British Rail 18100
British Rail 18100 was a prototype main line gas turbine–electric locomotive built for British Railways in 1951 by Metropolitan-Vickers, Manchester. It had, however, been ordered by the Great Western Railway in the 1940s, but construction was delayed due to World War II. It spent its working life on the Western Region of British Railways, operating express passenger services from Paddington station, London.
The locomotives basic parameters were stipulated by then chief mechanical engineer of the Great Western Railway. These requirements were that it should be suitable for hauling the heaviest passenger trains on the Western main routes, particularly that between London and Plymouth, and at speeds up to 90 m.p.h.
This needed a maximum starting tractive effort of the order of 60,000 lb and, with the stipulated maximum axle loading, that requires six driving axles. The same considerations led to fixing the continuous rating at 30,000 lb tractive effort. Electric transmission was adopted as the only practicable and reliable means of satisfying these conditions.
Images
The main image is of 18100 at Bristol on 5 April 1952, having brought in the Merchant Venturer. There are images available of the locomotive in front of The Bristolian and in the works at Metro-Vickers in Manchester. Nearby are images of 18100 in retirement having been "stored" on a disused section of the GCR link between Ashendon and Grendon junction. The site was near the A41 bridge and mile post 168. It seems that one of the coaches was used as weather station. Another image at the bottom of the page was also taken at Akeman street in 1969.Overview
It was of Co-Co wheel arrangement and its gas turbine was rated at. It had a maximum speed of and weighed. It was painted in BR black livery, with a silver stripe around the middle of the body and silver numbers.Technical details
A simple open cycle gas turbine without heat exchanger is the prime mover and the cycle of compression, heating and expansion of the air is carried out in a compressor, combustion chamber and turbine arranged in line and built into a single straight through unit. The compressor is a 15-stage axial-flow machine with a pressure ratio of 5.25 at 7,000 r.p.m. The turbine is a five-stage unit with its rotor is directly coupled to that of the compressor. The turbine drives three main traction generators at 1,600 r.p.m. through single reduction gearing. The reduction gear unit has two output shafts; one drives two of the main generators in tandem and the other drives the third main generator, the auxiliary generator and the exciter.The gas turbine was of a type which would now be called a turboshaft engine but it differed from modern free-turbine turboshaft engines in having only one turbine to drive both the compressor and the output shaft. It was based on aircraft practice and had six horizontal combustion chambers and no heat exchanger.
The emphasis was on power, rather than economy, and the fuel consumption was high. It was designed to use aviation kerosene and was much more expensive to run than No. 18000, which used heavy fuel oil.
Each main generator powered two traction motors. Unlike No. 18000, there was no auxiliary diesel engine and the turbine was started by battery power, using the main generators as starter motors.
Comparison of 18000 and 18100
The following table gives a comparison between 18000 and 18100. There are some anomalies and these are described in the notes.| Value | 18000 | 18100 | Notes |
| Weight | 115 | 129 | - |
| Turbine horsepower | 10,300 | 9,000 | |
| Power absorbed by compressor | 7,800 | 6,000 | |
| Output horsepower | 2,500 | 3,000 | |
| Number of traction motors | 4 | 6 | - |
| Total traction motor horsepower | 2,500 | 2,450 | |
| Starting tractive effort | 31,500 | 60,000 |
Notes:
- In 18000, output horsepower is 24% of total horsepower and in 18100, output horsepower is 33% of total horsepower. This suggests that 18100 had the higher thermal efficiency but, in practice, 18000 had the higher thermal efficiency. The horsepower figures should, therefore, be regarded with some scepticism.
- Where electric transmission is used, the horsepower of the traction motors is usually 81% that of the prime mover. The figure for 18100 is therefore about right but the figure for 18000 looks anomalous.