The study of the behavior of the airflow as it passes around a moving object and the forces exerted by the air on the object. In car design the positive and negative lift of the airflow is studied in wind tunnels. Negative lift is preferred to press the vehicle closer to the ground. Car air resistance is also studied. Also called automatic gearbox.
Operation can be electrical or hydraulic.
Today many of the engine-driven auxiliaries use belt drives. World War I, it described a closed luxury car with small windows, which allowed the occupants to see out but to be barely seen from the outside. The measure of an engine's horsepower without the loss in power caused by the gearbox, generator, differential, water pump and other auxiliaries. The actual horsepower delivered to the driving wheels is less. Also called a drophead coup .