Baulk road
Baulk road is the name given to a type of railway track or 'rail road' that is formed using rails carried on continuous timber bearings, as opposed to the more familiar 'cross-sleeper' track that uses closely spaced sleepers or ties to give intermittent support to stronger rails.
Baulk road was popularised by Isambard Kingdom Brunel for his 7 ft (2,134 mm) broad gauge railways in the UK, but has also been used for other railways and can still be found in modified form in special locations on present day railways.
Brunel sought an improved design for the railway track needed for the Great Western Railway (GWR), authorised by Act of Parliament in 1835 to link London and Bristol.
He refused to accept received wisdom without challenge. The 4 ft 8 1⁄2 in (1,435 mm) gauge that had been adopted by most railways at that time had been fine for small mineral trucks on a horse-drawn tramway, but he wanted something more stable for his high-speed railway. The large diameter wheels used in stage coaches gave better ride quality over rough ground, and Brunel originally intended to have his carriages carried in the same way – on large diameter wheels placed outside their bodies. To achieve this he needed a wider track gauge and he settled on a 7 ft (2,134 mm) broad gauge but it was soon eased slightly to 7 ft 1⁄4 in (2,140 mm). When the time came to build the passenger carriages they were designed conventionally with smaller wheels under the bodies, but with the broad track gauge the bodies could be much wider than on the standard gauge. His original intention to have the wheels outside the width of the bodies was abandoned.
Early locomotive-powered railways had used short cast iron rails carried on stone blocks. A few were trying timber sleepers to support the rails and to maintain the gauge between them. These rails were brittle and broke easily, and they gave a rough ride due to the difficulty of maintaining a smooth line between the blocks or sleepers. Wrought iron rails were being manufactured but they were of poor quality due to the difficulty of cooling them evenly during manufacture. Brunel decided to use a continuously supported wrought iron rail, a bridge rail with a smaller rail section that cooled more evenly. This was an inverted-U section with wide flanges that could be bolted to the timber bearer, which was known as a 'longitudinal' baulk. The rail was usually kept off this by small wooden packing pieces that could be replaced when they were worn out by the passage of the trains, and therefore avoid the expense of replacing the heavier longitudinals. The rails were bolted to the longitudinals by long fang bolts or coach screws, and the rail joints were later supported by a base plate formed with a plug in the void of the inverted U shape rails so as to keep the rails in line with each other.
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