Self-Decoupling Dual Mass Flywheel

Flywheels are essentially a rotating mass most commonly used to smooth out the pulses of a piston engine. Car engines have them, usually a few kg worth on the end of the crankshaft. In practice, they smooth out the power pulses from the engine to reduce shock loads on the transmission in addition to adding to the total rotational momentum of the engine at low RPM. This gives a little bit of leeway when engaging the clutch, a slight mismatch between engine output and clutch friction can be drawn from energy stored in the flywheel.

At high RPM this is much less important, the power pulses are much closer together, the rotational momentum of the engine without the flywheel starts to become significant in its own right and the power output meets or exceeds the energy demands of accelerating up the drive-train. At this point, a heavy flywheel becomes a liability. At high RPM the engine has far more energy stored in the flywheel than it needs and RPM changes become difficult. For this reason, racing engines have much lighter flywheels. This destroys much of the low RPM benefits needed in regular driving however.

The solution. A two part flywheel. Closest to the engine, mounted to the crank is the driven flywheel #1. This contains weights on radial tracks held close to the center by springs. As the rotation speed increases the weights are driven centrifugally outward moving levers. Through significant mechanical advantage the levers retract pads, similar to brake pads, into the flywheel, so that they no longer contact flywheel #2. The second flywheel, mounted in front of the first is not driven by the crank. It is bearing- mounted and now may spin freely. As the engine speed falls again, the weights move inward and the pads emerge a small distance from the face of flywheel #1 where they contact flywheel #2 and accelerate it up to engine speed.

This engine will perform like one with a heavy flywheel at low RPM and an engine with a light flywheel at high RPM. Smooth low speed driving and good throttle response at high speeds. I'm aware that dual mass flywheels already exist, however these are radially coupled by springs. The dual masses cannot decouple. The second sprung mass functions to dampen torque oscillations. This idea is essentially a second flywheel actuated by a reverse- centrifugal clutch.