Glass-fiber has become a must for British sports car specialists because it is the only way to make small quantity of cars economically. In 1957, Lotus pioneered Glass-Fiber Monocoque chassis in Elite (see picture). The whole mechanical stressed structure was made of glass-fiber, which had the advantage of lightweight and rigidity like today's carbon-fiber monocoque. Engine, transmission and suspensions were bolted onto the glass-fiber body. As a result, the whole car weighed as light as 660 kg.
However, this radical attempt caused too many problems to Colin Chapman. Since the connecting points between the glass-fiber body and suspensions / engine required very small tolerances, which was difficult for glass-fiber, Lotus actually scrapped many out-of-specification body. Others had to be corrected with intensive care. As a result, every Elite was built in loss. Since then, no any other car tried this idea again.
Today, no matter
Marcos, GM's Corvette / Camaro / Firebird, Venturi and more, employ
in non-stressed upper body. In other words, they just act as a
enclosure and provide aerodynamic efficiency. The stressed chassises
usually backbone, tubular space-frame, aluminium space-frame or even
|Advantage:||Lightweight. Cheap to be produced in small quantity. Rust-proof.|
|Disadvantage:||Lower visual quality. Unable to act as stressed member.|
|Who use it ?||Lotus, TVR, Marcos, Corvette, Camaro, Firebird ...|
There are several Carbon-fibers commonly used in motor industry. Kevlar, which was developed by Du Pont, offers the highest rigidity-to-weight ratio among them. Because of this, US army's helmets are made of Kevlar. Kevlar can also be found in the body panels of many exotic cars, although most of them simultaneously use other kinds of carbon-fiber in even larger amount.
|Porsche 959, employed carbon-fiber in body panels only, is obviously ....|
|.... inferior to McLaren F1's carbon-fiber monocoque. This structure not only supports the engine / drivetrain and suspensions, it also serves as a very rigid survival cell.|
Most so-called "supercars" use carbon-fiber in body panels only, such as Porsche 959, Ferrari 288GTO, Ferrari F40 and even lately, the Porsche 911 GT1. Since body panels do nothing to provide mechanical strength, the use of carbon fiber over aluminium can barely save weight. The stress member remains to be the chassis, which is usually in heavier and weaker steel tubular frame.
What really sophisticated is carbon-fiber monocoque chassis, which had only ever appeared in McLaren F1, Bugatti EB110SS (not EB110GT) and Ferrari F50. It provides superior rigidity yet optimise weight. No other chassis could be better.
Carbon Fiber Monocoque made its debut in 1981 with McLaren's MP4/1 Formula One racing car, designed by John Barnard. No wonder McLaren F1 is the first road car to feature it.
|Ferrari 288GTO (1985)||carbon fiber panels||steel tubular space frame|
|Porsche 959 (1987)||carbon fiber panels||steel monocoque|
|Ferrari F40 (1988)||carbon fiber panels + doors||steel tubular space frame|
|McLaren F1 (1993)||carbon fiber panels||carbon fiber monocoque|
|Ferrari F50 (1996)||carbon fiber panels + doors||carbon fiber monocoque|
|Lamborghini Diablo SV (1998)||mostly aluminium panels, with carbon fiber bonnet + engine lid||steel tubular space frame|
|Lamborghini Diablo GT (1999)||mostly carbon fiber panels + aluminium doors||steel tubular space frame|
F50's rear suspensions are directly bonded to the engine / gearbox
This means the engine becomes the stressed member which supports the
from rear axle. Then, the whole engine / gearbox / rear suspensions
is bonded into the carbon fiber chassis through light alloy. This is a
first for a road car.
Advantage: lighter still.
Disadvantage: engine's vibration directly transfers to the body and cockpit.
|Advantage:||The lightest and stiffest chassis.|
|Disadvantage:||By far the most expensive.|
|Who use it ?||McLaren F1, Bugatti EB110SS, Ferrari F50.|
ASF consists of extruded aluminum sections, vacuum die cast components and aluminum sheets of different thicknesses. They all are made of high-strength aluminium alloy. At the highly stressed corners and joints, extruded sections are connected by complex aluminum die casting (nodes). Besides, new fastening methods were developed to join the body parts together. It's quite complex and production cost is far higher than steel monocoque.
The Audi A2 employed
second generation of ASF technology, which involves larger but fewer
hence fewer nodes and requires fewer welding. Laser welding is also
used in the bonding. All these helped reducing the production cost to
extent that the cheap A2 can afford it.
|Advantage:||Lighter than steel monocoque. As space efficient as it.|
|Disadvantage:||Still expensive for mass production|
|Who use it ?||Audi|
|Elise's revolutionary chassis is made of extruded aluminium sections joined by glue and rivets. New technology can make the extruded parts curvy, as seen in the side members. This allow large part to be made in single piece, thus save bonding and weight.|
Renault Sport Spider bonds them by spot welding, while Lotus Elise uses glue and rivet to do so. Comparing their specification and you will know how superior the Elise is:
|Glue can be clearly seen during production.|
|Advantage:||Cheap for low-volume production. Offers the highest rigidity-to-weight ratio besides carbon fiber monocoque.|
|Disadvantage:||Not very space efficient; High door sill.|
|Who use it ?||Lotus Elise, forthcoming Lotus M250, Opel Speedster|