TM 5-3895-346-14
POWER STEERING
DESCRIPTION
DESCRIPTION
General
The VTM27, VTM28, VTM40, VTM41, and VTM42 are identical in basic operation and performance
characteristics, but have certain major differences involving reservoirs, pump volumes, mountings, and drive
shaft configurations. The Typical Model Code Breakdown table illustrates a complete breakdown of the model
number codes which cover all standard units in this model series. Special features are identified by a three
digit suffix to the model number.
NOTE
Service inquiries should always include the specific model number which may be
found on the pump name plate.
Assembly and Construction
The cutaway views of the pumps in this series illustrate the differences between these units. The VTM40 and
VTM41 units are designed with integral reservoirs. The VTM27, VTM28, and VTM42 pumps have externally
mounted reservoirs or can be adapted to manifolds for remote reservoir location. (The VTM42 is not shown but
is similar to VTM27. ) Principal components consist of the reservoir, body, cover, ring, rotor, vanes, pressure
plate, relief valve, and drive shaft assembly. The VTM27, VTM41 and VTM42 Series pumps are designed for
external mounting and indirect drives; however, special application approval must be obtained for gear drives.
NOTE
Helical gear drives must not be used with the VTM27 and VTM41 pumps.
The VTM28 and VTM40 Series pumps are designed for direct mounting. Most of the bearing load is carried by
the external mounting. The VTM27, VTM28, and VTM42 units may be equipped with pump-mounted reservoirs
or may be fitted with manifolds. (Refer to Fig. 7.) When manifolds are used, the pump is connected to a
reservoir located elsewhere in the circuit.
Flow Control and Relief Valves
These pumps are equipped with integral flow control and relief valves. Volume greater than the rated flow is
bypassed to the inlet, within the pump through action of the flow control valve which operates on a pressure
differential. The relief valve limits the maximum pressure in the hydraulic circuit.
Application
Consult Vickers Mobile Division application engineering personnel to determine correct pump ratings, methods
of installation, and application.
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