Steering engine
A steering engine is a power steering device for ships.
History
[edit]Prior to the invention of the steering engine, large steam-powered warships with manual steering needed huge crews to turn the rudder rapidly. The Royal Navy once used 78 men hauling on block and tackle gear to manually turn the rudder on HMS Minotaur, in a test of manual vs. steam powered steering.[1]
The first steering engine with feedback was installed on Isambard Kingdom Brunel's Great Eastern in 1866.[2] Designed by Scottish engineer John McFarlane Gray and built by George Forrester and Company, this was a steam-powered mechanical amplifier used to drive the rudder position to match the wheel position. The size of Great Eastern, by far the largest ship of her day, made power steering a necessity. Steam-powered steering engines were employed on large steamships thereafter.
The Mississippi River style steamboat Belle of Louisville, (originally Idlewild and oldest in her class), is fitted with a steering engine. Original equipment when the boat was launched at Pittsburgh in 1915, the engine consists of a single double-acting steam cylinder mounted aft of and above the engines, coupled to the rudders, with the motion of travel abeam. The steam valves of the engine are controlled by mechanical linkages which extend up to levers mounted either side of the engine order telegraph, just aft of the pilot wheel in the pilot house above. The steering engine is open to public view. A functional description is given in the 1965 book Str. Belle of Louisville, by Alan L. Bates, the marine architect who supervised the restoration of the boat, who comments that when in use, the steering engine causes the pilot wheel to whirl "as fast as an electric fan." The same source also describes the functional need for steering hard-to in vessels of its type, whose combination of shallow draft and high above-water profile require rapid changes in rudder under shifting wind conditions, a need which is addressed by the steering engine.
Operation
[edit]
The system invented by John McFarlane Gray in 1866 for the steamship Great Eastern was the first to incorporate feedback to stop and hold the rudder in the position demanded by the wheel. The mechanism incorporated shafts, bevel gears, and differential gears between the wheel and the rudder stock, so that the combined output of the gears controlled (through a screw mechanism and a lever) a reversible steam valve. When the wheel was first moved, the steam valve opened and the engine turned the stock through a pinion wheel and quadrant gear. When the position of the gears attached to the stock and the wheel “agreed”, the output from the differential gear returned the steam valve to its central position and the rudder was held. Returning the wheel reversed the process.[3]
In a later system, a rotating shaft and gears carried the movement of the steering wheel to a large screw-threaded shaft next to the steering engine. Turning the shaft opened a reversible steam valve, through a "nut" (a sturdy metal sleeve with an internal thread) and a lever. When the ship's wheel was turned steam was admitted to the steering engine, which moved in the required direction. However, at the same time, the nut was being rotated by gearing from the engine along the screw in the direction that closed the valve. Therefore, only when the ship’s wheel was actually being turned was steam admitted to the engine, otherwise the nut’s movement along the shaft restored the valve to the closed position, stopping the engine. An indicator at the wheel showed the angle of the rudder.[4]
See also
[edit]References
[edit]
- ↑ White, W.H. (1900). A Manual of Naval Architecture for Use of Officers of the Royal Navy, Officers of the Mercantile Marine, Yachtsmen, Shipowners, and Shipbuilders. J. Murray. p. 669. ISBN 978-0-7277-5040-2. Retrieved 2015-01-10.
{{cite book}}: ISBN / Date incompatibility (help) - ↑ Bennett, S. (1986). A History of Control Engineering, 1800-1930. Peregrinus. p. 98. ISBN 9780863410475. Retrieved 2015-01-10.
- ↑ Bennett, Stuart (1986). A History of Control Engineering, 1800-1930. London: Institute of Electrical Engineers. pp. 98–99. ISBN 978-0-86341-047-5.
- ↑ Sennett, Richard; Oram, Henry J. (1898). The Marine Steam Engine. London: Longmans. p. 374. OCLC 861241141.
