Douglas Mark III
Encyclopedia
The Douglas Mark III was a British motorcycle
designed and built by Douglas motorcycles
in Bristol
between 1949 and 1951. The 350 cc flat twin engine in the Douglas Mark III was based on a Second World War electricity generator. As well as the 1949 Douglas Mark III, Douglas also produced a Mark III "De Luxe", a Mark III Sports, and a rigid-framed motorcycle trials Competition version.
-based Douglas motorcycle company produced stationary generator
engines using their 348 cc overhead valve flat twin. One of these Douglas generators was used at Winston Churchill
's wartime summit meeting held next to the Sphynx in Giza. By the end of the war in 1945, Douglas re-started motorcycle production – much to the surprise of the industry, as it was generally expected that the war had led to other interests, with the company being taken over by Aero Engines Ltd, so there were not many engineering staff left for the development of new motorcycles. The Douglas T35 used the same flat-twin 350 cc as the generator, mounted in a duplex fame with torsion bar rear suspension. The T35 was an unexpected export success; 1947 factory records show them being exported to Canada
, Switzerland
, Belgium
, Santiago
, and Russia
.
designer Erling Poppe as Technical Director, Freddie Dixon
as their specialist engine tuner and Walter Moore (who designed the Norton CS1
) as Works Superintendent. The result was the 1949 Douglas Mark III, which had improved performance through an uprated cylinder head, combustion chambers, and pistons. Douglas also produced a Mark III "De Luxe", a Mark III Sports, and a rigid-framed motorcycle trials Competition version with high-level exhausts and a less deeply valanced front mudguard. There never was a Douglas Mark II, and the Mark IV was short-lived, so the end of the line of development was the Mark V produced between 1951 and 1954, when it was replaced by the Douglas Dragonfly
.
Motorcycle Trials
rider David Tye worked for Douglas as a sales rep, competing at weekends in the factory trials team. In 1950 he won the Nevis Trophy and the Special First Class Award in the demanding Scottish Six Days Trial
riding the Douglas Mark III Competition model. The low centre of gravity of the flat twin was useful for trials control but it did have a clearance problem over the rough ground. Occasionally one of the carburettors would be knocked off, but the team developed a "quick change" replacement and always kept spares ready.
Works rider Don Chapman on the Douglas Mark III Sports gave Douglas their only major successes in motorcycle racing by winning at the Silverstone Circuit
in 1950. Securing a win by 19 seconds, Chapman was awarded the Motor Cycling
magazine prize for "most meritorious" performance in the Clubmans races.
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...
designed and built by Douglas motorcycles
Douglas (motorcycles)
Douglas was a British motorcycle manufacturer from 1907–1957 based in Kingswood, Bristol, owned by the Douglas family, and especially known for its horizontally opposed twin cylinder engined bikes and as manufacturers of speedway machines...
in Bristol
Bristol
Bristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...
between 1949 and 1951. The 350 cc flat twin engine in the Douglas Mark III was based on a Second World War electricity generator. As well as the 1949 Douglas Mark III, Douglas also produced a Mark III "De Luxe", a Mark III Sports, and a rigid-framed motorcycle trials Competition version.
History
During the Second World War the BristolBristol
Bristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...
-based Douglas motorcycle company produced stationary generator
Engine-generator
An engine-generator is the combination of an electrical generator and an engine mounted together to form a single piece of equipment. This combination is also called an engine-generator set or a gen-set...
engines using their 348 cc overhead valve flat twin. One of these Douglas generators was used at Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
's wartime summit meeting held next to the Sphynx in Giza. By the end of the war in 1945, Douglas re-started motorcycle production – much to the surprise of the industry, as it was generally expected that the war had led to other interests, with the company being taken over by Aero Engines Ltd, so there were not many engineering staff left for the development of new motorcycles. The Douglas T35 used the same flat-twin 350 cc as the generator, mounted in a duplex fame with torsion bar rear suspension. The T35 was an unexpected export success; 1947 factory records show them being exported to Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
, Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
, Santiago
Santiago, Chile
Santiago , also known as Santiago de Chile, is the capital and largest city of Chile, and the center of its largest conurbation . It is located in the country's central valley, at an elevation of above mean sea level...
