Design And Analysis of Light Weight Helical Gear Limited Slip Differential For Racing Car Applications

Abstract

The purpose of this paper is to study and designing of light weight limited Slip Differential. The LSD is transmission device that improves traction capabilities leading to high performance road cars, racing cars. Concentrating on the ability of Helical gear limited slip differential to adapt to different cornering conditions, we designed light weight differential for achieving better performance in racing cars. For the designing purpose mathematical equations were used. All the parts of differential are design under static condition and modelled. Design was then iterated to give various models and analysis was carried out on each design for the improvement. Testing of this differential is then carried out on a Formula SAE car in order to verify the performance of differential. This paper considers use of differential in Formula SAE or similar auto racing competition. Casing of differential that is designed consist of 2 parts left hand casing and right hand casing, Left hand casing gives support to 3 planetary gears which is in mesh with left sun gear. Right hand casing gives support to all planetary gears and right sun gear along with star idler. The planetary gears of left and right casing are in mesh. On extension of both casing there is provision for taper roller bearing mount. Differential is provided with mounting of sprocket. Differential is a device that differentiates or splits the engine torque and allow both drive wheels to rotate at different speed hence the name differential. Commonly used differential (open differential) allows each of driving wheels to rotate at different speed when each wheels travels different distance through the turn. But it splits the torque equally between both the drive wheels. When one of the drive wheel looses traction due to slippery condition or cornering neither of the wheel gets torque for the propulsion of vehicle. the maximum torque that can be supplied by the engine to the wheels is limited by the traction capabilities of the tire. Since the torque is distributed equally between both wheels, the maximum total torque transferred to the ground is twice the maximum torque available at the tire with the least traction. This is a major disadvantage for low traction situation such as on off-road terrain, or in cases of large weight transfer like that occurring during racing. During tight cornering weight is transferred from the vehicles inside wheels to the outside ones. The open differential will lead to slipping of the inside wheel thus decreasing the rate of acceleration out of a corner. To overcome this problem Limited slip differential is used. As it differentiates torque and speed, it improves cornering stability and better traction control with direct impact on handling characteristic of car. In the racing application due to cornering condition, leading to weight transfer on wheels hence there are different traction load on different wheel. Also inertia and weight plays an important role in overall performance of a car. Hence LSD is used which fulfil the needs of different tractional load requirement by differentiating torque.