Equalising beam

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 photo shows a Commonwealth bogie on a South Australian Railways Bluebird railcar, first manufactured under licence in 1954 by Bradford Kendall, Sydney, Australia.

Other components are, from left to right: an axlebox with roller bearing; 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.