Transcript Truck Assignments and Systems

Truck Assignments and
Systems
©Dr. B. C. Paul 2000
Job Assignments of
Trucks
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Single Purpose Machine - Haul
Something
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Overburden
coal
ore
aggregates
Drive Systems in Trucks

Mechanical
• Engine connected through gear
boxes - torc converters and
differentials to wheels
• Similar to your car
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Electrical
• Engine turns a generator
• Wheels have electric motors
Engine to Wheels
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Mechanical and Electric both
about 85 to 90% delivery
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
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Both use about 10 hp/ton cap
Mechanical 10% to parasitic
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coolant pumps
engine friction
transmission (8% for first 3)
steering hoist and converter rest
Electric
• Smaller engine cool load - more even run
• Generator Driven Exciter and Blower
Blows the lead

Mechanical Wins by 1.8%
Vehicle Weight

Electrical Components Heavier
than Mechanical
• Other Factors in Truck Design may
well cover
• Does mean mechanical may be
built heavier

No Clear Winner
Retarding
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Retarding means non-braking
speed reduction - not the
impact of this class on your
mental condition
Electric has simple retarding
• Run the Wheel Motors as
generators and dump through a
resistor bank
• Takes load off engine and tranny
Mechanical Retarding
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Uses a Hydraulic Retarder
Engine and Drive Train Take the
Drag
Engine Gets a lot more reved
and less even run in mechanical
In past size limited to 120 tons
• Now 300 tons are mechanical
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Recent Trend Favors
mechanical
Advantages of Trucks

Flexibility
• Rapidly moveable
• easily rerouted for road changes or
blending control
• Variable range of movement for
materials
Disadvantages of
Trucks

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

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)
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Expensive to Maintain
• Large shop equipment needed
• field breakdowns hard to handle
• Past problems with Electric and
Mechanical
Still More Problems

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
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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

Environmental Target
• Diesel emissions
• fugitive dust - speed limit restrictions
• Tarping laws becoming more common
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Require a lot of Support
Equipment
• Can’t load itself
• Needs a private highway department
Trends in Trucks
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Recovering from the Fiascoes of
the 70s and 80s
Mechanical Taking Over Market
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
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Almost all are diesel engines
2 cycle are simpler but tend to have
poor acceleration and power
• Responsible for first 350 ton truck fiasco
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4 cycle perform better + cost more
• Turbo-charging was common to avoid
altitude deration
• Computer controls getting some
impressive performance without