Assignment for Engineering Education Studies 2

1. EDUC6505 Assignment 3
CASE STUDIES
Abstract: Concepts relevant to fluid mechanics are introduced.
A range of applications of hydraulics in transport and lifting
devices are examined.
Innovations in braking systems and lifting devices are discussed.
Anton Taverne

2. The Use of Fluid Mechanics in Braking Systems
Fluid statics Fluid dynamics
At rest
In motion
Fluid Mechanics
- the study of liquids and gases
Pressurised air Pressurised liquid
Pneumatics Hydraulics

3. Fluids can be liquids or gases
Liquids take the Gases fill the
shape of the container by
container diffusion
Liquids - Hard to compress Gases - Easy to compress

4. Liquids display capillary action and
surface tension

5. Pressure in fluids
Pressure = Force / Area
Fluids exert pressure in all directions, and
perpendicular to walls of container.
In a static fluid (i.e. gas or liquid), the pressure at any
point will, as a result of gravity, depend on the depth.
The more fluid there is above a point, the greater the
pressure

6. Pascal’s Principle
Any change in pressure, from the application of an external force, results in the same change of
pressure anywhere in an enclosed static fluid.
This is Pascal’s Principle and is the basis for hydraulics and pneumatics.
In the hydraulic press shown, the input pressure = the output
pressure, so F1 / A1 = F2 / A2
This allows a small force
(e.g. a foot on a brake pedal)
to become a much larger force
(e.g. pushing a brake pad against a brake disc)
Basic hydraulic systems include :
a fluid (such as oil)
a reservoir
a means of increasing the pressure (such as pushing a pedal)
a valve to control the direction of flow
a method for relieving any excess pressure
an actuator (e.g. the pistons pushing against a brake shoe)
filters to remove dust or metal particles
http://hyperphysics.phy-astr.gsu.edu/hbase/pasc.html

7. A comparison of Hydraulics and Pneumatics
Hydraulics (liquids) Pneumatics (gas)
All force is directly transferrable. Liquid Gas absorbs excess force, so less damage by
does not absorb any supplied energy shock. Less maintenance.
Capable of much higher loads
Minimum spring action
More immediate response when effort Need to bleed off excess pressure
is applied / removed
Oil used is flammable, but also No fire risk
protects parts
Compressed gas can be stored. No need for
electricity
http://en.wikipedia.org/wiki/Pneumatics

8. Archimedes principle
The buoyant force on a submerged object is equal to the weight of the liquid displaced by the object.
A solid object placed on a liquid will push down on it, displacing it.
The displaced liquid is also pulled down by gravity and will, by pushing other liquid particles, apply an upward
force on the solid. The denser of the two will apply the greater force.
As a result, a solid object partially or wholly submerged in a liquid will experience an upward force (the
buoyant force) that is equal to the weight of the liquid that the object has displaced. If the object floats, its
mass will equal the mass of the liquid displaced by it.

9. Braking systems
One purpose of any braking system is to prevent something from moving.
The second is to reduce a moving object’s kinetic energy (KE = ½ mv2) by reducing its velocity.
The work done in achieving this is given by W=Fd.
A force F needs to be applied over a distance d (the stopping distance of the object).
Often this force is frictional:
the kinetic energy is converted to heat by two surfaces rubbing against each other.
Alternatives include
• electromagnetic braking (the production of eddy currents and hence magnetic fields when metal wheels spin
in an applied magnetic field) used in trains
• regenerative braking (using the kinetic energy to produce electricity to charge a battery) used in hybrid cars
• reversing the direction of spin of propellers or using propellers at the front or sides of ships
• firing retro rockets (space crafts)
• extending the wing flaps of aeroplanes.

10. Braking Systems
As the Kinetic Energy depends on the mass of the vehicle,
the braking force for a bicycle will be much less than that of a
train or truck moving at the same speed.
Ideally, a braking system will start to respond instantaneously
to the driver’s input, reduce the velocity smoothly over a
very short distance, and require minimal physical effort from
the driver.
A brake can be applied by squeezing hand-grips, pressing
pedals or pushing a button.

