1. Trucks and Loaders
© Dr. B. C. Paul
Hi!

2. The Rear Dump Truck

3. Truck Configurations Rear Dump
Solid bed elevates and dumps material over the back
Solid bed can take abusive handling and loading
Can be lined
Traditional liners steel
Carbon composites now
Lighter bed liners avoid loss of payload

4. Variations
Most manufactures offer different bed for different material weights
Coal and iron ore for example
Trucks are sized by weight and volume - most limiting controls productive service
Like to get both to limit at same time

5. Maneuverability Issues
Back dumping forces drivers to back into spaces blind
Most rear dumps are two axle with double tires on rear - fair maneuverability
Some very large have had double rear axle - hard to turn
Articulated versions are smaller but highly maneuverable - often have flotation tires for soft underfoot

6. The Tree Axle Rear Dump

7. Rear Dump Power Have relatively high HP to payload ratios
makes very gradable
gas mileage marginal makes best for short in pit hauls
Generally geared low so 35 mph typical peak speed
Weight centers on drive tires for traction (can have 4 wheel drive)

8. Powering Haul Trucks Diesel Engine (common in US) Trolly Electric
gas guzzlers frequently around 1 mpg
Trolly Electric
Rare in U.S. because it limits mobility to areas with developed lines
Trolly Assist
Keeps down engine size
boost power on steepest grade
Loosing ground because full electric drive systems loosing to mechanical

9. Three Axle Bottom Dump
More of a tractor trailer arrangement - open top and bottom opens to unload
More popular with lighter material like coal because of bed bottom abuse issues
More of vehicle is hauler
less power to payload
larger bed relative to size

10. The Three Axle Bottom Dump

11. Properties of Bottom Dumps
Geared higher for more speed
Gives poor gradability
SMCRA limits most ramps to 10% anyway
Speed and payload to power favors longer hauls - coal to processing facility
Have lower loading height - works better with FELs

12. Impact of Bottom Dump Can’t stand impacts
Allows truck to use regular truck dump
Dump time may be 25% of rear dump
Material must be free flowing and not prone to freeze
Three axles tend to maneuver poorly

13. Getting the Best of Both Worlds
Two Axle Bottom Dump
Improved Maneuverability
Looks like a three axle body only solid and on two axles
Has Intermediate Power to Payload ratio
Bottom dump still means light free flowing non freezing material

14. Two Axle Bottom Dump