FRICTION FIGHTERS

They have been active since a long while. They work hard with little fanfare. It is easy to forget about them in a jungle of complex machinery. These little friction fighters a.k.a. Bearings, constrains relative motion to only the desired motion & reduces friction between moving parts.

The image attached shows a NEEDLE BEARING used in ABUS PILLAR JIB CRANE (model LS), which may lead you to questions such as: What are needle bearings? Why weren’t the widely held stereotype ball bearing used?

Needle roller bearings are the smallest, lightest & the most economical type in the whole of the roller bearing family. When the ratio of diameter & length (d/L) of the roller is between 0.1 to 0.4, that roller bearing is called a needle roller bearing.

Being the smallest & the lightest in the roller bearing family gives them specific advantages for certain applications, particularly those requiring reduced weight & space. Why ABUS used a needle bearing in model LS type Jib crane? First, while the ball bearing can handle some axial loads too depending on the race design, needle bearings are used in loads that are strictly radial in nature (perpendicular to the supported shaft). Second, needle bearings transmit the load to the shaft over the length of the needle, so they have more contact area with the shaft, which is great for protection of shaft in terms of more supporting surface & better heat transfer. Third, they have excellent rolling characteristics within a small cross section. Fourth, in a low capacity jib crane, where strictly radial load is applied, ball bearings have less contact area with the inner race & thus have greater single point forces on the balls. Consequently, ABUS chose to use a needle bearing over the much hyped ball bearing in their particular version of a jib crane handling loads not more than 1 ton.