International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 02 | Feb -2017
p-ISSN: 2395-0072
www.irjet.net
OPTIMUM DESIGN OF BRAKING SYSTEM FOR A FORMULA 3 RACE CARS WITH NUMERIC COMPUTATIONS AND THERMAL ANALYSIS Rutvik H Rana1, Nishant H Jakhiya1, Anand K Savani1, Atmiya K Bhalodi1 1C. M. Department of Mechanical Engineering, Changa, India ---------------------------------------------------------------------***--------------------------------------------------------------------2. SELECTION OF COMPONENTS: Abstract - Weight reduction is one of the prime concerns for a formula 3 cars. It was decided to reduce the weight of brake system by using the disc rotor and calipers of a bike instead of using a bulky hat type disc rotor. In this paper, the component selection of braking system is discussed. Various calculations of braking force, braking torque and brake bias are shown. Also, the safety of using bike’s rotor is validated by calculations and thermal analysis. This brake system was implemented by team Ojaswat for the event Supra 15 organized by SAE, India.
A.
Brake rotor and Calipers:
It is beneficial to select a rotor having the diameter as large as can be accommodated in the rims of the car. This is because of the reason that for the transmission of same torque, with the increase in diameter, the respective force decreases. Hence a bike’s front rotor with diameter of 200 mm was selected for a 13inch wheel rim. The rotor was petal typed to facilitate heat transfer. The thickness of the disc was 3.5mm and suitable calipers with dual pistons were selected.
Key Words: Formula 3 Car, Thermal Analysis, Abaqus, Braking System, Ansys.
B. 1.INTRODUCTION
Master Cylinder:
A tandem type master cylinder was selected so that independent two hydraulic circuits can be obtained and it can be obtained by a single control from brake pedal. It contained DOT3 as brake oil. A diagonally split-connections were given to the wheels so that the car maintains stability in case of failure of one of the circuits. The circuit is made up of rigid pipes followed by flexible brake lines going to the calipers through a Benjo bolt.
Brake system is one of the vital systems of a formula 3 race car. It’s perfect functioning in all the conditions is a necessity for the safety point of view. Our primary aim was to come up with a braking system that is simple and has an optimized weight along with being reliable. As per the rule book of SAE, India, it was compulsory for the system to consist of two independently operated hydraulic circuits. Also, all the four wheels must lock simultaneously. In order to implement fool proof safety, we also had to keep a brake over travel switch.
C.
Brake Pedal:
The brake pedal was machined from checkered Aluminum plate having thickness 5mm. It was designed to withstand a force of 2000N at the footrest. The leverage of the pedal was set to 2.3.
Lakkam, Suwantaroj, Puangcharoenchai, Mongkonlerdmanee and Koetniyom [1] determined the film coefficient of convective heat transfers by investigating thermal gradients on the disc rotor. They experimentally determined the convective heat transfer coefficient and used it to perform numerical simulation by finite element method. Thus, they studied the temperature diffusion and heat ventilation of front and back vented brake discs.
D.
Proportioning Valve:
There is a dynamic load transfer during braking which increases the load at front axle than at rear axle. Hence the rear brakes lock earlier than the front brakes. For the simultaneous locking of all four wheels, proportioning valves are required in the brake lines going to the rear wheels so that less pressure is reached there. Proportioning valve helps in setting this brake bias as per the calculated load transfer taking place in the car. The brake bias in our car was 0.51 at the front and 0.49 at rear.
Sheikh and Srinivas [2], wanted to study the amount of deformation due to tangential Force and pressure loading. So, in their work, they performed analysis without considering the effects of thermal expansion. They performed thermal + structural analysis of disk rotor of Honda Civic using Ansys. Iersel [3] used a computer controlled test rig to find out the friction coefficient of brake pads. The brake pads were tested at various conditions and it was shown that optimal operative temperature lies around 220 . Also, it was shown that the resulting brake torque depends linearly on brake pressure.
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