Flywheels are a good storage of kinetic energy

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Discussion Overview

The discussion revolves around the role and functionality of flywheels in automotive engines, particularly focusing on their contribution to kinetic energy storage, power delivery, and engine performance. Participants explore both theoretical and practical aspects of flywheel operation in various engine types.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about how flywheels are started in cars and their necessity once the engine is running.
  • Another participant explains that flywheels help turn the pistons back up after their stroke, providing necessary torque to the crankshaft.
  • Some participants note that flywheels act as a buffer to smooth out power delivery, which is beneficial for engine performance and reducing stress.
  • Concerns are raised about the potential for jolty motion in engines without flywheels, particularly in high-performance engines with lighter flywheels.
  • There is a discussion about the types of engines that can operate without a flywheel, with some participants suggesting that straight 6 and V12 engines can be balanced without one, but still require a flywheel for smooth operation.
  • One participant mentions the necessity of a flywheel for connecting to the clutch plate and starter in their car.

Areas of Agreement / Disagreement

Participants generally agree on the importance of flywheels for power delivery and engine smoothness, but there are competing views regarding which engine types can function effectively without a flywheel. The discussion remains unresolved on the specifics of engine configurations and their reliance on flywheels.

Contextual Notes

Some claims about engine types and their balance may depend on specific definitions and configurations, which are not fully explored in the discussion. There are also unresolved questions about the implications of using lighter flywheels in different driving conditions.

Who May Find This Useful

Individuals interested in automotive engineering, mechanics, or those seeking to understand the operational principles of flywheels in engines may find this discussion informative.

Jones1987
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So, these things are baffling my mind. I understand they are a good storage of kinetic energy, and help keep momentum of motion.

What I cannot get my head around is, how are they started say within a car, also I assume once the engine is turning over, why is the flywheel needed, so what is the purpose of it?

This may sound really retarded to some people, but I just cannot picture how it comes into play. Any information or for someone to explain these questions would really clear this mess inside my head.
 
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In a car the flywheel is needed to turn the pistons around at the end of their stroke.
Picture a car piston engine (or a steam engine) when the fuel has burned and the piston pushed down to bottom where does the turning force come from to push it back up?

Without a flywheel the crank shaft would just sit there.
Some engines don't need a crankshaft flywheel because of the arrangment of the cylinders, this was BMW argument for why you should only have 6cylinder engines - when they only made 6cylinder cars, the same thing applies to boxer engines http://en.wikipedia.org/wiki/Flat_engine
 


Excellent, now I can see why they are used. I have been watching videos on youtube of little flywheel hot air engines and couldn't figure out, but pushing the piston back after the cycle make perfect sense. Now I think about the crank shaft I can see why it is needed.

Thanks for that, cleared a right mess in my head.
 


However on all cars, it doesn't matter if they have overlapping powerstrokes you should have a flywheel. As it acts as a buffer to smooth out power delivery. Which is good for both stresses and the 'feel' of an engine.
 


Yeah I was thinking about that last night, would you not get jolty motion without a flywheel. Once the main use was explained I think my brain just began to overflow with ideas of its uses, haha
 


You would, yes. This is one reason (but not the main reason) that a high performance race engine (with very light flywheel) is a bugger to drive under normal road conditions.
 


IIRC the only balanced engines without a flywheel (or balanced crankshaft) other than boxers are a straight 6 and V12?
 


All the straight 6s and V12s I've ever dealt with have had a flywheel, although they are considered to be 'balanced' from a reciprocating mass point of view. They still need a flywheel for providing inertia to damp out transient effects and improve smoothness and driveability.
 


mgb_phys said:
IIRC the only balanced engines without a flywheel (or balanced crankshaft) other than boxers are a straight 6 and V12?

You can technically run a I6 or V12 without a flywheel, but you will have a nasty driving experience.

Also you will also find both I6 and V12 cranks with couterwights, even though they are fully balanced as it reduced variations in bearing loads. racing engines won't have this, but road engines will.
 
  • #10


My car needs a flywheel to connect to the clutch plate and to the starter.

Bob S
 

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