Volvo Group is hoping a fresh addition to its range of in-house truck and bus gearboxes will win it a greater share of Europe’s burgeoning heavy-haulage truck sector.
Despite a general trend towards lighter, low-density road freight, demand for specialised heavy haulage trucks is growing strongly. These vehicles are classified as “special types” in the UK because they carry loads that take them way beyond normal weight and dimension limits.
One reason for this growth is the increasing need for giant wind turbine blades, up to 70 metres in length, to be carried to and from electricity-generating wind farms, often accessible only by road and track. The heavy-haulage sector in the German state of Bavaria, for example, is said to have grown more than threefold over the past 20 years.
Trucks used for these operations, with gross weights up to 250 tonnes or more, need special transmissions, not least with the ability to cope with ultra-low-speed manoeuvring. Volvo’s latest answer is an addition to its I-Shift automated manual gearbox (AMT). Instead of the normal 12 forward ratios, the new box has two extra “crawler” gears, with a ratio as deep as 32:1. The whole gearbox has been beefed up to withstand exceptionally high input torques and gross combination weights up to 325 tonnes.
Gearbox weight increases by 48kg compared with a standard 12-speed I-Shift. The new gearbox is also 12 centimetres longer than a standard I-Shift. But heavy-haulage operators are not expected to be the only ones taking an interest in the new Volvo gearbox. Tipper and other construction truck operators are also expected to specify it for vehicles that often go off-road under difficult conditions. Trucks can be driven at speeds as low as 0.5km/h without any clutch slip with the new transmission, it is claimed.
Peter Hardin, Volvo Trucks Product Manager, said, “I-Shift with crawler gears offers an entirely new scope for heavy trucks with automated transmission to regulate their speed when crawling slowly and reversing.
“The driver can haul a heavy load without worrying about getting into situations that may lead to costly downtime. The improved driveability and startability with the new crawler gears makes the driver’s job far easier when operating in difficult terrain on slippery surfaces with heavy loads, such as in the construction, forestry or mining sectors. The heavier the transport operation and the poorer the surface or the terrain, the more the driver gains from a truck with crawler gears.”
Challenge already met by Mercedes-Benz
The challenge of low-speed manoeuvring at extremely high gross weights has been met in a different way by Mercedes-Benz. Its latest SLT range of heavy-haulage trucks employs a Voith “turbo retarder clutch” (a combined fluid coupling, lock-up clutch and hydrodynamic retarder) mounted behind its PowerShift 3, 16-speed automated manual gearbox.