![Bullied Firth Brown Boxpok wheel](https://upload.wikimedia.org/wikipedia/commons/3/35/Bullied_Firth_Brown_Boxpok_wheel.JPG)
The Bulleid Firth Brown wheel (BFB) was a locomotive wheel developed for the
Southern Railway in the late 1930s. It was a disc wheel, in contrast to the usual
spoked wheel
A spoke is one of some number of rods radiating from the center of a wheel (the hub where the axle connects), connecting the hub with the round traction surface.
The term originally referred to portions of a log that had been riven (split l ...
s in general use on British railways. The wheel was designed by
Oliver Bulleid
Oliver Vaughan Snell Bulleid CBE (19 September 1882 – 25 April 1970) was a British railway and mechanical engineer best known as the Chief Mechanical Engineer (CME) of the Southern Railway between 1937 and the 1948 nationalisation, d ...
and developed by the steel company
Firth Brown of
Sheffield
Sheffield is a city in South Yorkshire, England, whose name derives from the River Sheaf which runs through it. The city serves as the administrative centre of the City of Sheffield. It is historically part of the West Riding of Yorkshire a ...
.
Design
The BFB comprises a single disc, with teardrop-shaped indentations to give rigidity, and
lightening holes
Lightening holes are holes in structural components of machines and buildings used by a variety of engineering disciplines to make structures lighter. The edges of the hole may be flanged to increase the rigidity and strength of the component.
...
to reduce weight. The advantage over a spoked wheel is that a disc wheel carries the tyre (the metal hoop shrunk onto the wheel to provide contact with the rail) more efficiently; spoked wheels are prone to shrink over time, causing the tyre to work loose, whilst in a disc wheel this is less pronounced. Disc wheels also distribute the weight more evenly, reducing the
hammer effect on, and thus the damage to, the rail.
The BFB weighed about ten per cent less than a spoked wheel of the same size.
[Day-Lewis p 146]
Name
The Bulleid Firth Brown, or BFB, is sometimes, but inaccurately, referred to as a
Boxpok in reference to the wheel used by a number of US railway companies. The BFB is visually similar to the Boxpok, but is of a different design; the Boxpok is composed of sections fixed together to make a hollow shape, while the BFB is cast in a single piece, like a spoked wheel, the shape giving the rigidity needed.
The wheel is named for Firth Brown as well as Bulleid to give equal credit for the design: while the idea was Bulleid's, the development work, and how to cast them, was done by the company. Therefore, both shared the patent. In fact one source gives BFB as meaning Beaumont Firth Brown, referring to the engineer at the firm who oversaw the development.
History
The BFB was developed in 1938 for use on Bulleid's innovative
Merchant Navy class of Pacific locomotives. He later used them on all subsequent designs: the
Q1 "austerity class" in 1942; his Light Pacifics (the
West Country
The West Country (occasionally Westcountry) is a loosely defined area of South West England, usually taken to include all, some, or parts of the counties of Cornwall, Devon, Dorset, Somerset, Bristol, and, less commonly, Wiltshire, Glo ...
and
Battle of Britain classes) in 1945; and his
Leader class in 1946. The pacifics also used a similar design of BFB for the non-driving carrying wheels. He also used them in his modifications to
the Maunsell Diesel shunters then in use on the Southern.
Assessment
Despite the advantages for which it was designed and well suited, the BFB had a number of drawbacks. It was difficult to maintain, the hollows collected undesired particles like oil, sand and water. In addition, the wheels were found to be prone to cracking, though this was later attributed to the poorer quality of available steel used during and after the Second World War than to some intrinsic design flaw.
The use of the BFB was discontinued in 1948 after the amalgamation of the Southern into British Railways and Bulleid's departure to work for CIE in Ireland. The next generation of steam traction in Britain, e.g. the BR Standards, would all use spoked wheels. Although many of the Bulleid pacifics were rebuilt and major features such as their valvegear replaced, the BFB wheels were retained.
See also
*
SCOA-P wheel
*
Wobbly-web wheel
The wobbly-web wheel is a form of metal disc wheel where the disc is 'wobbled' into spokes. This provides a stiffer, lightweight wheel.
Wobbly-web wheels are best known through their iconic use on Lotus racing cars of the late 1950s and 1960s.
...
Notes
References
* CJ Allen: ''Bulleid Pacifics of the Southern Region'' (1951)
* S Day-Lewis: ''Bulleid Last Giant of Steam'' (1968)
{{use British English, date=December 2013
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