Technology – Carbon-Fiber Monocoque Chassis

11 05 2009

Monocoque – Wikipedia, the free encyclopedia

Carbon-Fiber Monocoque designs are favored amongst high-performance cars and racing cars today for their overall structural integrity and the fact that one can design a monocoque out of lightweight materials such as carbon fiber and expect the resulting vehicle to be light, stiff, and stable at high speeds and in tight corners. These types of particularly advanced monocoques can even be molded to create diffusers and ground effects which generate huge amounts of downforce.

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Technology – Monocoque Chassis (Unibody)

11 05 2009

AutoZine Technical School – Chassis

Monocoque, from Greek for single (mono) and French for shell (coque)


Is a construction technique that supports structural load by using an object’s external skin as opposed to using an internal frame or truss that is then covered with a non-load-bearing skin.

Today, 99% of conventional cars produced in a planet are made of steel monocoque chassis. The most common form of chassis construction for passenger cars and, ever more so, 4WD cars. thanks to its low production cost and suitability to robotised production.Monocoque is a one-piece structure which defines the overall shape of the car. While ladder, tubular space frame and backbone chassis provides only the stress members and need to build the body around them,  monoque chassis is already incoporated with the body in a single piece.

In fact, the “one-piece” chassis is actually made by welding several pieces together. The floorpan, which is the largest piece, and other pieces are press-made by big stamping machines. They are spot welded together by robot arms (some even use laser welding) in a stream production line. The whole process just takes minutes. After that, some accessories like doors, bonnet, boot lid, side panels and roof are added.Monocoque chassis also benefit crash protection. Because it uses a lot of metal, crumple zone can be built into the structure.

Another advantage is space efficiency. The whole structure is actually an outer shell, unlike other kinds of chassis, therefore there is no large transmission tunnel, high door sills, large roll over bar etc. Obviously, this is very attractive to mass production cars.

There are many disadvantages as well. It’s very heavy, thanks to the amount of metal used. As the shell is shaped to benefit space efficiency rather than strength, and the pressed sheet metal is not as strong as metal tubes or extruded metal, the rigidity-to-weight ratio is also the lowest among all kinds of chassis bar the ancient ladder chassis. Moreover, as the whole monocoque is made of steel, unlike some other chassis which combine steel chassis and a body made of aluminium or glass-fiber, monocoque is hopelessly heavier than others.


Advantage: Cheap for mass production. Inherently good crash protection. Space efficient.

Disadvantage:
Heavy. Impossible for small-volume production.

Who use it ? Nearly all mass production vehicles.





Technology – Aluminium Space Frame chassis.

11 05 2009

AutoZine Technical School – Chassis

Aluminum Space Frame chassis. Developed in conjunction with US aluminium maker Alcoa, ASF is intended to replace conventional steel monocoque mainly for the benefit of lightness.Audi claimed A8’s ASF is 40% lighter yet 40% stiffer than contemporary steel monocoque. This enable the 4WD-equipped A8 to be lighter than BMW 740i.

SF consists of extruded aluminum sections, vacuum die cast components and aluminum sheets of different thicknesses. They all are made of high-strength aluminum alloy. At the highly stressed corners and joints, extruded sections are connected by complex aluminum die casting (nodes).

Body-in-white and closure breakdown pictorial of the 2002 Audi A8.

Advantage: Lighter than steel monocoque. As space efficient as it.

Disadvantage: Still expensive for mass production. Mainly only high end vehicle use this technique of chassis due to its high level of skill and tricky production needed.

Who use it ? Mainly the high end performance vehicle brands use this type of chassis. Audi, BMW, Mercedes etc





Technology – Tubular space frame

11 05 2009

AutoZine Technical School – Chassis

Tubular space frame. One of the earliest examples was the post-war Maserati Tipo 61 “Birdcage” racing car. Tubular space frame chassis employs dozens of circular-section tubes (some may use square-section tubes for easier connection to the body panels, though circular section provides the maximum strength), position in different directions to provide mechanical strength against forces from anywhere. These tubes are welded together and forms a very complex structure, as you can see in the above pictures.

For higher strength required by high performance sports cars, tubular space frame chassis usually incorporate a strong structure under both doors (see the picture of Lamborghini Countach), hence result in unusually high door sill and difficult access to the cabin.

In the early 50s, Mercedes-Benz created a racing car 300SLR using tubular space frame. This also brought the world the first tubular space frame road car, 300SL Gullwing. Since the sill dramatically reduced the accessibility of carbin, Mercedes had to extend the doors to the roof so that created the “Gullwings”.Since the mid 60s, many high-end sports cars also adopted tubular space frame to enhance the rigidity / weight ratio. However, many of them actually used space frames for the front and rear structure and made the cabin out of monocoque to cut cost.


Advantage: Very strong in any direction. (compare with ladder chassis and monocoque chassis of the same weight)

Disadvantage: Very complex, costly and time consuming to be built. Impossible for robotized production. Besides, it engages a lot of space, raise the door sill and result in difficult access to the cabin.

