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Ao


Arc Roof Carriage
19th century carriage with the roof formed of a simple (fairly flat) arc, sometimes known as a “compass” roof. Like most other railways, the LNWR in the 20th century built larger carriages with low elliptical (”cove”Explain 'Cove-roof coach') or high elliptical roofExplain 'Elliptical-roof Coach' profiles.
See examples in this part of the Carriages exhibtion (and following pages) which show examples of Arc and Cove roofs.
At Danger
A signalExplain 'Signal' in the OnExplain 'On (Signal)' position I.e. horizontal with a red lamp showing.
Atlantic Wheel Arrangement
A generic name for the the 4-4-2 wheel arrangement. See Whyte wheel arrangementExplain 'Whyte Wheel Arrangement'.
Automatic Warning System (AWS)
A device which indicates the position of a distant signalExplain 'Distant Signal' , or colour light signal, in the cab of a locomotive, and applies the brakes if a caution indication is not acknowledged.
Axle
The steel shaft on which the locomotive wheels are mounted. The axle not only holds the wheels to gaugeExplain 'Gauge', but also transmits the load from the Axle-boxesExplain 'Axle-box' to the wheels.
Axle-box
This provides the bearing between the axleExplain 'Axle' and locomotive frameExplain 'Frame'. These were usually simple bearings designed to take the load (for driving wheels) of the alternating piston thrusts as well as the weight of steam locomotive. They were mounted in vertical slidesExplain 'Horn Blocks' within the frames and sprung to allow for uneven track. Relying upon a simple film of oil for lubrication, it was not uncommon for an axle box to overheat and seize (hence the term ‘hot box’Explain 'Hot Box'). Later designed steam locomotives and diesels use roller bearings.
Axle Guard
A modeller’s term (often one word) to describe the hornguidesExplain 'Horn Guides', springs, spring hangers, axleboxesExplain 'Axle-box' and everything else to hold an axle in place beneath a solebarExplain 'Solebar'. The term originated when early models represented this by a single casting.
Axle Load
The static weight carried by an individual axle. This determined the routes over which vehicles (especially locomotives) might run taking into account the strength of the infrastructure, that is bridges and track work. From the 1930s it was realised that the dynamic axle load (allowing for the “hammer blow”Explain 'Hammer Blow' effect of reciprocating parts) was more relevant and significant.
Axle Weight
The weight carried on any axle of a train. The maximum allowed would be limited by the track design, bridges and other structures on the line.
Aylesbury Railway (AR)
Incorporated 1836. Transferred to L&B in 1846.
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