Needle roller bearings are specialized roller bearings that employ long, thin, needle-like cylindrical rollers. While standard roller bearing rollers are just minimally longer than their diameter, needle bearings have rollers that can be four times longer than their diameter or even more. Similar to a standard bearing, the purpose of needle roller bearings is to reduce the friction of a rotating surface. A significant advantage of needle roller bearings is their large surface area in contact with the tracks/races, allowing them to support a heavier load. Despite their large surface area, they are also thinner, meaning they require less clearance between the axle and surrounding component. This blog will provide some insight into needle roller bearings and their function in the aerospace and aviation industries.
There are five primary types of needle roller bearings: needle rollers, heavy-duty needle bearings, thrust needle rollers, track rollers, and airframe needle bearings.
These needle roller bearings appear in applications where a hardened ground gear borse serves the outer raceway. These bearings are the lowest cost per pound of capacity and are particularly advantageous when used with automated assembly equipment. The most common applications of needle rollers are in U-joints, planetary gears, and constant mesh gears.
Heavy-Duty Needle Roller Bearings
These bearings are thick and feature a machined and ground outer ring. Compared to other bearings, the hardened outer ring enables these rings to handle much more shock and tension. These bearings also consist of a cage to separate and guide the rollers through their races, allowing them to withstand high speed and misalignment. Applications of heavy-duty needle bearings include use in heavy machinery, hydraulic pumps, and steering gear.
Thrust Needle Roller & Cage Assemblies
These assemblies are designed to carry axial loads in tight spaces. Although they do not take up more space than a standard thrust washer, they provide superior frictional characteristics and can bear a much heavier load. If the adjacent surfaces can not reach a high enough hardness level, separate thrust washers can provide the necessary quality. These assemblies are often found within automatic transmissions.
Track Rollers are a type of roller bearing that can operate on cam-controlled or track-type equipment. The bearing features a thick outer ring that allows it to withstand heavy rolling and shock on the equipment to which they are affixed. There are two designs of track roller bearings. The first, yoke type, is for straddle or clevis mounting, and integral stud type, used for cantilever mounting. The ductile core of the stud makes it tougher and more resistant to shock loads. Common applications of track rollers are in machine ways, cam followers, and mast rollers.
Airframe Needle Bearings
Although this type of bearing is used in many different industries, they are designed specifically to meet the stringent requirements of the aerospace industry in airframe applications. These bearings consist of heavy outer rings that support high static or oscillating loads. They are machined from high-carbon chrome steel and supplemented by a protective finish on the external surface. Some airframe needle bearings are intended for use as mounting in housings, while others are used as track rollers. Bearings for heavier loads have two rows of roller. While these are used throughout an airframe, they are most commonly found in wing flaps, slats, and pivot positions.