MAE 442 Heavy Trucks 1

8/12/2019 MAE 442 Heavy Trucks 1

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Heavy Trucks

MAE 442

Spring 2009Beth Harrington


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Overview Who am I?

Commercial Vehicles

Trucking Industry Chassis

Engine

Transmission Axles

Brakes

Suspension Manufacturing

Fuel Consumption and Alternative Fuels

Environmental Regulations


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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


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Commercial Vehicles

Trucks

BusesConstruction Equipment

Farm Equipment

Defense VehiclesEmergency Response Vehicles


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Trucking Industry Quick Facts

In 2008, the trucking industry hauled 10.2 billion tons offreight, 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 StatesTotal industry employment is 8.7 million, or one of every15 people working in the United States.

Most individual long-haul drivers average from 100,000 to

110,000 miles driving per year. Manufacturers designtrucks to run 1 million miles or more. The US long-haul,heavy-duty truck transportation industry is currentlyexperiencing a national shortage of 20,000 truck drivers.

A Class 8 truck reflects a heavy duty truck over 33,000 lbsGross Vehicle Weight Rating.

The trucking industry is a backbone of the Americansociety, and a key indicator of the economic situation.When the trucking industry is in trouble, so are we.


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North American Trucking

Navistar - International Paccar - Peterbilt & Kenworth

Volvo Group- Volvo & Mack

Daimler Freightliner & Western Star

There are 4 competitive class 8 truck manufacturers in the US:


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Global Industry Trucking can be found

around the world, but in

drastically differentapplications:

Rough, long haul over the Australian outback.

Cold and icy in Canada

Tractor + trailer length regulations in Europe


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Truck Applications

Highway

Long Haul Heavy duty

Regional

Vocational

Construction

Refuse


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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 onit. It must be able to twist to varying road conditions

while supporting the other truck functions.


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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)


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Fuel Tanks

Exhaust equipment

After treatment

Fifth Wheels

Mudflaps Battery Boxes

Back of Cab Access

Steps

Deck plates

Chassis Equipment


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Powertrain - Engines Diesel engines I assume you all know about the dieselengines 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 dont normally

go together


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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


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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.

%100SpeedRatedatTorque

RiseTorqueinDifference

(%)RiseTorque =

Example:

Peak Torque Rise = 1500 lb-ft

Torque at Rated Speed = 1300 lb-ft

% Torque Rise = (1500-1300)/1300 x100

Torque Rise = 15%


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Powertrain - Transmission The transmission and rear axle(s)

provide the necessary gear ratios to

effectively utilize engine power. Wewant to obtain the most efficient

working range, which encompasses

maximum horsepower produced per

gallon of fuel consumed.


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Powertrain - Gear ratios Selection of gear ratios by mating transmission and rearaxle:

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 about90% 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


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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 itmakes 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


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Rear Axles Rear axles may be classified as follows:

The dead axle carries the required load only. If the axle is infront 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 therequired 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 adverseterrains.


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Rear Axles


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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 axlesfor these reasons listed above. In Europe, a single rear axle ismore common.

These trucks are often labeled by the number of wheels theyhave:

4x2 4 wheels, 2 drive which means this is a single rear axle

6x4, 8x6, 8x4 are all common numbers to see.


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Brakes

Disc brakesUtilizes a caliper (1),brake pad (2), and rotor(3). Air pressure isconverted to mechanicalmovement when it

enters the brakechamber (A). When thepush rod in the chamberis extended, the slackadjuster (B) is rotated,transmitting movementto the powershaft (C)which in turn pressesthe brake pads (D)against the rotor (E).

There are two types of wheel brakes that occur on heavy trucks


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Drum brakesUtilizes a brake shoe to pressagainst the brake drum. Thereare multiple types of drumbrakes, but the most common isS Cam Brakes. These are

applied when air pressureenters the brake chamber (1)extending the push rod, whichis connected to the slackadjuster (2). As the slack

adjuster moves, it rotates thecamshaft pushing the brakeshoes (3) against the brakedrum.

BrakesThere are second type of brakes are the:


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Axle Suspensions Good axle suspension must provide the following

characteristics:

Capacity for supporting the load Transmission of full brakes and tractive effort to chassis

frame

Articulation of both axles for all road conditions

Cushioned ride for driver and commodity, laden and

unladen

Proper tracking to promote safe steering and prevent

excessive tire wear Easy maintenance and light weight


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Axle Suspensions Types of Axle Suspensions:

Air

Rubber Leaf Spring

Solid Mount

Air Suspensions:

Ride is the most important quality to design for here comfort for the driver and protection for the goods being

transported. Mechanical Suspension:

These are more performance based, where roll control isking and ability to handle difficult loads and changingterrain. To obtain these, ride is often compromised.


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Trailing arm air suspensions Most popular for highway use

Common characteristics:

Axle clamped to a leaf

spring Air spring sits on the rear of

the leaf spring

4 shock absorbers

Roll stiffening accomplishedby twisting the axle housing.

Pros:

Light weight, inexpensive

Good ride

Good roll stiffness, high roll center

Cons:

Torque reactive ride height and axle

angles change in response to wheel torque

Ride height adjustment critical for driveline

Poor cross articulation

Spring to axle connection is highly stressed.


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Parallelogram Designs Alternative air suspension design 6 torque rods to control axles

Torsion bar for roll control integrated into lowertorque rods.

V-rods on top

4 air springs per axle Limited axle travel highway use


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Parallelogram Design Off-highway air suspension, designed for over 25% offhighway.

Tubes across bottom provides roll stiffening not found in

trailing arm set up.

