TRANSMISSION 2 PROFESSIONAL ENGLISH IN USE FOR ENGINEERING

 

PROFESSIONAL ENGLISH IN USE FOR ENGINEERING UNIT 42. TRANSMISSION 2

 

A Chains, sprockets and pulleys Drive can be transmitted from one shaft to another, across a distance, by roller chains (or chains). Chains drive, or are driven by, toothed wheels called sprockets. Pairs of sprockets with different numbers of teeth can provide different gear ratios. A bicycle is an example is an example of a machine with chain drive. B Conversion between reciprocating and rotary motion The reciprocating linear motion of pistons is converted to rotary motion by connecting rods (or conrods) and a crankshaft. The shape of the crankshaft allows the connecting rods to exert force at a distance from its centre. This increases the turning moment they generate. Bicycle pedals are an example of a simple crank. In an engine, a heavy wheel – called a flywheel – is fitted to the end of the crankshaft. This provides momentum, giving the pistons more constant motion.   EXERCISES 42.1 Circle the correct words to complete the text about how chain drive works on bicycles. Look at A opposite and Appendix XI to help you. APPENDIX XI MANAGING ROTARY MOTION   On a bicycle, the pedals – which provide support for the rider’s feet – are fitted to a (1) crank/ sheave at either side of the frame. These are fixed together by a short shaft, called a spindle which runs through a tube at the bottom of the frame. The tube contains (2) bearings/ roller chains, which allow the spindle to turn freely. A (3) pulley/ sprocket, fitted to the shaft, drives a (4) cable/ chain, which drives a second (5) crank/ sprocket at the rear of the bike. This turns the rear wheel. 42.2 Complete the text about the advantages of chain drive on bicycles, using the words in the box. You will need to use some words more than once. Look at A opposite to help you. belt chain pulley toothed sprocket wheel The advantages of using chain drive on bicycles are: ·       its ability to transmit drive over a distance – from the centre of the bike to the rear ·       that a (1)__________ will not slip as it travels around a (2)__________ - unlike a (3)__________, which is more likely to slip as it travels around a (4)__________ ______________ 42.3 Answer the questions below using words from B opposite and Appendix XI. 1. In an engine, which revolving component generates the up-and-down motion required to open and close a valve in the cylinder head? 2. How can the motion of an engine’s crankshaft be transmitted to the camshaft? 3. What term is given to a component which presses against a cam and moves with a reciprocating action?

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