Derivation of Test Schedule for Jerk Test on Manual Gearbox Using Road Load Data

Shock loads/Jerk is a major cause of gearbox failure which occurs during abusive driving condition. In passenger car torque spikes are experienced by the transmission during launch/sudden clutch release events on flat road or off-road. Whereas, in case of commercial vehicle torque spikes are generated while operation in mines and off-road application especially in tipper vehicles. Torque spikes experienced by the gearbox can lead to gear failure, gear slippage and structural failure of housing. Research has been done till now to improve the design of gearbox to address such failures. However, with increased focus on transmission downsizing and improved vehicle performance (by weight reduction and more powerful engine) it is necessary to have optimum design to meet transmission life. This paper discuss the test setup and methodology used to simulate the torque spikes on test bench. To develop the test procedure huge data was collected on commercial vehicles. Road load data was collected in various road mix conditions like mines, rough road, vehicle launch in 1^st gear & Reverse gear on straight and gradient road for few hundred kilometers. During data collection gearbox output torque and gear position were recorded against time scale. After analyzing the vehicle data test procedure was derived and existing production & prototype transmissions were validated on test bench and vehicle to establish co-relation. With increased competition vehicle development time has reduced drastically in recent past. Bench test procedure discussed in this paper will help to reduce development time and cost. Process briefed in this paper can also be used for similar test specification for passenger car transmission (gearbox/transaxle).