All terrain reliability – A case study
Dump trucks fitted with automatic transmissions are making a big difference to the mining sector. Construction Week India presents a case study
Kudos to the mining workforce, whose hard work in the challenging environments of coal mines, keeps much of India powered and running. These mines use heavy equipment such as Dozers, Excavators, Hauling vehicles, Drills; as well as Dump Trucks, which are used to transport coal from the mining phase to coal receivable hoppers.
The roads in these mines are sometimes flat, often with gradients, and almost always have rough surfaces with loose mud, gravel, potholes and bumps, causing abnormal stresses to the trucks. Therefore, a major challenge for tippers and dump-trucks in this industry is delivering performance – safety, productivity and minimum downtime.
Over the decades, development of high-tech machinery and equipment have made the mining industry safer, less tiresome & more productive. The mining workforce earlier used relatively old-technology machines, which was dangerous for operators, and often resulted in deterioration of their health, sometimes even claiming lives. Today’s modern technologies can provide much higher levels of productivity, comfort and safety; and at a very competitive life-cycle cost.
Allison Transmission, the world’s leading supplier of fully automatic transmissions for on & off highway commercial vehicles, has developed a range of automatic transmissions for mining and construction trucks of various sizes & capacities.
Coal India Ltd (CIL), a Government of India enterprise (through the Department of Coal and the Ministry of Mines and Minerals), is responsible for 88% of coal output in India. In Nagpur, CIL has a total fleet of 216 dump trucks (BH50 and BH35) fitted with Allison automatic transmissions. CIL agpur has been using these automatic transmissions for over 22 years.
A survey was done with the objective to understand the usage of dump trucks by CIL and the challenges faced in the mines. Following is the feedback gathered from a cross section of drivers, maintenance head and the chief engineer of a CIL site off-Nagpur.
Reliability on all terrains
Losing control or traction on muddy, sticky, slippery or hilly ground is always a problem for truck drivers at mining sites. Sites are known for their uneasy working conditions, and can even become dangerous in bad weather conditions. “When you extract coal, ground conditions can be really bad,” says an operator of a BH50 tonne dump truck at the CIL mining site since 1985. “We only use dump trucks fitted with Allison automatic transmissions, as automatics are easy to run and maintain even in the toughest ground conditions.” The maintenance engineer on site says,
“Thanks to the torque converter in the gearbox, whatever the ground might be like, the truck pulls away really gently and easily without getting stuck or splattering mud. And it’s great to have the engine power continuously delivered to the wheels with no interruptions at all. It gives me complete control of the truck!” Few distinguished elements like a torque converter, planetary gearing and an advanced electric control unit makes an Allison different from other transmissions.
All these features on a dump truck equipped with an automatic make it very easy to drive on irregular & uneven grounds. A Chief Engineer at a Coal India mine is similarly impressed and says: “Our drivers drive over a lot of rough terrain and the Allison’s really demonstrate true value. The vehicle moves forward smoothly and never stops. It can stop on a steep grade, and easily re-start without rolling down backwards, and then climb up the gradient”. The driver is always in control of the truck.
One of the major gripes about manual gearboxes is power loss during shifting. This is not so withan automatic transmission, where smooth shifts happen without any loss of power, speed or control. This can be important in all kind of situations, like, driving uphill & manoeuvring on site. For drivers, this enhanced power & control makes the job much easier and safer. “Everything is comfortable and easy,” he says.
“I can drive up the hill very easily, without losing power or control. And the job gets done much faster with an automatic transmission, such as getting coal to a location up a hill-slope. With a manual gearbox you have to frequently use the clutch, change gears, every time you go forward or reverse. With the Allison automatic, I just go to the “Drive” or “Reverse” positions, and the truck moves easily. The torque converter also minimises shift-shocks on the entire drivetrain.
A Chief Engineer at a Coal India mining site says, “We also get longer driveline life from the automatics than any other manual alternative and the Allison ensures our coal stays on the move.”
Testing has demonstrated that trucks fitted with automatic transmissions are typically able to complete the journey up to 15% quicker than similar vehicles with manual or automated manual transmissions. This enhanced performance has a big impact on overall productivity, speeding up the progress of mining through faster trips. This means, over the course of an average workday, more deliveries / round-trips can be made, hence more productivity.
Safety & Comfort
In mining, both on-road and off-road transportability holds equal importance. A driver who drives a BH50 tonne dump says “For the past 22 years we have only been driving vehicles fitted with automatic transmissions. While mining, we can comfortably stop the dump truck at a steep angle. This eliminates the hassle of pressing the clutch and changing gears, which is the biggest advantage of automatic transmission. This importantly allows the driver to concentrate on other
driving aspects, thus avoiding an unanticipated mishap.”
Interestingly, many drivers have noticed the comfort and safety by not having to use gears in an automatic transmission truck. Constant gear changing takes a toll on the knees and shoulders of the toughest of drivers. Like many drivers in the industry, some drivers at mines also suffer from muscular pain. He says, “The reason that I chose an automatic transmission dump-truck was because I started to get pain in my left knee due to severe clutch use & gear changing. A
colleague who drives an automatic transmission vehicle said “It is so comfortable with an automatic transmission that there is always power at the driving wheels. The driver is likewise impressed with the comfort factor and says, “This transmission is as nice to my shoulder and leg as it is to the vehicle’s own power train. It will only be an Allison automatic in the future.”
Savings and profits
As the driver of a BH50 tonne dump says, “We have seen that our maintenance costs have decreased with the automatic. Also the cost of the transmission is easily covered. From our experience, a dump truck fitted with an Off-Highway Allison automatic transmission typically works 6000 hours to 8000 hours, after which it requires overhauling at an approximate cost of Rs. 4-6 lakh. Then it can again work for another 5000-6000 hours after its 1st. Overhaul.” Thus, the first
life, overhauled life, and overhaul cost of an Allison is very economical.
And as the driver says “I can drive very easily, without losing power or control. And the job gets done much faster with an automatic transmission.” Drivers, engineers and maintenance managers at these coal mines have experienced the wealth of benefits offered by the automatic. Happier, more satisfied and comfortable drivers are able to do a better job: drive with greater precision; make more deliveries therefore improving productivity and profitability for the company.
Case study by Allison Transmission