Torque required to spin a hollow cylinder

[Slikatel]

TL;DR Summary

Hello all and thanks for viewing this, I am in need of some assistance to solve a problem to size an AC motor rotating this load (power transmission will be trough belt & pulley).

Hello all and thanks for viewing this, I am in need of some assistance to solve a problem to size an AC motor rotating this load (power transmission will be trough belt & pulley).

I have a hollow cylinder (pipe) that needs to spin 25 RPM:

- OD = 50 mm
- ID = 48 mm
- M = 200 kg
- Total length = 40m

The formula for inertia (Z-axis) i found when searching for a hollow cylinder = I = M * r^2 this gives me a solution of I = 0.1201 kg/m²

If i put this in the torque formula of T = I x angular acceleration = 0.1201 kg/m² x 2.618 rad/s2 (25RPM - 1 sec - ) = 0,3144218 Nm?

I'm stuck here :) would like to have some advice in where to search. Thanks so much for the advice.

 

[JBA]

The torque you calculate from your I equation is the torque required to accelerate (or decelerate ) the rotational speed of the pipe from one rpm speed to another rpm speed; but, must also include any external rotational resistances, such as the pipe's supporting roller's contact and bearing frictions (which for the support of 40 m long pipe could be significant).

Once your cylinder is rotating at a fixed rpm speed (i.e. 25 rpm) then the only torque required to keep it rotating at that speed is the torque to resist forces applied to the cylinder from the external effects, such as the pipe's supporting roller's contact and bearing frictions and any external forces from whatever is being done to the pipe while it is rotating.

Then with that information your best route is to contact an electric motor manufacturer/supplier for motor sizing.

 

[Slikatel]

Hi JBA and thanks for the reply, greatly appreciated.

So if i read your message correctly you are saying that for starting of the rotation (from non-turning formula) i need another formula?