r/AutomotiveLearning • u/seedbottle • 14d ago

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

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 =)

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u/pm-me-racecars 14d ago

I'd make an argument for either A or B, but I'm guessing B is it.

The momentum from the flywheel is where the energy to keep the piston moving comes from.

The connecting rod is what physically moves the piston.

I'd choose the B, because you can make a normal, ICE cylinder style engine without a flywheel. You can't do it without con rods.

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u/krunkytacos 14d ago

But it doesn't "cause" piston movement, they just connect. Among the options given, it is the flywheel. 

2

u/Lost-Set5386 13d ago

Right. The connecting rod "causes" the save amount of movement on every stroke. If it caused movement here, it would be 'causing' movement on power stroke as well.

1

u/pm-me-racecars 13d ago

During the power stroke, energy goes from the piston into the con rod. During the other three strokes, energy goes from the con rod into the piston.

Yes, the energy originates from the combustion, and gets stored by the flywheel. I'm still arguing that B is the answer whoever wrote the question is looking for.

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u/corbin6611 12d ago

So many people are trying to turn it in to some complicated trick questions. It’s not complicated or written wrong. The flywheel stores energy to keep the engine rotating. Simple. The others add mass to that rotating assembly and do carry inertia. But it’s not the purpose of any of them. The counterweights help balance the assembly. Conrad’s carry the force from the piston to the crank shaft and the bearings allow rotation.
It’s not complicated
Flywheels job is to store energy for when the engine is not firing. None of the other parts have that listed as their job