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Hey everyone,

After a little help with some deflection caused by a rotating offset shaft.

This is the scenario.

We have a vertical shaft (165kg ~3.3m, supported at one end only) rotating at 14.67rad/s and getting some undesirable deflection and odd dynamic behaviour.

I'm trying to establish if this is caused by the shaft not being vertical before it even starts rotating. There is some static deflection (relatively small, ~2mm) and I'd like to see if this has a significant effect once it starts running.

My calculations with the actual data give a smaller than expected deflection. I'm wondering if this is my units or my process....or just not a big deflection.

My thought process.

1. Assuming the shaft itself is straight (it's been checked to within 0.05mm/m)

2. Force = mrw^2 ( mass x radius x square of angular velocity )

3. Use this force and standard beam deflection formulae to establish deflection caused by rotation.

My 'Worries'

1. There should be a force due to the modulus of elasticity in the shaft to prevent this deflection (to a point). Otherwise

2. Is there something else I'm missing?

3. Am I making any unfair/false assumptions?

Would you guys please take a look at my calculations in the attached pdf and see if:

a. My process is valid

b. My assumptions are fair and reasonable

c. My units are correct

Thank you all very much for any assistace!

After a little help with some deflection caused by a rotating offset shaft.

This is the scenario.

We have a vertical shaft (165kg ~3.3m, supported at one end only) rotating at 14.67rad/s and getting some undesirable deflection and odd dynamic behaviour.

I'm trying to establish if this is caused by the shaft not being vertical before it even starts rotating. There is some static deflection (relatively small, ~2mm) and I'd like to see if this has a significant effect once it starts running.

My calculations with the actual data give a smaller than expected deflection. I'm wondering if this is my units or my process....or just not a big deflection.

My thought process.

1. Assuming the shaft itself is straight (it's been checked to within 0.05mm/m)

2. Force = mrw^2 ( mass x radius x square of angular velocity )

3. Use this force and standard beam deflection formulae to establish deflection caused by rotation.

My 'Worries'

1. There should be a force due to the modulus of elasticity in the shaft to prevent this deflection (to a point). Otherwise

*any*deflection would accelerate and behave similiar to when the rotation reaches the critical frequency. I don't know how to calculate this force.2. Is there something else I'm missing?

3. Am I making any unfair/false assumptions?

Would you guys please take a look at my calculations in the attached pdf and see if:

a. My process is valid

b. My assumptions are fair and reasonable

c. My units are correct

Thank you all very much for any assistace!

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