Above is the Torotrak variator, it affects the speed of rotation of the sun gear and is responsible for the smooth variation of ratios, which the Torotrak transmission produces.
Inside the variator are two pairs of discs. The space between each pair of discs forms a hollow doughnut shape or 'toroid'. Within each toroidal space there are three rollers. These rollers transmit drive from the outer, engine driven, discs to the output discs located in the centre. The rollers transfer power between the input discs and the output discs via a traction fluid.
Each roller is attached to a hydraulic piston. The pressure in the pistons can be increased or decreased to create a range of reaction torque within the variator.
The variator shown on this page is an inline piston design, where the packaging requirements require a compact lever arrangement can be used as shown in the picture below.
Click on image to view full size version
A new even more compact version of the variator has recently been developed where the rollers are all controlled by one piston. Torotrak have termed this design 'Epicycloidal Roller Control' (ERC). A movie clip showing the basic operation can be accessed form the bottom of the related links section. More details on this new design will be added to this website early in 2006.
Various movies explaining how the variator works can be found in the related links section below.
