The last three parts of articles on the selection of rolling element bearings dealt a lot with the parameters required for the selection. Based on the data gathered, we have to select the bearing based on some calculated values derived from the parameters required for the selection (based on data’s already dealt with in the previous 3 parts). All the parameters discussed along with the numerical values have to be considered thoroughly.
Any bearing listed in the catalogue of the manufacturer contains the following major details for one specific bearing. They are as follows
· Inner Diameter of the bearing
· Outer Diameter of the bearing
· Thickness of the bearing
· Basic Dynamic Load rating – Radial
· Basic Static Load rating – Radial
· Maximum Permissible or Limiting speed of the bearing
· Fatigue Load Limit
· Weight of the bearing
Of these the Basic Dynamic Load rating – Radial and Basic Static load rating play a very vital role for the selection of the bearing.
Before we proceed to see what Dynamic Load rating and Static Load rating is we have to first know about Equivalent Load (P). The equivalent load is derived from the radial and axial forces acting on the bearing. The equivalent load is something like a resultant of the radial and axial force on the bearing.
The equivalent load is derived from the formula
P =V X Fr + Y Fa, N
P – Equivalent Load
Fr – Radial Force/Load
Fa – Axial Force/Load
X, Y – are factors that vary with the type of bearing and the bearings ability to carry radial and axial load together. This factor does not include the size of bearing.
V – A factor derived based on the running speed of the bearing
The X and Y factors can be selected from the data books of the respective bearing manufactures. The equivalent load is the important term that is used in the calculation of the dynamic load carrying capacity of the bearing. The equivalent load in turn is also plays a vital role in the calculation of the life of the bearing.
We will look into the Dynamic and Static Load carrying capacity of the bearing in the next article.