sleeve bearings
TRANSCRIPT
-
7/30/2019 Sleeve Bearings
1/18
Summary
Description
Selection characteristics
Advantages/Disadvantages
Applications
-
7/30/2019 Sleeve Bearings
2/18
Sleeve Bearings
Plain Bearings
Journal BearingsBushings
-
7/30/2019 Sleeve Bearings
3/18
Sleeve Bearing
-
7/30/2019 Sleeve Bearings
4/18
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.
-
7/30/2019 Sleeve Bearings
5/18
Selection Characteristics
Inner Diameter
Outer Diameter
Length
Material
Type of Lubrication Tolerances
PV rating
-
7/30/2019 Sleeve Bearings
6/18
Press Fit and Shaft Clearance
Considerations
-
7/30/2019 Sleeve Bearings
7/18
Sleeve Bearing Materials
Relative softness (to absorb foreign particles),
reasonable strength, machinability (to maintain
tolerances), lubricity, temperature andcorrosion resistance, and in some cases, porosity
(to absorb lubricant).
A bearing element should be less than one-third as
hardas the material running against it in order to
provide embedability of abrasive particles.
-
7/30/2019 Sleeve Bearings
8/18
Materials
Whitemetal - usually used as a lining bonded to
bronze, steel or cast iron.
Copper Based alloys - most common alloys arecopper 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.
-
7/30/2019 Sleeve Bearings
9/18
Materials (contd)
Ptfe - suitable in very light applications
Sintered bronze - Sintered bronze is a
porous material which can be impregnatedwith oil, graphite or Ptfe. Not suitable forheavily loaded applications but usefulwhere lubrication is inconvenient.
Nylon - similar to Ptfe but slightly harder:used only in very light applications.
-
7/30/2019 Sleeve Bearings
10/18
Types of Lubrication
Hydrostatic
Hydrodynamic
Boundary Lubrication
Dry Bearings
-
7/30/2019 Sleeve Bearings
11/18
Hydrodynamic Lubrication
-
7/30/2019 Sleeve Bearings
12/18
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 asshown 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
-
7/30/2019 Sleeve Bearings
13/18
Design Considerations
Plain bearings should be kept as short aspossible. (Length/diameter ratio of 0.75 -
1.5) Two well-spaced short bearings are better
than one long one.
Dry bearings of the impregnated sinteredbronze type are available in stock sizes andthese should be used if possible.
-
7/30/2019 Sleeve Bearings
14/18
Advantages of Sleeve Bearings
over Roller Bearings
Wont 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)
-
7/30/2019 Sleeve Bearings
15/18
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
-
7/30/2019 Sleeve Bearings
16/18
Typical Applications
Automotive Industry: transmission shafts, links,pins, crankshafts and camshafts
Marine Industry: thrust bearings of shipdriveshafts
Bike Industry: rear suspension linkages,suspension forks, brake arms, shifters
Ideal for oscillating, intermittent-motion or less-than 360-degree rotation
-
7/30/2019 Sleeve Bearings
17/18
Available Sizes
-
7/30/2019 Sleeve Bearings
18/18
Interesting Application
Space Shuttle Transport Vehicle:
wheels turn on bronze sleeve bearings