Romaine Electric, in partnership with the Litens Automotive Group, have brought to fruition a four-year project to introduce the first overrunning alternator decoupler pulley, AKA The Monster OAD™, to the transit market.

The pulley is specifically designed to eliminate systemic belt drive failures known to exist on every transit OEM engine platform. This revolutionary pulley design was created by the Litens Automotive Group over 15 years ago for use in the automobile industry and has become the industry standard on nearly all of the world’s cars manufactured today.

The Monster OAD™ pulley has two primary functions that eliminate belt drive issues. First, the pulley has an overrunning feature that allows the alternator rotor to dissipate its inertia by overrunning or “freewheeling.” This feature is important during engine operation at transmission shift points as well as at engine shut down. The current application of a standard solid pulley, the alternator rotor inertia exceeds the horsepower carrying capacity of the belt resulting in noisy belt screech, where belt slippage and wear occur. 

The second and most important feature of system is its ability to absorb the torsional vibration created by the engine. Torsional vibration is created when the engine’s cylinders fire. Each time the piston moves up or down, it speeds up and slows down the crankshaft creating torsional vibration that is being transmitted into the belt drive system. In the current system, what is being installed to absorb this vibration is the belt drive tensioner. The tensioner, in most applications, is not able to withstand the punishment of this vibration and is failing prematurely, due to the excessive loads/demands exerted on the belt drive system from the torsional vibration.

The Monster OAD™ utilizes a patented torsion spring design that is specifically engineered for each intended application. This spring connects the pulley to the alternator rotor; it absorbs and dissipates nearly all of the torsional vibration created by the engine acting like a “suspension system” for the belt drive. The overrunning design is also unique and patented. This too is a similar torsion spring that compresses and releases force on the shaft hub as inertia acts upon the pulley. Driving the alternator and releasing it when needed.

The system eliminates all of the common failure points of the FEAD, front-end accessory drive, or belt drive system, according to the companies.