Which of the following mechanical elements undergoes sliding motion________________?
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Answer: D. cross-head
Explanation
The cross-head connects the piston rod to the connecting rod in large reciprocating engines. It travels back and forth inside fixed flat or cylindrical bearing surfaces. This constrained linear movement represents pure sliding motion along the guide path. Reciprocating engines convert linear piston motion into rotary crankshaft power output. Cross-heads prevent side-thrust forces from pushing the piston sideways against cylinder walls. Sliding pairs require continuous lubrication to minimize friction and thermal wear.
Large marine two-stroke diesel engines universally employ cross-head designs for durability. Steam engines also utilized cross-heads to guide piston rod motion smoothly. Maintenance technicians regularly inspect cross-head guides for scoring and alignment wear. Cranks rotate in a circle rather than undergoing linear sliding motion. Connecting rods experience complex combined planar motion involving both rotation and translation. Crank pins undergo pure rotation relative to the bearing journal rather than sliding.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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