英文原文Boom timeAhealthy market means that underground truck and LHD markers are enjoying high order levels, with new models and technology also coming .in the LHD sector, several new models are already on the market from firms including EJC, Fermel, Rham Equipment and Schopf (WME Oct & Nov 2004), while Atlas Copco intends to launch at least one new design in 2005 possibly an St14.But it is the truck sector that is the most active right now with renewed emphasis on power to weight ratios right through the payload range The latest models are taking advantage of advances in diesel technology by fitting more powerful engines and allowing better speeds on steep ramp hauls .The impact of this is significant, as higher speeds mean lower cycle times and offer major gains in productivity, even allowing reductions in fleet sizes.At the top of the payload scale competition is now particularly fierce. Sandvik Tamrock is certainly pushing the boundaries with its Toro 60, a three axle truck with a rigid chassis and a 60 tonne capacity. This Cummins-powered truck offers a good power to weight ratio and a payload advantage over Caterpillars AD55 and atlas Copos MT5010 that Sandvik Tamrock says should allow mines to trim fleet size, especially over longer ramp hauls. sandvik Tamrock expects the Toro 60 to take back some of the market claimed by Cats successful AD55,with its 55 tonne payload. However Atlas Copco is fighting back against both Caterpillar and Sandvik tamrock with yet another upgrade to its MT5010 truck, providing a power increase from 488-597kw/650-800hp. The new Cummins Qsk19 diesel boosts the MT5010s power to weight ratio from 5.27-6.5kw/tonne, allowing it to reclaim ground over the AD55 and Toro60, despite their larger payload. Atlse Copco also says that driveline problems which afflicted earlier truck designs have long since been eliminated. The company points out that MT5010 is a successful design with units operating I Australia recording speeds of 14kph on 1:10 ramps, despite having 23,000 hours on the clock. Evaluating which of these three trucks offers the highest productivity could only be achieved by detailed study(and perhaps require testing), possibly with a different result depending on the nature of the specific mining application. The revised MT5010 has a higher power to weight ratio than either the AD55 or the Toro 60 but these trucks have bigger payloads of 55 and 60 tonnes respectively. The machine that best suits a given mining operation may be due to a number of basic factors such as haul distance and ramp gradient as well as ventilation infrastructure, ambient temperature and even material type. Overall though the customer will be the winner, with the latest large Atlas Copco, Caterpillar and Sandvik Tamrock trucks all offering much better productivity and reliability than was ever available to the 50+tonne class before.The same dort of power to weight ratio gains can be seen further down the truck payload range. Atlas Copco, Caterpillar, Dux, EJC, MTI and Zanam legmet have all fitted more powerful diesels to trucks with payloads in the 12-30tonne range,with similar benefits to those seen at the top of the capacity scale. For example, one Canadian mine replaced its earlier generation 16 and 17 tonners with newer 20 tonners,which offer short travel times on ramp, despite their increased payload and this has resulted in a substantial productivity gain overall. That the new generation of engines produce more power from similar outer dimensions is important, as they give a better payload/litre of fuel burned. However the cleaner emissions have added benefits, with cost advantages to mine ventilation requirements.In general, the new small-mid sized trucks themselves are externally similar to previous models, but are fitted with stronger drivetrains and axles to cope with the additional power (WME Oct2004&WME Nov 2004). Small detail changes like extended oil life or filters with replaceable elements make identifiable benefits to service costs. While the basic designs of these updated trucks remains similar, the better drivelines and new generation diesels mean that the machines require less maintenance are more reliable and are considerably cheaper to run.Self-driveAutomation is still on the agenda with regard to LHDs and trucks, with the many benefits being shown at those mines that have taken the plunge and opted for this technology. These is still progress to be made with regard to orders but Caterpillar and Sandvilk Tamrock are both pushing hard to sign up customers for their LHD(and truck)automation systems, MINEGEM and Automine respectively. At the moment only Codelco is using the full Automine automation system at the Pipa Norte and Diablo Regimiento zones of its EITeniente copper mine in Chile. But DeBeers and Sandvik TAmrock are developing a system for the Finsch mine in South Africa. And while Caterpillar has yet to notch up a commercial sale for MINEGEM, th