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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
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.
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