11. Mechanisms
Methods for transferring the force (or signal) from the driver to the braking mechanism include:
Mechanical linkages
Bowden cables
Hydraulic cables
Electrical cables

12. Brake Types

13. Air Brakes
Heavy vehicles such as trucks and buses typically use air brakes.
The high pressures needed to stop such heavy vehicles with hydraulics-
based braking can lead to catastrophic leaking.
The slide valve controls which way the pressure is directed.

14. Safer Braking
ABS
To brake effectively, the brake should not lock. If the wheels stop turning
while the vehicle is still in motion, the driver loses control over the steering as
the tyres glide over the road. Anti-lock Braking Systems adjust the pressure
on each brake so that the wheels stop quickly but smoothly. Prior to the
introduction of ABS, good drivers knew to “pump the brakes”.
ESP
To calculate how much braking force is needed, a vehicle needs to be
equipped with an Electronic Stability Program (ESP). The ESP maintains the
stability of the car during braking with the aid of different sensors integrated
into a vehicle.
An Electronic Stability Program maintains the stability of a car during braking.
A range of sensors in the vehicle provide data which is used to adjust the
braking effect of each wheel.

15. Vacuum Boosters
Braking can be assisted by making use of the partial vacuum in the exhaust manifold of petrol-driven cars
(or a vacuum pump in diesel-driven buses).
When the brake pedal is pressed, air at atmospheric pressure is let into the booster unit by a valve.
http://auto.howstuffworks.com/auto-parts/brakes/brake-types/power-brake2.htm>

16. INNOVATION
Innovations in brake technology aim to facilitate one or more of the following:
Brake energy recuperation
Lighter vehicles
Efficient, controlled braking on increasingly crowded roads
One such innovation combines “brake by wire” (using electronic signals)
with Electronic Wedge Braking (EWB)

17. Electronic Wedge Braking
Electric motors (3, 4)
move the brake pad (2)
using a series of rollers (5)
that move along wedge-shaped surfaces (6).
This immediately brakes the rotating disk (1).
http://www.zigwheels.com/news-features/auto-insight/brakebywire-technology-
the-future-of-automobile-braking-system/10519/1>
Every 10 milliseconds a set of sensors measure the speed of the wheel, the forces on the
brake and the wedge’s position.
Under software control, the electric motors then adjust the position of the brake pad.

18. Electronic Wedge Braking
http://www.zigwheels.com/news-features/auto-insight/brakebywire-technology-
the-future-of-automobile-braking-system/10519/1
Pressure from the wedge on the disk applies the brake.
The disk’s rotation drags the wedge with it, enhancing the braking, so the EWB needs less energy
than hydraulic braking systems.
A common drawback of vacuum boosted brakes is the ease with which locking can occur.
This locking is considered an advantage in EWBs, as the wedge’s position can be so finely adjusted.
The wedge is pulled in just enough to achieve the desired braking.
It is prevented from being fully dragged in and locking the wheel.

19. Advantages over conventional hydraulic braking systems
As the activation of the brake is done within the wheel assembly itself, the system is a bolt-on and plug-in assembly
without the need for vacuum boosters and brake fluid reservoirs (freeing up space in the engine compartment) or the
hydraulic connection between the brake pedal and individual wheel brakes.
It allows a quicker response – it can take up to a second for the brake signal to reach a rear trailer in trucks fitted with
air brakes. (Aschenbrenner)
Conventional ABS typically take around 150 ms to generate full braking power. The EWB only needs around 100 ms.
( Aschenbrenner)
It is “less expensive and more efficient than conventional hydraulic systems.” (Aschenbrenner)
It has smaller dimensions and therefore reduces total vehicle weight.
The EWB’s software can help bring the vehicle to a smooth halt by reducing the braking force just before it stops, and
can prevent the vehicle from reversing while pulling away up a hill.
The concept of using a wedge
is not new.
The ability to control its movement to the nearest micrometer
(using sophisticated sensors and electric motors precisely controlled by software)
is new.

