Bearings, Lubricants and Couplings Chapter 16 Bearings, Lubricants and Couplings

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 failure Lubricants 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