The NER class Z (LNER Class C7) was an Atlantic class of locomotives designed by

Vincent Raven Sir Vincent Litchfield Raven, KBE (3 December 1859 – 14 February 1934) was an English railway engineer, and was chief mechanical engineer of the North Eastern Railway from 1910 to 1922. Biography Vincent Raven was born the son of a clergy ...

. It was introduced in 1911.

Construction

Originally classified NER Class V2, the first 20 were built in 1911. Ten were saturated and the others were superheated. The saturated locos were superheated between 1914 and 1915, while all subsequent locomotives were superheated. 50 class Zs were built between 1911 and 1918, in 5 batches. Originally the locomotives were built with Schmidt

superheater A superheater is a device used to convert saturated steam or wet steam into superheated steam or dry steam. Superheated steam is used in steam turbines for electricity generation, steam engines, and in processes such as steam reforming. There ar ...

s, however from 1931 onwards 27 C7s were fitted with Robinson superheaters.

Variations

No.2212

The last of the 50 locos, No.2212 was built with Stumpf Uniflow cylinders. This arrangement had been used on LNER Class B15 No.825 with an untidy result, however the arrangement had been tidied up for No.2212. Double-length cylinders were required, thus a longer front bogie and smaller wheels were fitted. This arrangement, although requiring special attention (as with No.825) was used until 1934, when No.2212 was fitted with standard cylinders.

C9

In early 1931, Gresly rebuilt No.727 and 2171 (who were entering Darlington for repairs) with an articulated booster bogie, thus making them technically

4-4-4-4 A 4-4-4-4 steam locomotive, in the Whyte notation for describing locomotive wheel arrangements, has a four-wheel leading truck, two sets of four driving wheels, and a four-wheel trailing truck. While it would be possible to make an articulated lo ...

s. However the articulated bogie was considered split between the loco and tender in order to simplify classification. Originally the booster gearing was 1.5:1, however the trials of C1 No.4419 (also having boosters) showed that the booster help was practically nonexistent above , meaning that the locomotives’ boosters were practically useless with the express, which would have to run with a speed of at least . Hence,

Darlington Darlington is a market town in the Borough of Darlington, County Durham, England. The River Skerne flows through the town; it is a tributary of the River Tees. The Tees itself flows south of the town. In the 19th century, Darlington underwen ...

recommended that the booster gearing was to be changed to 1:1. This required larger cylinders to supply the same tractive effort, which required the boiler to operate at 200psi (25 psi higher than the C7s, which are 175psi) . Some have concerned about engaging the booster at higher speeds, however the unitary 1:1 gearing was considered to make this easier. The boilers were “Diagram 100” boilers (the ones used on the B17s), and followed Doncaster practises, rather than

practises (which was used on the standard C7s). They also have Robinson

s, rather than Schmidt ones. The growing amount of Gresley A1s, A3s and A4s marked the experiment redundant (seeing the A4s were scheduled to climb Cockburnspath hauling a 312 tons load at an average speed of ).

Withdrawal

Withdrawal of the C7

Had World War 2 not intervened, withdrawal would have started before 1940. However withdrawal was pushed back to August 1943. Withdrawal was quick, however, with only 14 surviving to nationalization. Within a year,

British Rail British Railways (BR), which from 1965 traded as British Rail, was a state-owned company that operated most of the overground rail transport in Great Britain from 1948 to 1997. It was formed from the nationalisation of the Big Four British rai ...

ways withdrew the remaining C7s, with none surviving into preservation.

Withdrawal of the C9

Their boilers were considered non-standard (compared to the C7s), thus they were withdrawn in April 1942(2171) and January 1943(727), before the first standard C7 was withdrawn. Neither of the two survived into preservation.

Loco details

Numbers in parentheses were allocated but not applied.

References

External links

LNER Class C7/NER Class ZLNER Class C9
{{LNER Locomotives Z class 4-4-2 locomotives Scrapped locomotives Standard gauge steam locomotives of Great Britain Passenger locomotives Railway locomotives introduced in 1911