Gresley P2 'Mikado' class & rebuilt Thompson A2/2

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neildimmer
LNER A3 4-6-2
Posts: 1489
Joined: Sat Jan 10, 2009 11:49 am

Gresley P2 'Mikado' class & rebuilt Thompson A2/2

Post by neildimmer »

The London and North Eastern Railway Class P2 was a class of 2-8-2 steam locomotives designed by Sir Nigel Gresley for working heavy express trains over the harsh Edinburgh to Aberdeen Line. As they were to serve on Scottish expresses, they were given famous names from Scottish lore.
Six locomotives of the class were built; introduced between 1934 and 1936. Between 1943 and 1944 the class were rebuilt under Gresley's successor Edward Thompson into the LNER Thompson Class A2/2 4-6-2 type. The locomotives were designed by Nigel Gresley to haul express trains over the difficult Edinburgh to Aberdeen section of the London and North Eastern Railway. In the design Gresley was influenced by recent French practice, in particular passenger locomotives of the Paris à Orléans railway.
The first locomotive of the class, No.2001 Cock o' the North, was introduced in 1934. It was built at Doncaster Works, with Lentz-type[citation needed] rotary-cam actuated poppet valve-gear supplied by the Associated Locomotive Equipment Company, and a double-chimney Kylchap exhaust, each chimney using four nozzle blastpipes. The chimney system was designed to take different fittings to allow experimentation with exhaust arrangementsThe boiler barrel was of the design used on Gresley Pacifics, fitted to a larger firebox. The front end design was of the same form as the Class W1 locomotive, No. 10000, derived from Dr. Dalby's wind tunnel research, and the attached tender was of the standard design used on Gresley Pacifics. The P2 introduced a vee-shaped cab front, designed to give a better view forward. (The same design was later used on the A4 and V2 express engines). No. 2001 was fitted with a Crosby chime whistle which Gresley had obtained from Captain Howey of the Romney, Hythe and Dymchurch Railway, and which was originally intended for one of that railway's Canadian Pacific style locomotives.The second locomotive of the class, No.2002 Earl Marischal was completed by 1935, also at Doncaster, and was fitted with Walschaerts valve gear, as used on Gresley Pacifics, and had a greater superheater heating area of 776.5 sq ft (72.14 m2), obtained by using larger diameter fire tubes. At low cutoffs smoke clearance on No.2002 was unsatisfactory: wind tunnel experiments led to an additional second pair of smoke deflectors being fitted inward of the first.
No. 2002 proved to be more efficient than 2001, due to a lower cylinder clearance volume and because the stepped-cam cutoff modifications made to No. 2001 reduced economical working relative to the infinitely variable cutoff of No. 2002. Consequently, the following locomotives were built with piston valves.
By June 1936 the third engine had been produced: No. 2003, Lord President, based on the design of No. 2002 but with the external design modified to resemble the Silver Link locomotives. The locomotive weight was reduced to 107 long tons 3 cwt (240,000 lb or 108.9 t). The wedge-shaped front was found to lift the engine's smoke clear of the driver's view; No. 2002 was altered to this form in 1936, and No. 2001 in 1938.Three further locomotives, Mons Meg, Thane of Fife and Wolf of Badenoch, were under construction at Doncaster in 1936. No. 2004 was fitted with an experimental butterfly valve blastpipe bypass, manually activated to prevent fire-lifting at high cutoffs. This was later replaced with a plug valve and higher bypass pipe diameter, but both designs had problems with sticking due to carbonised deposits. No. 2005 lacked the Kylchap double chimney of the rest of the class and No. 2006 had a different boiler design, with a longer combustion chamber, and firebox heating area and volume of 253 sq ft (23.5 m2) and 319 cu ft (9.0 m3) respectively with a Robinson superheater. The production series was completed in 1936. The class was rebuilt into Class A2/2 4-6-2 'Pacifics' during 1943/4 According to B. Spencer, an LNER employee, the class was rebuilt due to reliability problems during the difficult conditions of the World War II period, and additionally to take the opportunity to try out a different valve gear arrangement. Other sources supposed that the rebuilding might be because the class's wheelbase was too long for the routes it worked, and that the railway would have been better served if the class had been transferred to more suitable routes. Railway author O. S. Nock suggested that Gresley's successor, Edward Thompson, may have made largely unsubstantiated criticisms of the class in order to justify the rebuilding.[26] According to O. Bulleid, the class were not an inefficient design but had been placed into services in which they were under-utilised, leading to poor fuel economy (From Wiki)

P2 Rebuilt with A4 front end styling
2003 Lord President
https://tinyurl.com/y2ulwb4x

I have added a lot of new photos of these locos starting off with the as built
2001 Cock O' The North
https://tinyurl.com/y4yult2d
and redesigned with A4 style front
https://tinyurl.com/y6fkxfjp

Full collection starts here with
2002 Earl Marischal before and after
https://tinyurl.com/yxoha3gu

Neil

https://tinyurl.com/y2ulwb4x
Last edited by neildimmer on Mon Jan 18, 2021 10:12 am, edited 1 time in total.
neildimmer
LNER A3 4-6-2
Posts: 1489
Joined: Sat Jan 10, 2009 11:49 am

Re: Gresley P2 'Mikado' class

Post by neildimmer »

