Free Flywheel Inertia & Energy Calculator
Calculate mass moment of inertia (J), rotational kinetic energy (Joules), released punching energy, and centrifugal rim hoop burst stress for mechanical flywheels.
⚙️ Flywheel Geometry & Material
Total Rotor Mass: 45.2 kg (99.7 lbs)
• Centrifugal Hoop Stress (σ): 7.1 MPa (1,030 PSI)
• Rim Peripheral Velocity: 31.4 m/s (≤ 40 m/s safe limit).
The Rim Efficiency Rule: For a given mass, a spoked rim flywheel stores nearly twice as much energy as a solid disc because rotational inertia scales with radius squared ($J = m cdot r^2$).
Recommended Tools & Equipment
Tested hardware and components for high reliability
Flywheel Energy Storage Physics
A flywheel acts as an electromechanical reservoir, absorbing excess energy during non-work strokes and discharging kinetic energy during high-demand peak load events:
Governing Equations
Hollow Rim Inertia: J = ½ × m × (R_o² + R_i²)
Kinetic Energy: E_k = ½ × J × ω² (Joules)
Released Energy: ΔE = ½ × J × (ω_max² - ω_min²) ≈ J × ω_mean² × C_s
Hoop Tensile Stress: σ_t = ρ × v² = ρ × (ω × R_o)²
Safety & Burst Containment
Hoop stress is caused entirely by centrifugal body forces and is independent of wheel thickness or width! Cast iron flywheels must never exceed a rim velocity of 30 to 40 m/s (100-130 ft/s) to prevent catastrophic explosive burst failure.
Frequently Asked Questions
Why do metal stamping punch presses require massive flywheels?
The stamping die requires 50 to 100 kW of instantaneous power during the 0.05-second blanking stroke. Without a flywheel, a gigantic 100 HP motor would be required. The flywheel delivers 90% of the blanking energy from stored inertia, allowing a modest 5 HP continuous motor to smoothly re-accelerate the wheel between strokes.
What is the coefficient of speed fluctuation (Cs)?
Cs is the allowable fractional change in speed during the work stroke: Cs = (N_max - N_min) / N_mean. For punch presses, Cs is 0.10 to 0.20; for electric power generators, Cs must be ≤ 0.02 to maintain grid frequency.
Can a carbon fiber composite flywheel store more energy than steel?
Yes! Energy storage density per kilogram depends on tensile strength divided by density (sigma / rho). High-strength carbon fiber can spin at over 800 m/s, storing 5 to 10 times more energy per kilogram than the finest aerospace alloy steels.