rotating shaft considering self load and overcome the friction

[designmechanical111]

I am trying to rotate 60" long shaft of dia 4" made of SST 630 need to rotate at 60 rpm. If the shaft is resting on a bearing at both the ends, which formula do I use to calculate the power required to rotate this shaft considering self load of shaft and overcome the friction of bearing.

 

[israelkk]

Are you a student?

 

[desertfox]

Hi designmechanical111

We need more information than you have given, can you tell us what the shaft is for and the bearing material, finally how soon do you want the shaft to reach running speed (ie how much time have you got between starting and reaching full speed).

regards

desertfox

 

[designmechanical111]

Consider shaft just needs to be rotate gradually increasing to 60 RPM. Consider Ball or roller type bearing of SST. Also if possible please let me know which formula do I use to calculate starting torque and required power to keep this shaft rotating. Thanks for responding.

 

[israelkk]

Student posting is not allowed.

 

[designmechanical111]

Hi israelkk, I am not a student just trying make somethig work. I have been out of school for long time.

 

[desertfox]

Hi designmechanical11

The power you need is given by this formula:-

P= 2*3.142*T*N/60

T = I*angular accel


where I= Moment of Inertia = M*r^2 where M= mass and
r= shaft radius

T= Torque

N= RPM
This assumes no friction

regards

desertfox

 

[designmechanical111]

I appreciate your time desert fox. Many thanks. I think this much of info can get me started. I was missing angular acceleration. And also I believe I can get the friction factor from the manufacturer of bearing and I can use that too in this formula.

 

[designmechanical111]

I was trying to use hp = T*n/63
Where T is in Kips,
represented T = I*angular accel

In the formula P= 2*3.142*T*N/60
What is the unit for T

 

[desertfox]

Hi designmechanical11

The T is Torque.

Also I think I made a mistake with moment of inertia it should be divided by 2.

ie I=M*r^2/2

Regards

desertfox

 

[designmechanical111]

Desertfox,
In the formula P= 2*3.142*T*N/60
What is the unit for T

I appreciate your help.
Thanks you,

 

[desertfox]

Hi designmehanical111

T is in Nm

desertfox

 

[designmechanical111]

Thank you.