alan mcnaughton design portfolio 2016
TRANSCRIPT
Alan McNaughton
Bachelor of Mechanical Engineering / Bachelor of
Commerce (Econometrics)
Monash University, Melbourne, Australia
2010-2016
Final Engineering Design unit: 91/100
Advanced Diploma of Engineering
Chisholm TAFE, Dandenong, Australia
2011
References (available upon request)
Formula SAE Experience: Monash Motorsport
2011
Suspension junior
Australasian pit crew and tool box
Australasian Champions 2011
2012
Manufacturing lead and TAFE manager
Formula student UK and Germany pit crew
Australasia Pit master
Suspension Design event
Australasian Champions 2012
2013
Suspension Leader
Rear Upright/Hub Design
Australasian Champions 2013
Alan McNaughton
Formula SAE Experience: Monash Motorsport
2015
Complete design of hydraulically interconnected suspension
Testing and troubleshooting of system
Research, benchmarking and concept generation relating to prototype
Outsourcing and manufacture of large subsystem
Assembly, testing and validation of concept.
The Brief
*Thanks to Jared Tyler for the image.
The Problem: Design the various
subsystems allowing forces to be
transferred to and from the sprung
mass and rear tyres.
The Objectives:
Support loads whilst not exceeding
maximum compliance values.
Minimise weight of final product
Utilise cost and manufacturing
resources efficiently
The Components:
Wheel hub assembly: Connects the
rotating wheel to the stationary
suspension and mounts brake rotor.
Upright assembly: Transfers loads from
wheel hub to chassis. Provides mounts
for the brake Caliper and wheel speed
sensor as well as allowing adjustment
of wheel alignment.
Upper Wishbone
Lower Wishbone
Shock Upright
Research - Operating Temperature
The outboard suspension provides a mounting point for
the various components of the braking subsystem
which operate at high temperatures. Physical testing
was carried out on a prototype vehicle to accurately
assess the temperature experienced at critical
locations.
There are a number of potential methods used to
measure the temperature reached by a component.
Direct simulation is time intensive while thermal-
stickers or pyrometers logged to the on-board ECU are
quite expensive. Thermal crayons were selected as they
represent the greatest freedom in test location, offer
suitable increments of temperature for the purpose and
were available at no cost.
Results revealed that the hubs reached up to 150
degrees Celsius and the uprights up to 120. Brake rotors
reached greater than 600 degrees ruling out direct
integration with an aluminium hub.
Figure 1: Results of test: the Hubs were found to reach between 120-150 deg
Celsius
Research - Forces
The basic loads applied can be
approximated by considering each part of
the system to be a rigid body.
An acceleration is assumed and the required
forces at each tyre calculated based on
simple vehicle parameters.
The generated forces travel from the tyre
contact patch through the wheel, hub,
upright and wishbones to accelerate the
sprung mass. By assuming that the A arms
react only force in plane, the load applied at
each ball joint may be calculated for
different accelerations. A similar approach is
used to find the hub forces with brake
torque applied to the rotor.
A parametric spreadsheet was used to allow
reduction of forces through geometric
refinement.
Figure 2: Free Body Diagram showing cross-section view of simplified rear right
outboard suspension.
Concept Generation
Concept selection is driven by two different sets of constraints: geometric and manufacturing resources:
Geometric
Large V small Bearing size
Brake rotor position
Minimum wall thicknesses
Packaging in wheel
Adjustability
Resources
Sponsored services
Man hours
Machining time/ difficulty
These constraints lead to 2 unique concept pairs of potentially equivalent specific stiffness and weight.
Fabricated steel upright with small diameter steel hub
CNC aluminium Upright with large diameter aluminium hub.
The 2nd concept was chosen, whilst slightly more expensive it significantly reduces the in house manufacture required freeing
resources to be used in other areas.
Material Selection
Figure 3: Summary of conditions and design stress for different combinations of components and materials
Having decided on a concept, suitable grades of aluminium are
compared. The selection is narrowed to 3 readily available
alternatives with 6061 being significantly cheaper than the
others.
2024-T4 is selected for both applications. Note that the
temperature testing allowed for localised design stresses leading
to more efficient designs
`
Figure 4b: Effect of temperature on Yield stress of various aluminiums
Figure 4a: Fatigue life of components at given stress levels for different grades of aluminium
Hand Calculations
Initial hand calculations provide the basis for all further analysis. A number of assumptions allowed some basic design
parameters to be calculated and their effect studied. As illustrated, the effect of increasing bearing size is to decrease
mass, inertia and deflection at the cost of increasing bearing mass and a thinner wall hub. 2mm was decided as the
lower limit to wall thickness to prevent buckling from stones and allow adequate bearing support.
Figure 5: Performance criteria as function of bearing size. Scaled to one graph for illustration purposes
0.000
1.000
2.000
3.000
4.000
5.000
6.000
7.000
8.000
9.000
10.000
0 20 40 60 80 100 120 140
Bearing Diameter
Performance Criteria
Mass/length(g/mm)
Mass Inertia(10000g*mm^2)
Min Wall Thickness(mm)
Deflection(deg*10)
Relative Bearing Mass
Hand Calculations
The range from 50-80mm bearings produces comparable mass estimates. From this, 70mm is the minimum
allowing integrated tripod housing within the hub which is desirable for loading, packaging and overall system
mass. 70mm is also the largest size requiring greater than 2mm wall thickness and so represents the best
trade-off of design requirements
Figure 6: Mass V Bearing size
0
200
400
600
800
1000
1200
1400
0 20 40 60 80 100 120 140
Gra
ms
Bearing diameter(mm)
Mass Vs Bearing size
Bearing mass
System Mass
Finite Element Analysis
Detail design using ANSYS allows accurate calculation
of stresses/deflections which are impractical to
calculate by hand. This requires careful consideration
of how to best represent reality in a computer model
whilst maintaining a reasonable solution time.
Considerable time was invested to ensure that the
forces/constraints/connections were representative
of the actual loading
Figure 7: Representation of applied forces
Figure 8: Stress analysis of upright clevis
Outsourcing and Manufacture
Figure 9: Hub Technical Drawings supplied to Marand
Providing technical drawings to a company that
usually manufactures fighter jets for the airforce
proved a challenge. As a result the quality of
drawings has significantly improved and a better
understanding of how the engineer can help the
machinist to manufacture a quality part was gained.
Outsourcing and Manufacture
With over 200 parts to be manufactured
it’s important to track which orders have
been placed and what information was
provided. The figure displays a quick
summary of the outsourcing required to
manufacture the upright subsystem.
Figure 10: Outsourcing overview for Upright
Validation
After each component was finished, it was
weighed and compared to original goals and
design mass. Other goals such as adjustment
time and manufacturing deadlines are also
validated. This allows for better estimations in
the future as well as highlighting any
advantages/disadvantages to the design that
were not previously considered.
The upright assembly was lighter than
expected and the hub assembly heavier so
that overall the total system was
approximately on target. The design
allowed a weight saving of over 17%
compared to previous years whilst still
maintaining compliance targets.
Adjustment times were also significantly
reduced and lock wiring of fasteners was
reduced to a single part of the subsystem not
requiring frequent servicing.
