North West Steam Spot – Caprotti Class 5 4-6-0s

Page

Probably the most recognisable – and, dare I suggest it – famous of William Stanier’s steam locomotive designs for the LMS.  Introduced as a conventional 2-cylinder steam locomotive in the 1930s, and no fewer than 842 were built.  The majority – only just! -were built by Armstrong Whitworh and Vulcan Foundry – a total of 427 locomotives, the remaining 415 were built at Crewe (241) and Horwich (120), and Derby (54).

Caprotti 5 Weight DiagramThey were almost all were relatively conventional in design, but with a number of detail variations until after the Second World War.  The chief protagonist for the post war experimental and innovative work was the LMS company’s new CME, H.G. Ivatt, and it was under his guidance initially that the 20 poppet valve gear fitted variants took to the rails.

Ten of these were allocated to depots outside the Northwest (I include Llandudno Junction in the Northwest) – 5 went to Bristol, and 5 to Leeds.  There was a reshuffling of the pack in the mid 1950s, and Bristol lost one of its allocations, whilst Leeds grew its number to 7.  By 1964, half of these locomotives had disappeared, and the remaining 10 split between Speke Junction (Liverpool) and Southport.

18 of this class have been preserved, but sadly perhaps, not one of them has poppet valve gear.

Leading DimenssionsThis relatively small c1ass of 22 locomotives found themselves 
for the greater part of their working lives in the Northwest, though of the original batch of 20 built in 1948,five were sent to Bristol; later returning to Leeds and Southport. The locomotives were basically the Stanier Class 5 4-6-0, with many detail improvements and developments introduced by H.G.Ivatt, though not brought into being Until afternat1onalisation, in1948. The idea, in essence, was to improve the already successful Stanier design.

 

LMS_Caprotti_Class_5_M4751 copy

LMS Stanier Class 5 Caprotti 4-6-0 M4751 at Manchester London Road in early 1948. This photo also shows the early BR lettering on the tender sides, and the ‘M’ prefix used briefly in 1948. The loco, stabled at Manchester Longsight ended its days at Speke Junction shed in Liverpool. ByRuthAS – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=5822920

Detail differencesThe most striking departure was of course the fitting of Caprotti poppet valve gear, using cams to open and close the inlet and exhaust valves at each end of the steam chest. This arrangement was later used with great success on a number of BR Standard locomotives. The cylinders themselves were the same size as other Stanier Class 5’s, as also was the boiler and firebox assembly.

The boiler was built up from two rings, with a length of just over 13ft, and tapering from 4ft 11ins at the smokebox end, to 5ft 8 1/2 ins at the rear. The firebox was the conventional Belpaire type, and measured 9ft 2ins long, by 3ft 11 7/8ins wide. The modifications introduced by Ivatt included two varieties of roller bearing axlebox for the coupled wheels, and double chimneys. Other externally visible departures from the Stanier lines were; the outside steam pipes carried to the front of the steam chest, ahead of the cylinders, and the running boards. The last two of these were fitted in what was essentially BR Standard style, mounted high up on the boiler side. All of the class was paired with 4,000-gallon water capacity; flush sided, LMS style tenders, with a bunker capacity of 9 tons of coal.

EPSON scanner image

Stopping train for Manchester leaves Southport (Chapel Street). A splendid view westward towards the buffer-stops of the main (ex-L&Y) Southport Station, taken from a footbridge just outside. The train is headed by one of the post-war modified LMS Stanier Class 5 4-6-0s, No. 44686, built 4/51 with Caprotti valve-gear, double-chimney and roller-bearings: it lasted until 10/65.    
By Ben Brooksbank, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=16964387

By the ear1y 1960s, most of the class had in fact been scrapped, leaving only the seven at Southport and three at Speke Junction. And, although the fitting of poppet valve gears was a more efficient steam distribution system than the traditional piston/slide valve methods, they were not widely acclaimed by footplate crews. It was said that engines fitted with this gear were not so quick off the mark as a conventional design, and some depots were reluctant to

AllocationsThe original distribution of five locos to each of four depots was rapidly altered, and by the mid-1950s, all bar three were working in the northwest. Two of Bristol’s allocation had been transferred to Leeds by 1954, and towards the end, two Longsight engines and one from Llandudno, were sent to Speke Junction. Soon afterwards though, the entire class was withdrawn.

Since all these locomotives were BR built, none ever carried LMS livery, and being classed as mixed traffic locomotives, for their entire working lives were painted black, lined red, cream and grey. Some of the 1948 examples built shortly after nationalisation sported plain black, with former LMS numbers on cabsides and no lining or insignia on either tender or locomotive.

EPSON scanner image

Manchester – Llandudno express approaching Llandudno Junction. View eastward, towards Colwyn Bay and Chester: ex-LNW Chester – Holyhead main line, with the branch to Blaenau Ffestiniog curving away to the right up the Conwy Valley. This is the 13.40 from Manchester Exchange via Chester, with No. 44687, one of the two later Ivatt-modified Stanier 5MT 4-6-0s with double-chimney, Caprotti valve gear and roller-bearings (built 6/51, withdrawn 1/66).                   By Ben Brooksbank, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=17666019

-oOo-