1
Q
What is the purpose of steering?
A
Keep us in contact with the road???
2
Q
What are the types of steering system?
A
Rack-and-pinion steering system
Linkage steering system aka conventional steering system
3
Q
What are the advantages of the rack-and-pinion steering suspension?
A
Has fewer component parts = more precise and compact
4
Q
What happens when the rack and pinion teeth are the same size?
A
Input and output of turning are the same
5
Q
What was the rac modified to, in order to make turning easier?
A
Variable ratio rack
6
Q
What are the components of the rack-and-pinion steering rack?
A
Universal joints
Steering gear = contains pinion
Rack housing = prevents dirt
Boot
Tie rod
Ball joint
Steering knuckle
7
Q
What is the purpose of the boot?
A
Flexible, usually rubber tube, covers joint between rack and tie rods to stop dust and dirt getting in rack
8
Q
What is the purpose of the tie rod?
A
Transmits force from steering rack/centre link to turn steering knuckles?
9
Q
What is the purpose of the steering knuckle?
A
Transfers movement of rack via tie rod into change of wheel angle
10
Q
What connects the tie rods to the steering knuckle?
A
Lower ball joint
11
Q
What is the purpose of the swivel pin and what is it also known as?
A
Aka king pin
Connects the axle to the steering knuckle and allowing the wheels to turn
12
Q
How is the tie rod adjusted?
A
Locknut and thread
13
Q
What does adjusting the tie rod do?
A
Changes the angle of the front wheels = toe angle
14
Q
If the rack is the behind the wheel, how does increasing/decreasing tie rod length change toe?
A
Increase tie rod length = toe in
Decreased tie rod length = toe out
15
Q
What is the purpose of ball joints?
A
Ball joints allow linkage components to swivel freely
16
Q
What happens when tie rods wear?
A
Can cause wheel shimmy and rapid tyre wear
17
Q
Why is rack preload / yoke lash needed?
A
Allows for expansion in heat
18
Q
What can be used to adjust rack preload/yoke lash?
A
Yoke bushing = spring-loaded
Shims
19
Q
Why do off-road vehicles use the linkage steering system?
A
Because the rack can be HIGHER on the wheel
20
Q
Whare the components of the linkage steering system?
A
Steering gear/box
Drop arm
Centre link
Tie rods
Steering knucles
21
Q
What are the types of steering gear/box?
A
Worm gear
Re-circulating ball
Worm and roller (older vehicles)
22
Q
What is the purpose of the idler arm?
A
Keeps steering centre link parallel to front axle and prevents any unwanted flexing of steering component parts
23
Q
What does idelr arm work in tandem with?
A
Pitman arm
24
Q
What is the purpose of the steerng gear/box?
A
Converts rotation of steering shaft into angular movement of pitman arm
25
What is the difference between the wormshaft and recirculating ball steering box?*
26
How does the worm gear adjuster work?
27
What is free play?
28
How much free play for rack-and-pinion vs linkage steering?
13mm max. for rack-and-pinion
75mm max. for linkage system
29
What type of joints can we find in the steering column and why?
UNIVERSAL joints = allow steering shaft to change angles
30
What is found between the steering wheel and universal joint?
Collapsible section = helps prevent forces generated in an accident being transfered to the driver
31
What does the collapsible column work in unison with?
Airbag
32
What are the different types of collapsible section in a steering column?
Breakaway bracket
Bending bracket
Energy absorption
33
What are the two types of hydraulic power steering systems and how do they differ?
Hydraulic engine driven
Hydraulic electric pump
Engine driven takes energy off the engin and gives assistance at all times
While the electric pump doesn't use the engines energy and can turn itself off when assistance is not needed (high speeds)
34
What is the purpose of power steering?
Provide extra force ot help the driver turn the steering wheel
Espescially, at low speeds and in heavy vehicles
35
What generates the pressure in a hyrauslic power steering system?
Fluid pump aka power steering pump
36
Where the high pressure fluid flow after the fluid pump?
