# Calculate the % fan shaft is out of balance

• thewall
In summary: So I'm thinking it would be something like the mass of the fan blade assembly divided by the mass of the fan. But again I'm not entirely sure.
thewall

## Homework Statement

A fan loses an 11 gram piece 460mm from the shaft center. It rotates at 1000 RPM and cannot operate if the shaft is out of balance by more than 8%. Prove whether or not the fan can still operate.

Fc = mwr2

## The Attempt at a Solution

I have found the force added by the imbalance to be 55.5N but can't figure out how to relate this to a % of unbalance as I would need to know the mass of the whole fan blade assembly. I am thinking that 11 grams missing from a 1 kg fan blade would cause a higher percentage imbalance than it would in a 100 kg fan blade.

Could someone tell me if I am going about this problem the right way and if so how to do this, or do I need to take a different approach other than using centripetal forces.

Welcome to PF.

What does it mean to be 8% out of balance?

I take imbalance to mean in the dynamic sense that the axis of the moment of inertia (running through the center of gravity) is off set from the center of the fan shaft. But I am unfamiliar with the idea of what a % dynamic imbalance means.

As you note given a tremendously massive fan blade and a lightweight one this can mean very different things as regards the absolute displacement of the center of mass from the center of the shaft.

Hence fan blade length, mass distribution look to be additional facets of information required.

There is no additional information supplied in the question.

I was unsure of what exactly what 8% out of balance meant as well. 8% of what? I was hoping someone could tell me.

If I work with forces or moments of inertia I still would need to somehow relate that to the original.

## 1. What is fan shaft balance and why is it important?

Fan shaft balance refers to the even distribution of weight around the axis of rotation of a fan shaft. It is important because an unbalanced fan shaft can cause excessive vibration, leading to equipment damage and decreased efficiency.

## 2. How do you calculate the % fan shaft is out of balance?

To calculate the % fan shaft is out of balance, you will need to measure the vibration of the fan shaft using a vibration sensor. Then, using a balancing formula, you can determine the percentage of imbalance based on the amplitude of the vibration and the fan speed.

## 3. What are the common causes of fan shaft imbalance?

The most common causes of fan shaft imbalance include manufacturing defects, dirt or debris buildup on the fan blades, uneven distribution of weight on the blades, and wear and tear over time.

## 4. How can fan shaft balance be corrected?

Fan shaft balance can be corrected through a process called dynamic balancing, which involves adding or removing weight from the fan blades to achieve a more even distribution. This can be done manually or with the help of specialized equipment.

## 5. What are the consequences of not addressing fan shaft imbalance?

If fan shaft imbalance is not addressed, it can lead to increased wear and tear on the fan and surrounding equipment, decreased efficiency, and potential safety hazards. It is important to regularly check and correct fan shaft balance to avoid these consequences.

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