Transport: Fluid Drive

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Every 1939 Custom Imperial Chrysler sold last week had as standard equipment a hydraulic clutch which eliminates any mechanical connection between the engine and the wheels. Called fluid drive. Chrysler's innovation removes the necessity for gear shifting and clutching except when a car is pulling heavily or backing up.

A conventional clutch is a cushioned disk (connected to the transmission gears), which takes power from the engine when it is forced against a disk on the face of the engine's spinning flywheel. In fluid drive the flywheel is equipped not with a disk, but with a sort of water wheel. Facing the blades of this water wheel is a similar set of blades on the transmission shaft. The two sets of blades are enclosed in a sealed compartment filled with light oil. As the flywheel gathers speed, the blades attached to it set the oil in motion, and the moving oil drives the opposite set of blades. These in turn rotate the transmission gears and, through them, the drive shaft and the wheels. A fluid drive automobile can be braked to a stop in high without killing the motor. It can be started in high without bucking or stalling.

Parent of fluid drive is the hydraulic turbine principle, almost as old as the automobile itself, but until recently not made efficient. Already in use in the British Daimler's "fluid flywheel," it is also the basis for hydraulic transmissions being installed this year by General Motors on 150 busses. The General Motors adaptation replaces not only the clutch, but all transmission gears except reverse, relieving the bus driver of the job of clutching and shifting gears in ordinary stop-and-go operation, making less harried the task of driving, opening and closing doors and collecting fares.