LNER Thompson Class A2/3

Disambiguation: LNER Thompson Class A2

LNER Thompson Class A2/3

No. 517 Ocean Swell in 1947

Type and origin Power type Steam Build date 1946 Total produced 15

Specifications Configuration 4-6-2 Gauge 4 ft 8 1⁄2 in (1,435 mm) Driver diameter 6 ft 2 in (1.880 m) Loco weight 101.5 long tons (103.1 t) Boiler pressure 250 psi (1.72 MPa) Cylinders Three Cylinder size 19 in × 26 in (483 mm × 660 mm)

Performance figures Tractive effort 40,430 lbf (179.84 kN)

Career Operators London and North Eastern Railway British Railways Class A2/3 Power class 8P7F Numbers LNER 500 and 511-524 BR 60500 and 60511-60524 Disposition All Scrapped

The London and North Eastern Railway (LNER) Class A2/3 was a class of 4-6-2 steam locomotives. They were newly constructed locomotives, fulfilling the requirement identified by Edward Thompson for a standard express passenger locomotive of the 4-6-2 arrangement with 6 ft 2 in (1.880 m) driving wheels. Fifteen engines were constructed according to this original design, but following the retirement of Thompson as CME, the remaining fifteen locomotives that were planned were immediately redesigned and ultimately emerged as Peppercorn Class A2., summer 1961 edition, part 4, page 27

Background

When Edward Thompson was appointed Chief Mechanical Engineer of the London and North Eastern Railway in April 1941, he envisaged a new standardisation programme involving ten locomotive designs including two Pacific types. These were an express passenger type (designated A1) with 6 ft 8 in (2.032 m) driving wheels and a ‘heavy passenger and freight’ type (designated A2) with 6 ft 2 in (1.880 m) driving wheels. He was not able to proceed with his plan due to the Second World War but did try out some of his ideas by rebuilding Nigel Gresley’s P2 class 2-8-2 as A2/2 pacifics and building the last four V2 class already on order as A2/1 pacifics. At last in April 1944 Thompson received authority to build thirty new locomotives of his A2 type during 1945, and a further thirteen during 1946.

Design

The basic design of the locomotive was similar to the A2/2 rebuilds in terms of the frames, boiler and motion, but boiler pressure was increased to 250 psi (1.72 MPa) and the cylinder diameter was reduced to 19 in (483 mm). The locomotives retained Thompson’s divided drive with the middle cylinder driving the first pair of driving wheels and the outside cylinders the middle pair. However, In order to have three connecting rods of the same length with three independent sets of Walschaerts valve gear, the outside cylinders were set back behind the bogie.

Building

The locomotives were due to be built at Doncaster works but were subject to various delays and so only the first, No. 500 appeared in traffic in May 1946, prior to Thompson’s retirement aged sixty-five, the following month. Fourteen further examples were then under construction and appeared under Thompson’s successor Arthur Peppercorn, between July 1946 and September 1947. After trials during the summer and autumn 1946 Peppercorn decided not to build the remaining locomotives authorised until he had made modifications to the design. In fact O.S. Nock has suggested that the Doncaster staff had begun amending the design before Thompson’s retirement. The class was then redesignated A2/3, and the Peppercorn design became the standard A2 class.

Performance

The class performed adequately but according to Nock, they suffered from ‘the long spacing between the bogie and the leading coupled wheels, resulting in undue flexing of the frames and constant troubles from the outside pipe connections to the valve chests.’ However, in the opinion of Allen the A2/3 class were ‘the best 4-6-2s turned out during his [Thompson’s] superintendence,’.

Stock list

LNER No.	BR No.	Name	Entered stock	Withdrawn
500	60500	Edward Thompson	May 1946	June 1963
511	60511	Airborne	July 1946	November 1962
512	60512	Steady Aim	August 1946	June 1965
513	60513	Dante	August 1946	April 1963
514	60514	Chamossaire	September 1946	December 1962
515	60515	Sun Stream	October 1946	November 1962
516	60516	Hycilla	November 1946	November 1962
517	60517	Ocean Swell	November 1946	November 1962
518	60518	Tehran	December 1946	November 1962
519	60519	Honeyway	February 1947	December 1962
520	60520	Owen Tudor	March 1947	June 1963
521	60521	Watling Street	May 1947	November 1962
522	60522	Straight Deal	June 1947	June 1965
523	60523	Sun Castle	August 1947	June 1963
524	60524	Herringbone	September 1947	February 1965

No. 60500, 'Edward Thompson' entering Retford 6 September 1962.

With the exception of 60500 all of the locomotives were named after the winners of major flat races in the immediate postwar period:

Accidents and incidents

On 7 January 1957, No. 60520 Owen Tudor was hauling an express passenger train which overran signals and crashed into the rear of a local train at Welwyn Garden City, Hertfordshire.

Withdrawal

The A2/3s were withdrawn from stock between August 1962 and March 1965. None was preserved.

Models

Apple Green Engines produce a ready-to-run model of the A2/3 in 4 mm scale. PDK and DJH both sell 4 mm scale kits of the A2/3. Crownline have also produced a 4 mm scale kit, but this is no longer available.

DJH also sell a kit of the A2/3 for O gauge (7 mm scale).

External links

• LNER Encyclopedia