TM 5-3895-346-14
POWER STEERING
INSTALLATION
INSTALLATION
Drive Connections
The VTM27 and VTM41 pumps are designed to be driven by belt, direct coupling, or spur gear. Helical gear
drives must not be used. The VTM28 and VTM40 units must be mounted and coupled directly to an electric
motor or generator. The VTM42 pumps have the same drive characteristics as the VTM27 and VTM41 pumps
but are designed for heavier drive loads or thrust loads.
Exercise care in mounting these pumps to assure correct coupling shaft alignment with the power source.
When belts and pulleys are used, they must be properly aligned and adjusted to prevent excessive side loads
on the pump shaft bearings.
Shaft Rotation
Pumps are manufactured for either right or left-hand rotation. They must be driven in the direction of rotation
indicated by the arrow cast on the surface of the pump ring.
Direction of rotation may be changed by reversing pump ring and replacing with appropriate body and pressure
plate. (See parts catalog and Overhaul.)Pumps may be damaged if driven in the wrong direction of rotation.
Hydraulic Tubing
Minimize the number of bends in tubing to prevent excessive turbulence and friction of oil flow in the circuit.
Do not bend tubing too sharply.
The correct minimum radius for all bends is three times the inside diameter of the tube.
Use as few connections and fittings as necessary for proper installation to minimize possible leakage and flow
resistance. Do not spring tubing into position. This will prevent undue strain at connections. Clean all tubing
thoroughly before installation. Use approved methods such as sand blasting, wire brushing, or pickling to
remove all dirt, rust, and scale.
Hydraulic Fluid Recommendations
Oil Type
Oils used in hydraulic systems perform the dual function of lubrication and transmission of power. Oil must be
selected with care and with the assistance of a reputable supplier. Crankcase oils meeting or exceeding the
Five Engine Test Sequence for evaluating oils for API (American Petroleum Institute) service MS (Maximum
Severity) best serve the needs of mobile hydraulic systems. These engine sequence tests were adopted by the
Society of Automotive Engineers, American Society for Testing Materials, and automotive engine builders.
The MS classification is the key to selection of oils containing the type of compounding that will extend the
operating life of the hydraulic system. Oils meeting Diesel engine requirements, DG and DS classifications,
may or may not have the type of compounding desired for high performance hydraulic systems.
Good oils are the most economical. Specifications can be set up which will indicate, to a limited degree, the
characteristics essential in a good hydraulic oil. These are listed herein and should be checked with the oil
manufacturer prior to the use of his product.
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