Use of transverse torque rods important for roll control as

well.


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Leaf Springs

Stack of leaf springs, connect at one end with a shackle.

The shackle prevents the leaves from elongating when

compressed, and allows for fore-aft movement.

Pros

Durable

Decent loaded ride

Good articulation and ground

equalization

Cons

Poor unladened ride

Low roll center

Difficult to align


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Walking Beam The walking beam replaces the spring and the trunnion The beam is welded or cast with bronze or rubber

bushings

Pros

Excellent articulation / ground load

equalization good mobility

High roll center, good rollover

resistance

Easy to align

Cons

Very expensive

Very heavy


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Static Roll Threshold A challenge here is what we call

roll control. The static rollthreshold (SRT) of a vehicle is ameasure of the likelihood of thatvehicle rolling over sideways.

Vehicles with a low SRT aremore likely to roll over thanthose with a higher SRT,especially when going

around sharp bends and insudden emergencymanoeuvres.

To ensure their stability,heavy vehicles with a gross

vehicle mass (GVM) greaterthan certain specified limitsneed to meet a minimumstatic roll threshold value. T = track width

H = CG height,

= the roll angle due to compliances(tires, suspension, etc)

= H

T

SRT 2


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Manufacturing Processes

Truck begins process withframe rails, axles, and crossmembers installed

Air lines, air tanks andelectrical harness

Brake hoses

Chassis is painted

-500 employees

-Current rate 36 trucks a day highest 107 a

day in 2006

-Truck in process of combining all sub

components is 6 hrs.

-Total build time from beginning to end

delivered to the customer 46 hrs.

Flexibility in plant allows forbuilding of: Dump, Highway,

Concrete pumpers, AWD, Telma

Retarders, Central Tire Inflation,

Tri Steer/Tri Drive, Lift Axles,Hybrid, LNG/CNG


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Manufacturing Processes

Fuel tanks installed

Engine installed with allpiping

Installation of DPF andbatteries

Power steering piping

Cab installation Air and electrical

connections betweenchassis and cab made

Tires installed

Fluids filled

Truck started and driven

offline


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Fuel Consumption

We talked about fuel efficient engines, however there are a few

other factors often considered when discussing fuel economy:

Weight the lighter the truck, the better fuel economy it

gets. This also goes hand in hand with the amount of cargo

that a truck can pull due to both local and federal weight

restrictions.

Operator driving style it is obvious that a driver canchange the fuel economy, but what can a fleet manager do

about it? Most truck brands now offer remote monitoring

systems that feed information such as rpm, fuel economy,

average speed, and more remotely from the truck to thefleet manager.

On highway trucks usually get between 5.5 and 6.5 mpg


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Alternative Fuels

Every aspect of the automotive industry is looking into alternativefuels, and the truckers are no exception.

The Volvo group is looking at 8 different ways ranking them from

best to worst in their opinion.

Peterbilt already offers hybrid vehicles in the market today, and the

other OEMs are not far behind. The best application for hybrids is

in the refuse division. With the stopping and starting of garbage

and recycling trucks, this is the perfect way to run off battery andallow it to charge. Mack Trucks has 2 vehicles being tested in NYC

waste management as we speak.


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Environmental Regulations Over the past 5 to 10 years, the trucking industry has been

burdened with environmental regulations, and most of the

product development money of most major corporations is

going to this. The step process: 2004, 2007, and 2010.

Trucks manufactured after January 1, 2010 must near-

zero emissions.

EPA 2010 Regulations aim

to reduce atmospheric

pollution by significantly

reducing nitrogen oxides

(NOx), particulate matter(PM), and hydrocarbon

(HC) emissions from diesel

engine-powered heavy

trucks.


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SCR

Selective Catalytic Reduction (SCR)is one of the most cost-effective and fuel-efficient vehicle emissions controltechnologies available to reduce diesel

engine emissions.

It is called "selective" because itreduces levels of NOx usingammonia as a reductant within a catalystsystem. The reducing agent reacts with NOx

to convert the pollutants into nitrogen, waterand tiny amounts of carbon dioxide (CO2) -natural elements common to the air webreathe everyday.

The reductant source is usually

automotive-grade urea, otherwiseknown as Diesel Exhaust Fluid, which can berapidly hydrolyzed to produce the oxidizingammonia in the exhaust stream. SCRtechnology alone can achieve NOx

reductions in excess of 90%.

http://www.mackscr.com
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Heavy Truck Engineering

Working with big trucks is extremely fun and challengingbecause everything is bigger, tougher, and engineered for

greatness. And remember behind every great car, there is

a great truck.


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Truck Information References

Motor Truck Engineering Handbook James William Fitch, 4th ed.

OEM websites: www.peterbilt.com

www.kenworth.com www.freightliner.com

www.volvo.com/trucks

www.macktrucks.com

Land transport safety authority SRT Calculator User Guide

EPA website www.epa.gov

Frost and Sullivan Automotive Practice EPA 2010 EmissionRegulations Start Showing Its Impact

Michael Brown Class 8 Truck Rear Suspension Overview

www.Factsaboutscr.com The truckersreport.com
http://www.peterbilt.com/http://www.kenworth.com/http://www.freightliner.com/http://www.volvo.com/truckshttp://www.macktrucks.com/http://www.epa.gov/http://www.factsaboutscr.com/http://www.factsaboutscr.com/http://www.epa.gov/http://www.macktrucks.com/http://www.volvo.com/truckshttp://www.freightliner.com/http://www.kenworth.com/http://www.peterbilt.com/

Documents

MAE 442 Heavy Trucks 1