An equalising beam, equalising lever or equalising bar (British: compensating beam) links the suspension of two or more adjacent axles of a vehicle, especially a

railway Rail transport (also known as train transport) is a means of transport using wheeled vehicles running in railway track, tracks, which usually consist of two parallel steel railway track, rails. Rail transport is one of the two primary means of ...

locomotive A locomotive is a rail transport, rail vehicle that provides the motive power for a train. Traditionally, locomotives pulled trains from the front. However, Push–pull train, push–pull operation has become common, and in the pursuit for ...

On steam locomotives

Equalising beam and linkages in a steam locomotive

On steam locomotives, the beam is connected at each end to a spring on an axle or to the end of another equalising beam (usually via a vertical spring hanger) to distribute the locomotive's weight between two or more axles. An equalising system links not only the driving-wheel axles but also the trailing and/or leading truck axle(s). Its purpose is to prevent inequalities in the track or roadbed putting an excessive load on an axle. There is one system on each side of the locomotive; on some steam locomotives, there may also be a transverse equalising system connecting them.

On diesel locomotives

On a contemporary diesel locomotive, equalising is confined to each bogie (US: truck); there is no linkage between bogies, which are inherently flexible compared with steam locomotive frames. Coil springs, matched to the weight bearing on the equalising beam, are a crucial element of the design.

On rolling stock

As with locomotives, equalising on rolling stock bogies aims to minimise reactionary force being transmitted to the rails because of track irregularities, which would occur if the axles were mounted rigidly. In addition, equalising beams and other linkages are configured to improve riding qualities for the comfort of passengers. Although features such as airbag springing and motion feedback devices on individual axles have featured in recent designs, currently the most prevalent designs are a mix of equalising beam, coil springs, hydraulic dampers, swing links and torsion bars. The most common designs throughout the world are variants of the "Commonwealth" bogie/truck manufactured by the successor company to the Commonwealth Steel Company, of Granite City, Illinois, United States. It has exceptional riding qualities. The photo shows a Commonwealth bogie on a

South Australian Railways South Australian Railways (SAR) was the organisation through which the Government of South Australia built and operated railways in South Australia from 1854 until March 1978, when its non-urban railways were incorporated into Australian Natio ...

Bluebird railcar, first manufactured under licence in 1954 by Bradford Kendall, Sydney, Australia. The central element is the equalising beam, on which a spring set (with an inner and an outer coil) rests at each end. Other components are, from left to right: an

axlebox A bogie or railroad truck holds the wheel sets of a rail vehicle. Axlebox An axlebox, also known as a journal box in North America, is the mechanical subassembly on each end of the axles under a railway wagon, coach or locomotive; it contai ...

with

roller bearing In mechanical engineering, a rolling-element bearing, also known as a rolling bearing,ISO 15 is a bearing which carries a load by placing rolling elements (such as balls, cylinders, or cones) between two concentric, grooved rings called race ...

; a pair of swing links and short beam supporting a nest of coil springs and a vertical hydraulic motion damper; and a horizontal

torsion bar A torsion bar suspension, also known as a torsion spring suspension, is any vehicle suspension that uses a torsion bar as its main weight-bearing spring. One end of a long metal bar is attached firmly to the vehicle chassis; the opposite end ...

. An air-brake cylinder is to the far right.

On steam locomotives

On diesel locomotives

On rolling stock

References

See also