Passes through fluid lines to a control valve, connected to the steering wheel
The valve controls a hydraulic actuator connected to the steering mechanism
37
What else can the power steering pump power?
Hydraulic brake booster
38
What is the role of the (hydraulic) actuator?***
39
Describe where the engine-driven fluid pump is located and how it is driven
Usually mounted on the engine and driven by a pulley and rubber drive belt
40
Describe where the electric fluid pump is located and how it is driven
Mounted on teh bulkhead and driven by an electric motor
41
Where can the fluid reservoir be located?
Either built-in to the pump or remotely mounted via pipe
42
What is the most common type of power steering pump?
Vane type
43
How does the vane pump operate?
Pulley or motor drives the roto that sits off-centre in a cavity inside the housing
Fluid enters the pump
It is trapped between spring-loaded vanes
Carried to the exit port
44
What other accessories are driven by the engine drive belts?
Alternator
Coolant pump
45
What are the different types of drive belt profiles?
V or Poly-V with a matching pulley shape to provide grip
46
What is the drive belt made of?
Rubber and reinforced with steel wires
47
What pulley alignment must be checked in power steering?
Power steering pump shaft must be parallel to the crankshaft
Pump pulley must align correctly with crankshaft pulley
Straight edge can be used to check alignment
48
How does the power steering control valve work?
Valve seneses relative rotation between the input and output shafts, uses it to direct presure to the steering actuator
49
What is the role of the splines in the power steering control valve?
Splines set a limit on the maximum twist
In case the htinner shaft that connectes input/output shaft fails
50
How does the power steering system operate?
Power steering rack has integral hydraulic actuator
Control valve can direct pressurized fluid to either side of piston
When steering is turned, control valve detects steering effort and directs pressure to help push the steering rack piston along
51
What does it means if power steering is servotronic?
A speed-dependent power steering system that adjusts the amount of steering assistance based on the vehicle's speed
52
What is the role of the power steering fluid?
Transfers energy from the pump to the actuator
Also lubricates and cools the moving parts
53
How much power steering flud does the system typically hold?
1 L
54
What should power steering flud not be confused with?
Automatic transmission fluid (ATF)
Which is not compatible with poewr steering system components
55
When checking power steering fluid, what might you see?
Fluid should either be clear, pink, or red = good condition
Common for power steering fluid to turn orange
If it is very dark or has burned smell = needs replacing
56
When topping up power steering fluid, should the engine be on or off?
ON because otherwise it will show higher than when it is being used
57
What is the purpose of the ECU-controlled acutator?
Electrically vary the gear ratio between the input and output shaft to produce variable ratio steering
58
What is teh gear ratio variation between?
0.75 and 1.25 to 1
59
Disadvantags of hydraulic power steering compared to electrip power steering (EPS)?
Hydraulic = heavy, absorb engine power, prone to leaks
EPS = lighter, quicker to manufacture and easier to maintain
AND assists steering but only when required = increases fuel economy because it is not constantly absorbing engine power
60
Where are the 4 locations an electic power steering motor can be laced?
Upper steering column
Pinion shaft
Second pinion = driving a second set of teeth on the rack
Steering rack housing, driving the rack through a worm nut
61
What adjustments need to be made for an electric motor to drive steering system?
High rotation speed of electric motor needs ot be reduced inorder to drive a steering system
62
How can an electric motor be slowed so it can drive a steering system?
Collemn assiss and pinion assist layout = use a reduction gearbox with a worm gear on the motor shaft
If the motor is mounted on the rack houes = belt takes hte drive from the motor to a worm and nut on the steering rack
63
Where is the steering storque sensor mounted?
At the bottom of the STEERING column (input shaft)
64
How does the torque sensor operate?
Cicular, hollow electromagnet = fixed to output shaft
Hall Effect sensor sits inside = attached to input shaft
Sensor detects changes in teh magnetic field when input shaft twists relative to output shaft
65
What is a disadvantage of electric power steering?
