Power and Mobility (P&M)


by John LaPlante; Don Flynn


Problem outline: Adding armor to protect vehicle occupants leaves conventional suspensions incapable of delivering ride quality and handling needed for mission objectives. The current up-armored HMWWV has exceeded the design weight for the M1113 variant by a considerable amount. The rated GVW is 11,500 lb, yet the mission ready weight often reaches 14,500 lb. This results in greatly reduced reliability and frequent breakage of suspension components. When the suspension is overloaded, the ride height is reduced and the vehicle is no longer capable of safely traversing rough terrain. In addition, the lack of available compression travel results in severe bottoming that transmits extremely high shock loads into the suspension, chassis and ultimately the occupants. A semi-active suspension upgrade kit for the up-armored HMWWV was developed with the objective of achieving comparable performance for the weight range of 8300lbs curb weight to 14,500lbs combat loaded. Objective: The performance target was equivalent handling, stability and ride quality as an M1113 HMMWV at rated GVW. The project developed a bolt on suspension retrofit kit for existing vehicles which is also compatible with new vehicles builds. The kit maintained ride height throughout the range of predicted loads and provided sufficient damping force to achieve comparable handling and performance to the target. Occupant comfort was improved through a reduction in absorbed power over RMS terrain courses. Testing demonstrated improved stability and balance during slalom and increased speed during NATO lane change maneuvers. This translated into a reduced danger of rollover, better control during aggressive or emergency maneuvers and a 50% reduction in unscheduled maintenance costs. The system has application for other vehicles that traverse rough roads or have large changes from curb weight to GVW. Conclusion: A semi active suspension significantly improves vehicle mobility and reduces maintenance cost. Complete study provided below.