Test: Gear Trains - 1 - Mechanical Engineering MCQ

In simple gear train having odd number of idler gears, the direction of motion of the driven gear will be same as that of the driving gear and vice- versa.

The reciprocal of the speed ratio (or velocity ratio) is known as train value of gear train.

An epicyclic gear train has at least one gear axis moving relative to the frame. Key characteristics include:

• The system includes a central gear (sun gear) and one or more planet gears that rotate around it.
• The planet gears are mounted on a movable arm or carrier, which can also rotate.
• This configuration allows for compound motion, providing various speed and torque outputs.

Solution:

• Compound gear train is typically used in an automobile gear box. It allows for multiple gear ratios, providing flexibility and efficiency in speed and torque management.
• An epicyclic spur gear train is used in the automatic transmission of automobiles. It helps in changing gear ratios automatically, enhancing driving comfort.
• The worm and worm wheel gear train is ideal for a speed reducer in lifts. This setup provides a high torque output and precise speed reduction.
• Epicyclic bevel gear train is commonly found in automobile differentials. It allows the wheels to rotate at different speeds, especially useful when turning.

The gear train used in clocks is typically a reverted gear train. This type of gear system is commonly chosen for the following reasons:

• Compact Design: It allows for a more compact arrangement of gears, which is ideal for the limited space in clocks.
• Accuracy: Ensures precise control over the movement of the clock hands, which is crucial for timekeeping.
• Simplicity: The design is straightforward, making it easier to manufacture and maintain.

The speed ratio and the train value, in a simple train of gears, is independent of the size and number of intermediate gears. These intermediate gears are called idle gears, as they do not affect the speed ratio or train value of the system.

In reverted gear train, first and last gear is on the same axis such an arrangement has application on speed reducers, clocks and machine tools.

If the axes of the first and the last wheel of a compound gear coincide, it is called a reverted gear train.