Bristol Tramp

Bristol Aeroplane Company

Industry	Aerospace
Founded	1910
Headquarters	Bristol , United Kingdom

Template:Infobox aircraft The Bristol Tramp was a British passenger and airmail transport aircraft powered by steam, developed by the Bristol Aeroplane Company. Although constructed, it never achieved flight.

Development

The Tramp evolved from Bristol's earlier Pullman passenger plane. In 1919, Frank Barnwell initiated talks with the Royal Mail Steam Packet Company regarding the potential use of flying boats as supplementary craft for ocean liners. While the Royal Mail Steam Packet Company had limited expertise with internal combustion engines, it possessed extensive experience with steam turbine technology and proposed employing a steam turbine to power the aircraft. Since Bristol’s heavy bomber, the Braemar—the predecessor of the Pullman—was originally designed with a central engine compartment driving wing-mounted propellers via shafts, the Pullman was considered an appropriate platform for integrating a steam turbine engine room.

The propulsion system was planned to include two Ljungstrøm-type steam turbines, each rated at 1,500 hp (1,120 kW), powered by closed-circuit high-pressure flash boilers. These turbines would collectively provide an unprecedented 3,000 hp (2,240 kW), transmitted through driveshafts and clutches to four-bladed tractor propellers located on each middle wing—consistent with the triplane configuration of the Braemar/Pullman/Tramp series. Ultimately, the steam turbine itself was not problematic; rather, it produced excessive power for the Tramp’s airframe, which had been engineered to accommodate approximately 1,600 hp (1,190 kW) generated by four 400 hp (300 kW) Liberty L-12 engines. The chief challenge lay in developing a dependable and lightweight closed-circuit boiler and condenser.

Two Tramp units were completed in 1921, each equipped with four 230 hp (170 kW) Siddeley Puma piston engines. However, persistent issues with the power transmission system—especially the clutches—prevented either aircraft from flying. Subsequently relocated to Farnborough in 1922, they served as ground test rigs for several years.

The Tramp Boat was a conceptual flying boat variant derived from the Tramp design.

Variants

Type 37 Tramp

An experimental triplane powered by steam, initially referred to as spares carriers, equipped with four 230 hp (172 kW) Siddeley Puma engines housed within a central engine compartment. Two units were constructed, though neither ever took flight.

Type 44 Tramp Boat

A conceptual flying-boat version of the triplane.

External links

• Photograph of the Tramp featured in Flight magazine