CONTROLLED COUPLING HYDRA-MATIC FUNDAMENTALS
(pg 85)

2. The main parts of each torus are  the outer shell, inner shell, hub and vanes. The two toruses are identical except for their hubs which differ in size so that they can fit their
respective shafts.
jhmCpg85.gif (149620 bytes)
3. The member to which power is applied is called the drive torus. The member to which power is transmitted is called the driven torus.
4. The fluid coupling offers a number of advantages: jhmCpg85.gif (149620 bytes)
a. It allows gears to be engaged while the car is stopped.
b. It transmits power smoothly as the engine is speeded up.
c. It makes an efficient connection between the engine and rear wheels at higher engine speeds.
5. In operation, when the drive torus turns, the oil within it is throwninto the vanes of the driven torus.The driven torus then turns in the same direction as the drive torus. 6. The higher the engine speed, the higher the speed of the drive torus,and the greater the force exerted by the oil on the driven torus.

7. The drive torus rotates very slowly when the engine is idling,
and produces only a low torque on the driven torus--a torque
not great enough to drive the car against wheel, tire and axle
friction. This is exactly what is needed to keep the car from
moving when the engine is idling.

To page 86