The London and North Eastern Railway Class A2/2 was a class of six 4-6-2 steam locomotives rebuilt by Edward Thompson in 1943 and 1944 from his predecessor’s P2 Class of 2-8-2 express passenger locomotives. The rebuilds were not particularly successful and all were withdrawn and scrapped between 1959 and 1961.
On taking up office as Chief Mechanical Engineer of the London and North Eastern Railway in April 1941, Edward Thompson proposed an unstreamlined mixed traffic version of Sir Nigel Gresley’s A4 class pacifics with 6 ft 2 in (1.880 m) driving wheels, but new construction would not have been authorised at this time.[1] He therefore rebuilt the six of his predecessor P2 Class of 2-8-2 express passenger as pacific locomotives to try out his own thoughts on their design. The P2 Class 2-8-2 had been built between 1934 and 1936 for service between Edinburgh and Aberdeen and had proved to be powerful and capable locomotives. However, the long fixed wheelbase was not ideally suited to the winding route, giving rise to maintenance problems on both the track and the locomotives, notably failure of the crank axle. However, O.S. Nock stated that the P2 class 'rode easily and elegantly around the sharpest curves.' In either event, rather than transfer the locomotives to other duties on the East Coast Main Line south of Newcastle, where this would have been less of a problem, Thompson saw this as a chance to try out his own ideas of locomotive design.

Design
The pony truck and front coupled wheels of the original design were replaced by a newly designed bogie. The boiler barrel was shortened by 2 ft 0.25 in (0.616 m)and a new front end was designed with 20 in × 26 in (508 mm × 660 mm) cylinders. Rather than have all three cylinders driving a single axle Thompson adopted divided drive with the middle cylinder driving the first pair of driving wheels and the outside cylinders the middle pair. However, In order to retain the original three connecting rods of the same length, the outside cylinders were set back behind the bogie, giving the locomotives an ungainly appearance. Thompson also removed the Gresley conjugated valve gear and instead fitted independent sets of Walschaerts valve gear to each cylinder. The first locomotive to be rebuilt at Doncaster Works was No. 2005, Thane of Fife, which was ordered in October 1942 and completed in January 1943. After trials the remaining five P2 locomotives were ordered to be rebuilt in September 1943 and they all appeared in traffic during 1944.

Performance
The new design steamed well and retained much of the power of the P2's. The reduced weight meant they had a high power to weight ratio, and were good at hauling high speed expresses, although in the opinion of O.S. Nock they 'acquired a particularly bad reputation for wild and unsafe riding at high speed!' However, there were other problems which prevented them from ever making an impact on the east coast main line. The first of these was a lack of adhesion causing wheel slip when starting, which meant that they could not be used on the Edinburgh-Aberdeen line for which they had originally been built. The second problem was that of reliability caused by their having been adapted from quite different locomotives. Both the A2/2 and the subsequent A2/3 suffered badly from frame movement, vibration and loose fittings. Using equal length connecting rods, as well as the divided drive meant that the centre cylinder was much further forward than the outside cylinders. During their lifetime in service Earl Marischal was the only A2/2 to cover over one million miles, 360,907 as a P2 and 673,947 as an A2/2.

Withdrawal

Withdrawals from stock began in 1959 starting with 60505 Thane Of Fife on 10 November 1959. The next A2/2 to be withdrawn was Lord President on 27 November 1959. 60501 Cock o' the North was withdrawn in 1960, while 60504 and 60506 were withdrawn in 1961, with 60502 the last member of the class withdrawn on 3 July 1961.
(From Wiki)

I have added over 20 new photos to this collection starting with
60501 Cock O' the North On Doncaster shed yard 17th June 1951
https://tinyurl.com/y3828hl9

60501 Cock o' the North Doncaster works 8th May 1960 waiting to be cut up behind is a S&D 7F 2-8-0
https://tinyurl.com/y5pk52zp

Full collection of new photos start here
https://tinyurl.com/y4g7qqab

Neil

https://tinyurl.com/y3828hl9
neildimmer
LNER A3 4-6-2
Posts: 1489
Joined: Sat Jan 10, 2009 11:49 am

Re: Gresley P2 'Mikado' class & rebuilt Thompson A2/2

Post by neildimmer »

Gresley P2 'Mikado' class rebuilt as Thompson A2/2 Pacifics
I have added a few new photos to this collection, showing 5 of the 6 locos
Starting here with
60501 Cock o' the North York Carriage sidings 16th July 1950
https://tinyurl.com/yeg95ldp

Neil
neildimmer
LNER A3 4-6-2
Posts: 1489
Joined: Sat Jan 10, 2009 11:49 am

Re: Gresley P2 'Mikado' class & rebuilt Thompson A2/2

Post by neildimmer »

I have added over 20 new photos of Thompson’s A2/2 Pacific locos, the rebuild of Gresley’s P2 design
Including this photo of
60505 Thane of Fife with a freight service at Hitchin
https://tinyurl.com/4xxsdftn
New photos start here with LNER era
503 Lord President Haymarket shed 1947
https://tinyurl.com/f6ztb57e
B.R. era new photos start here
60501 Cock o' the North at Doncaster March 1953
https://tinyurl.com/m9mw4b6x
including
60502 Earl Marischal with BR number but still with LNER on tender Ferryhill 16th June 1949
https://tinyurl.com/6xzpt3u8

Neil
https://tinyurl.com/4xxsdftn
neildimmer
LNER A3 4-6-2
Posts: 1489
Joined: Sat Jan 10, 2009 11:49 am

Re: Gresley P2 'Mikado' class & rebuilt Thompson A2/2

Post by neildimmer »

I have added a couple of new photos of Thompson’s A2/2 Pacific locos, the rebuild of Gresley’s P2 design
60503 Lord President at York 3rd August 1957
https://tinyurl.com/4j4uwzew
60504 Mons Meg with a parcels service at York 3rd August 1957
https://tinyurl.com/5r983x85

Neil
https://tinyurl.com/4j4uwzew
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