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NewsletterSpecial

Design PresentationDUT13

Formula Student Team Delft

DUTRacing TeamContent

- Introduction- Powertrain- Drivetrain- Vehicle Dynamics- Chassis

Formula Student Team Delft

DUTRacing Team Introduction

In this newsletter, we will tell you about our latest car, the DUT13. What does a car that can accelerate from 0-100 km/h in 2,5 seconds, and drive upside down at 130 km/h look like? From every department the chief will tell you what makes the DUT13 unique. They will tell you why we think that this car will be able to reach the podium on the competition and why this car will again be better than its predecessor.

Back in October, we presented the guidelines for the design of the DUT13. From that moment on we focussed on a car which will be lightweight, will have a low centre of gravity, a 50-50 weight distribution and produces downforce while using a minimal amount of energy.

Now, over 2 months later, we have designed this car. From 5 abstract guidelines, 55 of our engineers, supported by the operations department, designed a whole racecar in under 80 days! An accomplishment every team member should be proud of. Because they have not just designed a car, but they designed a car of which they are convinced that it is possible to win the competition.

© Paul Brussee

- Reinier Alberda, Chief Engineer.

Formula Student Team Delft

DUTRacing TeamPowertrain

The most important part of the powertrain is the accumulator. The accumulator is the part where all the energy, that will be used to propel the car, is stored. Because the amount of energy is quite large, it can also be a very dangerous part if handled incorrectly. The accumulator will therefore be divided into several modules in order to keep the voltage at a safe level during the largest part of the assembly phase.

A rule change in the efficiency scoring made it more tempting to drive fast during the endurance event. This strategy will go hand in hand with using much more energy compared to the previous years. This year we will therefore take 6.3 kWh with us to the start. Because of this, the accumulator will be much heavier. This is why we opted to design a pack with a center-of-gravity (CoG) that is as low as possible. Therefore, the accumulator cells will be stacked on top of each other, and not placed next to each other.

Because we will be driving faster, the accumulator will get hotter and this means it needs to be cooled. To increase efficiency and reduce heat generation in the pack, we decided to go for a new method of interconnecting the cells, namely laser welding. Refining this welding process takes some effort but a nice and constant connection will be the result.

accumulator

Formula Student Team Delft

DUTRacing Team

Furthermore, we aimed at optimizing the complexity of the high-voltage wiring. Shortening the wiring harness, enable us to increase reliability and serviceability while decreasing the weight. Most of the electronics is dealt with by the powertrain department as well. Fundamental research is being performed to make sure the communication system is working according to the specifications. The driver interface has been designed such that it can also be used as a debug interface. This enables us to fix accidental problems in the system more quickly during the testing phase.

accumulator module with bms

accumulator module

motor controller and splitbox

dashboard

Formula Student Team Delft

DUTRacing TeamDrivetrain

In theory, because of the extra down force, we should be able to accelerate faster. But this would only be true when enough torque is transferred to the wheels and the track. The complete drivetrain of the DUT13 is designed such that it could deliver this torque and also be as light as possible. Furthermore, we have chosen to place the whole transmission inside the wheels. A logical choice for the front wheels, because otherwise the motors would be very close to the drivers legs. That is not desirable as a designer, but certainly not as a driver. At the back, the transmission will be placed in the wheels as well. This removes the need for driveshafts and also results in an integrated design which favours the weight.

A second advantage is that we can place the motors lower than it would be when it was placed inside the chassis.

As mentioned before, a lot of torque has to be transferred to the track. Because we want to keep the car as light as possible, we had to find an optimum between motor, motor controller and the transmission. The motors, which we design in cooporation with AMK-antriebe in Stuttgart, weigh about 4 kg and can produce 26 kW each. The energy density of these motors can thus be compared to the KERS system of a Formula 1 car. We will redesign the casing of the motor controllers and make it out of carbon fibre. The motors and the motor controllers need to be cooled. This year we will place the radiators in the side pods because we don’t want to disturb the airflow to the rear wing and want upright assembly

gears

Formula Student Team Delft

DUTRacing Team

the brake discs of last year. The centres of the rims will get an update as well, because they have to be able to withstand the heavier loads entailed by the aerodynamics.

