Gudgeon Pin & Connecting Rod MCQs with Detailed Explanation

Correct Answer: D. Connect the piston to the connecting rod

• Gudgeon pin is fitted through the piston bosses and the small end of the connecting rod.
• Its main purpose is to connect the piston with the connecting rod.
• It also acts as a bearing or pivot for the connecting rod.
• Because of this pin, the connecting rod can oscillate while the piston moves in a straight line.
• Option B is wrong because crankshaft connection is done at the big end of the connecting rod, not by the gudgeon pin.

Correct Answer: A. Piston pin or wrist pin

• Gudgeon pin is commonly called piston pin because it is fitted in the piston.
• It is also called wrist pin because it acts like a joint between piston and connecting rod.
• The pin allows relative angular movement at the small end of the connecting rod.
• Crank pin is a different part associated with the crankshaft and big end of connecting rod.

Correct Answer: B. Crankshaft

• The connecting rod is the link between the piston and the crankshaft.
• The small end of the connecting rod is connected to the piston through the gudgeon pin.
• The big end of the connecting rod is connected to the crankshaft through the crank pin/bearing arrangement.
• It transmits the force produced on the piston to the crankshaft.
• This helps in producing rotary motion at the crankshaft.

Correct Answer: B. Rotary motion of the crankshaft

• The piston moves up and down inside the cylinder, so its motion is linear/reciprocating.
• The crankshaft must rotate to deliver useful engine output.
• The connecting rod works between the piston and crankshaft to transfer force and change the type of motion.
• Thus, the reciprocating motion of the piston is converted into rotary motion of the crankshaft.

Correct Answer: C. Alloy steel

• The connecting rod must be strong enough to withstand heavy gas pressure, inertia force and twisting/bending effects.
• At the same time, it should be light in weight to reduce inertia load at high speed.
• Therefore, connecting rods are usually made of high-grade alloy steel.
• Aluminium alloys are also used in some engines, but the usual exam answer is alloy steel.
• Cast iron is not preferred for this function because the connecting rod needs high strength and toughness.