# Need help calculating bearing life for gearbox in mixer application?

• SevenToFive
In summary, to calculate the bearing rating and life for a gearbox in a mixer application, you will need more information such as the actual and worst case loadings, a free body diagram showing all of the loads on the output shaft, and the output shaft RPM. The design life of the bearings supporting the output shaft can be calculated at the design load and worst case load, and then discussed with others involved in the project. It is important to consider the type of bearing and RPM of the shaft, and resources such as the Timken Engineering Manual can be helpful in this process. Ultimately, the decision may be made to redesign a component if the design life is not sufficient or if it is deemed to be too long.
SevenToFive
TL;DR Summary
How do I calculate bearing life with provided data?
I am a little confused on how to calculate the bearing rating and life for a gearbox in a mixer application. The only information that they are providing is the following, using a 1/4HP motor, 0.08 HP expected loading, a max torque of 87.2 in-lbs, 175.8 in-lbs bending max, and 632 psi expected bearing stress.
Wouldn't I need to know the run time(hours)? I feel that I am missing some information to help me set up the equations. Could someone please help me out. Thank you in advance.

The numbers that you presented are not enough information to do any calculations. You need to find the actual and worst case loadings, then put together a free body diagram (search the term) showing all of the loads on the output shaft. That diagram will include the loads from the impeller, the loads from the driven gear, and the bearing loads. That, plus the output shaft RPM, allows you to calculate the design life of the bearings supporting the output shaft.

You calculate the bearing life at the design load.
Then you calculate the bearing life at the worst case load.
Then you discuss the results with the other people concerned, starting with your supervisor.
Then the decision is made as to whether the design life is good enough.
If not, somebody needs to redesign something.
Or management may decide that it will last too long, in which case it will be redesigned to reduce cost.

Hint: Do NOT try to speed the process by skipping the FBD.

berkeman
For a start, type of bearing, i.e. lubricated sleeve (if so, then the bearing material) or roller/ball bearing and the rpm of the shaft.

## 1. How do I calculate the bearing life for a gearbox in a mixer application?

To calculate the bearing life for a gearbox in a mixer application, you will need to consider factors such as load, speed, lubrication, and environmental conditions. You can use standardized formulas or software programs to calculate the bearing life.

## 2. What is the importance of calculating bearing life for a gearbox in a mixer application?

Calculating the bearing life for a gearbox in a mixer application is important because it helps to ensure the reliability and durability of the equipment. It also allows for proper maintenance and replacement of bearings, which can prevent costly breakdowns and downtime.

## 3. Can I use the same bearing life calculation for different types of mixers?

No, the bearing life calculation may vary depending on the type of mixer and its specific operating conditions. It is important to use the correct calculation for each application to ensure accurate results.

## 4. How often should I recalculate the bearing life for a gearbox in a mixer application?

The bearing life should be recalculated whenever there are changes in the operating conditions or when new equipment is installed. It is also recommended to recalculate the bearing life periodically to ensure the equipment is functioning properly.

## 5. Are there any other factors that can affect the bearing life in a gearbox for a mixer application?

Yes, other factors that can affect the bearing life include the quality of the bearings, proper installation and alignment, and regular maintenance. It is important to consider all of these factors when calculating the bearing life for a gearbox in a mixer application.

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