The steam engine

Steam engine : purpose and means

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the means: the piston activated by steam
the purpose:to rotate a wheel which will activate the factory machinery


Steam engine: steps

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the piston
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the piston and its tubes alternately providing steam and sending it to the condenser
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the piston with boiler and condenser
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the apparatus with the governor
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the apparatus linked to the wheel


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The principle: steam expands 1800 times more than water; condensed water produces a vacuum.

Steam engines were:

  • first used for pumps,
  • then to activate machinery when Watt found the means to transform their motion into rotary motion through his ’sun and planet’ system.

Watt’s improvements:

  • in the steam production process:
    • condensing the water in a separate condensor so that cold water would not diminish the efficiency of the machine
    • the double-effect piston
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Steam engine with governor
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  • the ’governor’ (earlier used for corn mills): when the machinery gathers speed, the balls of the governor start flying outwards and upwards (centrifugal force) and activate the lever which closes the valve to diminish the speed; the balls of the governor fall again, opening the valve to increase the speed again when it becomes too low. This is the earlist example of ’feedback’, and a model of a self-regulating system.

’Parallel motion mechanism’ is needed to adjust the vertical motion of the piston into the arc of the movement of the ends of the rod.