Question

In the context of balancing of rotating and reciprocating masses, which one of the following options is true?

• A. An unbalanced rigid rotor can be completely balanced using a single balancing mass
• B. An unbalanced rigid rotor can be completely balanced using two balancing masses attached in two distinct planes
• C. A single-cylinder internal combustion engine can be completely balanced using a single balancing mass
• D. A single-cylinder internal combustion engine can be completely balanced using two balancing masses

Hint:

When balancing rotating machinery, always consider the number of planes and the positioning of balancing masses to ensure complete equilibrium.

Answer 1

The Correct Option is B

Step 1: Understanding the concept of balancing
Balancing involves eliminating the unbalanced forces and moments that are created by rotating or reciprocating masses. This ensures smooth operation of machinery and minimizes vibration. A rigid rotor, when unbalanced, creates forces that can be controlled using balancing masses.

Step 2: The role of balancing masses in different planes
To completely balance an unbalanced rigid rotor, the balancing masses need to be placed in two distinct planes. This arrangement allows for balancing the forces and moments in both the radial and axial directions.

Step 3: Analyzing the options
- Option (A) suggests using a single balancing mass, which would only address the radial forces but cannot balance the axial forces. Therefore, it is not a complete solution.
- Option (B) is correct, as two balancing masses placed in two distinct planes can completely balance the rotor by addressing both radial and axial forces.
- Option (C) refers to a single-cylinder engine, which typically cannot be completely balanced using a single mass due to the nature of the reciprocating masses involved.
- Option (D) suggests using two balancing masses for a single-cylinder engine, which is not sufficient for complete balancing because a more complex setup is required.

Step 4: Conclusion
Thus, the correct answer is (B), where two balancing masses in two distinct planes can completely balance an unbalanced rigid rotor.