Design Analysis and Development of a New 5F/1R Synchromesh Rear Mounted Gearbox for Mini Truck for an Emerging Markets 2009-26-0021

The need of a matched power train is a primary goal to meet vehicle performance and emission characteristics. The engine provides its highest torque output, approximately in the middle of its speed range, while often the maximum torque is required when the vehicle is starting from rest and when it is on the gradient. This often requires matching, ensuring a good compromise between the engine torque and speed, thereby optimizing speed ratios in the gear box, climbing performance, acceleration, emission and fuel consumption of the vehicle. Gearing and gear operating mechanism is one of the most critical challenges in the automotive power transmission systems.

This paper explains theoretical and practical process from virgin concept to design, analysis, development and test validation of synchromesh transaxle with 5 forward and 1 reverse shifting, matched to a rear mounted 2 cylinder direct injection diesel engine for 4-wheeled 1.5 T GVW mini truck. This transaxle has capacity of theoretical input torque of 54 Nm and power of 20 horsepower. Extensive use of analysis software tools and test methods were used for design and analysis of this gearbox for robust design. Gear analysis software, FEA software and standards like ISO, DIN, and AG MA were referred to define gear parameters like teeth contact, stiffness, transmission casing strength and deflection. Shafts and bearings were analyzed for strength, critical speed, bearing life and deflection.

All the technical targets were achieved through the validation of transaxle on durability test vehicle, and on endurance test rig for targeted running kilometers and hours.