Heavy Trucks MAE 442 Spring 2009 Beth Harrington Overview Who am I Commercial Vehicles Trucking Industry Chassis Engine Transmission Axles Brakes Suspension Manufacturing Fuel Consumption and Alternative Fuels Environmental Regulations Who am I Beth Harrington Associate Engineer for Volvo 3P Rear Suspension Department International Graduate Program Alumni BSME from NCSU May 2008 MSME from NCSU EOL December 2010 Wolfpack Motorsports Baja SAE Alumni Commercial Vehicles Trucks Buses Construction Equipment Farm Equipment Defense Vehicles Emergency Response Vehicles Trucking Industry Quick Facts In 2008 the trucking industry hauled 10 2 billion tons of freight or 69 percent of total U S freight tonnage collecting 83 1 of total transport revenue There are 3 5 million truck drivers in the United States Total industry employment is 8 7 million or one of every 15 people working in the United States Most individual long haul drivers average from 100 000 to 110 000 miles driving per year Manufacturers design trucks to run 1 million miles or more The US long haul heavy duty truck transportation industry is currently experiencing a national shortage of 20 000 truck drivers A Class 8 truck reflects a heavy duty truck over 33 000 lbs Gross Vehicle Weight Rating The trucking industry is a backbone of the American society and a key indicator of the economic situation When the trucking industry is in trouble so are we North American Trucking There are 4 competitive class 8 truck manufacturers in the US Daimler Freightliner Western Star Volvo Group Volvo Mack Navistar International Paccar Peterbilt Kenworth Global Industry Rough long haul over the Australian outback Trucking can be found around the world but in drastically different applications Tractor trailer length regulations in Europe Cold and icy in Canada Truck Applications Highway Long Haul Heavy duty Regional Vocational Construction Refuse Chassis Components Chassis Frame Rails The frame of a heavy truck is the backbone of the whole operation Everything must mount to it or sit on it It must be able to twist to varying road conditions while supporting the other truck functions Frame Bending The bending moment is the force acting on the frame from all the components on it as well as the input from the trailer and the road below The Resisting Bending Moment is the maximum load or force that the frame can support without permanent damage RBM S I C Where RBM resisting bending moment in lb S stress or yield point of the rail lb in2 I C Section modulus in3 Chassis Equipment Fuel Tanks Exhaust equipment After treatment Fifth Wheels Mudflaps Battery Boxes Back of Cab Access Steps Deck plates Powertrain Engines Diesel engines I assume you all know about the diesel engines and if not you can Wikipedia it The standard sizes for heavy duty diesel engines ranges from 11 liters to 16 liters Fuel economy and Power are both extremely important in the trucking industry Unfortunately these don t normally go together Engine Components Engine Block Cylinders Valves Pistons Crankshaft Flywheel housing and oil pan Timing gears Overhead Camshaft Oil system Fuel injection system Air intake and exhaust Turbocharger Intercooler Cooling system Powertrain Torque To find a happy median these diesel engines are high torque This means that we can increase performance and better fuel economy through a high torque rise Torque rise is the difference between torque at rated speed and peak torque expressed as a percentage of torque at the rated speed Torque Rise Difference in Torque Rise 100 Torque at Rated Speed Example Peak Torque Rise 1500 lb ft Torque at Rated Speed 1300 lb ft Torque Rise 1500 1300 1300 x100 Torque Rise 15 Powertrain Transmission The transmission and rear axle s provide the necessary gear ratios to effectively utilize engine power We want to obtain the most efficient working range which encompasses maximum horsepower produced per gallon of fuel consumed Powertrain Gear ratios Selection of gear ratios by mating transmission and rear axle Important points to remember Use past experience Gear ratios should be numerically fast enough to assure desired speed for highway operation Top speed should be approximately 5 10 mph faster than cruising speed or about 90 of governed speed Gear ratios should be numerically slow enough to provide maximum grade performance with lowest gear combinations and maximum start ability under all operating conditions Overall gear reduction Main Transmission Ratio x Aux Transmission Ratio x Drive Axle Ratio Rear Axles Rear axles on a truck are the drive axles while front axles are steer axles It is possible to get up to 3 of either although it makes one funny looking truck To decide which rear axle you need you must look at Gross weight of combination Type of terrain Road speed Tire size Axle ratio required Transmission ratios Engine torque Engine speed Maintenance Rear Axles Rear axles may be classified as follows The dead axle carries the required load only If the axle is in front of the drive axles it is known as a pusher and if it is behind it is known as a tag The live axle includes all necessary gears and parts for the transmission of power as well as facility for carrying the required load When looking at the live axle we classify according to gear drive Examples Straight bevel gear Hypoid gear has more tooth contact than a straight bevel and therefore is stronger and quieter Double reduction provides greater overall gear reduction and is ideal for peak torque development and transmission Especially desirable for starting heavy loads in adverse terrains Rear Axles Rear Axles Tandems two drive axle combination Advantages Greater legal loads Greater traction Greater flotation Better braking for greater safety Better load distribution over axles tires an frame Reduced road shock Most over the road trucks in North America have tandem axles for these reasons listed above In Europe a single rear axle is more common These trucks are often labeled by the number of wheels they have 4x2 4 wheels 2 drive which means this is a single rear axle 6x4 8x6 8x4 are all common numbers to see Brakes There are two types of wheel brakes that occur on heavy trucks Disc brakes Utilizes a caliper 1 brake pad 2 and rotor 3 Air pressure is converted to mechanical movement when it enters the brake chamber A When the push rod in the chamber is extended the slack adjuster B is rotated transmitting movement to the powershaft C which in turn presses the