Highland Railway Clan Class

The Highland Railway's Clan Class was a class of passenger 4-6-0 steam locomotives designed by Christopher Cumming. The design is derived from that of the slightly earlier Clan Goods although the similarity is more visual than real.

They had 21-by-26-inch (533 by 660 mm) cylinders outside with outside Walschaerts valve gear, 6 ft 0 in (1.83 m) driving wheels and a boiler pressured to 175 lbf/in² (1.2 MPa). Weight was 62 tons 5 cwt (63.25 t) for the locomotive and 42 tons (42.7 t) for the tender. Piston valve diameter is given as 10 inches (quite large for the period), but they had the conventional short lap, short travel valves. Bearing in mind that they probably spent a large part of their time slogging uphill or coasting down this was probably not too important.

Total heating surface (including superheater) is given as 1,723 sq ft (160.1 m²) and grate area as 25.5 sq ft (2.37 m²). The first four were built in 1919, and the remaining four in 1921.

Two survived into British Railways hands, but only Clan Mackinnon received its BR number.

Early in 1921 Clan Stewart was used for experiments with oil firing. They seem to have been successful, but was not applied to any other locomotives. Just when Clan Stewart reverted to coal operation does not seem to be recorded.

The LMS classified them '4P'.

The Clan names were later reapplied to the BR standard class 6.

References

• Casserley, H.C. & Johnston, Stuart W. (1974) [1966]. Locomotives at the Grouping 3: London, Midland and Scottish Railway. Shepperton, Surrey: Ian Allan. p. 152. ISBN 0-7110-0554-0.