20. Fluid mechanics in lifting devices
Usually the task of a lifting device is to raise an object with minimal effort.
This can result from changing the direction of a force
e.g. single pulley first-order lever
or by reducing the force needed by applying it through a greater distance
e.g. inclined plane

21. Car jacks and car hoists
When a car has a flat tyre, a simple mechanical car jack is used to raise one corner of a car.
Although such jacks have a significant mechanical advantage, there is still significant effort
involved.
They do not allow much working space under the car
and are not considered safe for that purpose.
(Oten: Lifting Devices)
The introduction of hydraulic car hoists, typically
electrically operated, provided a more rapid and
higher lift of the entire car, and a safer, more
comfortable work space for mechanics.
(Oten: Lifting Devices)

22. Elevators
As buildings have become taller, there has been a greater need for elevators.
Hydraulic elevators such as that show diagrammatically have a number of advantages.
There is no need for cables, pulleys or motors
above the elevator itself and there is no need for a
counterweight.
The telescopic, hydraulically controlled piston
takes up little space.
The pumping unit need not be near the shaft.
They are fairly cheap to install and run, but their
use is limited to low-rise buildings and relatively (OTEN Lifting Devices p. 46)
slow speeds

23. Cherry Pickers
Special platforms, lifted hydraulically, provide a safe working space for working
with power lines, or changing light bulbs in high places.
It reduces the risks associated with setting up and climbing ladders, and, when
not in use, take up limited space.
Tower Cranes
To build modern skyscrapers, building materials need to be lifted high into the air and moved
across floors. It would be very difficult to manoeuvre large cranes safely in our crowded
cities, so the cranes used for this are built on-site.
A Derrick crane sits on top of a tower.
As construction of the next building level
begins, the derrick crane is lifted on its
hydraulic legs, the crane is used to lift
materials to build the next layer to support
it, and the legs are retracted.
The crane’s tower can be strapped to the
existing building for safety.
On completion of the building, the tower is
dismantled in a similar fashion.

24. Innovation:
Problems with the use of tower cranes include the wind affecting the operation of
the jib, and torsion forces occurring in the tower.
These limit the possible size of the jib.
www.ggcrane.com/press/crane2-spring2010-lo.pdf
Cranes with two jibs were first patented in Gaspard Gillis in 1968, and were redesigned in
2008 by his son, in response to a greater number of large construction projects.

25. Two-Jib Crane
A central tower has two jibs, one on each side. Rotation of the jibs around the
tower is achieved with propellers (driven by electric motors) on the ends of the
jibs. These propellers also provide braking. The force to turn the jibs is not
applied at the tower, and less force is needed, saving energy.
Areas in which the two-jib tower crane represent an improvement on existing cranes include:
Longer jibs
Higher rotation speeds
Better braking power
Wind has less effect
Torsion is minimised
Improved work efficiency
Energy savings
www.ggcrane.com/press/crane2-spring2010-lo.pdf
Computer modelling studies conducted at the University of Alberta indicate the two-jib
crane can complete the same task as two separate cranes, but at half the cost.

26. Hydraulics in the aeronautical industry
The most important use of hydraulics in aircraft is moving the various control surfaces
in response to pilot input, to control the plane’s speed, orientation and direction.
Ailerons trailing edge sections near the ends of the wing that
help control roll (turning about the longitudinal axis).
Elevators hinged sections on the horizontal stabiliser (or tail
plane) that can lift or lower the tail, thereby
controlling the pitch (turning about the lateral axis).
A rudder the trailing edge section on the fin at the rear of the
plane. It controls yaw, the sideways movement of the
tail and nose (turning about the vertical axis).
Flaps trailing edge sections of the wings, closer to the
fuselage. These help control the lift and also help
slow down a plane after landing.

