The Bristol Tramp was a British steam-powered passenger and

airmail Airmail (or air mail) is a mail transport service branded and sold on the basis of at least one leg of its journey being by air. Airmail items typically arrive more quickly than surface mail, and usually cost more to send. Airmail may be t ...

transport

aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or by using the Lift (force), dynamic lift of an airfoil, or in ...

Bristol Aeroplane Company The Bristol Aeroplane Company, originally the British and Colonial Aeroplane Company, was both one of the first and one of the most important British aviation companies, designing and manufacturing both airframes and aircraft engines. Notable a ...

. It was built but never flew.

Development

The Tramp was a development of Bristol's earlier Pullman passenger aircraft. In

1919 Events January * January 1 ** The Czechoslovak Legions occupy much of the self-proclaimed "free city" of Pressburg (now Bratislava), enforcing its incorporation into the new republic of Czechoslovakia. ** HMY ''Iolaire'' sinks off the ...

Frank Barnwell Captain Frank Sowter Barnwell OBE AFC FRAeS BSc (23 November 1880 – 2 August 1938) was a Scottish aeronautical engineer. With his elder brother Harold, he built the first successful powered aircraft made in Scotland and later went on to a c ...

entered discussions with the

Royal Mail Steam Packet Company The Royal Mail Steam Packet Company was a British shipping company founded in London in 1839 by a Scot, James MacQueen. The line's motto was ''Per Mare Ubique'' (everywhere by sea). After a troubled start, it became the largest shipping group ...

about the feasibility of using

flying boat A flying boat is a type of fixed-winged seaplane with a hull, allowing it to land on water. It differs from a floatplane in that a flying boat's fuselage is purpose-designed for floatation and contains a hull, while floatplanes rely on fuselag ...

s as auxiliaries to ocean liners. The Royal Mail Steam Packet Company had very limited experience with

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal co ...

s, but long-term and deep knowledge of

steam turbine A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884. Fabrication of a modern steam tu ...

powerplants, and so suggested the use of a steam turbine to power the aircraft. As Bristol's

heavy bomber Heavy bombers are bomber aircraft capable of delivering the largest payload of air-to-ground weaponry (usually bombs) and longest range ( takeoff to landing) of their era. Archetypal heavy bombers have therefore usually been among the larg ...

, the

Braemar Braemar is a village in Aberdeenshire, Scotland, around west of Aberdeen in the Highlands. It is the closest significantly-sized settlement to the upper course of the River Dee sitting at an elevation of . The Gaelic ''Bràigh Mhàrr'' pr ...

– the progenitor of the Pullman – had originally been designed to have a central engine room with driveshafts to wing-mounted propellers, the Pullman seemed a suitable candidate as a testbed for the installation of a steam turbine engine room. The powerplant was to consist of two 1,500 hp (1,120 kW) steam turbines of the Ljungstrøm type, with closed-circuit high-pressure

flash boiler A flash boiler is a type of water-tube boiler. The tubes are close together and water is pumped through them. A flash boiler differs from the type of monotube steam generator in which the tube is permanently filled with water. In a flash boiler, ...

s. The unprecedented 3,000 hp (2,240 kW) would be delivered though driveshafts and clutches to four-bladed

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propellers mounted on each middle wing (the Braemar/Pullman/Tramp family were

triplane A triplane is a fixed-wing aircraft equipped with three vertically stacked wing planes. Tailplanes and canard foreplanes are not normally included in this count, although they occasionally are. Design principles The triplane arrangement ma ...

s). In the end, the only problem encountered with the steam turbine itself was that it delivered far too much power for the Tramp airframe, which had been designed to handle the 1,600 hp (1,190 kW) of four 400 hp (300 kW)

Liberty L-12 The Liberty L-12 is an American water-cooled 45° V-12 aircraft engine displacing and making designed for a high power-to-weight ratio and ease of mass production. It saw wide use in aero applications, and, once marinized, in marine use both ...

engines. The main problem turned out to be designing a reliable lightweight closed-circuit boiler and condenser. Two examples of the Tramp were completed in

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, powered by four 230 hp (170 kW) Siddeley Puma

piston engine A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common feat ...

s, but the power transmission system, particularly the clutches, gave continual trouble, and neither ever flew. They were moved to

Farnborough Farnborough may refer to: Australia * Farnborough, Queensland, a locality in the Shire of Livingstone United Kingdom * Farnborough, Hampshire, a town in the Rushmoor district of Hampshire, England ** Farnborough (Main) railway station, a railw ...

in 1922 where they were used as ground test rigs for several years. The Tramp Boat was a proposed

development of the Tramp.

Variants

;Type 37 Tramp :Experimental steam-powered triplanes, originally described as ''spares carriers'' with four Siddeley Puma engines in a central engine room. Two built but never flown. ;Type 44 Tramp Boat :Proposed triplane flying-boat variant.

Specifications (Tramp with Puma engines)

References

External links

picture of Tramp in ''Flight'' magazine
{{Bristol aircraft 1920s British airliners

Tramp A tramp is a long-term homeless person who travels from place to place as a vagrant, traditionally walking all year round. Etymology Tramp is derived from a Middle English verb meaning to "walk with heavy footsteps" (''cf.'' modern English ''t ...

Steam-powered aircraft Triplanes Abandoned civil aircraft projects of the United Kingdom

Development

Variants

Specifications (Tramp with Puma engines)

See also

References

External links