FACING pressure to improve productivity and increase the competitiveness of their rail freight operations, several European railways are looking at the scope to raise axleloads beyond the classic 22·5 tonnes laid down in the current UIC standards. British Rail adopted a 25·5 tonne limit many years ago for its then-isolated network, and Swedish iron ore operator Malmtrafik AB and Banverket are investigating 30 tonne axleloads for the dedicated Luleå - Kiruna - Narvik corridor.

Now two bogie manufacturers are coming up with alternatives to the traditional Y25 freight bogie which offer reduced track forces at higher axleloads, and could allow operation at 25 tonnes throughout the mainland European network.

Powell Duffryn Rail has announced plans to develop a 100 km/h European version of its successful TF25 ’track-friendly’ bogie, designed to carry 25 tonne axleloads on routes cleared for 22·5 tonnes under UIC standards. And last month, Germany’s Federal Railway Office was expected to complete trials to test the compliance of ABC-NACO’s Axle Motion III bogie to the dynamic and ride quality specifications in UIC leaflet 518.

Introduced to the British market at the end of 1999, the TF25 was derived from the LTF25 low track force bogie developed in the 1980s. It is approved for 25·5 tonne axleloads at a maximum speed of 120 km/h. Powell Duffryn has received orders for almost 1000 bogies from several wagon leasing companies, to be fitted to hoppers, tank wagons and vans.

The modular bogie has a bolted H-frame using two cast steel sideframes and a fabricated bolster. Two-stage steel coils provide the primary suspension, with a radial arm giving controlled steering of the wheelsets. Instead of a centre pivot, two rubber secondary suspensions have stiff vertical characteristics and greater freedom for lateral movement and yaw. Total weight of the tread-braked version is 4·4 tonnes.

German Railway has tested an LTF25 with load-measuring wheelsets, which met the UIC518 specifications at both 22·5 and 25 tonnes; even at the higher loading the wheel contact force Q was within the limiting value. Last year, Powell Duffryn’s 160 km/h single-axle TF25sa derivative with disc brakes was fitted to a fleet of postal vans in Sweden.

The Axle Motion III has already been approved for operation in Britain, Sweden and Finland. ABC-NACO is currently supplying bogies for 490 infrastructure maintenance wagons being built for Railtrack, as part of an order worth around US$16m.

Axle Motion III is a hybrid of North American and European practice, which in Britain is allowed to operate at up to 100 km/h with a 25 tonne axleload, and at 120 km/h when the loading is reduced to 22·5 tonnes. The latest German tests included runs at up to 132 km/h with a 25 tonne axleload, and ABC-NACO hopes to obtain approval to operate at 120 km/h with this loading.

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