Service Manual

1
BDP-10A/16A/21L
A fixed displacement gerotor charge pump is pro-
vided in the BDP units. Oil from the external res-
ervoir and filter is pumped into the closed loop by
a charge pump. Fluid not required to replenish
the closed loop flows either into the pump hous-
ing through a cooling orifice, or back to the charge
pump inlet through the charge pressure relief
valve.
Check valves are included in the pump end cap
to control the makeup oil flow for the system. The
size and type of check valve can play an impor-
tant role on the system pressure, response, and
amount of heat generated, due to the recircula-
tion of makeup oil flow. Additionally, some BDP’s
may be equipped with System Check Reliefs
(SCR’s). SCR’s are factory preset pressure regu-
lating check valves.
In some applications of the BDP’s, it is desirable
to move the machine for short distances at low
speeds without operating the engine. An increase
in resistance will occur with movement at higher
speeds. A screw type bypass valve is utilized in
the pumps to permit movement of the machine.
The bypass valve is fully opened when unscrewed
two (2) turns maximum. The bypass valve allows
oil to be routed from one side of the pump/motor
circuit to the other, thus allowing the motor to turn
with minimal resistance. The bypass valve must
be fully closed during normal operation.
WARNING
Actuating the bypass will result in the loss
of hydrostatic braking capacity. The ma-
chine must be stationary on a level sur-
face and in neutral when actuating the
bypass.
Additionally, some BDP’s may be equipped with
an Auxiliary Pump. The Auxiliary incorporates
the principles of the charge gerotor assembly and
provides the capability of an external auxiliary flow
for an alternate hydraulic circuit to operate ac-
cessories without loss of drive.
INTRODUCTION
The purpose of this manual is to provide infor-
mation useful in servicing the Hydro-Gear Ban-
tam Duty Pumps (BDP’s). This manual includes
the BDP’s general descriptions, hydraulic sche-
matics, technical specifications, servicing and
troubleshooting procedures for BDP models
10A, 16A and 21L.
The BDP’s normally will not require servicing dur-
ing the life of the vehicle in which it is installed.
Should other servicing be required, the exterior
of the BDP’s will need to be thoroughly cleaned
before beginning most procedures.
The models BDP -10A, 16A and 21L differ from
the BDP model 10L. The physical distinction in
appearance of the BDP-10A, 16A and 21L is
signified by the design of an aluminum end cap.
This end cap improves versatility in the applica-
tion of these products.
GENERAL DESCRIPTION
The BDP’s can be combined with wheel motors
and other remotely located units. These pumps
provide an infinitely variable speed range be-
tween zero and full displacement in both forward
and reverse modes of operation.
The BDP-10A, 16A and 21L are of the axial pis-
ton design, utilizing spherical nosed pistons. A
compression spring, located inside each piston,
holds the nose of the piston against a thrust bear-
ing race.
The variable displacement pump features a
cradle swashplate with a direct-proportional dis-
placement control. Reversing the direction of
the angle of the swashplate reverses the flow of
oil from the pump and thus reverses the direc-
tion of motor output rotation.
Movement of the directional control shaft pro-
duces a proportional swashplate movement and
a change in pump flow and/or direction.
SECTION 1. DESCRIPTION AND OPERATION