TRANSMISSION 1 PROFESSIONAL ENGLISH IN USE FOR ENGINEERING

 

PROFESSIONAL ENGLISH IN USE FOR ENGINEERING UNIT 41. TRANSMISSION 1

 

A Gears Gear wheels, or gears, are wheels with teeth (or cogs). The teeth interlock (fit together) with those of other gear wheels. When one gear wheel revolves, the other revolves with it – in the opposite direction – as their teeth mesh together. Gears are normally fitted to shafts. They transmit rotary motion from one shaft to another – that is, they transmit drive. Drive, usually supplied by an engine or motor, causes a shaft to revolve. A shaft connected directly to an engine or motor is called a driveshaft – or an input shaft. A gear wheel on a driveshaft is called a driver. The second gear wheel, which mashes with the driver, is called a follower – the driver drives the follower. B Gear ratios Gears can provide a mechanical advantage by using different gear ratios. In the diagrams above, the driver has 20 teeth and the follower has 60 teeth. Therefore the driver rotates three times to make the follower rotate once. So the gear ratio is 3:1 (three to one). This means that if, for example, the input speed of the driver – is 3,000 rpm, the output speed (of the follower) will be 1,000 rpm. C Types of gear wheel ·      Spur gears are the simplest gears. The teeth run straight across the wheel. ·      Helical gears have curved teeth, so that they mesh together more smoothly. ·      Bevel gears allow drive to be transmitted through an angle – often 90˚. EXERCISES 41.1 Change four words in the text below to make it correct. Look at A opposite to help you. An engine is connected to a driveshaft. Fitted to this output shaft is gear wheel called the idler. As this gear wheel turns, it drives another gear wheel alongside it a driver, which is fitted to an output shaft. 41.2 Complete the text about continuously variable transmission using the words in the box. Look at A, B, and C opposite to help you. automatic higher ratio shafts transmit helical manual selection shift wheels CONTINUOUSLY VARIABLE TRANSMISSION (CVT) (1)________________ gearboxes allow the driver of a vehicle to (2)________________ gears as required. If a (3)________________ gear is selected, the speed of the output shaft will increase relative to the input shaft, for a given an engine speed. In a typical (4)________________ gearbox, however, the gear (5)________________ system is automated, requiring no action by the driver. In addition, most 41.3 Make word combinations with gears using words from A and C opposite. Then use the word combinations to complete the sentences (1-4) below. Sometimes there is more than one possible answer. 1. ________________ gears are used to transmit drive through an angle. 2. ________________ gears run more quietly than spur gears.

ANSWER KEY