A Gear Train is a combination of two or more than two gears which work together by engaging
their turning and teeth with one another. This combination works like a single integrated system
and utilize to generate torque and power. The main objective to build a gear train is to create
larger gear ratio. In a gear train, there are multiple gears of different sizes. For instance, the
largest gear of a Gear Train is five times greater than the smallest one. To reduce the gear speed
and enhance the gear torque in the gear system (gear train), electric motor is used. This electric
motor is mounted on the test platform and the electric motor is connected to the driving end of
each train. A large magnetic particle brake is used to measure the magnitude of the output torque
and therefore, it is connected to the output end of the gear train.
Types of Gear Train
Simple Gear Train
This is the simplest kind of Gear Train. The teeth of the gear pair in this type of Gear Train
connecting parallel shafts. The teeth of this type of Gear Train may either be herringbone, helical
or spur. The angular velocity is inversely related to the tooth ratio. One of the biggest
disadvantage of this type of Gear Train is that its maximum speed change ratio is only 10:1. To
get larger speed change ratio, the Gear Train size has to be enlarged. This size enhancement may
produce imbalance in wear capacities and strength of the Gear Train.
Bicycle chain and sprockets are simple type of Gear Trains. By pushing the paddle, the front gear
is turned and it interstices with the chain links. The chain continue to move and meshing occurs
continuously with the links in the rear gears that is affixed to the rear wheel. This makes the
bicycle to move.
Compound Gear Train
Compound Gear Train arrangement is preferred when large velocity is needed. To keep the
output and input shafts in a line, two keys are adjusted to a single shaft. For this type of
adjustment, equal distance from the center for pinions and gears is chosen.
Epicyclic Gear Train
The system of Epicyclic Gear Train is alike of epicyclic gears. In this type of system of epicyclic
gear, minimum one wheel axis revolves around another fixed axis.
Planetary Gear Train
This type of Gear train consists several components. At the center, there is a small gear, which is
called as sun gear, a big external gear which is called as ring gear and several medium size gears
which are known as planet gears. The ring gear rolls on the planet gear and the planets revolve
and roll around the sun gear. This type of gear train has many advantages.
These are the following advantages of the Planetary Gear Train:
The gear ratios are high.
For automatic transmission in automobiles, these gear train are suitable.
Suitable in bicycles for both manual as well as automatic paddling control.
These are also useful for the power train between an electric motor and a internal
Applications of Gear Trains
Although, the Gear Trains have many applications, but, some specific applications of Gear
Trains are as follows:
On a clock or a watch dial, to represent the phases of moon, gear trains are used.
To drive a traditional two-disk lunar display off the day-of-the week shaft of the cylinder,
Gear trains are used.
Planetary Gear Trains Vs Traditional Gear Trains
If we compare the traditional gear trains with Planetary gear train, we will find that there are so
many advantages are prevailed in the second type of gear trains over the first type. Some of the
advantages are as follows:
In a smaller package of gears, planetary gear train provides higher train ratio than the
traditional gear train.
By default reversion is available in Planetary gear trains, which is not found in traditional
From a single unidirectional input of Planetary gear train, bi-directional, concentric and
simultaneous output can be derived.
The above mentioned features of Planetary gear trains make them suitable for automatic
transmission in automobiles over the traditional gear trains.