How Many Eggs to Turn a 40lb Flywheel in a Vacuum?

[gibsnax]

TL;DR Summary: How many large AA chicken eggs does it take to turn a 40lb flywheel 1 revolution in a vacuum.

Me and my friends are stupid and somehow we got to thinking how much energy is in an egg. We decided to measure this in egg power, or how many eggs it takes to turn a 40 lbs fly wheel 1 revolution. For simplicity we’ve standardized the eggs as large AA chicken eggs (~58g) and are assuming this is taking place in a vacuum under normal earth gravity. If you can help us figure out the air resistance as well, that’s awesome. Thanks!

 

[berkeman]

Welcome to PF.

What are your thoughts? What if the flywheel bearing friction is zero?

 

[gibsnax]

Welcome to PF.

What are your thoughts? What if the flywheel bearing friction is zero?

Well if the friction is zero then any force at all would move it right? So then we need to figure out what the resistance is. If I follow correctly anyway.

 

[berkeman]

Correct. A frictionless flywheel takes almost no imbalance to start rotating, so if you put an egg on one side and that starts the flywheel rotating and the egg falls off a little later, the flywheel keeps rotating at that speed forever.

For a more real-world situation, you can search items like flywheel bearing friction to try to get some ideas. Are you familiar yet with the difference between static and dynamic friction?

 

[erobz]

How many eggs could you stack there (such that it will rotate the flywheel)...In theory?

 

[gibsnax]

How many eggs could you stack there (such that it will rotate the flywheel)...In theory?

View attachment 349653

I mean in theory infinite if you perfectly balance them. I think I understand that this is a meaningless question with a non answer, but now I have a primal need for an answer. How can we change the question so that it has an answer?

 

[gibsnax]

Correct. A frictionless flywheel takes almost no imbalance to start rotating, so if you put an egg on one side and that starts the flywheel rotating and the egg falls off a little later, the flywheel keeps rotating at that speed forever.

For a more real-world situation, you can search items like flywheel bearing friction to try to get some ideas. Are you familiar yet with the difference between static and dynamic friction?

No I’m not, I mean just based on context clues I think I could figure it out, but I would love to be enlightened

 

[berkeman]

No, it's a good thought exercise, but it's an exercise in understanding friction, bearing friction, rolling resistance, etc.

Practical calculations of the power of motors required to lift/drive stuff involve bearing friction and rolling resistance and desired angular (rotational) acceleration. If you want a more practical problem statement to learn more about real-world calculations, find a flywheel datasheet in a vendor catalog where they specify bearing friction (or bearing frictional torque), and go from there.

 

[erobz]

I mean in theory infinite if you perfectly balance them. I think I understand that this is a meaningless question with a non answer, but now I have a primal need for an answer. How can we change the question so that it has an answer?

You said you wanted it to go one rotation ( I presume you mean and stop). I assume you are just misusing the word "power".

If the egg were attached here ( fixed to the wheel) instead and let go from rest how far would the wheel rotate in a perfect idealization without friction? Feel free to draw on the diagram.

If the egg falls off as @berkeman suggests then there are noticeable differences in behavior between the two scenarios.

 

[berkeman]

Are you familiar yet with the difference between static and dynamic friction?

No I’m not, I mean just based on context clues I think I could figure it out, but I would love to be enlightened

Static friction is the friction between two surfaces that are still "stuck" together and not sliding against each other. It is usually larger than dynamic friction, which is between two surfaces that are sliding against each other.

The classic demonstration of this is when you put a block on a board and tilt the board up until the block starts sliding down it. It starts sliding when you reach the limit of static frictional force, but you can then decrease the angle of the board some and the block keeps sliding because the coefficient of dynamic friction is less than the coefficient of static friction which is what was needed to start the block sliding.

https://en.wikipedia.org/wiki/Friction

 

[Ranger Mike]

Ok, this should be good....i want to know wat you boys been drinking or smokin... it is great that you posit this question.
prove my hypostasis wrong
there are only two sources of energy that effect this earth - gravity and solar.
ifin i remember rightly, to move something you need force
where does the force come from?
ok lets say you want to move a fly wheel you.. needs work
Work = Force times Distance = Energy
where does the energy come from?
Gravity?
Humans?
do humans exist without solar?
do crops grow without solar?
wind? is solar some way involved?
fossil fuel? hmmmm could be solar causing crops compressed by,,gravity?
so if you put a 50 pound weight on the top of the flywheel. it is not going anywhere but compressing the seals on the bearing eventually causing failure due to lubrication loss. The force vector is 90 degrees to earth. Gravity...

It is simple a matter of calculation of the mass of the flywheel overcoming the weight of the object. it matters not what the object is but where the introduced mass is, and how much the mass is relative to the resistant force of the flywheel. You can put a egg on a 100 foot lever and rotate the flywheel ..simple matter of leverage. give me a ever and i will move the earth, some old guy said. Now you know why us racers went from a 10 inch flywheel to a 4 inch flywheel with multi clutch discs.

good job on the skull session tho..keep it up!