to place the mass as low as possible.The transmission has a gear ratio of 14:1 to transfer the relatively low torque of the motors into sufficient torque on the track. To achieve this a high gear ratio with two stages was needed. The first stage is from the motor is spur gear transmission (4:1). The second stage, is a planetary transmission (3.5:1). This year we opted to go for four planets because for our application it is lighter than three. An extra advantage is that the motor can be placed eccentric on the upright (and also lower). The upright is a part where everything comes together. This part connects the drivetrain with the rest of the car, and because this contains the gearbox, brake system and motor,

it is a nicely integrated whole.The brake disc is made of an aluminium composite alloy with a high thermal capacity. This results in brake discs which are approximately half the weight of gears

motor

upright with gearbox

aluminium composite brake disc

Formula Student Team Delft

DUTRacing TeamVehicle

DynamicsThis year the vehicle dynamics department covers all the math behind the car. They determine how the car should behave in theory such that the other departments can make it all happen. This year the vehicle dynamics department covers aerodynamics, the geometry, the spring-damper-system, the control systems and telemetry as well.

First let us say something about the aerodynamics. Under the car there will be a venturi tunnel, which creates a low pressure zone underneath the car. The benefit of this tunnel is the large area that can be used. The car will

also have a front and a rear wing in order to generate more down force. The front wing will only be in front of the wheels such that it does not influence the Venturi.

Because of the aerodynamics it is disadvantageous if the car rolls, pitches or heaves a lot. Therefore the suspension is this year will be much stiffer compared to last year. But in order to bound the vertical displacement of the car, the springs are stiff enough to prevent the car from much roll. Therefore this year the car does not need an anti-roll bar. Furthermore, the geometry of the car will be designed to counteract pitch

during accelerating and braking.The control systems will contain a slip ratio controller and a yaw rate controller, which were also implemented on the DUT12. The slip-ratio controller is acting as a traction control system. The yaw-rate controller will control the cornering behaviour of the car. There will also be a sensor which measures the velocity in forward and sideward direction. Therefore, not only the slip can be measured more accurately, but also the lateral velocity (which you always have in corners). The data from this sensor is then used for the control of the car.

DUT13 with aero

Formula Student Team Delft

DUTRacing Team

Lastly, this year telemetry will be implemented on the car. This enables communication with the car without physical contact. This can be very useful when the car is driving. It will be integrated on the ECU (the computer of the car) except for the antenna.

DUT13 with aero

venturi

venturi

front geometry & spring-damper

geometry & spring-damper system

DUT13 wings & venturi

Formula Student Team Delft

DUTRacing Team

ChassisAs already mentioned, the front of the monocoque is designed to fit tightly around the driver. Because different drivers have to fit into the car, it was opted to go for an adjustable pedal box. This way the legs of the taller drivers can be lowered, such that the centre of gravity of the legs can be lowered. The driver seat will be formed to fit a bigger driver. For smaller drivers the seat will be fitted with filler, such that the driver does not slide through the seat. Furthermore, the steering system design of last year was nice, therefore this system was mainly perfected.

This year the monocoque will again be designed with safety as main requirement. It is not allowed to break with a deceleration of 20g. Furthermore, the front of the monocoque will be tightly shaped around the driver. In the back all the incoming forces have to be withstood. The motors and transmissions are located within the wheels this year, this means that no space has to be cleared for these parts. After some hand calculations the first lay-up (strategy for laying the carbon fibre mats) was determined, after which this was optimized with a computer using Finite Element Analysis (FEA). The production of the monocoque will be done by ourselves using prepreg carbon fibre mats (the resin used to stitch the fibres together is already impregnated in the fibre mats) and an aluminium honeycomb. Together they form a sandwich structure. As already described by vehicle dynamics, the design of the DUT13 is focussed on achieving an efficient aerodynamic design. Therefore, the underside of the monocoque will be curved in order to fit a Venturi tunnel.

adjustable pedal boxsteering system

driver interface

Formula Student Team Delft

DUTRacing Team

With the motors and transmissions within the wheels and the driver, motor controllers and ECU inside of the monocoque almost all parts have found their place. Except for the two parts of the accumulator which have not yet found their final place yet. They will be placed inside of the side-pods next to the driver. The fairings of the side-pods which contain these parts have been formed such that the airflow around the driver can be used to cool the accumulator and also lead the air into the radiators.

monocoque

custom seat steering wheel

cockpit lay-out

Formula Student Team Delft

DUTRacing TeamSponsors

advanced engineeringlightweight

- Faculty of Aerospace Engineering

- Faculty of Applied Sciences

- Faculty of Industrial Design Engineering

- Faculty of Mechanical, Maritime and Materials Engineering

- Faculty of Technology, Policy and Management

- Faculty of Electrical Engineering, Mathematics & Computer Science

Formula Student Team Delft

DUTRacing Team

Specialists in fibre reinforced composites

We wish youa merry Christmas

and a happy

2013