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DONCASTER LOCOMOTIVE DRAWING OFFICE
Edward Thompson was Mechanical Engineer at Stratford (1927-34), Darlington (1934-38), Doncaster (1938-41) and became Chief Mechanical Engineer on 28th April 1941, after Gresley’s death. He had had design work experience at Stratford, Darlington and Doncaster (where he had overall control of their respective Drawing Offices), so had a clear idea of what needed to be done in the forthcoming 5 years before his retirement, and (as he publicly intimated) he did not intend wasting one minute.
His Pacific frames conformed to expected practice. The four Class A2/1 engines were a diversion from Class V2 so their rear ends were identical. The six Class A2/2 engines were rebuilds from the Gresley Class P2 2-8-2s. Their narrower main frames (3ft.-11˝in. apart) were retained, set in at the rear to the same 3ft.-2˝in. distance apart. The separate front-end frames were the usual 4ft.-1˝in. apart and the rear outside frames were also unchanged. The solitary Class A1/1 rebuild No. 4470 “Great Northern” received new frames, with the parallel section under the cab set in 3ft.-2˝in. apart (as in Class A4) instead of 3ft.-5in. The frames of his fifteen Class A2/3 Pacifics were similar to those of Class A2/2, i.e. with separate front end sections, (and Peppercorn followed the same arrangement for his two Pacific designs).
In Gresley's 3-cylinder designs for his big engines, all three cylinders drove on the the second coupled axle. Thompson instead went in for divided drive, with the centre cylinder driving the leading coupled axle, and the outside cylinders driving the intermediate coupled wheels. To this end, the bogie was place well forward ahead of the outside cylinders.
DIAGRAM 17A. This was Thompson’s first boiler design (N1070, February 1942) for conversions from Class Q4 0-8-0 to 0-8-0T which would release their tenders needed for new Class O2. Twenty-six new boilers were constructed, and a further five were provided by Doncaster Works shortening the barrels of Diagram 17 boilers taken from withdrawn Q4s. There were thus thirty-one boilers for a class of thirteen engines.
DIAGRAM 100A. This boiler, of which 710 were constructed, was an up-graded version of the "Sandringham" boiler (Diagram 100) which Thompson intended to fit to as many classes as possible. In the event, these proved to be Classes B1, B2, B3/3, B17/6, O1, O2/4 and O4/8. The firebox was 10ft.-1˝in. long overall, including a combustion chamber, but the length measured at the foundation ring was 9ft.-0in. The figure of 9ft.-0in. was the one that usually appeared on engine diagrams, but on the diagram for Class O2/4 for example the overall dimension appeared instead. Diagram 116 (for Class K1) was based on Diagram 100A but having a shorter barrel.
DIAGRAM 106A. These were boilers rebuilt from Diagram 106 for Thompson’s Class A2/2 rebuilds. The last boiler to be rebuilt remained at Doncaster Works in its original state after removal from No. 2004 (October 1944). A year later there was an urgent need. The boiler was rebuilt in October 1945 and sent to Cowlairs Works for immediate fitting to No. 2002 (November 1945). After five years with this engine it was removed (January 1951) and replaced by a Diagram 118 boiler. The displaced boiler was simply scrapped, the first Diagram 106A to go, after a working life of just over thirteen years.
DIAGRAM 108A. The solitary boiler to Diagram 108 was carried by No. 2006 (September 1936 to May 1944), rebuilt to Diagram 108A by shortening the barrel (June 1944) and fitted to No. 2002 (August 1944 to November 1945). After nine years useful work, it was no longer needed and so left spare at Doncaster Works awaiting a decision. It was eventually scrapped (July 1946) when it was clear that there would be no requirement for it in the future.
DIAGRAM 96A. Thompson redesigned the Diagram 96 boiler in Class K3 to operate at a higher working pressure and have a steel inner-firebox as a war-time measure (N1115, August 1943). Thompson had second thoughts about the firebox and a fresh drawing was prepared (N1141, February 1944) with the boiler now having a copper firebox. Only one engine was rebuilt from Class K3 to K5 No. 206 (June 1945). A further ten boilers were built in 1950 and when fitted to the K3s they worked at the lower pressure.
DIAGRAM 109. These boilers were fitted to the four A2/1s diverted from Class V2 (introduced May 1944).
DIAGRAM 107. This A4 boiler was used for Class A1 No. 4470 (rebuilt September 1945).
DIAGRAM 115. This boiler (N1149, May 1944) was used for his prototype Class L1 2-6-4T No. 9000, and subsequent contract engines built after Nationalisation.
DIAGRAM 116. This boiler (N1160, March 1945) was used for his prototype Class K1/1 2-6-0, and subsequent contract engines built after Nationalisation.
DIAGRAM 117. Thompson designed this boiler for new construction of Pacifics, based on Diagram 106A but with thicker boiler plates to withstand the higher working pressure. Fifteen were constructed, at Darlington as if to snub Doncaster, and Gresley’s perforated steam collector was omitted. No spare boilers were made, the design having been superseded by Diagram 118. A lighter version of Diagram 117 was drawn out (March 1946) employing 2 per-cent nickel steel. After Thompson retired (in June 1946), the perforated steam collector was added to the drawing.
