Watt Rotative Engine

1788 · Rotative Engine · Work 84 of 1,871

Watt Rotative Engine, 1788, Rotative Engine

A rotative beam engine with its great flywheel and sun-and-planet gear, governor balls spinning at the top of their spindle, drive belts disappearing through the ceiling.

What it was used for
The Lap Engine of 1788 stood in Boulton's own Soho Manufactory in Birmingham and drove 43 lapping and polishing machines there. The Science Museum, where it now stands in the Energy Hall, gives 70 years of service, so to 1858. Bore 18.75 inches, stroke 4 feet; Watt rated it at 10 hp, and 13.75 hp was measured. The maker was its own customer: the firm that sold steam power used it in its own button and buckle works to replace hand labour at four dozen small machines.
What was new
What was new was not rotary motion from steam but that a single engine drove many small machines evenly through a line shaft. Regulation was part of it: according to the Science Museum this was the first engine fitted with a centrifugal governor. Getting there was a detour. Watt could not use the plain crank because another man's patent covered it, so on 25 October 1781 he patented other ways of producing rotary motion, among them the sun-and-planet gear, which turns the flywheel a full revolution for each stroke of the piston. By 1800, when the partnership ended, 451 engines had been built, of which 268 were rotative.

Connections

Every connection names its kind. “Forerunner” on its own would be a claim.

  1. Follows fromWatt Double-Acting Engine1782The Lap Engine of 1788 works double-acting. The Science Museum describes it as double acting, the piston giving a power stroke in both directions of movement. That is what produces the even pull with which it drove 43 lapping machines through a line shaft for seventy years.Source: Science Museum Group Collection: Rotative Steam Engine by Boulton and Watt, 1788 (Objekt co50948; 'being double acting', Sonnen- und Planetengetriebe, 43 Maschinen) · David Hulse Steam Engines: The Lap Engine (1788, doppeltwirkend, 43 Läpp- und Poliermaschinen, Soho Manufactory bis 1858, Sonnen- und Planetengetriebe)
  2. Works withCentrifugal Governor1788The Science Museum calls the Lap Engine of 1788 the first to be fitted with the centrifugal governor. The governor sits on this engine and holds the speed at which it drove 43 lapping and polishing machines at the Soho Manufactory for seventy years.Source: Science Museum Group Collection: Rotative Steam Engine by Boulton and Watt, 1788 (Objekt co50948; 'the first to be fitted with the centrifugal governor', double acting, 43 Maschinen, 70 Jahre)

Further reading