Shaft design

[Bambila]

Hi,

I need the help on calculating the maximum rotating mass on shaft.
Suppose I have a shaft of .5 inches diameter and Torque is 20lbf-in. How to calculate the maximum weight this shaft can rotate using given torque.

Thanks

Bambila
Mechanical Engineer

 

[zekeman]

If the maximum torque delivered to the shaft is T, then the only limitation on the weight might be.
1)the time needed to come up to speed
2) the braking torque, if greater than T
3) the startup torque of the prime mover (could be as much as 5 times the nominal)
In any event, you get the torsional stress
stress=TR/J
T= maximum torque delivered either by prime mover or braking
R= radius of shaft
J=polar moment of inertia

 

[dvd]

The question is not bounded very well.

Does the 0.5 inch shaft support the weight, or merely connect to an independently supported object with this amount of weight?
What is the geometry of the object which connects to the shaft?
How is the object attached to the shaft, i.e. welded, bolted, verbally, etc.?
Does the 0.5 inch shaft have a keyway?
How is the 0.5 inch shaft supported?

 

[Bambila]

Hi All,

Thanks for the reply. Here I have attached the image of my problem. I hope this would help.

Thanks


Bambila
Mechanical Engineer

 

[Bambila]

Hi,

That was wrong link. Image is attached in this thread. please have look.

Thanks

Bambila
Mechanical Engineer

 

[Engdoitbetter]

Dear Bambila,

This is not a problem related to weight but to inertia.

If bearing friction is neglected, the momentum equation is like this: Torque = moment of inertia (shaft + disc) * angular acceleration

So the torque you have to apply, in an ideal situation, when the shaft is rotating at costant velocity (whatever its value may be), is ZERO. This is because the torque is needed to accelerate the shaft till it reaches full speed. The only thing you have to know is the acceleration needed to reach that speed. Since torque is known, you can easily calculate inertia and then the disk thickness.

The problem is obviously more complicated if a braking torque is needed to keep the shaft at costant velocity.

Regards,

Stefano

 

[chicopee]

The inertia of the rotating weight is to be based on the type of load you are expectings to handle. So you you describe the purpose of the rotating shaft. If you research ME handbooks on for example flywheels integral to mechanical presses, you'll have a good idea how to figure out the size of the rotating mass to maintain the rotational energy that such press require.

 

[chicopee]

OOps"...handle. So you you describe the purpose of the rotating shaft..." I meant to say "...handle. So you should describe the purpose of the rotating shaft..."