Weight Reduction of Shifter Forks using Steel Inserts

Shift quality of a manual transmission is a critical characteristic that is requires utmost care by the designers while structuring the transmission. Shift quality is affected by many factors viz. synchronizer design, shift fork design, shifter design, gear design, transmission oil selection etc. Designers have realized that shift fork is critical element for improving shift feel of a transmission. This paper focuses upon the reduction in weight of the overall transmission shift system by using steel inserts in aluminum shifter forks. No compromise on the stiffness and strength of the shift fork of a manual transmission is done. Stiffness and strength of shifter fork is optimized using contact pattern analysis and stiffness analysis on MSC Nastran.

All the subsystem (i.e. synchronizer and the shift system component) are constrained to optimize the shift fork stiffness. A 5-speed manual transmission is used as an example to illustrate the same. A data base will be developed to define how parts will function for the required load. Abuse load value was established using load cells on gear shifting knob. Data was collected for approximately 100 drivers of various age groups and different riding styles. After data collection a mean average of 50 kg load on the gear shift knob was taken as abuse load for a sport utility vehicle segment. Therefore a load of 50KG multiplied by Leverage was taken to test forks for abuse loading condition.