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Power Transmission Gears 243
there is no starting and stopping, adequate clean oil is supplied, and the
speed is high enough to generate a hydrodynamic oil film. The journal
bearing can easily be manufactured in a split configuration for effortless
removal. Also, it can be repaired with a roll of solder and an acetylene
torch when absolutely necessary, and machined in almost any shop where
an engine lathe of sufficient size is available.
Unlike some machine bearings, gear bearings have imposed operating
loads in addition to loads due to rotor weights. These operating loads are
directly proportional to the transmitted torque, and since gears are basi-
cally constant torque machines, the bearing loads are basically constant.
Figure 6-22 is included to show the approximate bearing load directions for
speed reducers and increasers with single stage gearing. Bearing load magni-
tude and direction can be determined from many handbooks and are differ-
ent for each type of gearing. Thrust loads are produced by both single helical
and spiral bevel gearing; the direction of thrust changes with the direction of
rotation.
Installation
Handling
A gear unit should always be moved by rolling on bars or skates or by
lifting it with slings through the lifting lugs or eye bolts found on all gear
units. Never lift or sharply pound on the shaft extensions or lubrication
piping as serious damage may result.
Most manufacturers’ gears are test run with a break-in oil that contains
a rust preventive which will protect the internal parts for at least six
months under normal storage conditions after they leave the factory. Do
not store gear units outdoors unless covered. If the inoperative period is
greater than six months, special treatment is required (see “Inoperative
Periods” under “Lubrication”).
Foundation
The foundation under a gear unit has great bearing on the unit’s opera-
tion and life. First of all, proper alignment is absolutely essential for
long, trouble-free operation, and obviously, to maintain the alignment re-
quired for satisfactory operation, the gear unit must be securely mounted
to a suitable rigid foundation. lbo of the more commonly used founda-
tions are the concrete foundation and soleplate combination, and the
common bedplate (baseplate).
The concrete foundation and soleplate combination is semi-permanent
and thereby allows for the removal of the gear housing at a later date