How does a car wash work?

How do these giant machines clean our cars?

The automated tunnel car wash is the largest robot most of us will interact with in daily life. With a tough aluminium, rust-resistant frame to carry the machinery and a conveyer belt able to move more than 30 tons of vehicle, a combination of chemicals, high pressure and mechanical friction ensures a thorough clean.

The first automated car wash as we know it was opened in 1951 in Seattle, and since then the industry and technology involved has developed exponentially. The modern tunnel car wash includes thousands of moving parts, various soaps and waxes, and regulators, sensors and gauges to effectively wash the car without damaging it. An effective car wash can remove insects, bird droppings and grease from the surfaces of the vehicle in just a few minutes.

The process generally starts with pre-soakers, usually with a mild alkali first and then rinsing with a mild acid. This is followed by the addition of detergents to deep clean. The main section contains two to five brushes known as ‘scrubbers’, and at least one is positioned horizontally to clean the top of the car. A wax is added to conserve the paint on the car and protect it from scratches and UV light.

Though it is a hydraulic power system that moves the frame and rotates the brushes, it is the computer system that controls the process. Some of the process is pre-programmed, such as to increase the speed of the brushes when passing the front of the car, as it tends to gather the most dirt. Other parts of the car wash rely on sensors and the feedback from them, such as photoelectric systems that are responsible for positioning and contouring detection. In the final drying stage of the car wash, the computer repeats the movement of the brushes memorised from earlier stages.

Inside an automated car wash

The complex conveyor belt of automated machinery we use to clean our cars

llustrations by Adrian Mann

This article was originally published in How It Works issue 102, written by Charlie Evans 

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