Gresley K1-K4 moguls

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The London and North Eastern Railway (LNER) Class K4 is a class of 2-6-0 steam locomotives designed by Nigel Gresley for the steep grades of the West Highland Line.

The North British Railway (NBR) West Highland line to Mallaig via Fort William, presented a combined triple operating challenge of: steep gradients; severe curves; and restrictive axle loading limits. Having used D34 'Glen' 4-4-0s, increased loads led to regular double-heading. Locomotive engineers proposed use of LNER Class K3, but they would not have been permitted to operate between Fort William and Mallaig.

Having proposed a new design based on a K3 boiler, in October 1924 a loan was made of a single LNER Class K2, which provided the required increase in power and adhesion. As K3s replaced K2 on the network, more K2s were loaned to the line, with the loan becoming permanent from October 1925.

With further increases in load and needs for additional traffic speed, in September 1934 Gresley instructed Doncaster Works to investigate the possibility of increasing the tractive effort of the K2s. After recommending against a design which increased boiler pressure 220 psi (1.52 MPa) and cylinder diameter to 21 inches (533 mm), in 1935 the Joint Traffic & Locomotive Committee signed off provision of a new design by reducing the 1936 build of K3s from 21 to 20.

The eventual May 1936 design was based on the 1924 proposal for a 2-6-0 with 5 ft 2 in (1.575 m) diameter coupled wheels, but with K3 cylinders, a K2 boiler, and a B17 firebox. The frame was 5 inches (127 mm) longer than the K3, with a design boiler pressure of 180 psi (1.24 MPa) giving a tractive effort of 32,939 lbf (146.5 kN), and an estimated factor of adhesion of 3.92.

Prototype

The prototype K4 No.3441 left Darlington for Eastfield depot, Glasgow on 28 January 1937. After five weeks of crew training and being confined to goods work it made its début on a passenger train on 4 March. It soon became apparent that the 180 psi (1.24 MPa) boiler pressure brought little improvement in average speeds over the existing K2, and that No.3441 responded sluggishly when up against the gradients of the West Highland line. Gresley reacted by raising the steam pressure to 200 psi (1.38 MPa) which saw the tractive effort leap to 36,598 lbf (162.8 kN), with a corresponding reduction in the factor of adhesion to 3.54. The K4 could now demonstrate its true capabilities handling 300 ton trains and with maximum speeds around 60 mph (97 km/h) on level ground. An advantage of the newcomer was that it used only marginally more coal in working 300 ton trains than the K2s did with considerably lighter loads.

The successful trials with No.3441 led to five more being built. Apart from the prototype Loch Long all were named after Highland chieftains and grandees.

Operations

The K4s quickly endeared themselves to the Scottish crews and, apart from some heavily loaded summer trains, eliminated uneconomic double-heading over the West Highland. However, as with all Gresley 2-6-0s it could be a rough ride at speed, and a locomotive designed to climb was not suited to the flat straight stretches of the line into Glasgow Queen Street railway station, or the 8.5 miles stretch alongside Loch Eil. Ride induced vibration was a problem on these stretches, and the middle big-end bearing would require regular nut tightening, with the middle connecting rod dropping off on one occasion: this resulted in increased maintenance inspections.

During the 1950s, the K4s' sphere of operation enlarged and they began to appear at locations such as Edinburgh, Perth, Forfar, Ayr and Tweedmouth. In 1959 all were concentrated at Thornton in Junction depot in Fife and all were withdrawn in October 1961.

Including this colour photo of
61996 Lord of the Isles at Thornton Jct
https://tinyurl.com/37vb4veb

LNER era
1994 The Great Marquess at Fort William
https://tinyurl.com/558p3a78
3443 Cameron of Lochiel Eastfield 17th April 1939
https://tinyurl.com/6s4d6x8p

B.R. era
61993 Loch Long Niddrie Yard 15th May 1954
https://tinyurl.com/9aejryx4
61994 The Great Marquess Eastfield
https://tinyurl.com/2nbapsjd
61995 Cameron of Lochiel fitted with snowplough unknown location
https://tinyurl.com/2yksk496
61996 Lord of the Isles Thornton Junction 16th August 1961
https://tinyurl.com/ybsjfdth
61998 Macleod of Macleod Eastfield shed August 1959
https://tinyurl.com/5dwvb4cp

Neil
https://tinyurl.com/37vb4veb

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Gresley LNER Class K4 number 3445 MacCailin Mor was rebuilt in 1945 at Darlington as a two-cylinder prototype of the K1 class, designated K1/1. Thompson entrusted the rebuilding of No.3445 as a two-cylinder Mogul to his principal assistant Arthur Peppercorn. This locomotive became British Railways no. 61997. And was withdrawn from service in 1962
I have added 12 photos to this collection
Including this colour photo
61997 MacCalin Mor unknown location Thompson K1-1 two cylinder rebuild of Gresley K4.
https://tinyurl.com/ps2zwpxk
Full collection of 12 new photos starts here
LNER era
1997 MacCailin Mor at Stratford shed
https://tinyurl.com/bhppt42b
3445 MacCailin Mor unknown location
https://tinyurl.com/5935pvwj
B.R. era
61997 MacCailin Mor unknown location
https://tinyurl.com/ykynp254

Neil
https://tinyurl.com/ps2zwpxk

[neildimmer]

Only one of the six strong class has survived into preservation, following the efforts of the late Viscount Garnock who bought No.61994 The Great Marquess from British Railways (BR), and had the engine overhauled to working order. Based at Leeds No.3442 undertook railtour work until forced into retirement by the ban imposed on steam working by BR in 1968.

I have added a large collection of over 40 photos of 3442 on railtours prior to August 1968
Including a couple of double headed tours with other now preserved locos
3442 The Great Marquess + 4472 Flying Scotsman near Harrogate 3rd October 1964 Ian Allan The Darlington Marquess Railtour
https://tinyurl.com/8vpk9jhn
3442 The Great Marquess + 44767 with a Lyons Maid Zoom Special 6th September 1964
https://tinyurl.com/sndyk8vf
Full collection starts here with
3442 Great Marquess complete with a bell 12th March 1967 Locomotive Preservation (Sussex) Ltd The Marquess Goes South West
https://tinyurl.com/5fznwysw
3442 The Great Marquess Bridlington SLS-MLS Whitby Moors Railtour 6-3-65
https://tinyurl.com/r9m6b627
3442 The Great Marquess close up of front end
https://tinyurl.com/44p6dh6f

Neil
https://tinyurl.com/8vpk9jhn