The CVT (Continuos Variable Transmission) devised by Girotti takes the move from the exploitation of the properties of a free wheel with two coaxial rotors, in order to transfer in controllated manner power and RPM from one rotor to the other. Between the two coaxial rotors or sleeves (shown in gray) some balls or rollers are placed (shown in red). Depending on the imposed eccentricity for the two rotors, the RPM transferred from one rotor to the other varies continuously.

Sundry inventions by Girotto involved this engine.

Nel disegno a fianco si possono apprezzare due particolari ghiere (in azzurro) che lavorano in cooperazione con due anelli (in giallo), ogni coppia posta sui lati dei rotori. Nelle scanalature sulle ghiere si infilano e scorrono dei perni solidali ai rullini.

Sundry inventions by Girotto involved this engine.

In the drawing on the side you can see two special ring nuts (shown in cyan) cooperating with two rings (shown in yellow), each couple being arranged on the rotors'sides. In the grooves provided in the ring nuts pins integral with the rollers are inserted and able to slide.

The engagement in the grooves assures the constant contact between the rollers and the rotors, in every phase of the rotary cicle. A simple idea, but one alleviating the great problem of the accidental detachment between rollers and rotors, leading to loss of torque at the output.

Another invention regards the mechanism for imposing the desired eccentricity between the rotors, i.e. for establishing the transmission ratio. Girotto's solution involves a pneumatic piston acting radially upon a rotor, in order to move it. The main benefit, absolutely not discernible at first sight, is that the piston retracts if the engine is too much overloaded and, therefore, the torque fed to the output decreses but the engine does NOT turn off.

However, the more relevant invention widening the application field of these transmissions, is probably the cascade of free-wheels. The worst and more limiting problem with these CVTs is the narrow variation in the achievable transmission ratio.

Girotto solved the problem arranging coaxially side by side several free-wheels and coupling them in pairs with a common rotor (see European patent application n.EP1688645A1), thereby setting them in cascade-connection. In this way any transmission ratio is, theoretically, achievable from a very compact and simply adjustable CVT, now being needed only to design the number of cascaded free-wheels.