Will not readily self-centre
Resistance caused by gearing means it takes a large amount of force from steering mechanism to make the motor turn
66
What factors does the ECU calculate to self-centre with EPS?
Steering torque input
Steering angle from centre
Rate of change of steering angle
Vehicle speed
67
What can electric power steering work in tandem with?
Automatic parallel parking
68
What are teh consequences of incorrect geometry?
Poor handling
Rapid tyre wear
Poor fuel economy
Oversteer
Understeer
69
Define directionally stable
This means that if there is a steering input, it should automatically return to the straight-ahead position when released
70
How is directional stability created on a car?
Steering axis intersects the ground ahead of the wheels contact patch
71
What type of caster angle is used on vehicle?
Positive caster angle
72
Decribe the design of roads?
Road Crown Effect = roads higher at centre than edge (central crown)
73
What type of cember is used in vehicles?
Negative camber = when top of sheel tilts inwards
74
What type of toe angle is ideal?
Zero toe
75
What are the toe angle of a front wheel drive vs rear wheel drive and why?
Front wheel drive (TOE OUT) = pulling car and wheel naturally pull inwards
Rear wheel drive (TOE IN) = pushing car and front wheel naturally are pushed outwards
76
What is the purpose of steering axis inclination (SAI)?
SAI causes the front of the vehicle to lift up if there is a steering input in either direction = creating directional stability
77
What is the inclination called on a HGV?
Kingpin Inclination (KPI) instead of steering axis inclinatoin (SAI)
78
What is the common centre point of all the wheels?
Centre of the turn is always in line with the rear wheels
79
When cornering, what happens to inner wheel vs outer wheel?
Steering must turn the inside wheel more than the outside wheel
80
What is athe Ackermann steering geometry?
Lies thorugh teh pivots of steering arms should intersect at the centre of the rear axle line
81
Define tracking
The ability of the rear wheels to folowin the tracks of the front wheels
82
What is a thrust line?
Indicates the direction the rear wheels are pointing
83
What two lines should be the same and why happens if they aren't?
Centre line and thrust line
If not, then this causes increased tire wear, low fuel economy, and poor handling
84
What does the front cradle hold?
Engine
Steering rack
Control arms in alignment with the frame
85
Why is front cradle geometry important?
Any movement or adjustment in the front cradle is likely to cause misalignment of the steering geometry
86
Define setback
Setback is a diagnostic angle that measures the difference in distances between the centers of the front wheels
87
What are the tread wear patterns of underinflated tyres?
The two outer parts of the tyre wear
88
the outer parts of the tyre wear of overinflated tyres?
The centre part of the tyre wears
89
What are the tread wear patterns of toe in/out problems?
One of the outer sides becomes worn
When caught early = chopped/feathered tread
90
What are the tread wear patterns of camber problems?
Tyres goes smooth early
91
What are the tread wear patterns of wheel balance problems?
Tyre wobbling = so driver will notice much earlier
92
What are the tread wear patterns of suspension problems?
Tyre will hit the road and so lumps will come out the tread
93
What should you do first in pre-alignemnt inspection?
First check tyres because it can affect how the car is sat on plates
94
How do you adjust CASTER?
By moving the control arm
Shims can be added or removed
Adjusting a strut rod
Turning an eccentric bolt
Moving shaft bolts in slotted holes
95
How do you adjust CAMBER?
Adjusted after caster has been set
Shims or slots are used to move the control arm out
Some strut types provide adjustments
The steering knuckle may be pivoted with eccentric adjusters
96
How do you adjust the TOE?
Track rod lengths are varied for toe adjustment
Track rod adjustment is dependent on where the track rod is situated, it could be either in front or behind the centre of the wheel
All track rods have an adjustment locking device for safety
Linkage type systems have adjustable sleeves
97
What steps are taken to adjust wheel alignment?
1. Pre-checks
2. Adjust rear axle first
3. Lock steering
4. Adjust front axle second
