GT3 (Gas Turbine 3) was a prototype mainline gas turbine locomotive built in 1961 by English Electric at its Vulcan Foundry in Newton-le-Willows to investigate the use of its gas turbines in rail traction applications. It followed 18000 and 18100 as gas turbines 1 and 2. It was designed by English Electric engineer J. O. P. Hughes in a project that started in the early 1950s. Externally it resembled a steam tender locomotive, but the tender carried kerosene fuel. The designer said the traditional chassis and mechanical transmission avoided complications with (at the time of its conception) relatively untried technologies for bogies and electrical transmission.
Overview
The National Railway Museum Archives hold the JOP Hughes papers which contain initial concept sketches for various 4-8-4 wheel arrangement single-unit configurations of the machine and early 4-6-0 tender locomotive drawings. These early concept drawings show various names, numbers and liveries, and were drawn with Boxpok-type wheels. The final design was for a 4-6-0 wheel arrangement locomotive with a fuel tender, looking much like a traditional steam locomotive in form.
As constructed the locomotive was built with bespoke heavy steel frames which not only bore the auxiliaries, combustion chamber, turbines, heat exchanger and locomotive cab, but also provided adhesive weight for the finished machine. The frames were carried by a leading two-axle outside-framed bogie and three main axles. The driving wheels were of conventional design in the finished locomotive and were of diameter with 19 spokes and conventional balance weights. The centre axle mounted a mechanical transmission shaft driven from the turbine assembly, with power to the outer axles being transmitted by side rods. Power came from an English Electric EM27L gas turbine arrangement of with high- and low-pressure turbines. The low-pressure turbine ran continuously in operation and was used to drive the locomotive's auxiliaries, with the high-pressure turbine operating as higher power outputs were required. Both the locomotive and its fuel tender were vacuum-braked, with vacuum brake ejectors being driven by air pressure bled from the turbine. The locomotive's other auxiliaries (housed in its leading end beneath the large side air intakes) were shaft- and belt-driven.
The tender was permanently coupled behind the locomotive and contained a Spanner train heating boiler at the leading end and fuel tanks either side of a central corridor with a boiler water tank beneath. A crew toilet compartment and British Standard corridor connection were located at the rear. The six-wheel chassis was based on then standard British Railways practice, albeit it with specially made and shaped side frames and bespoke tank and bodywork assembled at Vulcan Foundry. The locomotive had a designed maximum speed of , weighed , and was painted in a lined Beech Leaf Brown Livery, earning it the nickname The Chocolate Zephyr by railway enthusiasts. Underframes, grilles and the front access and cab doors were painted Brunswick Green with lettering and lining in Orange.
Testing
The locomotive was taken to British Railways' Rugby test centre in an incomplete state for testing on rollers, and then on a short section of specially laid track. After returning to Vulcan Foundry for final assembly, the locomotive was then based at the former locomotive shed at Whitchurch in Shropshire for initial light testing and crew training on the Malpas line between Crewe and Chester, before commencing loaded test runs to Llandudno Junction. One of these runs was filmed from on board the locomotive by British Movietone News and the resulting film also showed the locomotive being turned on Llandudno Junction turntable. In the event not all of the planned North Wales Coast Line test runs were completed.