Two-cycle engines use few moving parts compared to many parts used for construction of four-cycle engines where sequence is controlled by valves opening and closing by the action of a rotating cam shaft. The simple two-cycle construction is one reason for their popularity early 1900. Two-cycle engines are dependable and easy to repair. From about 1900 to 1920, many organizations manufactured two cycle marine engines. By 1950 most small marine engines were outboard style. Now because of environmental concern, almost all small marine engines use the four stroke cycle. St Lawrence Engine Company manufactured two-cycle marine engines from 1905 to about 1949 at a facility located in Canada at Brockville, Ontario. Only minor improvements occurred during the period, notably changing to aluminium pistons about 1935.
Typical two cylinder St Lawrence two-cycle marine engine Circa 1935 Bore 3 1/4", Stroke 3/1/2' x 2 Flywheel is 14" diameter 6 HP @ 850 RPM
Typical single cylinder St Lawrence two-cycle marine engine Circa 1949 Bore 3 1/4", Stroke 3 1/2'" Flywheel is 12" diameter 3 HP @ 850 RPM
The advancement of gas engine use occurred as a result of understanding the advantage of compression prior to ignition. This occurred in 1876 in Germany by Nikolaus Otto. Otto's engine used a four-stroke cycle where combustion occurred once during two engine revolutions. Even now the four-stroke cycle is referred to as the Otto cycle.
During 1890 a Scottish engineer, Sir Dugald Clerk, introduced an engine where combustion occurred each engine revolution. This is referred to as the two-stroke cycle. Clerk's engine used a separate chamber for taking in the combustible charge and transferring it to the power cylinder. In 1892, Frederic Caswell Cock, an Englishman, patented the two-cycle method where combustible charge entered the crankcase before transfer to the combustion chamber via an integral transfer port.
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Old two stroke marine engines - their construction and operation
Building Gertrude - Swampscott Dory powered by vintage 3HP 2 cycle engine
Owner built using techniques developed for single handed construction
Buy these and other rebuilt St Lawrence engines - contact goslowboat
Kitchen Rudder, invented 1914 reinvented 2003 to steer and maneuver Gertrude a goslowboat powered by a vintage 3 HP St Lawrence two-cycle engine. This old two-stroke is direct connect to propeller. The owner built Kitchen Rudder uses Clam Shell deflectors that provide superior boat control compared to an ordinary transmission. Be sure to view the video to experience this amazing 100 year old boat rudder and ancient one lunger.
Gertrude's two cycle engine is directly connected to propeller. This was typical during the early 1900s. Transmissions were heavy, costly and not common.

To provide maneuverability Gertrude is fitted with an owner designed/built Kitchen Rudder.

Using Kitchen Rudder engine always operates at preset speed, always in forward direction.

Kitchen's 1914 British Patent #869,051 ( USA patent #1,186,210) described a clever mechanism consisting of two clamshell like deflectors that encircled a boat's propeller. These can be opened or closed in unison. When closed, all of the propeller stream is reversed and then acts in a forward direction causing the boat to move backwards. Although this reversing capability was the main objective of the invention, it was soon discovered that a boat fitted with a Kitchen Rudder can be maneuvered at least equal to a vessel with twin screws. This unprecedented maneuverability encouraged the British Admiralty to install Kitchen Rudders on open vessels used for rescue missions where ability to maneuver was crucial.

Operation is seamless. Engine manipulation or speed change is unnecessary.

Clamshells are manipulated by a tiller mounted mechanism
Concentric shafts connect to clamshells

Coxswain rotates tiller mounted crank to open and close clamshells

At same time Coxswain moves tiller from side to side for steering and to control stern thrust
How a Kitchen Rudder works
Kitchen Rudder, invented 1914 in England by John Aulesbrook Kitchen
Two-cycle engine sequence during one revolution
Reversing capability is only one feature of a Kitchen Rudder.
Maneuverability including speed control, direction control, stern thrust etc provided by the device is much better than provided by a standard transmission. The video at is intended to display this maneuverability.

When viewing the video, focus on all Kitchen Rudder features, clam shell position , tiller manipulation, then how the boat behaves particularly directional control when clam shells are closed or almost closed and when stern thrust is applied.

As an example at minute 2 in the video, the boat is stationary. If this were a standard transmission propeller would be detached from engine. Boat would float without control until transmission is engaged. When using Kitchen Rudder engine and propeller remain connected, thus very subtle moment of tiller and clam shell crank provides instant control of boat position, direction and speed.
Kitchen Rudder Video
Building Gertrude
Information at bottom of this page

click white arrow to play video - to pause video click double bars ll - best viewed full screen