The basic function of car crushers hasn't changed much since they were invented in the 1970s. Improvements in car crusher design focus on two areas: ease of use, and set-up and crushing speed. Older crushers needed more than one operator, and setting up and tearing down a portable crusher could take a lot of time. New crushers have automatic push-button set-up and can be easily run by a single operator. Faster crushers mean more cars crushed per minute, and the more efficient a crushing operation is, the more money the crusher's owner can make.
Once a car reaches the junkyard, it goes through several steps before finally being shredded to scrap metal.
- The car is stripped of all working parts. For example, a car may have a cracked engine block, but the transmission is fine. Salvage crews pull out the working parts for resale. A huge number of parts can be resold - body panels, carburetors, wheels and tires, suspension parts and entire engines can be refurbished and sold to do-it-yourselfers.
- Hazardous materials are removed. The battery is pulled out and chemicals in the air-conditioning system are drained. The gas tank is removed and drained (and resold if it's in good condition).
- The car is left in the junkyard until it's time to be crushed. It could be there for a few hours or even a few months, depending on how big the backlog of cars that need to be crushed is.
- The operator drives the crusher to the junkyard and sets it up (if it's a portable crusher).
- Cars are loaded onto the crushing bed with a forklift, an excavator with a huge claw on the end or a magnet. Some crushers have a crane with a lifting claw or magnet built into the crusher itself.
- The operator activates the hydraulics, crushing the cars as flat as possible. The crushed cars will take up less than half of the space they originally required, and in some cases as little as ten percent. How flat they get depends on the crusher and what kinds of cars are being crushed. Baler crushers can reduce a car to a brick of crushed metal that's about three and a half feet high, two feet wide and three to five feet long [Source: Al-jon].
- There may be an additional storage period before the cars are shipped to a shredder.
- The cars are loaded onto trucks or a train and shipped to a recycler where they will be shredded down to chunks of scrap metal. Often, the stripping and salvaging steps above are skipped - whole cars, tires and all, are fed into the crusher, and then shipped to the shredder where the shredded chunks themselves are sorted.
Granutech's Big MAC portable crusher needs about 45 seconds per car, and can crush four or five cars at a time. Overbuilt's Model 10 crusher is built with a higher clearance on the bed, allowing trucks and buses to be crushed, or six cars at one time. A special hydraulic system that allows rapid transfer of hydraulic fluid increases overall crushing speed [Source: American Recycler].