Thompson dispensed with the steam collector on his boilers for Class A2 (later A2/3) 4-6-2 Nos. 500/11-24 (new 1946-47). His successor Peppercorn restored them for his Classes A1 and A2 4-6-2s.
Darlington Works fitted BJ superheaters (but with V-bolt attachments instead of Through-bolt) to new V2s commencing with No. 4899 (January 1942) except that Nos. 3646/66 received the Robinson type from stock. Existing engines were not affected unless they needed new headers, for example Nos. 60858/62/80, 60902/03 when they acquired double chimneys (1961). Doncaster Works continued to fit Robinson superheaters to new V2s, but the V4s did receive the BJ type (with Through-bolt attachments) as a last minute change of plan.
The Diagram 100A boilers fitted to numerous classes all had BJ superheaters. The first ten boilers (constructed at Doncaster) had V-bolt attachments. All later 100A boilers had the Through-bolt type.
Thompson straightaway introduced the B1 bogie which basically differed from the Gresley bogie in having laminated bearing springs instead of helical, a return to Stirling practice. Whether or not this was in response to a war-time shortage is not known. The bogie was fabricated by welding from steel plates, to eliminate the need for castings during war-time austerity conditions. The construction of the bogie meant a return to 1in thick plate for their frames. After the war had ended castings were used for future construction.
Quoting BR numbers, these bogies were fitted to Classes A1/1 No. 60113; Classes A2/1, A2/2, A2/3 Nos. 60500-23; Class B1 Nos. 61000-61339; Class L1 No. 67701.
Doncaster built a number of L.M.S.-type 2-8-0s in 1943-1946. Their pony trucks had 3ft-3˝in wheels and helical spring side control.
Classes L1 (prototype No. 9000), K1 (rebuild from Class K4) and K5 (rebuild from Class K5) had pony trucks with 3ft-2in wheels and L.M.S.-style helical spring side control. Their bearing springs were the laminated type, a departure from current Doncaster practice which may have been dictated by war-time supply difficulties.
Thompson perpetuated Gresley’s designs, with minor modifications. In particular he fitted his tenders with steam brakes instead of vacuum.
GROUP STANDARD 4200 GALLONS
TO76/77/78 (about 4/1941) 25 V2s, Nos. 3675-99. Orders transferred to Darlington (9/6/1941).
TO79 (9/6/1941) 10 O2s. Order cancelled, new O2s 3843-52 to receive D49 tenders. These latter had been released by providing the D49s with surplus GCR 4000 gallon tenders.
TO80 (9/6/1941) 9 (later 5) O2s. Order cancelled, new O2s 3853-57 to receive D49 tenders. These latter had been released by providing the D49s with surplus GCR 4000 gallon tenders.
These were the last 4200 gallon tenders ordered from Doncaster, though none was actually built. Instead large numbers were built at Darlington Works, Gorton Works and by contractors, for his Classes B1 and K1, mostly after his retirement.
GROUP STANDARD 5000 GALLONS
Thompson ordered 15 A2s (Nos. 200-14) in 1944, 15 further A2s (Nos. 215-29) in 1945, and 16 A1s (numbers not allocated) in 1945. Tender Orders were placed at the same time, followed at the end of 1945 by an order for 4 8-wheel tenders for Nos. 3696-99 by then almost complete at Darlington. Progress with the remaining orders was painfully slow, as staff eagerly looked forward to Thompson’s retirement. 15 of his A2’s came out in 1946-47 (by then as Nos. 500/11-24) and Peppercorn altered the design for the later A2s (60525-39) and A1s (60114-29).
TO86 (12/6/144) T.704-13 for Class A2 Nos.
Instead attached to Nos. 500/11/09/12-18
The attachment of T.706 to A2/1 No. 509 was done at Darlington Works.
TO87 (12/6/1944) T.714-18 for Class A2 Nos. 210-14.
Instead eventually attached to Nos. 519-23.
TO88 (4/4/1945) T.719-28 for Class A2 Nos. 215-24.
Instead eventually attached to Nos. (60)527-36.
TO89 (4/4/1945) T.729-33 for Class A2 Nos. 225-29.
Instead eventually attached to A2 Nos. 60537/38, A1 No. 60114, A2 No. 60539, A1 No. 60115.
TO90 (15/11/1945) T.734-43 for Class A1s.
Instead eventually attached to Nos. 60116-25.
TO91 (15/11/1945) T.744-49 for Class A1s.
Instead eventually attached to A1 Nos. 60128/26/27/29, A2/1 No. 60508 (6/1949), 60510 (9/1949)
TO92 (15/12/1945) T.700-03 for Class A2/1 Nos. 3696-99.
Instead the salvaged tender T.5672 from Class A4 No. 4469 (withdrawn April 1942) was attached to No. 3696 (new 12/1945). Only three new tenders were built to this order and eventually attached to Class A2/3 No. 524 and A2 Nos. 525/26, as by then Nos. 3697-99 had acquired tenders from earlier orders.
STANIER 8F 4000 GALLON TENDERS
TO81 (19/5/1942) T.10237-46 for LMS Nos. 8510-19.
TO82/83 (29/12/1942) T.10247-56, T.10257-66 for LMS Nos. 8520-29, 8530-39.
TO84/85 (26/2/1944) T.7699-7708, T7709-18 for Class O6 Nos. 3148-57, 3158-67.
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