Bearings, Lubricants and Couplings Chapter 16
Feb 22, 2016
Bearings, Lubricants and Couplings
Chapter 16
Bearings
Used to reduce friction between two surfaces
Different designs to accommodate rotational or linear motion
Different designs for different load directions
Bearing Loads
Radial Load Load acting perpendicular to the axis
of the shaft
Thrust Load Load parallel to the axis of the shaft
Combination Load Both radial and thrust loads applied
to the bearing
2 categories of bearings
Plain bearings Rolling element bearings
Plain Bearings
Operation is based on sliding action between 2 parts
Bearing will have a press fit into the housing and a clearance fit to the shaft
No moving parts Also called sleeve bearings, journal
bearings and bushings
Plain bearing materials
Bronze-needs to be lubricated Phosphor bronze-oil impregnated Various plastics
These materials allow low friction movement
Rolling Element Bearings Have moving parts to reduce friction Several types
Ball Bearings Most common High speed applications
Roller Bearings Cylindrical roller element Higher load capacity, lower speeds Several styles
Bearing Symbols
Bearings are purchased parts Different symbols used depending on
drawing type Schematic symbols used for machine
layout drawings
3D models of products using bearings can use a simplified 3D model of any bearings in the product
Machine Layout Drawing
Lubrication
Roller bearings require lubrication Too much can result in high temps
and bearing failure Too little and friction will cause heat
and failureLubricants Oil-slippery hydrocarbon liquids Grease-semisolid, a fluid lubricant
with a thickening agent
Assets of Oil Easy to control
volume Travels well Carry away heat Carry away
products of wear
Assets of Grease Stays put Less
maintenance Seals out
moisture
Couplings
Devices used to join two shafts together
3 categories
1. Solid Couplings
Used only when driving and driven shafts are mounted to a solid base (can’t move around)
2. Flexible Couplings
Compensate for unintentional misalignment
Prevent shock from being transferred between the shafts
3. Universal Couplings
Used when shafts are at an angle to each other (angle can change)
Also called universal joints
Flexible Shafts
Transmits power at angles and around corners
Helically wound wire designed to transmit rotary motion
TEST REVIEW Mechanism Linkage Cam Cam follower Bearings Plain bearing Roller bearings Ball bearings Couplings Flexible couplings Universal couplings
Gear types and orientation of their shafts: Spur Bevel Worm Rack and pinion
Gear train problem Plastic gear advantages (3) Bearing loads list and explain Assets of oil Assets of grease