Pines, FL, USA

 

[desertfox]

Hi pb10101

I agree with the other posters on this one.

Your torque will be governed by your driver which I assume is a motor. What you need to make sure of is that your driven shaft and keyway can transmit that torque from the motor without becoming over stressed.
have a look at this link.

http://www.utm.edu/departments/engin/lemaster/Machine Design/Lecture 19.pdf

regards
desertfox

 

[pb10101]

Thanks everyone, you've been a big help!