SOLUTION

• A fractional horsepower motor (FHP) is an electric motor with a rated output power of 746 Watts or less.
• The term ‘fractional‘ indicates that the motor often has a power rating smaller than one horsepower.
• Plain bearing or sleeve bearing is used in this type of motor because it is the simplest type of bearing, comprising just a bearing surface and no rolling elements.
• Plain bearings, in general, are the least expensive type of bearing. They are also compact and lightweight, and they have a high load-carrying capacity.

Type of bearing

There are two main categories of bearings. The first is known as “plain” or “sleeve” bearings. The second type is “rolling element” bearings. The most familiar type of rolling-element bearing is probably the ball bearing.

Plain or Sleeve Bearings

Plain bearings have no moving parts and depend on a continuous thin film of oil to keep the surfaces from making contact. Most equipment we encounter uses plain bearings. Plain bearings are lubricated with oil, never with grease.

There are some types of plain bearings that do not require lubrication. One type is known as Oilite bearings (pronounced Oil-light). Oilite bearings are made of porous cast bronze impregnated with oil at the factory. The oil contained in the metal is slowly released to the bearing surface and is designed to last the lifetime of the equipment. Oilite bearings do not need to be re-lubricated. Many fractional horsepower motors and other types of small equipment use Oilite bearings.

Other bearings are known as “self-lubricated” and are made of materials that can slide easily without needing additional lubricants. A few of the more common types are Teflon (PTFE), graphite or molybdenum disulfide (MoS2) bonded with epoxy resins, graphite, powdered metal, or ceramics. Lubricating these materials with oil can actually cause damage to the bearing.