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 Caterpillar's AD55 and Atlas Copco's MT5010 that Sandvik Tamrock says should allow mines to trim fleet sizes, especially over longer ramp hauls. Sandvik Tamrock expects the Toro 60 to take back some of the market claimed by Cat's 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 488-597 kW/650-800 hp. The new Cummins QSK19 diesel boosts the MT5010's power to weight ratio from 5.27-6.5 kW/tonne, allowing it to reclaim ground over the AD55 and Toro 60, despite their larger payloads. Atlas 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 in Australia recording speeds of 14 kph 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 sort 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 12-30 tonne 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 Oct 2004 & 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.

Automation is still on the agenda witWhilst h regard to LHDs and trucks, with the many benefits being shown at those mines that have taken the plunge and opted for this technology. There is still progress to be made with regard to orders but Caterpillar and Sandvik 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 ElTeniente 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, the technology is being used for production at the Northparkes and Olympic Dam mines in Australia.

There are a lot of similarities in the way MINEGEM and Automine work, with laser equipment mounted on-board the LHDs. These scan the tunnels ahead of the machines as they tram, picking up changes in the tunnel profile and allowing the machine to recognise its position in milliseconds. The lasers update tunnel maps continuously to, resulting in large volumes of data shuttling back and forth constantly. Cat's MINEGEM system operates on a wireless LAN infrastructure with an 11 Mbps capacity - Sandvik Tamrock's Automine system requires similar broadband communications capabilities. Both MINEGEM and Automine are controlled by conventional and readily available computing hardware, while a good deal of the components are standard off-the-shelf items selected for their ability to cope with the tough mining cycle.

With these technologies, one operator can supervise the running of up to three LHDs that run more or less autonomously, with the only manual input being for the bucket loading part of their operating cycle. Caterpillar's MINEGEM is a package built up of several layers and this allows customers to select the separate components they require. The tactical layer of MINEGEM provides automatic steering for an LHD and prevents it from colliding with the walls of the tunnel or against other vehicles. The operator fills the bucket and selects forward or reverse, with the system providing automated tramming and bucket dumping. The strategic layer is more complex as this integrates the operation of up to three LHDs, oversees their operation and has higher level planning capabilities. It is the strategic layer that is in charge of traffic control functions, so that multiple cycles can be 'scripted' for blending ores from different drawpoints for instance, with the overall benefit of increasing production efficiency.

Safety is improved as the operators can be situated away from where the machines are running (they don't even have to be in the mine at all and in theory, could be sitting in an office on the other side of the world). Moreover, the machines require less maintenance and have lower running costs as gearchanges are made at optimum times, engines are not over-revved, there is less wheel-spin and the risk from collisions with tunnel walls or other machines is all but eliminated.

However, the complete Automine and MINEGEM technologies are not inexpensive and suit applications in purpose-built mine areas (or even mines). The automated equipment runs in parts of the mine that are separated from other operations and with personnel access carefully controlled. There are however comparatively few large (and/or new) mines with the sort of block caving or sub-level caving applications that best suit this sophisticated full automation technology and can justify the investment. As a result, Caterpillar and Sandvik Tamrock (separately) identified a need for less sophisticated systems that offer many of the same operating benefits, while being substantially less costly. By opting for just the tactical layer of MINEGEM (called Co-Pilot), a mining firm can introduce an effective and comparatively low-cost technology for single LHD automation. And Co-Pilot comes with a manual over-ride, allowing it to be used as a conventional remote control if/when required. In this respect Sandvik Tamrock has a broadly similar product in the shape of its Automate system, which is also designed for single LHD automation and has equivalent control specifications.

With Automate or Co-Pilot, mines can introduce single LHD automation into applications where conventional remote control systems are used at present. The advantage of this is that single machines can benefit from the automated tramming, without the expense of the complete machine automation package (or the inherent changes to infrastructure and mine layout). Both Caterpillar an Sandvik Tamrock point out that this technology has huge potential with firms using conventional remote controls and will be of particular benefit at mines with high incidences LHD collision damage. And, as anyone who has ever operated a radio-controlled car can attest, it can be difficult to judge distances between a moving machine and its surroundings from a distance. The single automation equipment will take away this risk of collisions and make substantial reductions in machine downtime and repairs, as well as boosting productivity. A study commissioned by Caterpillar from Australian body STEM shows that replacing conventional remote controls with simpler single LHD systems would provide payback times of three years (and even less in some instances), while providing productivity gains of up to 37%.

For the moment, mining firms seem reluctant to invest in full LHD automation due to the expense and complexity of the technology. But with the production and cost benefits offered by Cat's MINEGEM Co-Pilot and Sandvik Tamrock's Automate systems for single LHD automation in existing mines, that situation could well change soon.

Russian firm MOaZ builds two underground trucks, the 7405-9586 for narrow operating conditions and the more conventional 7529, both of which have 22 tonne payloads. The 7405-9586 weighs 19.5 tonnes unladen, has a canopy as standard, is powered by a JMZ-238KM2 diesel rated at 140 kW and measures 2.9 m wide for use in narrow access areas. As this model has 2WD it can cope with 9° maximum slopes and best suits flat hauls or tunnelling applications, offering a maximum speed of 40 kph. The 7529, weighs 24 tonnes unladen, features 4WD and has a more powerful JMZ-238BN2 engine delivering 190 kW, allowing use on steeper ramps. This machine also has a top speed of 40 kph and is equipped with an enclosed cab as standard. Both the 7405-9586 and 7529 trucks can be fitted with Deutz engines if required.

German firm Paus built two tractors for Kali & Salz that tow pallets on trailers using a gooseneck connection. The vehicles are powered by 176 kW Deutz BF6M1013 engines. These offer payloads of up to 30 tonnes and are used to carry equipment, spare parts and materials underground, though product haulage is still by truck. Paus also has a number of loaders now operating at mines in Russia, with a number of enquiries coming in a well from Australia. These are from engineering firms carrying out feasibility studies and are not expected become equipment orders immediately, but the firm is confident that these will translate into actual deals. The company adds that it is now receiving interest in the novel undercutting type machines, of which it built 15 units for operations in Belarus. In addition, Paus is building a number of ditch cleaning machines for Norilsk Nickel in Russia. These are based around a small mine locomotive, with an excavator boom that allows the machine to clear the dewatering ditches running alongside the tracks.