Who use it ?
All Ferrari before the 360M, Lamborghini Diablo, Jaguar XJ220, Caterham, TVR etc.





Technology – Vehicle Chassis

11 05 2009

UNIBODY VEHICLE CHASSIS STIFFNESS STUDY USING ABAQUS

Most street driven cars are manufactured using a construction technique known as unibody spaceframe chassis construction. This means that the body itself provides the stiffness and structure of the vehicle. Many older vehicles had separate stiffening structures and bodies, the body being solely designed as an aesthetic exterior and as a safety and environmental housing for the passengers. This technique is both heavier and requires more materials raising costs. Modern vehicle chassis are made entirely out of formed sheet metal sections which are usually spot welded together to form the structure of the vehicle. Designing these chassis is no easy task, the geometries being incredibly complex. Making these designs both cost effective, lightweight, stiff and safe is always a tradeoff.

Production vehicle chassis vary substantially in the degree to which they maximize the variables previously mentioned. Higher performance vehicles are often designed with maximum stiffness and lightweight in mind. A lighter weight chassis promotes an overall lower vehicle weight and better performance. Chassis stiffness though is also important for vehicle performance.

As a vehicle is driven, various forces are applied by the suspension on the chassis. This occurs under braking, cornering, driving surface variations, or any other vehicle movement. In higher these loads are, the more is demanded of a chassis. The chassis obviously has to be strong enough not to fail under these loads, but beyond that it must not deflect appreciably. Suspensions are carefully designed to position the wheels and tires of the vehicle for optimum performance under all conditions of vehicle use. If the chassis deflects when the forces are high, it causes suspension mounts and attachment points to temporarily shift, which destroys the careful suspension design when it is needed most. Chassis stiffness is most important in high performance or racing cars, where suspension loads are at their highest and suspension adjustment is most critical.

Chassis Development

Through out the development of the motor vehicle, many different types of chassis have been designed and tested. Through the years many advances have been made in chassis technology, and many old technologies have been thrown out as inferior. Here are some of the basic types which were or are in common use.

Ladder Chassis

This is the earliest kind of chassis. From the earliest cars until the early 60s, nearly all cars in the world used it as standard.Major structure of chassis is supported by central rails connected by cross braces. Still used in trucks and SUVs due to good isolation between passenger cabin and road vibration. Since it is two dimensional it is not very stiff, and needs to be built heavier than a good space frame.

Its construction, indicated by its name, looks like a ladder – two longitudinal rails interconnected by several lateral and cross braces. The longitude members are the main stress member. They deal with the load and also the longitudinal forces caused by acceleration and braking. The lateral and cross members provide resistance to lateral forces and further increase torsional rigidity.




Hummer H1& H2 SUV Ladder chassis


57 Chevy Classic Ladder chassis
http://autoweldchassis.com/56chevy.ivnu

Advantage: Well, it has no much advantage in these days … it is easy and cheap for hand build, that’s all.

Disadvantage: Since it is a 2 dimensional structure, torsional rigidity is very much lower than other chassis, especially when dealing with vertical load or bumps.

Who use it ? Most SUVs and all classic cars. I.e 57 Chevy





Technology – Electronic Air Suspension System

7 05 2009

Continental Automotive -Electronic Air Suspension System

The Electronic Air Suspension System EAS unleashes the possibilities of electronic engineering to improve the automotive chassis providing drivers with safer driving, better comfort, and sportier handling. EAS automatically adapts damping and spring characteristics, along with the vehicle’s body level to driving conditions and load changes.

Advantages of EAS

  • Reduction of roll and pitch movements
  • Reduction of other vehicle body movements
  • Reduction of variations in wheel loading
  • Distinct improvement in driving dynamics and comfort.





Technology – Wheel motor

7 05 2009

Siemens wheel motor diag.jpg (JPEG Image, 400×377 pixels)

The Tech Specs
A 7 kilogram (14.4 pound) in-wheel motor forms the heart of the Michelin Active Wheel. Packing in a sophisticated active shock absorption system, with its own dedicated motor, and disk braking brings the wheel to a hefty 43 kg (95 pounds). But Michelin Director for Sustainable Development and Mobility of the Future, Patrick Oliva points out in Die Welt that the sprung weight in the Heuliez Wheel is 35 kg (77 pounds) on the front axle and 24 kg (53 pounds) on the rear.

Together, the two front wheels deliver a steady 41 horsepower, which can spurt up to 82 hp for short sprints. The Will should do 0-100 km (0 – 62 mph) in 10 seconds and will have a max speed of 140 km/h (87 mph).

Lithium ion batteries will be delivered in three modular configurations, offering ranges of 150, 300 and 400 km (93, 186 and 248 miles). Just like hybrids, the Active Wheels recover energy during braking to extend vehicle range. The in-wheel motors are reported to be 90% efficient, compared to about 20% efficiency for a conventional vehicle in city driving.