A 4t off-road military application vehicle was offered to the customers for assessment. During the evaluation adverse feedback of 1) harsh ride in off-road terrain, particularly during hump-crossing and 2) issues during high mobility were reported. Vehicle configuration was front and rear rigid axle suspension with leaf spring anti-roll bar, 4×4 and all terrain tyres. Vehicle application was “on-road” [GS (General-services)], as well as “off-road” (Reconnaissance purpose). The feedback was critically analyzed on the vehicle with the simulation of field conditions. Since the vehicle was still under customer evaluation, solution for the feedback required was quick and within boundary condition (maximum possible allowable limits of modification) of no major change in the suspension design as it was affects homologation cycle.
Present paper describes the detailed analysis of the influence of each parameter on system. The above parameters were studied in isolation as well as in combination, its modifications and optimization carried out to meet the requirement. During evaluation it was observed that, the anti-roll bar deletion caused steady state roll deterioration by 10%, however this enhanced mobility to a large extent. Quantifiable parameter of mobility viz. articulation improved by 18% and ramp-travel index (RTI) score improved by 23%. Characteristics of the shock-up were studied and designed to have stiffer characteristics in the re-bound condition and acceptable ride characteristics in bump condition. Hence, although steady state roll deteriorated but with improved roll rate by 18% and yaw rate by 5.7% in dynamic performance, military personnel felt proposed configuration safer and better compared with proposed configuration. Hump crossing and landing was also observed to be much smoother and acceptable.