The Lap Engine

Soho Manufactory, Birmingham, 1788

Boulton & Watt’s own works engine, polishing (“lapping”) buttons and buckles at Soho for seventy years — and the oldest surviving engine with a flyball governor and Watt’s parallel motion. She stands in the Science Museum in London to this day, the very machine, dead centre of the story of power. Our specimen is set to her recorded dimensions.

Eighteen and three-quarter inches of bore, four feet of stroke, about 21 revolutions — rated some 10 horses.

On our bed she turns her twenty revolutions and makes about fourteen horses at twenty-four millions of duty.

One of the cabinet’s specimens, each ready for the test bed.