Tools 0 to 100 km/h in under 4 s

| Author / Editor: Nico Sauermann / Mag. Victoria Sonnenberg

By using tools from Horn, the mechanics department of Team Raceyard at Kiel Technical University could solve even tricky machining tasks. As participants in Formula Student, they have built a high performance electric racing car.

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Milling a steering knuckle using the DSA system.
Milling a steering knuckle using the DSA system.
(Photo: Horn)

Under four seconds from 0 to 100 km/h, 160 kW of power and team spirit: that is the experience for the Formula Student participants of Team Raceyard at Kiel Technical University. Having developed and manufactured the electric racing car themselves, they have entered in Category E.

For component manufacture for the car, the students from Kiel received advice from Horn for turning and milling work. “We value their know-how in machining. From our dialogue partner at Horn, Thomas Wassersleben, we always receive good advice and quick support,” says Lukas Schlott, member of the Raceyard team and responsible for the areas marketing and event management.

The cooperation with the Institute of Computer-Integrated Manufacturing – Technology Transfer (CIMTT) started some years ago. Thomas Wassersleben advises the mechanical workshops at the Institute regarding machining solutions and tools. Fieldworkers from Horn brought back an enquiry from the racing team in 2017/2018. Horn answered the enquiry with a set of tools including the Supermini system type 105, the pierce-and-part system S100, Boehlerit ISO indexable inserts, and DS aluminium milling tools. “With this toolset, our mechanics department was able to solve even tricky machining tasks in which access was difficult because of long overhangs and narrow boreholes,” recalls Schlott.

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Every season in Formula Student, a new racing car takes the stage. Like the racing car, part of the team also changes every year, since some students finish studies. This means that every new team is entirely responsible for development, manufacture, assembly and tests of the car. At the same time, experience from the previous season goes into the new development. The Team Raceyard 2017/2018 consists of 50 members, divided over four main areas: sponsoring and finances, mechanics, electrics, and marketing & event management.

Developed and manufactured themselves

With the exception of a few components, they developed and manufactured the racing car themselves. For the brake caliper, the Kiel students relied on SLM technology (Selective Laser Melting). With this additive manufacturing process, they printed the brake calipers they had designed themselves using an aluminium alloy. To remove material from the cylinder bore contact surface of the brake piston, the mechanics responsible put their trust in Horn’s Supermini Typ 105 system. “Due to the three-dimensional shape of the caliper and the close cylinder tolerances, manufacture was a challenge for our mechanics,” says Schlott.

To machine the aluminium steering knuckles, they used a three-bladed VHM shaft milling tool, with polished chip spaces, from the DS system. With this component, the difficulty lay in the long overhang of the tool. Furthermore, the technicians chose an extra-long milling tool because of the component geometry. “With the polished chip spaces and because of the geometry of the milling tool, we have no problems during machining with adhering cuttings and chatter marks“, Wassersleben tells us.

The racing car chassis consists of a CFRP monocoque. For the aero­dynamic components and other parts, such as the steering linkage, the students likewise selected this carbon fibre material. Help in producing the moulds and laminating the parts was available to the machine from a further sponsor. “The laminating of the individual fibre layers was a challenge, since the direction of the fibres in the individual CFRP layers determines the later stiffness of the chassis and other component groups,” says Schlott. When calculating the aerodynamics and the stiffnesses of the chassis and other components, the students used a high-performance computer available at Kiel CIMTT.

Ready to go with four-wheel-drive

The components for the electric drive were likewise developed by team members themselves. In the removable accumulator, only the individual cells were bought in. The joining up of the 288 cells, the electronic design and the manufacture of the safety and charging electronics were carried out by the students.

The racing car took its place on the grid in the 2017/2018 season for the first time, with four-wheel-drive. Each wheel is driven by its own electric motor, located on the wheel hub. Together they produce a total power of 160 kW (around 217 PS). With an empty vehicle weight of around 230 kg, this constitutes substantial power. To compete in the Formula Student series, however, the power had to be throttled back to 85 kW.

In the individual disciplines of Formula Student, more is taken into account than just the car’s performance. The assessment covers static and dynamic disciplines. In the static disciplines, the economic questions and the team’s design approach play a large role. Accordingly, the students must explain the business plan and the cost report in two presentations. A further static discipline is the engineering and design event. For this, the team has to persuade the jury about his design engineering. Of particular importance here is the discussion in which good arguments and justification have to be given in response to the jury’s remarks.

The dynamic events include acceleration, skid pad, autocross and endurance. The discipline acceleration involves an acceleration test on a straight track of 75 m. Here, the racing cars accelerate from 0 to 100 km/h in under four seconds. On the skid pad, the cars drive on a track in the form of a figure 8. Large centrifugal forces or transverse accelerations can lead to breaking out on the vehicle.

In autocross, drivers are timed as they drive the cars alone over a marked course. Great demands are made here on the drivers and the driving dynamics of the vehicle over a one-kilometre course. Endurance is the biggest and final discipline in each Formula Student event. Here the racing car has to prove its reliability on a circuit of 22 km length. This discipline makes up one third of the possible total points.

Formula SAE was founded in the USA in 1981 and spread to Europe later as Formula Student. Since 1999, there have been annual events at Silverstone in Britain and, since 2006, in Germany as well, at the Hockenheimring. In the meantime, Formula Student also visits Italy, Spain, Brazil and Japan to organise competitions there. Formula Student enables students to gain intensive practical experience in design engineering, manufacture and financing of all aspects of the vehicle – and all of this outside the lecture theatre. For this purpose, every team develops a single-seater racing car constructed according to comprehensive rules.

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* Nico Sauermann is editor and photographer at the Paul Horn GmbH in 72072 Tübingen. Further information: Hartmetall-​Werkzeugfabrik Paul Horn GmbH, tel. (00 49-70 71) 70 04-0, info@phorn.de

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