Truck Assignments and Systems ©Dr. B. C. Paul 2000

Job Assignments of Trucks l Single Purpose Machine - Haul Something Overburden coal ore aggregates

Drive Systems in Trucks l Mechanical Engine connected through gear boxes - torc converters and differentials to wheels Similar to your car l Electrical Engine turns a generator Wheels have electric motors

Engine to Wheels l Mechanical and Electric both about 85 to 90% delivery l Electric Drops more at extremes 6-10% grade and 8 to 20 mph no difference Has problems with flat high speed Problems with extreme grades

Parasitic Engine Loads l Both use about 10 hp/ton cap l Mechanical 10% to parasitic coolant pumps engine friction transmission (8% for first 3) steering hoist and converter rest l Electric Smaller engine cool load - more even run Generator Driven Exciter and Blower Blows the lead l Mechanical Wins by 1.8%

Vehicle Weight l Electrical Components Heavier than Mechanical Other Factors in Truck Design may well cover Does mean mechanical may be built heavier l No Clear Winner

Retarding l Retarding means non-braking speed reduction - not the impact of this class on your mental condition l Electric has simple retarding Run the Wheel Motors as generators and dump through a resistor bank Takes load off engine and tranny

Mechanical Retarding l Uses a Hydraulic Retarder l Engine and Drive Train Take the Drag l Engine Gets a lot more reved and less even run in mechanical l In past size limited to 120 tons Now 300 tons are mechanical l Recent Trend Favors mechanical

Advantages of Trucks l Flexibility Rapidly moveable easily rerouted for road changes or blending control Variable range of movement for materials

Disadvantages of Trucks l Expensive to Operate Large gas and lubricant expenses tires are wear prone and expensive Lots of operators 1 per truck in contrast to automatable conveyors or rail systems Driverless configurations were going no where until GPS Cables and radio controls

More Disadvantages l Expensive to Buy Pound for pound like T bone steak Limited life 20,000 to 30,000 hours (except for some very large units with 50,000) l Expensive to Maintain Large shop equipment needed field breakdowns hard to handle Past problems with Electric and Mechanical

Still More Problems l Reliability Problems Typical 70 to 85% availability compared to 95% plus on other machines Significant progress with modular systems Lease options - guaranteeing up to 95% but change trucks out frequently Quarries with old equipment still a nightmare

More Problems l Safety Problems Fast big machines moving on steep grades and around limited visibility corners Backup problems on rear dumps Swinging in to be loaded problem with loading equipment Smashing the Foreman's Truck

Truck Problems l Environmental Target Diesel emissions fugitive dust - speed limit restrictions Tarping laws becoming more common l Require a lot of Support Equipment Can’t load itself Needs a private highway department

Trends in Trucks l Recovering from the Fiascoes of the 70s and 80s l Mechanical Taking Over Market l Approaching the 300 ton truck (some are coming out) Avoiding the 3 axles that ruined maneuverability Dual engine configurations to avoid problems of engine size

Engine Types l Almost all are diesel engines l 2 cycle are simpler but tend to have poor acceleration and power Responsible for first 350 ton truck fiasco l 4 cycle perform better + cost more Turbo-charging was common to avoid altitude deration Computer controls getting some impressive performance without