Belden Inc., Broadview, Ill., was recently contracted to supply a complete universal joint drive shaft assembly for a Mine Resistant Ambush Protected (MRAP) multi-role armored military vehicle. The drive shaft assembly was needed to connect the diesel engine and the compressor for the air conditioning unit in the vehicle.


The end user originally specified a standard 32 mm OD needle bearing drive shaft with stainless steel yokes and a quick release hub feature for the initial testing phase. In 2007, the entire vehicle was placed into a climate chamber to replicate environmental elements the armored vehicle might encounter in various regions of the world. The tests proved to be extremely demanding on the universal joint drive shaft, resulting in premature failure.


Belden then evaluated the application in the field. Company engineers suspected that a combination of an undersized joint that couldn't handle the torque and rpm of the diesel engine, plus the harsh temperature and operating environment inside the vehicle’s engine compartment, contributed to the drive shaft failure. Belden was further challenged by the space limitations for a more robust joint. The distance was very short and a telescoping feature was mandatory for the assembly. The severe space constraints limited the possible bearing size.


The redesigned drive shafts now include a larger, heavy-duty bearing that is sealed and equipped with a lubricant that can handle a greater range of operating temperatures. The bearing seal was also improved to better retain lubrication during longer periods of extreme operation. Stainless steel yokes incorporate a custom profile and hub, as well as the quick release feature.


The selected needle bearing universal joints provide precise positioning, operate continuously at high speeds, feature rigid axial stiffness for push/pull loads, and can handle higher angles and rpm. The joint is available in a variety of hub materials, including high-grade alloy steel, grades of stainless steel, and an extruded aluminum for high strength-to-weight ratios; specialty plating is available for additional corrosion resistance. Boot covers are recommended in gaseous and abrasive environments for added protection of the cross and bearing. The joints are manufactured in both inch and metric sizes and operating angles up to 45 degrees.


Visit Belden Inc. for more information.