Download L3 Advanced Technical Extended Diploma in Land

Qualification title: 0171-38
Level 3 Advanced Technical Extended Diploma in
Land-Based Engineering (1080)
Test title: External test 011
Version: Sample for submission
Base mark: 80
Proposed grading boundaries: p/m/d
Duration: 90 minutes
Question 1
Identify the components of a drum braking system on the illustration below. (2 marks)
http://www.infovisual.info/05/013_en.html
Answer
x1 mark for 3 correct answers, x2 marks for 6 correct answers. Max x2 marks
1: drum
2: pad or friction lining
3: adjustment spring or return spring
4: adjuster, screw or nut
5: cylinder, piston, ram or actuator
6: shoe.
Test spec reference: Unit 354
Total marks: 2 marks
1
Question 2
Modern tractors are typically fitted with oil-immersed disc braking systems, which are
enclosed inside the transaxle housing. The brake actuation system is different to that
employed in external disc braking systems.
a) State two functions of oil in an immersed braking system. (2 marks)
b) State what happens when the brakes are actuated in an oil-immersed multi-disc braking
system on a modern tractor. (3 marks)
c) i) State a common source of premature brake wear in a modern tractor with an oilimmersed multi-disc braking system. (1 mark)
ii) Describe how premature brake wear can be avoided. (1 mark)
d) Explain the benefits of split/dual brake pedals to modern tractors. (3 marks)
Answers
a) x1 mark any two of the following, maximum x2 marks
 to help cool the brakes/components
 to dissipate heat
 to reduce wear
 to prevent excessive wear.
Sample answer
b) The brake linkage moves which causes the two expander plates to rotate in opposite
directions through a few degrees.(1)
This causes steel balls located in grooves between the expander plates to move along the
grooves. (1)
The expander plates are forced about to push against the rotating brake discs, forcing
them against the outer stationary plates. (1)
c) max x1 mark from ci) and max x1 mark from cii) answers must agree (A & A or B
& B)
i)
A - Trailing a loaded machine with no brakes or badly worn/adjusted brakes.
B - Not driving with due care/not anticipating hazards.
ii)
A- Ensuring that the brakes on the trailer, tanker or other trailed
implement/machine are adjusted and are working properly.
B - This can be avoided by changing driving habits.
d) Split brake pedals allow the operator to apply the brakes to one wheel when turning while
doing some types of low-speed field work. (1)
Approaching the headlands when doing field work and depressing one brake pedal will
cause one rear wheel to brake (lock up) and can help the tractor turn around more
sharply. (1)
This saves time by not having to shuttle back and forth to complete a manoeuvre. (1).
Test spec reference: Unit 354
2
Total marks: 10 marks
Question 3
Name the equipment which is used to test the condition of the electrolyte in a lead-acid battery (1
mark)
Answer
Hydrometer
Test spec reference: Unit 355
Total marks: 1 mark
Question 4
State the type of acid that is normally found in each cell of an automotive (tractor) lead-acid
battery. (1 mark)
Answer
Sulphuric acid
Test spec reference: Unit 355
Total marks: 1 mark
Question 5
The fundamental principle that underpins the operation of an automotive (tractor) leadacid battery is electro-chemical energy.
What fundamental principle underpins the operation of a solenoid or an electric motor? (1 mark)
Answer
Electro-magnetic energy/electro-magnetism
Test spec reference: Unit 355
Total marks: 1 mark
Question 6
a) Explain how a solenoid works. Make reference to the operation of the principle
components. (3 marks)
b) Explain how a DC electric motor works. Make reference to the operation of the principle
components. (3 marks)
c) Outline how a DC electric motor and solenoid combine to form a starter. Make reference
to the engine component that the starter engages with. (3 marks)
Model answers
a) The operation of a solenoid uses a magnetic field to create (lateral) movement of a
physical component. (1)
A metal core, used by the electromagnet to strengthen the magnetic field is positioned so
that it is partially outside the electromagnetic coil and free to move in and out. (1)
When the coil is energized (by passing an electric current through it), the magnetic field
draws the armature into the centre of the coil.(1)
3
b) Electric motors use magnetic fields to create rotary movement. (1)
The main components (armature and field) contain electromagnets. (1)
The interaction between the stationary field coils and the moveable armature coil causes
the armature to rotate. (1)
c) A starter switch or key allows a small current to flow to a starter solenoid relay and
operate a plunger attached to a drive pinion engagement lever. (1)
The plunger movement engages the drive pinion with the ring gear and closes a set of
contacts. (1)
This allows a large current to flow from the battery to the starter motor, rotating the
armature and drive pinion, and causing the crankshaft to spin.(1)
Test spec reference: Unit 355
Total marks: 9 marks
Question 7
State a function of a transistor in an electric/electronic system in a modern tractor. (1 mark)
Answer
x1 mark any one of the following, maximum x1 mark
 amplify a signal
 switch a signal
 routes signals based on polarity.
Test spec reference: Unit 356
Total marks: 1 mark
Question 8
A thermistor is a type of resistor. It is commonly used in modern automotive (tractor)
applications.
State the cause of changes to a thermistor’s resistance. (1 mark)
Answer
Temperature
Test spec reference: Unit 356
Total marks: 1 mark
Question 9
A capacitor is frequently used in automotive (tractor) electric/electronic circuits.
State its function. (1 mark)
Answer
x1 mark any one of the following, maximum x1 mark
 stores energy
 store electrical energy
 stores an electrical charge.
