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

The Rear Dump Truck

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

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

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

The Tree Axle Rear Dump

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)

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

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

The Three Axle Bottom Dump

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

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

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

Two Axle Bottom Dump