Summary Description Selection characteristics Advantages/Disadvantages Applications.

Summary

• Description

• Selection characteristics

• Advantages/Disadvantages

• Applications

Sleeve Bearings

Plain Bearings

Journal Bearings

Bushings

Sleeve Bearing

Description:

• Bearing used to constrain, guide, or reduce friction in rotary

applications.

• Work by means of sliding action as opposed to the rolling action used by

ball, roller and needle bearings.

• Proper lubrication is required to reduce wear and friction.

Selection Characteristics

• Inner Diameter

• Outer Diameter

• Length

• Material

• Type of Lubrication

• Tolerances

• PV rating

Press Fit and Shaft Clearance Considerations

Sleeve Bearing Materials

Relative softness (to absorb foreign particles), reasonable strength, machinability (to maintain tolerances), lubricity, temperature and corrosion resistance, and in some cases, porosity (to absorb lubricant).

A bearing element should be less than one-third as hard as the material running against it in order to provide embedability of abrasive particles.

Materials

• Whitemetal - usually used as a lining bonded to bronze, steel or cast iron.

• Copper Based alloys - most common alloys are copper tin, copper lead, phosphor bronze: harder and stronger than whitemetal: can be used un-backed as a solid bearing.

• Aluminium based alloys - running properties not as good as copper based alloys but cheaper.

Materials (cont’d)

• Ptfe - suitable in very light applications• Sintered bronze - Sintered bronze is a

porous material which can be impregnated with oil, graphite or Ptfe. Not suitable for heavily loaded applications but useful where lubrication is inconvenient.

• Nylon - similar to Ptfe but slightly harder: used only in very light applications.

Types of Lubrication

• Hydrostatic

• Hydrodynamic

• Boundary Lubrication

• Dry Bearings

Hydrodynamic Lubrication

PV Rating

• P - Bearing Pressure (psi)• V - velocity in feet per minute of the wear surface• PV is then obtained by multiplying P x V as

shown in the following example:3/4" shaft @ 341 RPM, 90 lb. total load, bearing length 1".

V = .262 x RPM x shaft diameter, or .262 x 341 x .750 = 67 sfpm.

P = total load ÷ projected area (area = .750 x 1.0 = .75 in.), or 90 lbs. ÷ .75 = 120 psi.

PV = 120 psi x 67 sfpm = 8040 PV

Design Considerations

• Plain bearings should be kept as short as possible. (Length/diameter ratio of 0.75 - 1.5)

• Two well-spaced short bearings are better than one long one.

• Dry bearings of the impregnated sintered bronze type are available in stock sizes and these should be used if possible.

Advantages of Sleeve Bearings over Roller Bearings

• Won’t fail from fatigue• Require less space in radial direction• Good damping ability• Lower noise level • Less severe alignment requirements • Lower cost• Lower Friction (hydrodynamic)

(Norton, 654-655)

Other Advantages

• Good capacity to absorb shock loading• Accept oscillating motion• Load is distributed over larger area• Operate efficiently over a wider range of PV

values than any other type (up to 3,000,000+ with the proper lubrication)

• Load-carrying capability of bronze oil lubricated sleeve bearings increase with rpm

Typical Applications

• Automotive Industry: transmission shafts, links, pins, crankshafts and camshafts

• Marine Industry: thrust bearings of ship driveshafts

• Bike Industry: rear suspension linkages, suspension forks, brake arms, shifters

• Ideal for oscillating, intermittent-motion or less-than 360-degree rotation

Available Sizes

Interesting Application

Space Shuttle Transport Vehicle:

• wheels turn on bronze sleeve bearings