4 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.
5 Selection Characteristics Inner DiameterOuter DiameterLengthMaterialType of LubricationTolerancesPV rating
7 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.
8 MaterialsWhitemetal - 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.
9 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.
10 Types of Lubrication Hydrostatic Hydrodynamic Boundary Lubrication Dry Bearings
12 PV Rating P - Bearing Pressure (psi) V - velocity in feet per minute of the wear surfacePV is then obtained by multiplying P x V as shown in the following example:3/4" 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
13 Design Considerations Plain bearings should be kept as short as possible. (Length/diameter ratio of )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.
14 Advantages of Sleeve Bearings over Roller Bearings Won’t fail from fatigueRequire less space in radial directionGood damping abilityLower noise levelLess severe alignment requirementsLower costLower Friction (hydrodynamic) (Norton, )
15 Other Advantages Good capacity to absorb shock loading Accept oscillating motionLoad is distributed over larger areaOperate 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
16 Typical ApplicationsAutomotive Industry: transmission shafts, links, pins, crankshafts and camshaftsMarine Industry: thrust bearings of ship driveshaftsBike Industry: rear suspension linkages, suspension forks, brake arms, shiftersIdeal for oscillating, intermittent-motion or less-than 360-degree rotation