·  LMS  ·  GWR  ·  LNER  ·  Misc  ·  Stations  ·  What's New  ·  Video  ·  Guestbook  ·  About

LNER Route: Leicester to Marylebone

Rugby Central Station: gcrcs197

An LNER built K3 Class 2-6-0 locomotive is silhouetted against the morning sun whilst crossing the GCR viaduct just north of the 'Birdcage'

An LNER built K3 Class 2-6-0 locomotive is silhouetted against the morning sun whilst crossing the GCR viaduct just north of the 'Birdcage'. The concept for the K3 2-6-0 began in August 1917 when Gresley started to consider a new express goods engine for the Great Northern Railway (GNR) based on his K2 2-6-0 (GNR Class H3), but with a higher boiler pressure of 180psi and 20in or 20.5in diameter cylinders with a 28in stroke. The greater piston loads resulted in a lot of attention being given to the coupling rod pin bearing surfaces which would have had to have been increased. This is thought to have been the main reason for the scheme being eventually dropped. By this time, Gresley's three cylinder O2 2-8-0 mineral locomotive was being built. This was the first locomotive to incorporate his patent 'conjugated' valve gear on the middle cylinder, and was quickly deemed a success. Gresley announced that his future designs would concentrate on three cylinder designs, and turned his attention to the 2-6-0 express concept from 1917. With three cylinders, he reduced the cylinder diameter to 18.5in but kept the boiler pressure at 180psi, with the net effect of an increase in tractive effort of 36 per cent over the K2s. The boiler was enlarged to a then-unprecedented 6ft diameter, in order provide an adequate supply of steam. The outside cylinders were almost horizontal, but the inside cylinder was steeply inclined to clear the leading coupled axle.

Although very similar to the K1s and K2s, the K3s looked different due to their large diameter boilers and stout boiler mountings. The cab continued the austere style started by Ivatt. No side windows were provided, but a 1ft 6in deep side cut-out was provided as a driver look out. The roof also extended back 9in over the cab entrance. Later batches of K3s would introduce side windows and padded seats to the design. The first ten locomotives (Nos. 1000-9) were constructed between 1920 and 1921. Their advent coincided with the coal strike of 1921. Although intended for fast goods work, the strike meant they they were often used on express passenger services as an economy measure. The K3s managed this very well, and quickly made a name for themselves hauling trains up to twenty bogies in size. Jazz music was just becoming popular in Britain at that time, and they quickly earned the name of "Jazzers" due to their syncopated exhaust beat and uneven gyratory movement at the rear. The exhaust beat was a side-effect of the three cylinder design, and would become a common sound with the advent of further Gresley types.

The poor riding, however, would pose problems for maintenance. Early testing showed an over-travel problem on the middle valve during high speed coasting. This was partly due to the design of the conjugated gear multiplying any slackness in the pins and joints, and partly due to a whip action in the motion levers at speed. The problem was avoided by limiting the maximum cut-off to 65 per cent. The K3 became a Group Standard design quickly after Grouping in 1923, and in total 193 locomotives would be built in seven batches between 1920 and 1937. Construction only stopped after the new V2s had proven themselves as good replacements. Each batch would show minor refinements, so between 1923 and 1935 each batch was classified chronologically by its part number, e.g.. the 1920/1 batch was K3/1, and the 1934/5 batch was K3/6. Due to the differences being deemed minor in nature, classes K3/4, K3/5, and K3/6 were merged in with K3/2 in 1935. The original ten K3/1s were built to the larger GNR loading gauge, but were reclassified as K3/2 when they were cut down to the Composite LNER loading gauge. The last K3/1 was cut down and reclassified in 1940. Usage of the K3/2 and K3/3 class parts was discontinued with Nationalisation in 1948.

Courtesy LNER Encyclopedia

back