Test spec reference: Unit 356
4
Total marks: 1 mark
Question 10
An oscilloscope can be used by a service engineer to assist in diagnosing faults,
typically in electronic engine management systems.
a) What does an oscilloscope measure? (1 mark)
b) How is this information relayed to the user? (3 marks)
Answers
a) Voltage changes over time.
b) the results are shown on a display (1)
time (seconds) elapsed is indicated on the X-axis (1)
voltage is indicated on the Y-axis. (1)
Test spec reference: Unit 356
Total marks: 4 marks
Question 11
Input devices in an engine management system send signals to the engine’s ECU.
Describe the difference between an analogue signal and a digital signal. (2 marks)
Answer
x1 mark for each answer, max x2 marks
 An analogue signal is a signal that represents a continuously changing, variable voltage.
 A digital signal is a signal that represents only two voltage levels.
Test spec reference: Unit 356
Total marks: 2 marks
Question 12
Explain the role of a throttle positon sensor as an input device in an electronic management
system.
Make reference to signal types, signal variance and how it interacts with the engine’s ECU. (6
marks)
Model answer
Its role is to communicate the position of the throttle to the engine’s ECU or the vehicle’s
electronic management system. (1)
In so doing, it is communicating the driver’s intention to the ECU or the vehicle’s electronic
management system.(1)
The throttle position sensor incorporates a variable resistor, which effectively changes the
sensor’s resistance. (1)
The voltage produced by the sensor is continuously variable (analogue signal), which can vary
from 0 to battery (full) voltage.(1)
Depending on the throttle position (and hence the sensor’s resistance), a signal will be sent to the
vehicle’s electronic management system. (1)
5
This information is used by the vehicle’s electronic management system (by using its internal
look-up tables) and it decides on an action based on this input. (1)
Test spec reference: Unit 356
Total marks: 6 marks
Question 13
Name the hydraulic component represented by the symbol below. (1 mark)
Answer
Filter with a bypass/by-passed filter
Test spec reference: Unit 357
Total marks: 1 mark
Question 14
Name the hydraulic component represented by the symbol below. (1 mark)
Answer
Bi-directional pump
Test spec reference: Unit 357
Total marks: 1 mark
Question 15
State the SI unit for pressure. (1 mark)
Answer
Pa/Pascal
Test spec reference: Unit 357
6
Total marks: 1 mark
Question 16
Closed-centre, load-sensing hydraulic systems are now commonplace on highhorsepower, high-specification tractors. The piston-type, swash-plate pump is typically
an essential component in a closed-centre, load-sensing hydraulic system in a modern
tractor.
a) Explain how a piston-type, swash-plate hydraulic pump works. (4 marks)
b) Describe two advantages of a piston-type, swash-plate pump over a simple gear pump
on a tractor (2 marks)
c) Explain how a load sensing line can be used to control the output of piston-type, swashplate pump. (3 marks)
Answers
a) Model answer
A piston-type, swash-plate hydraulic pump varies its displacement (volumetric output) by
altering the angle of its swash-plate. (1)
The swash-plate itself does not rotate.(1)
The greater the angle of the swash plate, relative to the drive-shaft, the further the
pistons stroke in and out (1) therefore the greater the fluid flow.(1)
b) 1 x mark for any two of the following; maximum two marks
 only pumps oil around the system when it is needed
 potential to save fuel
 potential to reduce noise
 potential to reduce the build-up of heat
 potential to reduce wear on some hydraulic components.
c) Model answer
When the system demands oil flow, the pump delivers only the flow required by the
system, this happens when oil flows through the load sensing line.(1)
This, in turn, causes the swash-plate to move.(1)
The amount of oil pumped depends on the position of the swash-plate.(1)
Test spec reference: Unit 357
Total marks: 9 marks
Question 17
Electronic control systems are integral parts of modern tractors and land-based
machinery. Such technology has brought about improvements in performance but also
brings challenges for the land-based service engineering industry.
Discuss how electronic control systems have brought about improvements in engine
performance. Also discuss the challenges brought about by the adoption of electronic control
systems:
Model answer:
1b) Answer:
Band 1: 0 – 3 marks
7
Basic discussion, showing some understanding of electronic control systems. There will be little
or no specialist terms. Answer will only consist of description of electronic control systems.
Answer may be disorganised and ambiguous.
Band 2: 4-6 marks
Some discussion, showing an understanding of electronic control system and the benefits of the
system. There will be some use of specialist terms, although they may not always be used
appropriately. The information is presented mostly in a structured format.
Band 3: 7-9 marks
Thorough discussion, showing a clear understanding of electronic control systems and a
balanced evaluation including both benefits and challenges of the system. Specialist terms will be
used correctly and appropriately. Information will be presented in a structured format.
Indicative content
Improvements
 Tighter control of engine parameters/performance, leading to improved fuel
consumption.
 Greater control of the engine, allowing for automatic load/cruise control and automatic
control of the tractors (electronic) transmission/gearbox
 Facilitates compliance with stricter emissions controls, making the engine more
environmentally friendly.
 Facilitates the use of electronic fault diagnosis equipment (scan tools and diagnostic
equipment), which allows service engineers to interrogate and fault-find without having
to remove major components first.
 Facilitates the use of electronic fault diagnosis equipment (scan tools and diagnostic
equipment), which allows service engineers to interrogate and fault-find without having
to remove major components in the first instance.
Challenges
 Electronic monitoring and control system can fail, requiring specific training/expertise to
fix or repair (or even diagnose the problem in the first instance).
 Diagnosis of repairs involving electronic monitoring and control systems may require
proprietary diagnostic equipment (manufacturer-specific scan tools, etc), which might be
costly (or might only be available to franchised dealers or authorised agents, etc).
 Diagnostic scan tools may require ongoing software updates, which can be costly. Older
software may not be compatible with some modern tractors, etc.
Test spec reference: Unit 356
8
Total marks: 9 marks