Help please with power calculations to turn a large flywheel at 1rpm

[powermanxx314]

How did you find PF?: Trying to find answers

Hi I’m trying to solve this problem .hope someone can find the answers, I need to find the hp needed to run a flying wheel ring shape. 42 ft in diameter weight 200.000 lbs the wheel is Suport by bearing inside and out of the edge of the rim, the rim has tooth throughout the outer side of the rim and will need to turn at 1 rpm .power will be transmitted through a pinion gear 2 inch in diameter in the outside side of the rim

 

[berkeman]

How did you find PF?: Trying to find answers

Hi I’m trying to solve this problem .hope someone can find the answers, I need to find the hp needed to run a flying wheel ring shape. 42 ft in diameter weight 200.000 lbs the wheel is Suport by bearing inside and out of the edge of the rim, the rim has tooth throughout the outer side of the rim and will need to turn at 1 rpm .power will be transmitted through a pinion gear 2 inch in diameter in the outside side of the rim

Welcome to PF.

That is indeed a big, heavy wheel. Can you say what the application is? Do you know how much torque will be required to overcome bearing friction? How long do you have to spin the flywheel up from zero to 1rpm?

 

[russ_watters]

Theoretically (neglecting losses) the power required to maintain a flywheel at constant speed is zero. Practically, it depends on the friction, air resistance and other losses.

Googling large industrial flywheel UPSs it appears the flywheel losses are so low they don't bother differentiating between that and other loss sources (electrical system losses). One CAT 750 KW system with a 15 sec runtime offers 97.3% total system efficiency (20.4 kW continuous loss).

If you're trying to build one or just design one, a good place to start would be looking up the friction coefficient of the bearing you select.

 

[powermanxx314]

Welcome to PF.

That is indeed a big, heavy wheel. Can you say what the application is? Do you know how much torque will be required to overcome bearing friction? How long do you have to spin the flywheel up from zero to 1rpm?

Is a personal project, frictions on normal bearings 0.2 , whell turning time is one minute

 

[berkeman]

I need to find the hp needed to run a flying wheel ring shape. 42 ft in diameter weight 200.000 lbs

Is a personal project,

A personal project?! Holy smokes, do you live in a castle or something? (I assume that 200.000 lbs is the European notation for 200 thousand pounds...?)

 

[Baluncore]

@powermanxx314
Can you please confirm if the weight of the wheel is; 200 thousand pounds = 90.72 tonne;
Or; 200 pounds = 90.72 kg.

HP is power, power is the rate of energy flow.
If you want to know power, you must specify the time available to accelerate, and then to decelerate the wheel. The problem with a big flywheel is accelerating and decelerating the mass. I doubt a 2” pinion will be sufficient for a 45.36 tonne wheel.

You need to specify clearly the section shape and dimensional size of the wheel. Then we can work out the inertia and energy storage of your system.

Are the bearings really 42 foot diameter? The bearing detail information is needed to work out the rate of energy loss through bearings. You might do better lowering the wheel density and then floating the massive wheel in a lake.

A pinion is a fragile thing when driving a heavy flywheel. One pinion will unbalance the forces on the bearings and mountings. You may need two or three pinions, on separate drive motors, that can be disengaged from the wheel.

 

[berkeman]

I need to find the hp needed to run a flying wheel ring shape. 42 ft in diameter weight 200.000 lbs

Oh dear, I finally used my Mentor superpowers to track the OP's location, and he is in the USA. And apparently has no clue about how to specify significant figures in problem statements. Sigh.

So a 42' 200 pound wheel. Whatever. Just use a 1 HP electric motor that is geared down. Problem solved.

 

[jrmichler]

frictions on normal bearings 0.2

By itself, this is meaningless. We need a sketch showing the dimensions of the bearing surfaces, and how the bearings support the flywheel.

When you refer to "flywheel", you are implying that it will be used to store energy. That means that energy is put into the flywheel, and energy is taken out of the flywheel. The rate of energy in and energy out is power. We need to know the maximum power put into the flywheel because the drive power is equal to the power into the flywheel plus bearing friction.

Unless you just want to turn it at constant speed. Then it is not a flywheel, but a rotating disk or rotating table.

 

[Baluncore]

My guess is that it is a novel design for a rotating fast food restaurant.