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Fuel Efficient Car -- Team Crocodile and Shell Ecomarathon
www.tcm.phy.cam.ac.uk/Team_Crocodile
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There are a wide variety of cars on the road today, from the high-cost and
high-speed Ferrari to the run-about Fiesta. The choice of car can depend on
factors such as cost, colour, parking space required and safety. Until the end
of the 1960's fuel efficiency was generally not considered important; petrol was
cheap and plentiful. However, an oil crisis developed in the early 1970's, forcing
the car industry and petrol companies to think about the possibility of only having
access to a limited amount of petrol at high cost. Drivers began to think more
about the cost of driving. In the 1980's and beyond the effect of greenhouse gases,
so of which are produced in part by car exhaust fumes, caused people to think
more deeply about the pollution produced by car use.
The answer to these problems lies in better fuel efficiency. The modern world
cannot function without goods being transported along roads, and many people live
a great distance from their place of work. Public transport can help many people,
but it cannot solve every transport problem.
Table 1 shows comparisons between a high-speed racing car, a sports car, a
standard family car and the Team Crocodile fuel-efficient car. Speed is not
always the most important thing to look for when choosing a car; some cars cannot
travel very far on the amount of petrol that an average family can afford.
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Table 1: Comparison of maximum speed and fuel efficiency for different
types of car.
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Type of Car
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Maximum Speed (miles/hour)
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Efficiency (miles/gallon)
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Formula 1 Racer
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185
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2
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Sports Car
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130
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35
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Family Saloon
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90
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50
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Team Crocodile Fuel-Efficient Car
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35
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2,800
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Figure 1: Team Crocodile fuel-efficient car and driver.
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To make a car more fuel-efficient we need to understand the scientific basis of
factors that affect the fuel-efficiency of the car, and have the technology to put
this knowledge to use. The major factors that affect the fuel-efficiency of cars
are:.
Friction:
How much grip is needed to help the engine push the car along? When is there too
much grip, slowing the car down? Are the car tyres made out of soft or hard rubber?
Aerodynamics:
What is the best shape for a high-efficiency car? What affects the stability
of the car?
Weight and Power:
What is the most appropriate engine size? A large engine may give extra power,
but is all that extra weight a good thing?
Technology:
What are the best materials to use for different parts of the car
(e.g. tyres, body shell, axle and bearings)? Why?
The Team Crocodile car was constructed with a great deal of help from the
University of Cambridge Engineering Department, where Dr. Alan Organ and his
colleagues devise student design projects to develop specific chassis structures
and body shell aerodynamics. Their models were tested in wind tunnels and the
final design was then constructed by the technical staff. The car chassis is
made from 25mm square Dural tubing (Dural is an aluminium-based alloy) and Dural
sheet to give a light but strong construction. The body shell is made from
fibreglass, which is light and smooth and easily shaped. The tyres are Michelin
(20" x 1 ¾") The brakes are calliper brakes, similar to those found on bicycles.
The Shell Eco-Marathon is a competition that has been held in the UK for over
20 years. The challenge of the competition is to build a vehicle powered by an
internal combustion engine to carry a passenger as far as possible on one gallon
of fuel. It is a world-renowned international competition in which schools,
colleges, universities, companies and individuals take part.
In the competition cars are required to drive at an average speed of at least
15 miles per hour for six laps around Rockingham racetrack, which is a total
distance of 10 miles. At the end of the six laps the amount of petrol used is
measured. The fuel-efficiency of the car can then be calculated.
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Figure 2: Team Crocodile fuel-efficient car at Rockingham Motor
Raceway, June 2001
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In 1998, our first attempt in the competition, Team Crocodile achieved 2nd place
in the "newcomers" category. The efficiency of the Team Crocodile car was found to
be 2,101 miles per gallon. This represented an overall position of 9th in the UK,
and 22nd in the world. This was an excellent result, especially considering that
the winning team had over £1,200,000 support from the car industry and achieved
an efficiency of 9,472 miles per gallon. In 2002, Team Crocodile were placed
5th in UK, and 6th in the world, having increased their fuel-efficiency to
2,712 miles per gallon. The winning team in 2002 had over £2,500,000 support
from the car industry and achieved an efficiency of 10,240 miles per gallon.
The results of our entries in competitions in 2003 will be available at the
Physics at Work 2003 Exhibition, and on our website.
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