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13/03/2013

SA university qualifies for German competition

Engineering News 22 February 2013                                By: Chantelle Kotzé

The racing team of Port Elizabeth tertiary education institution Nelson Mandela Metropolitan University (NMMU), NMMU Racing, will in August compete for the second time in the international design competition, Formula Student Germany (FSG), at the Hockenheim Formula One circuit, in Germany.

This year, the team has entered its electric racing car, DibaTwo GT, in FSG’s Formula Student Electric (FSE) event, for which it qualified last month. NMMU Racing previously competed in FSG’s 2011 Formula Student Combustion (FSC) event with its combustion car, DibaOne, which was placed sixty-sixth out of 78 vehicles.

NMMU Racing secured the thirty-eighth spot of 40 available positions for this year’s FSE event, with 75 teams qualifying for the FSC event, NMMU mechanical engineering lecturer and NMMU Racing formula student project manager Trevor Stroud tells Engineering News.

To successfully enter the competition, teams worldwide had to take part in an online regis- tration process, which opened at 13:00 on January 14. The process required the teams to answer about 20 questions that tested technical knowledge and understanding of the competition rules.

The design of DibaTwo GT started at the end of 2011, shortly after NMMU Racing returned from the FSC event, and incorporates all the lessons learnt during the construction of DibaOne, which was the university’s first attempt at building a car.

The most significant design characteristics of DibaTwo GT is the use of the 100 kW, 450 Nm brushless direct current (dc) electric motor powered by lithium polymer batteries, an aerodynamic body that incorporates front and rear wings and a Formula One-style under- body diffuser.

These technologies aim to increase the cornering of down-force and reduce the vehicle’s weight, aerodynamic drag, emissions, operating costs and energy consumption, says Stroud.

DibaTwo GT features a traditional racing car suspension layout, with double-wishbone suspen- sion, which operates pull-rods to fully adjustable coil-over dampers at the front and rear.

The main structure of DibaTwo GT is a tubular space frame that includes composite stress panels to increase the rigidity of the vehi- cle and reduce its weight. The body, wings and seat are of composite construction and incorporate carbon-fibre reinforcement, which is designed and manufactured in partnership with composites manufacturer Custom Works Composite Engineering.

DibaTwo GT’s tyres are purpose-built racing slicks, manufactured by tyre manufacturer Continental and imported specifically for NMMU Racing by Continental Tyre South Africa.

Once completed, the electric racing car will weigh about 70 kg less than DibaOne and will have a lower centre of gravity to enhance vehicle dynamics, a shorter wheelbase for better cornering and improved vehicle ergonomics to ensure easy control of the vehicle.

Further, DibaTwo GT will use comprehensive engineering simulation, physical component testing, strategic use of composites and integrated data acquisition to ensure that it performs at capacity.

Stroud explains that the development process of DibaTwo GT followed a similar path as that of an automotive manufacturer, which would first determine a design strategy and key design objectives – such as reduced weight, a lower centre of gravity, a shorter wheelbase and improved aerodynamics – before engineering the components in the virtual environment.

To ensure that the lightest and strongest components are engineered, the electric car’s components were modelled using Autodesk Inventor three-dimensional computer-aided design software, while engineering simulations were performed with MSC Adams motion-simu- lation software, MSC Nastran finite element analysis software and OptimumKinematics suspension kinematic optimisation software.

In addition, Star-CCM+ software was used to simulate the airflow over the vehicle to ensure that the front and rear wings and an underbody diffuser was designed to increase down-force, says Stroud.

During 2012, the frame, suspension and composite seat for DibaTwo GT were manufactured, while DibaOne was used to test the new technologies destined for DibaTwo GT.

The suspension, mechanicals and aero- dynamic components will be completed at the end of this month, which will be followed by a testing phase, notes Stroud.

The mechanical and aerodynamics testing will include a combination of track testing and wind-tunnel testing, in partnership with the Council for Scientific and Industrial Research. This involves calculating the best suspension settings to achieve a dynamically balanced racing car by correlating a computational fluid dynamics simulation with real-life wind-tunnel results from down-force and drag testing, explains Stroud.

The team plans to initially power the vehicle using the spare 600 cc combustion engine of DibaOne. On completion of the bench tests, which are under way, the dc motor will be installed in the car and tested between May and June this year to ensure that the system is as reliable as possible before the race.

Bench testing of the electric powertrain will include setting up the complete system, such as the motor controller and testing of the water- cooling and battery management system, to ensure optimum and safe operation of the lithium polymer battery cells under various load conditions.

The vehicle will finally be subjected to track testing of the entire system. NMMU Racing plans to run the vehicle through all the events experienced at the competition in 2011. This includes a 75-m-long acceleration test, a skidpan test, an autocross and a 22 km endurance test. These tests will enable the team to improve vehicle performance for each event and give the drivers an opportunity to familiarise themselves with the dynamics of the vehicle.

NMMU Racing needs to raise about R500 000 in addition to what has already been raised to complete the electric car as most of the funding will be used to buy the electric engine and lithium polymer batteries.

Hence, the team is exploring new sponsorship opportunities from local and international companies besides working with its current sponsors.

“We are determined to build on the ‘first South African University’ accolade to being the first student formula team from Africa to compete in the challenging FSE event and gain respect as one of the top teams in the world,” he concludes.