start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 13, the reader should be able to: • • • • • Explain kinetic energy and why it is so important to brake design Discuss mechanical advantage and how it is used in a vehicle Explain the coefficient of friction Describe the difference between heat and temperature Describe the methods used to identify plastic, iron, steel, and aluminum Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: acid material • alkaline • brake • brake horsepower (bhp) • BTU (British Thermal Unit) caustic material • Celsius (centigrade) • conduction • conductor • convection • dynamometer (dyno or dyn) energy • Fahrenheit • first-class lever • force • fulcrum horsepower • hypothesis • inertia • insulator kinetic energy • leverage • mass • mechanical advantage Newton’s laws of motion Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: pedal ratio • pH • potential energy • power • propagation radiation • root cause scientific method • second-class lever third-class lever • torque weight • work • wrought alloys Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SCIENTIFIC METHOD The scientific method is a series of steps taken to solve a problem. It  help eliminate errors and achieve an accurate result. A scientific method  involves: Step #1  Observe the conditions or problem; define or describe Step #2  Formulate an explanation that could be the cause Step #3  Use the explanation (hypothesis) to see if it matches the  existing problem. If not, return to step 2 Step #4  After the explanation has proved to be a possible solution  to a problem, additional tests should verify the method Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Using the Scientific Method  While a service technician will not  perform research, a scientific approach to problem solving is very  important This means that every fault should be investigated to determine  the root cause, the true cause of the failure, rather than solving  what at first is thought to be the problem or fault Many techs ask themselves “why” when they discover a fault.  Often this leads to another possible problem and then the  technician should ask another “why.” This scientific method of finding the root cause of an automotive  problem is often called the “five whys.” By the time the tech has  asked “why” five times, the root cause is usually discovered Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Examples of the Five Whys  As an example, an owner may state   that the vehicle does not start and the battery appears to be dead.  Applying the five whys: First why—What caused the battery to become discharged? To  answer this question requires observation and creating of a  hypothesis, such as “is the battery defective” or “did the  customer leave the lights on?” This requires questioning the  owner and testing the battery Second why—Assume the battery was in good condition but  discharged. Now the technician should ask the second why.  “Why did the battery become discharged?” A battery ignition  off drain test and testing of the charging system needs to be  performed. Assume the battery drain test was OK, but  the  charging system was not working OK Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Third why—The charging system was not working correctly. A  visual inspection found that the generator (alternator) drive belt  was not tight enough. The third why: “Why is the accessory  drive belt still loose?” Fourth why—“Why was the accessory drive belt loose?” The  cause could be a defective tensioner. If the tensioner was not a  problem, then another “why” needs to be asked Fifth why—If the accessory belt and tensioner were okay,  further investigation would be needed to find the root cause.  For example, “Is one of the tensioner retaining bolts loose,  maybe from a previous repair?” This could be the root cause Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 ENERGY PRINCIPLES Energy is the ability or the capacity to do work. Chemical,  mechanical, and electrical energy are the most familiar kinds  involved in automobile operation Energy is called kinetic energy if it is in the form of a moving object.  An example is a moving vehicle Potential energy is capable of being  changed to useful energy, such as  energy stored in a battery or a vehicle at the top of a hill In both of these cases, there is no  energy being released Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman Figure 13–1 Energy, the ability to perform work, exists in many forms ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 TORQUE Torque is the term used to describe rotating force that may or may  not result in motion, measured as force multiplied by the length of  the lever through which it acts. If a one­foot­long wrench is used to  apply 10 pounds of force to turn a bolt, then you are exerting 10  pound­feet of torque.  The metric unit for torque is Newton­meters 1 pound­foot = 1.3558 Newton­meters 1 Newton­meter = 0.7376 pound­foot See a conversion chart on Page 97 of your textbook Figure 13–2 Torque is a twisting force equal to the distance from the pivot point times the force applied expressed in units called pound-feet (lb-ft) or Newton-meters (N-m) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 10 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Relative intensity (loudness), using the decibel scale, includes the  following examples: Whisper 10–20 dB Normal conversation 60 dB Thunder 110 dB Threshold of pain 120 dB Acoustics  Is the study of sound and how it is generated and  transmitted. Acoustic engineers are employed by manufacturers to  help reduce noise and design methods to reduce or noise from  being transmitted into the passenger compartment According to acoustic engineers, about 80% of  noise created by  the movement of the tires on the road is transmitted through the  chassis and body of the vehicle 39 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Wear Hearing Protection According to audiologists (hearing and speech doctors), a person should wear ear protection if the level of sound requires that your voice be raised in order to be heard Any level that exceeds 90 dB requires the use of ear protection to avoid hearing loss This means that ear protection should be worn when using a power mower or using an air tool, such as an air impact wrench or air ratchet Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 40 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PLASTIC There are two basic types: Thermoset Plastic  This type of plastic is changed chemically  when cured and shaped. It cannot be reheated or reformed. Rubber  an example of a thermoset plastic material that cannot be remelted  and reformed after curing. Other examples of thermoset plastics  include: Bakelite (phenol formaldehyde resin) Polyester resin Epoxy resin 41 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Thermoplastic  Flexible at