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Chapter 16

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Used to reduce friction between two surfaces Different designs to accommodate rotational or linear motion Different designs for different load directions

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Radial Load Load acting perpendicular to the axis of the shaft

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Thrust Load Load parallel to the axis of the shaft Combination Load Both radial and thrust loads applied to the bearing

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Plain bearings Rolling element bearings

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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

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Bronze-needs to be lubricated Phosphor bronze-oil impregnated Various plastics These materials allow low friction movement

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Have moving parts to reduce friction Several types Ball Bearings Most common High speed applications

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Roller Bearings Cylindrical roller element Higher load capacity, lower speeds Several styles

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Bearings are purchased parts Different symbols used depending on drawing type Schematic symbols used for machine layout drawings

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3D models of products using bearings can use a simplified 3D model of any bearings in the product

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Machine Layout Drawing

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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

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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

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Devices used to join two shafts together 3 categories

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Used only when driving and driven shafts are mounted to a solid base (cant move around)

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Compensate for unintentional misalignment Prevent shock from being transferred between the shafts

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Used when shafts are at an angle to each other (angle can change) Also called universal joints

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Transmits power at angles and around corners Helically wound wire designed to transmit rotary motion

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TEST REVIEW Mechanism Linkage Cam Cam follower Bearings Plain bearing Roller bearings Ball bearings Couplings Flexible couplings Universal couplings

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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