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The all new Volvo C70 – Convertible with advanced body construction

22 September 2005

• Effective deformation even without a fixed roof
• Doors designed to remain shut
• Zoned frontal structure made of differing steel grades
• Compact engines and efficient packaging
• Controlled deformation in a rear-end collision
• Protection for other road-users

The all new Volvo C70 has an extremely advanced body structure for a convertible, with all the systems and components interacting to distribute and absorb incoming collision forces as effectively as possible – thus contributing to reduced injury risk for the occupants. The lack of a fixed roof has been compensated with reinforcements and sophisticated technology.

The all new Volvo C70 was developed to provide the same safety level as a sedan model of the same size. What differentiates a convertible from a sedan is that in the open-top car, collision forces cannot be diverted up into the body structure.

"The lack of a fixed roof means that the incoming forces must instead be diverted along the body sides in a frontal or offset collision," says Ingrid Skogsmo, head of the Volvo Cars Safety Centre.

This imposes stricter demands on the doors, which have been reinforced with a robust longitudinal aluminium beam at the upper edge. Its purpose is to help keep the passenger compartment intact by leading the impact forces further back into the body structure. What is more, the doors are designed to hook into the B-posts and remain shut in a collision.

At floor level, the forces are led backward via sturdy still beams.

Advanced front structure with separate zones
In a compact body, the preconditions for effective deformation differ from those of a large car body.

"The deformation has to be retarded in a shorter distance than in a larger car," explains Ingrid Skogsmo. "And in order to absorb as much as possible of the incoming energy, we have to exploit the material’s properties to the maximum."

The front body structure of the all new Volvo C70 has been divided into several zones, each with a different deformation role. The outer zones handle most of the deformation. The closer the collision forces come to the passenger compartment, the less the material is deformed. In order to give each such zone the appropriate characteristics, the type of steel used varies. Four different steel grades are employed. In addition to conventional body steel, three different grades of high-strength steel are found in the body panels: High Strength Steel, Extra High Strength Steel and Ultra High Strength Steel.

With this zone system, incoming collision forces are absorbed in a very intelligent and effective way:

Zone for deformation at low speeds
The front bumper features a very stiff cross-member made of boron steel (Ultra High Strength Steel). Its attachment in the body’s longitudinal beams consists of collapsible "crash boxes" that help absorb low-speed impact forces without damaging the remainder of the body’s network of beams.

Zone for deformation at high speeds
The straight sections of the longitudinal beams are made of High Strength Steel (HSS), a very strong type of steel that is optimised for high energy absorption. This zone accounts for most of the deformation.

The all new Volvo C70 is also equipped with upper side-beams. They contribute to enhanced passenger protection in a collision with an object such as a truck’s cargo bed or a loading-bay platform.

Backup zone
The beam that curves out towards the A-posts serves as a barrier for the passenger compartment and as a backup to help reduce deformation. Its design also helps minimise the risk of the front wheel penetrating into the passenger compartment. Instead, the wheel helps absorb the collision forces. This section is very stiff and is made of Extra High Strength Steel.

Three-way attachment
A stiff cross-member links the A-posts and the lower side-members so they form an extremely stiff three-point attachment on each side. This construction plays a vital role in maintaining the passenger compartment’s integrity in a severe collision.

Compact engine and efficient packaging
The engine too boosts protective safety in the all new Volvo C70, thanks to compact design and efficient packaging under the bonnet. Since the engine is installed transversely, the compact dimensions create generous space between the engine and passenger compartment. In a collision, the engine can be pushed about 150 mm to the rear before the crankshaft comes into contact with the cross-member alongside the bulkhead.

The steering column can deform up to 140 mm. During deformation, it moves horizontally so that the airbag can deploy in the most effective position for this particular car model.

Rear-end impacts
The all new Volvo C70 is also designed to offer effective protection in a rear-end collision.

The rear longitudinal beams deform in a controlled manner. They link to the sill beams to distribute impact forces forward into the body structure. At the top, the horseshoe-shaped beam behind the rear seat and a double steel bulkhead behind the backrests help reduce the risk of penetration into the passenger compartment.

"The retractable hardtop too is part of the collision protection system," says Ingrid Skogsmo. "When it is opened and stored in the luggage compartment, it works together with the double wall to absorb collision forces."

What is more, the robust ROPS (Roll-Over Protection System) bars come up in a collision from the rear. The aim is to reduce the risk of the passengers being struck by loose objects from the rear-impacting car.

Volvo’s system for avoiding neck injuries – WHIPS (Whiplash Protection System) – is one of the most effective on the market and is fitted as standard in the all new Volvo C70. In the event of a severe impact from behind, the backrest and head restraint accompany the passenger’s body as it responds to the force of the impact.

The seats and backrest have a very sturdy construction. They are dimensioned to withstand high loads. At the same time, they are designed to give in a severe impact, where the balance between strength and flexibility is vital to occupant safety.

"Our seats are far stronger than is usual in this type of car," relates Ingrid Skogsmo.

Protection for other road users
The body’s rounded shapes and smooth surfaces help reduce the risk of injury to pedestrians, cyclists and other road users in an accident. What is more, the front has a soft, energy-absorbing structure in front of the bumper to counter the risk of leg injuries. The bonnet and front wings too are designed to absorb energy and reduce the risk of injury.

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