room temperature. Thermoplastic can  be recycled by grinding it into pieces and remolding it into  another shape. Examples of thermoplastics include: Polyethylene (PE) Polystyrene (PS) Polyvinyl chloride (PVC) PA nylon (polyamides) ABS (acrylonitrile butadiene styrene) Plastic Identification  While it is not important for the average  tech to know what kind of plastic is being used for an application,  it is important to know when restoring a part or refinishing a  plastic part. For example, interior parts can be made from: Polypropylene plastic (PP) Polyethylene (PE)  ABS plastic ABS/PVC plastic Vinyl (PVC) plastic 42 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Most large plastic pieces are labeled on the inside with letters,  such as PP or PE. If no marking is visible, it is still possible to  identify the type of plastic using a simple basic test Often replacement plastic parts are available in only one color and  must be painted to match the original. A burn test is used to test if  the plastic part Step #1  Remove a small piece from a hidden back side of the  plastic part being tested Step #2  Hold the small piece of plastic with tweezers and ignite  the plastic Step #3  Observe the burning of the plastic: • No visible smoke means that the plastic is  polypropylene • Visible black smoke means that the plastic is ABS Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 43 Continued ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Step #4  To determine if a part is polyvinyl chloride, a copper  wire test is performed. Heat a copper wire and touch the heated  wire to a hidden surface of the part. After melting some plastic  onto the wire, return the wire to the flame and observe the color of  the flame. If the color is green/blue or turquoise, then the plastic is  polyvinyl chloride (vinyl) After the plastic has been  identified, check service  information and paint  literature to determine the proper paint and  preparations needed to  refinish the plastic part Figure 13–12 This interior plastic part is labeled PE-HD, which means polyethylene-high density Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 44 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 IRON AND STEEL Iron is a chemical element with a symbol of Fe. One of the most  commonly available elements on earth, refined from iron ore Steel is made from iron, the between iron and steel being the  amount of carbon. Carbon is critical to the strength and other  characteristics of iron and steel Cast Iron  Contains 2% to 4% carbon, usually in the shape of  flakes of graphite 0.001 to 0.004 inches long. Cast iron is used in  engine blocks, rear axle assemblies, and suspension components Ductile Cast Iron  In ductile iron, the carbon in the alloy with  silicon are small ball­shapes called spheroidols. Ductile iron is  also called malleable iron and is used to make crankshafts 45 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Gray Cast Iron  Gray cast iron is cast iron that has silicon in the alloy giving the metal a gray color. Gray cast iron is used for  engine blocks NOTE: Cast iron contains graphite, which acts as a lubricant when being  machined. As a result, cooling oil or water is not needed when making cast  iron brake rotors or brake drums Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 46 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SAE STEEL DESIGNATIONS Steels are designed by a system established by the SAE and  includes numbers to indicate the main element used in the alloy,  plus the “parts of carbon” each equal to 0.01%. 100 parts of  carbon is equal to 1%. The percentage of carbon in steel has a  huge input on the strength and characteristics of the steel Mild (low carbon) steel  has less than 20 parts of carbon  (0.02%). Soft and easily formed; not very strong. Common  usage is in vehicle body parts where strength is not an issue Medium carbon steel  usually between 25 and 50 parts carbon  (0.25% and 0.50%). This type can be heat treated to create steel  that is ductile (flexible) and has good strength. Usually used in  forgings and machined components 47 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 High carbon steel  usually between 60 and 100 parts (0.60 and  1.00%) carbon and is very strong. Commonly used in vehicle  springs and can be hardened CAUTION: Both medium carbon and high carbon steel can be hardened  by heating and then cooling, using water or oil to rapidly cool the metal.  Therefore, if heating any metal, always allow it to cool slowly to avoid  changing the hardness of the steel 48 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The SAE numbering designation includes four numbers: 1xxx plain carbon steels 2xxx nickel steels 3xxx nickel­chromium steels 4xxx molybdenum steels 5xxx chromium steels 6xxx chromium­vanadium steels 7xxx tungsten­chromium steels 9xxx silicon­manganese steels A common alloy for forged crankshafts is SAE 4340. The analysis  of this designation is: 4340—An alloy containing 1.82% nickel,  0.5% to 0.8% chromium, 0.25% molybdenum, 40 parts of carbon Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 49 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 ALUMINUM AND ALUMINUM ALLOYS Aluminum is a lightweight metal used in many applications,  including suspension components, engine blocks, and cylinder  heads. It is almost always combined with small quantities of other  metals to form an alloy, using copper, manganese, zinc, or silicon.  Aluminum and alloys that are mechanically shaped are called  wrought alloys and are labeled according to the International  Alloy Designation system. The system uses a four­digit number,  which identifies the alloying elements, followed by a dash (­) and  then a letter identifying the type of heat treatment.  The numbering system for cast aluminum alloy is similar but is  designed by standards of the Aluminum Association (AA) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 50 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY Energy is the ability to do work. A vehicle in motion represents  kinetic energy which must be absorbed by the braking system  during a stop Torque is a twisting force that may or may not result in motion Work is actually accomplishing movement when a force is  applied to an object Power is the rate of doing work 51 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) Horsepower is the power it takes to move 550 pounds, one  foot in one second or torque RPM 5252 Kinetic energy is the energy of mass in motion Mechanical principles include levers, pulleys, and screws Heat is measured in BTUs and temperature is measured in  degrees The pH of water is 7 with acids being lower than 7 and  caustic chemicals higher than 7 Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 52 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 53 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458