Question

In a clock mechanism, hour and minute hands are connected by _________ gear train.

• A. Simple
• B. Epicyclic
• C. Compound
• D. Reverted

Hint:

Whenever you see a gear train application where the input and output shafts are concentric (aligned along the same line), such as in clocks or industrial speed reducers, the answer is always a reverted gear train.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify the type of gear train used to connect the concentric hour and minute hands in a mechanical clock.

Step 2: Key Formula or Approach: A gear train in which the first gear and the last gear have the same (coaxial) axis of rotation is classified as a reverted gear train.

Step 3: Detailed Explanation:

• In a clock, the minute hand and the hour hand must rotate about the exact same central axis.

• However, they must rotate at different angular speeds. Specifically, the minute hand must complete one full rotation in 1 hour, while the hour hand must take 12 hours to complete one rotation.

• To achieve this coaxial configuration with different output speeds, a specific layout of gears is required.

• A reverted gear train achieves this by placing two parallel shafts such that the output shaft is aligned coaxially with the input shaft.

• The first gear on the input shaft drives a gear on an intermediate shaft, and another gear on this intermediate shaft drives the final coaxial gear. This ensures both concentricity and the necessary velocity reduction.

Step 4: Final Answer:
In a clock mechanism, the hour and minute hands are connected by a reverted gear train.