The GWR 5101 Class, commonly known as the ‘Large Prairies’, was introduced by Charles Collett in 1929 as a further development of Churchward’s earlier 3100 and 5100 series. Rather than being an entirely new design, the class represented the culmination of nearly three decades of incremental improvement to the original large prairie concept.
Intended primarily for suburban and local passenger services, they combined the proven 2-6-2T wheel arrangement with a series of refinements that reflected the Great Western’s evolving requirements. The result was a highly capable and adaptable tank engine suited to intensive passenger work.
Design and Characteristics
A total of 140 locomotives was built at Swindon between 1929 and 1949, making the 5101s one of the Great Western’s most numerous tank engine classes. They were fitted with the Standard No. 2 boiler at 200 psi, 5ft 8in driving wheels, and had a tractive effort of 24,300 lbf.
With 2,000 gallon water tanks and a four-ton coal capacity, the class was well suited to sustained suburban operation. Their tank engine layout made them particularly effective for frequent stops and turn-round workings without the need for turning facilities.
Although closely related to the earlier Churchward locomotives, the 5101 class incorporated a number of recognisable features from new. These included curved front end frames, outside steam pipes, brake rodding arranged inside the driving wheels, and prominent external sandboxes beneath the cab. The class was also built to the GWR’s blue route availability, reflecting revised weight distribution compared with earlier engines.
Automatic Train Control equipment was fitted either from new or shortly afterwards, in line with wider GWR practice.
Service Use
Initially, the 5101s were concentrated on suburban services in the London and Birmingham areas, where their acceleration and flexibility made them ideal for intensive stopping trains. Over time, they spread across the Western Region and became a familiar sight on branch lines, cross-country services, and general mixed-traffic duties.
As traffic patterns changed after the Second World War, the class proved highly versatile. In addition to their core passenger work, they were regularly employed on heavier duties, including banking over the South Devon banks and piloting trains through the Severn Tunnel.
Though never glamorous, they became a dependable and widely used type, valued for their ability to handle a wide range of duties without fuss.
Variants and Development
The 5101 class formed part of a broader family of large prairie developments. Related classes included the 61xx series, which used higher pressure boilers to increase power, and the 8100 rebuilds, which combined higher pressure boilers with smaller driving wheels to improve tractive effort and acceleration.
Within the 5101 class itself, a number of detail variations appeared across different batches and over time. These included differences in safety valve bonnet height, cab shutters, bunker recesses, water filler types, and later additions such as bunker steps and modified handrails.
More subtle variations, including rivet patterns and fittings, also existed between locomotives, particularly where rebuilds or later modifications had taken place.
Preservation
Withdrawals began in 1956, though most of the class survived well into the 1960s, with the final members withdrawn in 1965. Ten locomotives entered preservation, several via Woodham Brothers scrapyard.
Of these, one has been converted into a 2-6-0 tender engine and another has been used as a source of parts for reconstruction projects. Several others have operated on heritage railways, while the remainder are at various stages of restoration. As a result, the Large Prairie remains a familiar and representative GWR tank engine in preservation.
Modelling
Sonic Models
- Sonic Models S2103-01 5101 Class Large Prairie 2-6-2T 5164 in GWR Green
- Sonic Models S2103-02 5101 Class Large Prairie 2-6-2T 6106 in GWR Geen
- Sonic Models S2103-03 5101 Class Large Prairie 2-6-2T 4144 in BR Green
- Sonic Models S2103-04 5101 Class Large Prairie 2-6-2T 5199 in BR Black with early crest
- Sonic Models S2103-05 5101 Class Large Prairie 2-6-2T 4167 in BR Lined Green with early crest
- Sonic Models S2103-06 5101 Class Large Prairie 2-6-2T 4141 in BR Lined Green with late crest
- Sonic Models S2103-07 5101 Class Large Prairie 2-6-2T 5101 in BR Lined Green with late crest
- Sonic Models S2103-08 5101 Class Large Prairie 2-6-2T 4156 in BR Black with late crest
Converting the Sonic Models Prairie to 2mm Finescale
Nigel Ashton has described a straightforward and effective conversion of the Sonic Models Large Prairie to 2mm finescale, demonstrating that the model can be adapted without major difficulty.
His starting point was the ready-to-run Sonic model, which already captures the proportions of the class well and runs smoothly. The conversion involved fitting 2mm Scale Association wheelsets, using 11.5mm driving wheels, with 6.5mm and 7.5mm wheels for the leading and trailing pony trucks respectively. Standard Association hornblock bearings were used, along with muffs and gears adapted from typical Farish conversion practice. Some adjustment to muff lengths was required to achieve sufficient side play, particularly on the rear axle. The model uses Farish-style hornblocks, which helps make the conversion comparatively straightforward.
The pony trucks were arranged to contribute to current collection, using a system comparable to Simpson springs, and lightly sprung against the body. This improved electrical reliability, especially on finer track.
For the coupling rods, Nigel adapted spare rods from a Manor class model. These required minor modification, including repositioning the crankpin hole by approximately 0.2mm. This was achieved by filing back the rod and soldering in a washer before re-drilling and reaming to the correct position.
In operation, the converted model retains the smooth and quiet running characteristics of the original. The Sonic model is lighter than earlier Farish-based conversions, which may have some impact on ultimate haulage, but is more than adequate for typical ready-to-run stock.
Overall, this work shows that the Sonic Large Prairie is a practical and accessible candidate for 2mm finescale conversion, requiring careful but entirely manageable mechanical adjustments rather than wholesale reconstruction.
More Information
- Maidment, David. Great Western Moguls & Prairies. Pen & Sword Transport, 2016.