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Methods of projecting (a) tractor hydraulic power and (b) cooling capacity available from the tractor for hydraulic motor usage have been desired to define the tractor hydraulic limits. A theory was developed to define a tractor hydraulic cooling capacity limit based on a pressure compensated (closed center) hydraulic system. The conservation of energy equation was modified for application to a tractor and implement control volume. The theoretical tractor hydraulic cooling capacity limit was compared to wind tunnel cooling test results. A graphical format was developed to present the maximum pressure, maximum power, and cooling capacity on the same plot.

A new hydraulic system was developed for a four wheel drive (4WD) agricultural tractor to coincide with the new modular design of the vehicle. Challenges such as lubrication and cooling of separated drivetrain components, adaptation to stand alone transmission modules, decreased maintenance time, and design of an optional electrohydraulic controlled 3-point hitch for implement lift were addressed. System considerations and design approaches are outlined.

A need to vary the wheel base during operation exists for some mobile equipment. This need can be caused by legal considerations or the geometry of the haul road. To meet this need, we consider a hydraulically-operated device used as a fifth wheel. This type of unit is being built and installed on some tractor trailer combinations. Since the apparatus can be operated with the vehicle in motion, the system needs to be analyzed under various dynamic conditions. System pressure peaks and component operation is examined under a variety of conditions involving road surface irregularities and the effect of striking obstructions such as loading docks. Some recommendations for design improvement are included. The analysis was carried out with the use of the IBM-CSMP (Continuous System Modeling Program) (1).* The purpose of the work was to gain preliminary knowledge regarding probable operation of the apparatus.