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How a Chassis Contributes to Car Safety

By: Kevin Watson MSc - Updated: 6 Oct 2011 | comments*Discuss
 
Chassis Safety Crash Engineers Driver

The chassis is a metal frame that runs along the bottom of a car. All other parts of the car lie on or around this frame.

The chassis is critical to car design and manufacture. Its strength and construction are also vital for car safety. In a collision, the visible area of impact is often the damaged metal or plastic of a car’s body. But the chassis absorbs crash energy and can help save lives.

Stress

As well as protecting drivers and passengers, a chassis endures a lot of stress from day-to-day use. It has to cope with the running of the engine and the movement of the wheels. It has to bear the weight of the car body and passengers. And it must deal with the rigours of potholes, bumps and poor quality roads.

Safety

But the most important aspect of chassis design is safety. The chassis must absorb as much of a crash impact as possible. If it doesn’t a car can crumple up, with the driver and passengers inside.

To avoid this situation, the chassis must be tough. It must also distribute crash energy along its length in the event of a rear or head-on accident. This “ripple effect” helps a car to stay in one piece and preserve the shape of the driver and passenger cabin. For a serious accident, this doesn’t guarantee that a driver and passengers will walk away from a crash. But it does help their chances of survival.

With a side impact, the chassis also takes much of the crash energy. Chassis cross-supports help to keep a car intact. And the seating position within the chassis helps reduce driver and passenger injuries. This is why car safety begins with the chassis. Other elements such as seat belts, anti-skid braking systems, and airbags are relevant. The chassis, though, is a safety fundamental.

Engineering

Chassis engineers begin their work by looking at a number of factors. To maintain a chassis’ strength, they use high quality steel. They shape the steel to create a frame that accommodates the car’s features. But first the engineers consider the height of a chassis’ steal beams. This height provides the strength to resist the forces applied to it when a car maker adds all the other parts of a car to the chassis. It must also cope with the weight of the driver, passengers, luggage and fuel.

Another factor for engineers to deal with is chassis twisting. The technical name for this is torsional resistance. A chassis must be strong enough not to twist during its use on the road. After all, the pressures on a chassis when a car has a full load and is turning a sharp corner can be immense. Engineers combat twisting with cross-supports. These come in various shapes, and may be in the form of an “X”, a “U” or a “K”.

These options allow engineers to combine different types of cross-supports within one chassis. For example, engineers may use a blend of support types to maximise strength while improving the quality of the ride.

Style and Power

The demand for stylish and powerful cars has inevitably affected chassis design. Seating positions, boot sizes and engines all have a bearing on the way engineers put a chassis together.

A chassis may not simply run straight from the front to the back, for instance. It may arch over the axles and rise up for the bumpers.

These adaptations don’t compromise safety. Tests on prototype vehicles ensure this. But an eye-catching style has to have a suitable chassis otherwise the car will never reach production stage.

Sports Cars

Some sports cars use a three-dimensional chassis. A tubular steel frame runs beneath the body of the car and around it. In effect, the chassis creates a cage. The manufacturer attaches the bodywork of the car to the cage and may use aluminium rather than steel panels to reduce overall weight. These body panels are not stress-bearing. The crash-resistant strength of the sports car lies mainly with the metal cage. The industry term for such a chassis is superleggera. This is Italian for super-light.

Chassis Damage

A damaged chassis directly affects the ability of a car to absorb crash energy as effectively as it should. Anyone unfortunate enough to be involved in a crash should therefore ensure the chassis of the car is still sound.

Garages can use lasers to measure a chassis and check that a crash hasn’t compressed or bent it. Such a check can minimise injuries and even save lives.

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