Gearbox is defined as a metal casing in which a train of gears is sealed.
Gearbox is also called gearhead, gear reducers or speed reducers. They are
available in broad range of sizes, capacities and speed ratios. Their job is to
convert the input provided by a prime mover into an output of lower RPM and
correspondingly, higher torque.
Input and output configurations for
gearbox include hollow shaft or coupling or bushing. A single input shaft can
drive multiple output shafts. The output shafts are usually parallel and
in-line. However, some unique configurations exist that allow for offset shafts
to be driven at different speeds. Some gearboxes are supplied with a reaction
arm. A reaction arm prevents the reducer housing from rotating when there is no
base mounts or flanges. Shaft alignment can be parallel in-line, parallel
offset, right angle and non-perpendicular angled shafts.
intended to be incorporated in a transmission for vehicles, particularly terrain
vehicles, preferably driven by an internal combustion engine.
||Types of Gearboxes
Automatic Gearboxes: Several factors have contributed to the development of automatic gearbox.
Firstly, the advent of electronics in the nineties and secondly, the wish of
having more gear speed. It is used for power transmission and offers automatic
gearshift. Automatic gearboxes are easy and pleasurable to drive. The only thing
to be done after engaging a gear is to press the accelerator to go and press the
brake to stop. The automatic gearboxes relies on hydraulic fluid pressure to
shift the gears up and down. This fluid needs to be checked regularly.
Manual Gearbox: Manual gearbox has widely spread into the market but Europeans still remain
faithful to manual gearbox. The manual gearbox has been as old as the car
itself. These gearboxes use conventional clutch that is activated each time a
gear is selected by an electronically controlled motor. This then disengages the
clutch, the gear is shifted and the clutch engages once more. It all happens
within a second and the system even allows for the car to come to a stop whilst
still in gear. The manual gearbox is virtually maintenance free except for the
checking of the oil level occasionally.
Gearing Arrangement for Gearbox
Gearing arrangement for gearbox includes spur, helical, planetary, bevel, worm,
and cycloidal. Bevel gear is a gear wheel meshed with another so that their
shafts are at an angle less than 180degrees. They connect intersecting axes.
Helical gears connect parallel shafts but the involute teeth are cut at an angle
to the axis of rotation. Two mating helical gears must have equal helix angle
but opposite hand. Spur gears connect parallel shafts, have involute teeth that
are parallel to the shaft and can have internal or external teeth. Planetary
gears are a set of gears usually two or more on or inside a larger gear. They
make drastic gear ratio possible. They are used when one wishes to turn the
input in the same direction as the output. Planetary gearboxes can be designed
with gear sets or a set of planetary cones. Cycloidal gears are used in pairs
and are set at an angle of 180 degrees used to balance the load and are driven
by multiple crank shafts to share the load and increase torsion rigidity.
Cycloid reducers use rolling elements and a multilobe cam to transmit torque and
provide speed reduction. A worm gear is an inclined plane wrapped around a
central axle. It is a gear with one or more teeth in the form of screwed threads.
Controlling Gear Box Contamination
Wear and tear is common in gearboxes. Wear commonly occurs as a result of the
contamination and degradation of the lubricant. Proactive maintenance is a
well-documented concept. It leads to longer life of the gearbox. In a gearbox,
there are moving components that transmit power through rotation and so
degradation of lubricant can lead to adhesion, abrasion and corrosion of
component surfaces, which finally leads to component failure.
used for lubrication must be free from contamination. Seals have the ability to
seal against oil leakage. Breathers are used for allowing airflow on the
gearbox. This is to allow for changes in volume as a result of top-ups, leakage
and temperature-related volume changes.
An annual check of all switches
and sensors should be performed to verify operation as per lubrication system
settings. Pumps and other motorized accessories should be checked at scheduled
intervals. Flows and pressure drops at the cooler, filters and inlet to the
rotating equipment should be routinely monitored and recorded to identify any
adverse trends. An annual check of cooler condition is important to maintain