27. Hydraulics in the aeronautical industry
In large commercial jets, flying at speed, the forces required to move these surfaces are enormous.
The hydraulic system’s components must therefore be able to withstand very high pressures.
At the same time they should be light weight (to maximize payload) and very reliable, as failure can
be catastrophic. Usually there are redundant systems in case of failure.
The constant vibrations in aircraft can lead to fatigue in materials, which must also be able to
withstand harsh operating conditions.
Hydraulic systems can also be found in:
the operation of external doors
dropping and raising the landing gear
shock absorbing struts

28. Part of an aircraft’s hydraulic system
Available from http://www.gen-aircraft-hardware.com/store.asp

29. Sources and references
Aschenbrenner, N(2005): “Pictures of the Future Fall 2005” retrieved on May 16th, 2012 from
http://www.siemens.com/innovation/en/publikationen/publications_pof/pof_fall_2005/auto_electroni
cs/braking_systems.htm
Copeland, P. L. (2005) Engineering Studies: The definitive Guide Volume 2 . (2nd ed.). Helensburgh, NSW: Anno
Domini 2000 Pty Ltd
Copeland, P. L. (2000) Engineering Studies: The definitive Guide Volume 1. Helensburgh, NSW: Anno Domini 2000
Pty Lt
Course Notes 2011: “1. Engineering Materials and Applications” EDUC6505 Engineering Education Studies 2
University of Newcastle
Gillis,P, Al-Hussein, M & Hasan, S (2010): “An Innovative Tower Crane: Tower Crane with Two Jibs” CRANE AND
HOIST CANADA, Vol 22, SPRING 2010 retrieved retrieved on May 27th, 2012 from
www.ggcrane.com/press/crane2-spring2010-lo.pdf
Metcalfe, P. & Metcalfe, R. (2009) Excel Senior High School Engineering Studies. (2nd ed.). Glebe, NSW: Pascal Press

30. Sources and references
OTEN “Aeronautical Engineering” (2000) Published by Learning Materials Production, Open Training and Education Network –
Distance Education, NSW Department of Education and Training, 2000. 51 Wentworth Rd. Strathfield NSW 2135.
Retrieved on May 4th , 2012 from
http://www.tale.edu.au/tale/components/includes/trap.html?uid=MzA2NkBUYUxFXzIwMDVfREVUTFJNX1Yy
OTEN “Braking Systems” (2000) Published by Learning Materials Production, Open Training and Education Network – Distance
Education, NSW Department of Education and Training, 2000. 51 Wentworth Rd. Strathfield NSW 2135. Retrieved on
May 4th , 2012 from
http://www.tale.edu.au/tale/components/includes/trap.html?uid=MjkzNEBUYUxFXzIwMDVfREVUTFJNX1Yy
OTEN “Lifting Devices” (2000) Published by Learning Materials Production, Open Training and Education Network – Distance
Education, NSW Department of Education and Training, 2000. 51 Wentworth Rd. Strathfield NSW 2135. Retrieved on
May 4th , 2012 from
http://www.tale.edu.au/tale/components/includes/trap.html?uid=MzA1OUBUYUxFXzIwMDVfREVUTFJNX1Yy
OTEN “Personal and PublicTransport” (2000) Published by Learning Materials Production, Open Training and Education Network
– Distance Education, NSW Department of Education and Training, 2000. 51 Wentworth Rd. Strathfield NSW 2135.
Retrieved on May 4th , 2012 from
http://www.tale.edu.au/tale/components/includes/trap.html?uid=Mjk3MEBUYUxFXzIwMDVfREVUTFJNX1Yy
http://hyperphysics.phy-astr.gsu.edu/hbase/pbuoy.html
http://en.wikipedia.org/wiki/Pneumatics

