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At
each stage the bike was extensively trialled with wind tunnel
experiments, strength assessment and test riding by Australia's
elite cyclists. A major aim of testing is to show that less
power needs to be generated by the cyclist to move the Superbike
at a particular speed compared with a conventional bike.
Activity
Read the following paper Engineering
the world's fastest bicycle to
find out more about the testing carried out. This paper is
suitable for students of engineering studies.
See
the Milestones in design
development for a summary of the paper.
Testing
techniques explained
Wind tunnel testing
Activity
Look at the photo of the artificial
legs rig used in wind tunnel testing; then read the passage
below, summarising the information into points, for example:
- artificial
legs used to simulate rider
- rider's
legs influence flow pattern and drag
- rear
wheel driven by motor…
In
order to minimise aerodynamic drag, new and innovative wind
tunnel testing techniques were developed. This included the
use of artificial legs to accurately study the airflow over
the bicycle. With this unique rig the aerodynamics of the
complete system could be represented.
Initial
investigations showed that the rider's legs dramatically
influenced the flow pattern and resulting drag. To obtain
accurate and repeatable wind tunnel results with live
athletes was extremely difficult. The sensitive wind tunnel
balance required precise knowledge of the centre of mass
in order to apply corrections for induced forces due to
moment couples. In the development of the 'Superbike'
the rider was replaced with a pair of lightweight Styrofoam®
legs. A similar lightweight torso, head and arms could
also be fitted. The rear wheel was driven by an electric
motor beneath the wind tunnel floor. A simple belt drive
under the floor also drove the front wheel. By having
the motor and drive system part of the bicycle accurate
and repeatable drag measurement was possible. (Thompson,
1996: 2)
Finite
element modelling (FEM)
Activity
Look at the FEM diagram
and read the explanation of the diagram below.
The
FEM diagram in the article illustrates how load is distributed
throughout the monocoque shell. Prototypes were modified using
data from:
- the
mathematical performance model
- the
testing of properties and materials
- the
track tests and race data of athletes.
Maximum
load is indicated by shades of red, minimum load by blue.
In this image of a prototype the greatest load is in the curved
section of the shell.
Activity
| 1. |
Identify
another area of performance design that might use FEM
during development and prototype testing. Remember, the
performance goals were: |
- optimising
weight
- frame
stiffness
- aerodynamics.
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