High-Mobility Multipurpose Wheeled Vehicle/High-Mobility Trailer (HMMWV/ HMT) Brake Analysis.
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The Army has a need for a companion High-Mobility Trailer HMT for its fleet of High-Mobility Multipurpose Wheeled Vehicles HMMWVs. The HMT is required to have a Gross Vehicle Weight GVW of 3400 pounds and be equipped with either surge or service brakes. Federal Motor Carrier Safety Regulations FMCSR 393.42 and 393.48 require that all trailers with a GVW of 3000 pounds and over be equipped with continuously operable brakes. A surge brake is not operable when the prime mover travels in reverse and is usually disconnected when traveling cross-country. Service brakes have the undesirable requirement of modifying the HMMWV. The raises the question Are the HMMWVs brakes adequate to safely brake the system in all of its operational scenarios If the brakes are found to be adequate, justification of a waver on the requirement for continuously operable brakes, allowing for the use of a surge brake, is applicable. In order to approach this problem without the necessary costly and time-consuming testing, a brake simulation model of the system was created. The model was validated with a short and inexpensive operational test, which determined a mean percent difference, between test and model predicted braking distances, of 9. This report contains a copy of the model which requires the use of Lotus 1-2-3, version 2. Using the model, the braking capability of the HMMWV coupled to the HMT was determined. By comparing this capability to its requirement, it was determined that the HMMWVs brakes are adequate and justify a waver of the FMCSR.
- Surface Transportation and Equipment