The Gresley O1 (later O3) 2-8-0 Locomotives
Ivatt in 1911, and found the Great Northern Railway's
(GNR's) Q1 & Q2 0-8-0 heavy goods engines were
being worked to capacity. Coal traffic on the mainline from Grantham to London was particularly heavy, and the GNR sought
to reduce the number of mineral trains by increasing train loads. To meet this need,
Gresley designed the O1 2-8-0 mineral engine.
The first order for five was placed in 1913, and was completed at Doncaster in 1914. The O1s were
nicknamed "Tangos" due to their introduction at a time when tango dance was appearing in Britain.
In January 1916, quotations were sought for fifteen more O1s, but World War 1 appears to have intervened and no
contracts were issued. However, the GNR really needed the extra capacity and a number of parts including
boiler plates, frame plates, and axles, were ordered from the USA in summer 1917. Boiler and engine orders were
issued in December 1917 and February 1918 respectively, but the entire construction order was transferred from
Doncaster to the North British Locomotive Co. in April 1918. This order represented ten locomotives, and was
followed in 1919 by a final order of five. Both orders were delivered in 1919, to give a total of twenty O1s.
The O1 had two 21in diameter cylinders powered by a 5ft 6in diameter boiler which was fitted with a
24-element Robinson superheater. The O1 was Gresley's
second design for the GNR and he incorporated a number of features from his first design, the
K1 2-6-0. The
K1's outside cylinder arrangement with
Walschaerts valve gear and 10in piston valves was used. The
K1's double-bolster swing-link pony truck design
was also used. This added better support for the front-end, but also proved advantageous when traversing the
frequent diversions on and off the slow lines on the line to London. The first batch of O1s were fitted with leaf bearing
springs on their pony trucks, but these were replaced with helical bearing springs in 1916.
The first batch was fitted with Doncaster-type 'double admission' valves. These were designed to open at the same
time, increasing steam admission to the cylinder. This also doubled the effective opening to 'lead' steam which was
disadvantageous on starting, so the steam lead was restricted to 0.0625in. The fitting of double admission piston valves
tended to result in carbon deposits on the supplementary portways and a loss of power. Hence in 1914-15,
the ports were opened up slightly.
The piston valves were originally built with a split ring design that was sprung inside the steam chest liner to
make a steamtight fit. This was difficult to lubricate and resulted in excessive wear, as well as a loss of energy.
In 1918, No. 460 was fitted with pistons of a Canadian Pacific design with two split rings and a centre ring. Steam tended to
leak through the fine gaps between the rings, and it was removed in 1922. After Grouping (1923), the problem was solved
by fitting Great Eastern (GER) pattern Knorr-type piston valves to the O1s from 1924.
Both the boiler and cylinders represented significant increases in size. There was doubt as to whether the
O1's injectors could feed the large cylinders, so the first five O1s were fitted with Weir feed pumps. These were
removed before Grouping in 1923.
No. 476 was fitted with a Worthington feed water heater and pump in 1922. This was found to be easy to operate, but
economy trials against another O1 were never carried out. It was replaced with a larger pump in December 1924, and
this was later removed in May 1927. Between December 1928 and October 1929, four O1s were fitted with
Gresham & Craven No. 20 feed water heaters. These had a special coned nozzle that mixed steam with the feed water
just before delivery. These were removed between January 1931 and April 1932.
The boiler was based on Ivatt's
boiler design for the C1 wide-boilered Atlantic.
The dome was moved further back, and the characteristic wide firebox was replaced a long narrow firebox. The boilers
were originally fitted with Ramsbottom safety valves, but Ross pop safety valves were fitted from 1924.
The same boiler design was used on the later three-cylinder O2 2-8-0s.
These engines were designed to haul the heavy coal traffic from Peterborough to Ferme Park (London).
The design load was eighty wagons carrying 1,300 tons, which represented twenty more wagons than a typical
Q1/Q2 load. All twenty locomotives
were initially allocated to Peterborough (New England shed) to perform this work. By 1920, three were allocated to Colwick to work two
coal trains a day from Colwick to New England. The Colwick allocation increased to four by Grouping (1923), but all
four moved back to New England in 1925. Four moved back to Colwick in winter 1926, where they would remain until 1934-5.
The Colwick locomotives were rarely seen south of Peterborough, but they did occasionally work to Woodford, and to
March (via Sleaford and Spalding). As well as coal, they also hauled Lincolnshire potatoes to Kings Cross.
The New England trains also worked northwards to Doncaster, taking empty wagons and returning with full loads.
From 1925, most of these Doncaster duties were taken over by O4s.
In 1932 congestion on the GNR main line was becoming a serious problem, and a move towards reducing the number
of slow moving coal trains was made. One solution was to haul smaller sixty wagon trains with
faster K3 2-6-0s. This eventually led to the displacement
of ten O1s from New England to Doncaster. Two also spent six months at Mexborough. The last of the New England O1s were
moved from New England to Grantham in November 1942, where they hauled iron ore on the steeply graded branches from
Highdyke to Stainby and Sproxton. They also hauled ore trains to Frodingham.
The O1s were occasionally seen further afield, including Gascoigne Wood and even St. Margaret's shed (Edinburgh).
Bombing closures during World War 2 resulted in O1s hauling coal trains via Sandy onto the LMS route to
Bedford, Bletchley, and Claydon Junction. Wartime also saw O1 coal trips to Stratford.
The O1s were reclassified as Class O3 in February 1944, enabling the 'O1' classification to be used for
Thompson's O4 rebuilds.
In 1945, the Grantham iron ore traffic was taken over by O2s, and the entire class was
allocated to Doncaster. In 1946, all twenty moved to Frodingham to haul trains to and from the steel works.
In 1948, the remaining locomotives moved to Immingham and Retford where they hauled lighter services.
Withdrawals started in 1947. Seventeen engines survived into Nationalisation (1948), with the last four being
withdrawn in 1952.
||1340.5 sq.ft. (160x 2in)
||528 sq.ft. (24x 5.25in)
||430.5 sq.ft. (24x 1.25in)
||(@ 85% boiler pressure)
||119 tons 6cwt
||76 tons 4cwt
||43 tons 2cwt
|Max. Axle Load:
||17 tons 12cwt
None of the O3s survived into preservation.
Little Engines sell a kit of the O1 for OO gauge (4mm scale).
Martin Evans has designed a live steam O1 for 2.5" and 5" gauge. Castings for both are still available.
The 2.5" gauge castings are available from the 2.5" Gauge Association.