Design of a Formula Student Race Car Spring-Damper …

1 Design of a Formula StudentRace Car van den Bos, RosielleTechnische Universiteit EindhovenDepartment of Mechanical EngineeringControl Systems Technology GroupEindhoven, March, 2010 AbstractUniversity Racing Eindhoven (URE) is a team of 50 students who compete in theFormula Student competition. For the 2009-2010 season, URE started building theirsixth car: the URE06 will be equipped with a newly designed front and rear multi-linkwheel suspension. The rear frame that holds the powertrain, drivetrain and suspen-sion will be shortened to reduce total mass and yaw inertia of the main subject of this report is the Design of a Spring-Damper system for theURE06.

2 First, the working principle of a suspension system is explained and a listof requirements the Spring-Damper system has to fulfill is determined. Subsequently,the kinematics of the front and rear Spring-Damper systems have been set. Thisresulted in a set of coordinates. The individual parts have been constructed next,taking the requirements into account. Components such as the anti-roll bars havebeen analyzed by hand calculations, while other parts have been optimized usingFEM Introduction12 The suspension Working principle .. Requirements ..43 Front Spring-Damper Final Design overview .. Front bump system .

3 Motion ratio .. rocker .. travel sensor .. Front anti-roll system .. of the anti-roll bar .. in the anti-roll bar .. connection ..114 Rear Spring-Damper Final Design overview .. Rear bump system .. versus pullrod .. rocker .. travel sensor .. Rear anti-roll system .. of the anti-roll system .. tubes .. of the anti-roll bar .. in the anti-roll bar ..235 Conclusion and recommendations24 References25A Front Spring-Damper system coordinates26B Rear Spring-Damper system coordinates27C Working drawings of the front and rear Spring-Damper system28 Paul van den BosIntroduction1 IntroductionUniversity Racing Eindhoven (URE) is a team of 50 students who compete in the FormulaStudent competition.

4 This competition was initiated in the United States in 1981 by theSociety of Automotive Engineers (SAE). The main goal is providing students with anopportunity to gain experience in Design , manufacturing, management, marketing andpeople skills by designing, building and racing a single seater race car. Nowadays, fourEuropean races are available in the United Kingdom, Germany, Italy and :Last year s car of University Racing Eindhoven: the get a lot of freedom to Design their own car. The most important rules a Formulastudent car has to comply with state that it has to have: a chassis that is designed in accordance with a number of safety regulations.

5 A four-stroke engine with a maximum displacement of 610cc. an inlet restriction with a maximum diameter of 20mm. a fully operational suspension the 2009-2010 season, URE started building their sixth car: the URE06. Besidesthat, it s predecessor, the URE05 (see figure ), will be converted from petrol driven tofull electric. It will be used to compete in new the Formula Student Electric URE06 will be equipped with a newly designed front and rear multi-link wheelsuspension. The rear frame that holds the powertrain, drivetrain and suspension will beshortened to reduce total mass and yaw inertia of the car. A new Spring-Damper systemhas to be designed to make this main subject of this report is the Design of a Spring-Damper system for the 2 explains the working principle of a suspension system and lists the requirementsthe Spring-Damper system has to fulfill.

6 The mechanical Design of the spring -dampersystems for the front and rear of the car will be discussed in chapters 3 and 4 van den BosWorking principle2 The suspension systemSuspension is the term given to the system of springs, dampers and linkages that connectthe body of a vehicle to it s wheels. This system serves a dual purpose: optimizing thevehicle s handling, and keeping the occupants comfortable. In case of a race car, thelatter is off course insignificant. The only goal of a race car is maintaining the maximumachievable acceleration in the appropriate working principle of a suspension system will be explained first.

7 After that, a set ofrequirements is Working principleTyres are the most important parts of a race car. They have to transmit all drive, brakeand steering forces to the road through a very small contact patch. This makes it veryimportant for a car to keep the tyres in optimal contact with the road at all times. Thatis the task of the suspension system . In case of a race car, the suspension system can bedesigned specifically for that goal, at the cost of driver schematic representation of a suspension system can be seen in figure The wheeland brake disc are connected to the upright by bearings. Carbon fibre rods with balljoints on each end connect the upright to the chassis.

8 One of these six rods (the inclinedone) is not mounted to the chassis, but to a rocker. If the wheel moves up with respect tothe vehicle body, the upright pulls on the rod, which in turn causes the rocker to rotateabout it s pivot point. A Spring-Damper is connected to the bellcrank on one end, and tothe chassis on the other. So by rotating the rocker, the Spring-Damper is :Rear view of a vehicle suspension Spring-Damper system consists of two subsystems: the coil-over damper itself (seefigure , and the anti-roll system . The coil spring absorbs the energy from a bump bycompressing, and releases it again at an uncontrolled rate. The spring will continue tobounce until all of the energy originally put into it is dissipated.)

9 Dampers are used tocontrol this energy dissipation. They slow down and reduce the amplitude of the wheelmotion by converting kinetic energy into anti-roll system consists of a torsion bar with a lever on each end. If the movementson each end of the bar are not exactly the same, it will be twisted. This results in areaction van den BosWorking principleThe main rocker connects the pull rod to the two subsystems. The geometry of this rockerdetermines the movement of the Spring-Damper and the anti-roll bar as a result of themovement of the operating conditions will be explained to show how the subsystems work to controlthe movements of the suspension.

10 Bump the car drives over a threshold, the left and right wheels will move up an equalamount. This results in the same angular rotation of the left and right main spring -dampers are therefore actuated equally. Since left and right levers of theanti-roll bar are rotated to the same angle in the same direction, it will not createa reaction moment. Cornering the car drives through a corner, it s body will roll to the outside of the bend. Asa result, the outer wheel moves up with respect to the chassis, and the inner wheelwill move down. This means the main rockers are rotated in opposite load on the outside spring will become higher, while the inside spring will be(partially) unloaded.