High-speed steam engine

Although these were not defining to the type, or were always the case, they were recognisably common: High speed was not needed for electrical power generation in the largest citywide plants.

Smaller examples were usually simple, as the difficulties of achieving good regulation outweighed the efficiencies of compounding.

[1] The valvegear driving these valves was usually simple, a single eccentric designed only to run at one speed, in one direction, for a fairly constant load.

Although these engines were contemporaneous with sophisticated and efficient valvegears such as the Corliss, these trip valves were incapable of working quickly enough.

[3][4][5] A key requirement for the high-speed steam engine was accurate control of a constant speed, even under a rapidly changing load.

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.

The difficulty was that on high-speed engines, oilers could no longer be mounted on moving parts, such as the crosshead or connecting rod.

The main crankshaft bearings of this engine were provided with separate oilers that drained into the crankcase sump.

A valve was provided for draining this collected condensate off from beneath the oil in the bottom of the deep sump.

The difficulty of a double-acting engine was that the direction of the forces in the connecting rod now reverses between compression and tension, so that the bearing clearances must be made tighter to avoid any rattling.