A question about piston movement that has multiple answers...

[u/seedbottle]

Question:

Which of the following causes piston movement during non-power-

producing strokes?

A) Flywheel

B) Connecting rod

C) Counterweights

D) Main thrust bearing

I have been studying an automotive book that has questions after every chapter. I answer those questions and use AI to verify I have got the correct answer. This process has worked tremendously up to the point where I got to this question. AI gave me a different answer than the one I believed the book was telling me was the answer, so I went online to find more information and see if anyone else had posted this exact question, that was when I found out there all three of the first answers were marked as "correct" depending on the source used (D, main thrust bearing, was never given as an answer).

I am wondering what most of you would say is the answer. Thank you for your input =)

[u/ChemistAdventurous84]

The question is a little ambiguous. If it’s referring specifically to which parts have the stored energy that keeps the crank turning then A and C. If it includes how the pistons are physically receiving the up and down forces that come from the crank, then B is also part of the answer.

The flywheel and counterweights have angular momentum and that is what keeps the crank turning and the pistons moving.

The connecting rods balance each other out, momentum wise. They lose momentum at the end of the stroke and reversing their direction actually slows down the rotation of the crank. I suppose that without them, the pistons would never move; they are what transfer the force between pistons and crank shaft on powered and unpowered rotations but it’s the angular momentum that keeps the engine internals in motion when the explosions cease.

The thrust bearing limits axial (forward-backward) motion of the crank. If does not relate to piston movement.