31. Additional images:
Bicycle – brake pads
http://www.google.com.au/imgres?q=images+bicycles&hl=en&sa=X&rls=com.microsoft:en-au:IE-
SearchBox&rlz=1I7ADFA_enAU475&biw=892&bih=549&tbm=isch&prmd=imvns&tbnid=LC3teuOR7IvPTM:&imgrefurl=http://www.pedalpushersonline.com/%3FCID%3D753
&docid=Z8kM5IVQELf_yM&imgurl=http://www.pedalpushersonline.com/images/bicycles_landing.jpg&w=420&h=296&ei=4nHBT8n-K-
miiAfN18ySCg&zoom=1&iact=hc&vpx=577&vpy=242&dur=1313&hovh=188&hovw=268&tx=139&ty=154&sig=107158942787319641740&page=10&tbnh=157&tbnw=223&s
tart=88&ndsp=9&ved=1t:429,r:5,s:88,i:295>
Bicycle – disc brakes
http://www.tale.edu.au/tale/components/includes/trap.html?uid=Mjk3MEBUYUxFXzIwMDVfREVUTFJNX1Yy
Drum brakes - car
http://www.google.com.au/imgres?q=images+car+brakes&hl=en&rls=com.microsoft:en-au:IE-
SearchBox&rlz=1I7ADFA_enAU475&biw=995&bih=549&tbm=isch&tbnid=LkhHuWv1B7MEtM:&imgrefurl=http://www.geddesautomotive.co.nz/brake-repairs-car-van-truck-
auckland-
01.html&docid=WBVvkEe79XSESM&imgurl=http://www.geddesautomotive.co.nz/Images/brake_lining01.jpg&w=640&h=480&ei=UHPBT97IBMegiQeiqPSNCg&zoom=1&iact
=hc&vpx=515&vpy=145&dur=3329&hovh=194&hovw=259&tx=73&ty=216&sig=107158942787319641740&page=2&tbnh=155&tbnw=191&start=18&ndsp=12&ved=1t:429,r
:2,s:18,i:114
Disc brakes - car
http://www.google.com.au/imgres?q=images+car+brakes&hl=en&rls=com.microsoft:en-au:IE-
SearchBox&rlz=1I7ADFA_enAU475&biw=995&bih=549&tbm=isch&tbnid=29cGvdEXmAKVfM:&imgrefurl=http://hillsidetireauto.blogspot.com/2011/06/your-car-brakes-
and-vehicle-braking.html&docid=fO0pViH2yMe9iM&imgurl=http://1.bp.blogspot.com/-
sqj4r_VMhFY/TgzhL4bf5JI/AAAAAAAAABg/sYic89u0YIM/s1600/brakes%252B3.gif&w=406&h=336&ei=UHPBT97IBMegiQeiqPSNCg&zoom=1&iact=hc&vpx=107&vpy=109&d
ur=234&hovh=204&hovw=247&tx=101&ty=83&sig=107158942787319641740&page=2&tbnh=152&tbnw=184&start=18&ndsp=12&ved=1t:429,r:4,s:18,i:119
Hydraulics diagram
http://www.google.com.au/imgres?q=images+car+brakes&hl=en&rls=com.microsoft:en-au:IE-
SearchBox&rlz=1I7ADFA_enAU475&biw=995&bih=549&tbm=isch&tbnid=BWFhi6090E0YmM:&imgrefurl=http://www.carbibles.com/brake_bible.html&docid=XI9qN2rOfYw
g-
M&imgurl=http://www.carbibles.com/images/singlecircuitactuator.gif&w=466&h=300&ei=UHPBT97IBMegiQeiqPSNCg&zoom=1&iact=hc&vpx=277&vpy=148&dur=28703&
hovh=180&hovw=280&tx=147&ty=123&sig=107158942787319641740&page=3&tbnh=138&tbnw=215&start=30&ndsp=12&ved=1t:429,r:9,s:30,i:158
Air-brake schematic
http://www.google.com.au/imgres?q=images+air+brakes&hl=en&rls=com.microsoft:en-au:IE-
SearchBox&rlz=1I7ADFA_enAU475&biw=1028&bih=502&tbm=isch&tbnid=mvgtmircrE0w8M:&imgrefurl=http://www.railway-technical.com/air-
brakes.shtml&docid=lWuvZJqPqnQL9M&imgurl=http://www.railway-technical.com/airbra-
app.gif&w=714&h=418&ei=2HTBT8rACamSiQemzf3ACg&zoom=1&iact=hc&vpx=265&vpy=195&dur=9672&hovh=172&hovw=294&tx=170&ty=99&sig=10715894278731964
1740&page=2&tbnh=117&tbnw=199&start=9&ndsp=13&ved=1t:429,r:5,s:9,i:102
Servo brakes
http://auto.howstuffworks.com/auto-parts/brakes/brake-types/power-brake2.htm
Hydraulic aircraft component
http://www.gen-aircraft-hardware.com/store.asp