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Belt Drives 1

Belt Drives 1. Transmitting of Power in Machinery Gears Chains Belts Belts preferred method: Between widely separated shafts Speed of the driven shaft different from driving shaft Advantages Quiet Smooth No lubrication required. Belt Drives 1.

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Belt Drives 1

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  1. Belt Drives 1 • Transmitting of Power in Machinery • Gears • Chains • Belts • Belts preferred method: • Between widely separated shafts • Speed of the driven shaft different from driving shaft • Advantages • Quiet • Smooth • No lubrication required

  2. Belt Drives 1 • Belts depend on friction to transfer energy and motion • (Except synchronous belts) • Friction belts exhibit: • Slip • Stretch • Creep • 3 basic types of belts • Flat belts • V-belts • Synchronous belts

  3. Belt Drives 1 • Flat belts • Light duty, high speed application • Examples – copying machines • Wide heavier belts to transport power over long distance • Examples – mining operations, people movers, luggage movers • V-Belts • Provide higher torque • Used with grooved pulleys – sheaves • Tapered shape bulges during operation, walls only • Bottom never contacts the sheave • Examples – cars • Standard sizes • Dimensions and designations – V-belt and sheave gauge

  4. Belt Drives 1 • Synchronous belts • Referred as timing belts • Flexible toothed belts used to synchronize the rotation of the driving shaft with the driven shaft without slippage • Wrap around toothed wheels – sprockets • No slippage, creep or stretch

  5. Belt Drives 1 • Sheave Characteristics • Outside diameter (O.D.) and pitch diameter (D) • Pitch diameter - diameter of the sheave measured from the center line of the belt wrapped around it. • O.D and belt type known – pitch diameter provided by the manufacturer

  6. Belt Drives 1 • Sheave Alignment • Misalignment • Uneven wear • Noise • High temperature • 3 types of Misalignment • Angular misalignment • Horizontal Angular • Vertical Angular • Parallel • Combination square (vertical) and straight edge (horizontal and parallel) check alignment.

  7. Belt Drives 1 • Belt Tensioning • Belt tension factor on obtaining maximum efficiency and service life • Tensioning done by moving pillow block and/or motor • Too little – belt slippage • Too much – excessive stress on belts, bearings and shafts • Tool – Belt Tension Tester • Two scales • Upper – deflective force • Lower – measured belt span

  8. Belt Drives 1 • Pitch diameter, speed and torque • D(1) – the diameter of the driving sheave • D(2) – the diameter of the driven sheave • n(1) – the speed of the driving sheave • n(2) – the speed of the driven sheave • T(1) – the torque of the driving sheave • T(2) – the torque of the driven sheave • To calculate any parameter use: • D(2)/D(1) = n(1)/n(2) = T(2)/T(1)

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