The first car-washing facilities appeared in the United States in the 1930s and were little more than conveyors along which the car was pulled while gangs of workers cleaned it by hand. One group applied detergent while another, farther along the line, rinsed it off. The space required, coupled with labor costs, made this an expensive operation. The first fully automatic car-washing machine was made in the United States in 1938; such machines did not appear in Europe until a German firm began production separately in 1964. Since then, a number of firms have produced variations or innovations.
A typical machine has three large cylindrical cleaning rollers made of very dense but flexible polyamide or polyethylene strands, the ends of which are splayed out. It is claimed that these bristles tend to flick away the dirt, whereas hand-cleaning methods are more likely to grind the dirt into the paintwork. The brushes rotate at speed, so that the strands stand out about 12 in. (31 cm).
The rollers, which are about 6 ft. (2 m) long, are arranged with one horizontal, to clean the upper surfaces of the car, and two vertical, to clean the sides. As they rotate, water and detergent sprays wash the car. The car is moved by a device such as a small roller, which is located behind one of the car’s wheels, or else the car remains stationary and the roller frame moves over it. The latter system is cheaper and requires less space, but the moving-car system allows a continuous line of cars to be dealt with, giving a higher production rate.
Most sets of rollers are equipped with limit switches, usually operated by simple levers that control the action of motors. When the rollers meet with some resistance, such as the front of the car or even a fixed wing mirror, the movement of the roller over the car is stopped, and the motors drive the roller upward or to one side, "feeling" the way round the obstacle. When the obstacle is overcome, the limit switches stop the motors, and the motion of the car through the rollers continues.
In one system, the vertical rollers are pivoted at the top and are free to swing apart easily. The horizontal roller is counterbalanced so that very little effort is needed to push it up, though it will move downward slowly if left to itself. These rollers have no limit switches or motors, but "crawl" their way around the car as it moves by virtue of their rotation.
After the brushes have cleaned the car, either it can be driven away to let the water dry off naturally, or with the more expensive machines, driers are used. Some driers blow warm air onto the car to evaporate the moisture away. Others blow the water off while the car is still in a mobile state, using intense jets of air directed downward and outward. This method is more economical, as the volume of air blown and heating required is rather less than in the other system. The final rinse may have a chemical added to lower the surface tension of the water, thus aiding the drying.
Some machines may have small separate brushes equipped with separate switches that clean the car’s wheels. Pillars containing sprayers that treat the lower half of the car with a degreasing fluid before the wash takes place, are also available.
Brushless washers
Commercial vehicle fleets sometimes use brushless machines, which consist of a narrow rectangular frame suspended from a hoist. On the inside of the frame are a large number of jets that produce a strong, finely divided spray. One of the cross members can be adjusted to the vary- ing lengths of different vehicles in a single commercial fleet.
In operation, the frame is lowered around the vehicle and then raised, during which an acidified detergent is sprayed on. After a pause of about a minute to allow the detergent to activate, the process is repeated using an alkaline detergent. Ten seconds later, the vehicle is rinsed thoroughly with water and the frame is removed.
