Question 12 AEL01 - Assistant Engineer - Limited

The Correct Answer is C ### Explanation for Correct Option (C) **C) crankshaft counterweight:** Component "U" is positioned on an arm extending radially from the axis of the crankshaft. Its primary function is to counterbalance the weight of the crank pin and the connecting rod assembly (including the piston) that are attached to the adjacent crank throws. This counterbalancing action ensures smooth rotation, reduces vibration, and minimizes the bending loads imposed on the main bearings. In internal combustion engines, these masses are specifically known as crankshaft counterweights. ### Explanation for Incorrect Options **A) frame stiffener:** A frame stiffener is a structural component added to a chassis or engine block primarily to increase rigidity and reduce flexing. While diesel engine blocks have stiffening elements, component "U" is a rotating mass attached directly to the crankshaft for balance, not a stationary structural part of the engine block or frame. **B) frequency tuner:** While engines are designed to avoid critical resonant frequencies, a "frequency tuner" is not the standard term for a rotating mass used for mechanical balance. Dynamic balancing components like "U" are called counterweights or balance weights, designed specifically to address inertia forces, not primarily for tuning system resonance (which is usually addressed through damping or structural design). **D) main bearing support assembly:** The main bearing supports (or main bearing caps/saddles) are the stationary parts of the engine block or bedplate that house the main bearings and support the crankshaft. Component "U" is an integral, rotating part of the crankshaft itself, not the stationary support structure.