, and Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
.
Development
In 1948 the company developed a series of motorcycles based on the T35. Designed by George Halliday, these featured Douglas "Radialraulic" forks with the front wheel spindle carried on short leading links pivoted at the rear of the fork stanchions – with springs and a damping mechanism inside the stanchions. Although the frame and suspension were innovative, the engine was essentially a generator, designed to run for long periods at a steady speed and it did not cope well with the varying engine speeds of motorcycling. There was also a tendency to sideways shaking at low RPM which was a feature of the horizontally opposed engine. Douglas hired former Sunbeam motorcyclesSunbeam (motorcycle)
Sunbeam was a British manufacturing marque that produced bicycles and motorcycles from 1912 to 1956. Originally independent, it was ultimately owned by BSA...
designer Erling Poppe as Technical Director, Freddie Dixon
Freddie Dixon
Frederick William Dixon was an English motorcycle racer and racing car driver. He was the designer of the motorcycle and banking sidecar system. He was also one of the few motorsport competitors to have been successful on two, three and four wheels. He was twice awarded the BRDC Gold Star...
as their specialist engine tuner and Walter Moore (who designed the Norton CS1
Norton CS1
The CS1 was a Norton motorcycle between 1927 and 1939. Originally built as a TT racer, and Norton's first design of an overhead cam engine, it proved successful as a TT Replica road bike....
) as Works Superintendent. The result was the 1949 Douglas Mark III, which had improved performance through an uprated cylinder head, combustion chambers, and pistons. Douglas also produced a Mark III "De Luxe", a Mark III Sports, and a rigid-framed motorcycle trials Competition version with high-level exhausts and a less deeply valanced front mudguard. There never was a Douglas Mark II, and the Mark IV was short-lived, so the end of the line of development was the Mark V produced between 1951 and 1954, when it was replaced by the Douglas Dragonfly
Douglas Dragonfly
The Douglas Dragonfly was a British motorcycle designed and built by Douglas motorcycles in Bristol. The last motorcycle produced by the company, the 1955 Dragonfly was an all-new motorcycle built to use an improved version of an existing engine...
.
Competition success
Motorcycle Trials
Motorcycle trials, also termed observed trials, is a non-speed event on specialized motorcycles. The sport is most popular in the United Kingdom and Spain, though there are participants around the globe....
rider David Tye worked for Douglas as a sales rep, competing at weekends in the factory trials team. In 1950 he won the Nevis Trophy and the Special First Class Award in the demanding Scottish Six Days Trial
Scottish Six Days Trial
The Scottish Six Days Trial is an internationally recognised Motorcycle trials competition, which has been running since 1909 making it the oldest motorcycle trials event in the world...
riding the Douglas Mark III Competition model. The low centre of gravity of the flat twin was useful for trials control but it did have a clearance problem over the rough ground. Occasionally one of the carburettors would be knocked off, but the team developed a "quick change" replacement and always kept spares ready.
Works rider Don Chapman on the Douglas Mark III Sports gave Douglas their only major successes in motorcycle racing by winning at the Silverstone Circuit
Silverstone Circuit
Silverstone Circuit is an English motor racing circuit next to the Northamptonshire villages of Silverstone and Whittlebury. The circuit straddles the Northamptonshire and Buckinghamshire border, with the current main circuit entry on the Buckinghamshire side...
in 1950. Securing a win by 19 seconds, Chapman was awarded the Motor Cycling
Motor Cycling (magazine)
Motor Cycling was one of the first British motorcycle magazines. Launched in 1903, its green cover led to it being called "The Green 'un" to distinguish it from its rival publication The Motor Cycle. The editor, Graham Walker, was a dispatch rider in the First World War and had a successful racing...
magazine prize for "most meritorious" performance in the Clubmans races.
