Review and summary

REVIEW AND SUMMARY

• A gear train is defined as a combination of gears that is used for transmitting motion from one shaft to another.

• Train value is the ratio of the speed of the driven gear to the speed of the driving gear.

• Types of gear trains are:

1. Simple gear trains,

2. Compound gear trains,

3. Reverted gear trains, and

4. Epicyclic gear trains.

• When there is only one gear on each shaft, it is known as simple gear train.

• Velocity ratio of a simple gear train:

• Intermediate gears, also known as idler gears, are used to change the direction of rotation of the driven gear without changing its angular velocity.

• Intermediate gears do not affect the velocity ratio/train value of the gear train. 

• When two gears are fixed on the same shaft, then the gears from a compound gear. 

• A gear train having one or more compound gears is known as compound gear train.

• Velocity ratio of compound gear train:

• A compound gear train in which the first and last gears are co-axial is called as reverted gear train.

• When the axis of rotation of one or more gears is allowed to rotate about another axis, then the gear train is known as epicyclic gear train.

• When there is only one gear on each shaft in any epicyclic gear trains, then gear trains are called as simple epicyclic gear trains.

• When there are more than one gear on a shaft in any epicyclic gear trains, then they "are called as compound epicyclic gear trains.

• The velocity for epicyclic gear train is found by using tabulation method or algebraic method.

• Torques and tooth loads in epicyclic gear trains can be determined using the following relations:

T1 + TO + TB = 0

Input power + Output power = 0

i.e., T1 ω1 + TO ωO = 0