# How to Calculate This Horsepower from a flywheel?

I have a flywheel (150 Kg, Diameter-18", RPM)

How I Calculate Horsepower from These information.

I am working on a project

Thank you
physicsforums

## Answers and Replies

lekh2003
Gold Member
The thread over here looks like it discusses the problem.

ar2x7ar
sophiecentaur
Gold Member
2020 Award
Summary: How to find horsepower...?
Information:
flywheel weight- 150 KG
Diameter - 18 inches
Flywheel speed* - 700 RPM's

How I Calculate Horsepower from These information.
The answer can only be obtained if you know how long you need the power to be available for. An unpowered flywheel has only a finite amount of stored Energy (Iω2/2 where I is moment of inertia and ω is the angular velocity). If the flywheel is kept at constant velocity then the available power out is whatever the motor that drives it can produce (none taken from the flywheel).
The interesting question is, in fact, what is the Instantaneous Power, available from the flywheel to deal with a shock load. That's basically what a flywheel is used for - even in a motor car engine, where it gets the shaft running at near constant speed between fuel burns. How 'near' constant speed is needed?
In the days of steam, traction engines had a big flywheel and there was always an Instantaneous Power specified, to indicate how well the engine would deal with instances such as then a plough catches on a stone.

lekh2003
Gold Member
Ah that's interesting sophie, I wasn't really sure how flywheels worked. Thanks.