The basic principle of the HyKinesys electro-mechanical IVT is that roughly half the energy flowing between the flywheel and the road wheels travels via a mechanical pathway at ~97% efficiency, while the rest flows at the lower efficiency of a 'flywheel battery'. In addition, where a flywheel battery solution requires two sets of 100 kW motor/generators and controllers to deliver 100 kW to the driving wheels, the electro-mechanical IVT requires only two 50 kW motors and a single 50 kW controller. It also requires a single-stage planetary gear set, but this is only a fraction of the cost of the 'missing' electrical equipment.
The diagram above shows how a PowerBeam surge power system could be installed in a compact front-wheel-drive car, truck or van. The flywheel casing is shown in green, on the left, with the two motor/generators positioned either side of a simple transmission connected to the differential. The engine is on the right, in red. Note that this layout might also be suitable for a small mid-engined sports car. If the motor/generator shown on the right is removed and connected to a differential on the othe axle, a very effective and low-cost AWD configuration can be achieved. The diagram might also be interpreted as showing a rear-engined installation, particularly if the option of a 'flat' engine is imagined. The new generation of two and three cylinder engines make this configuration fully practical.
To eliminate the effects of gyroscopic forces when high-energy flywheels are used, they can be mounted in counter-rotating pairs. In a car driven by a professional racing driver on a repeating and predictable circuit, it is quite reasonable to expect the driver to learn to cope with the precession effects of a single high-energy rotor and compensate accordingly. However, the product liability and safety issues of such an approach in road cars leads us to prefer a twin-rotor configuration unless the peak rotor energy level is low relative to vehicle weight, which it can be in certain entry-level applications. Where a single rotor might be acceptable in a powerful race car, in our opinion it would not be in a road sports car requiring a similar level of energy storage.