page_title: High-speed steam engine
section_title: "Automatic" engines
hierarchical_section_title: High-speed steam engine / "Automatic" engines
caption_attribution_description: Ames automatic governor (New Catechism of the Steam Engine, 1904).jpg
context_page_description: High-speed steam engines were one of the final developments of the stationary steam engine. They ran at a high speed, of several hundred rpm, which was needed by tasks such as electricity generation.
context_section_description: A key requirement for the high-speed steam engine was accurate control of a constant speed, even under a rapidly changing load. Although the control of steam engines via a centrifugal governor dates back to Watt, this control was inadequate. These early governors operated a throttle valve to control the flow of steam to the engine. This gives an inadequately responsive control for the constant speed needed for electricity generation.
  The solution developed for high-speed steam engines was the "automatic" governor. Rather than controlling the flow rate of steam, it controlled the timing or 'cut-off' of the inlet valves. This governor was interspersed between the crankshaft and the eccentric driving the valve gear. It was often made as part of the engine's flywheel. A centrifugal bob weight in the governor moved out against a spring with increasing speed. This caused the eccentric's position to shift relative to the crank, changing the valve timing and causing an early cut-off. As this control acted directly at the cylinder port, rather than through a long pipe from a throttle valve, it could be very fast-acting.
caption: Ames automatic governor, with centrifugal bob-weight and leaf spring
exif: {}