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# Rotating Shaft Diameter

## Rotating Shaft Diameter

(OP)
How would one approach calculating the minimum diameter of a rotating shaft if:

- it is initially spinning ~1-3k rpm
- it is decelerated at any moment when a generator is activated on one side (through a clutch mechanism)

Looking through Shigley's Mechanical Design book, I came across some shaft type calculations, but it does not seem to consider anything about rotational speed/acceleration... I am not sure if that should affect anything or not.

If you have any guidance, please share.

### RE: Rotating Shaft Diameter

Is it a student project?

### RE: Rotating Shaft Diameter

(OP)
Negatory, but thanks.

### RE: Rotating Shaft Diameter

It's still all about torque.  Calculate the deceleration.  Determine the inertia of components.  Calculate deceleration torque (and sum of all torques). Determine changes in bending moment due to deceleration.  Plug new torque and bending values into your shaft equation.  Just work through all of the nasty details.

### RE: Rotating Shaft Diameter

greendoor4,

Depending upon the shaft length, you may also need to consider its critical speed and natural frequencies.

Good luck.
Terry

### RE: Rotating Shaft Diameter

(OP)
Yeah, the resonance frequency was going to be next on that list.

I am having trouble simplifying the shaft calculation. We have a handful of unknowns:

- 2 bearings - 4 unknowns
- forces from weight of main shaft
- forces from large component spinning with shaft (mid shaft)
- 2 components on ends of shaft giving us a torque and 2 reactions per component
- Can't forget inertia from shaft and large spinning component on midshaft

Looking back a resources such as Shigley and old notes from college.... I am having a hard time finding a way to simplify / approach this.

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