Open Road

How automobile bodies evolved through history from wood to carbon fiber

"You don't have to study physics to understand the laws of motion to drive a car. You don't have to understand any of this stuff ..." -Steve Jobs, Apple designer

Steve Jobs enjoyed driving powerful luxury cars. Could this have been the early inspiration for Apple to get involved with autonomous automobiles?

Another creative genius, Frank Lloyd Wright, also enjoyed fast and beautiful vehicles. He tried designing a few, but he had better success as an architect than as a carchitect. At the time he practiced his art, the automobile was in its infancy. Cars were crafted from wood, just as horse-drawn wagons had been constructed for hundreds of years. Heavy they were, but weight did not matter at a time when fuel was inexpensive and plentiful.

Today, the auto industry is shedding weight wherever it can to improve fuel consumption and lessen emissions. New materials are helping designers and engineers to accomplish that objective. Why then is it a good thing that we praise carbon frames and carbon body panels when we condemn carbon fuel? That's a 'weighty' question.

It had started with wood. Why would wood not be the choice material in the early automobiles, when it was well known for centuries in wagons wheels and cherished chariots of all types. When horseless carriages were converted into 'auto-buggies', they retained their wood frame. Skilled craftspersons also created the body structures. These were covered with treated canvas, before being painted. (BTW, that feature is making a modern comeback.)

As in every occupation, people experimented: Some cars were built differently, using diverse materials: Already the Model T combined wood and metal; a Hanomag of the 1920s had a wicker body; the budget version of the steel version.

Even when steel frames were used, many manufacturers sent the running gear (called 'chassis', from French) to coachbuilders to complete the automobile by fitting a wood body to the frame. Boat builders were skilled in this type of work, and the style of car we still know today as a ' boat-tail' is a holdover from that era.

As the automobile matured, fewer skilled craftspersons were on hand, and steel and aluminum panels were used to cover the wood-framed body. Already during the second decade of the last century, forward-thinking individuals were envisioning a better way to make automobiles. During a lecture at an early meeting of the Society of Automotive Engineers (SAE), someone interrupted the presenter H. Jay Hayes by asking, "What do you think about the controversial theory of combining the body and frame into one unit?"

He surprised his audience by announcing that his coach-building company would produce 3,000 cars just like that, starting the week after the SAE conference, named the Ruler Frameless. Hayes explained the advantages of a combined frame and body unit: making the car smaller and lighter, reducing cost and vibration.

It was difficult for automakers to abandon the frame, and complicated to produce cars in that radical new way. It took many years before one of the mass-producers attempted to fabricate a unibody. 'Unibody' is also known as 'monocoque'; (from the Greek mono (single) and the French coque, meaning shell.)

In the meantime, frames made progress in their own right; new alloys were developed, ladder frames advanced into perimeters frames; the X-frame improved roll-stiffness for better handling, and so on.
The first popular mass-produced unibody car came in 1928 from DKW (now Audi) with a fabric-covered wood frame. Today, Audi builds cars with an aluminum ' spaceframe'. The Chrysler Airflow and the Citroen Traction Avant of 1934 used stressed body panels, and the Opel Olympia of 1935 was General Motors' first unibody car.

The Volkswagen Beetle had a platform frame to which the body attached, making it extremely stiff. An additional benefit of the platform frame made it possible to adopt different body shapes, the early Porsche, Karmann Ghia, the VW 'Micro Bus', dune-buggies, and others.

Most pickup trucks, vans, and SUVs of today still use a body-on-frame construction, while the 'crossovers' are frameless. Honda's Ridgeline is a unibody exception. Manufacturing cars that way is almost universal today.

Open-wheel racecars (IndyCars and Formula 1) and prototype sports cars (Le Mans type) have gone a step further in monocoque construction. Through the marvels of modern chemistry, the body of these cars is stronger than steel and lighter than aluminum.

Fiberglass cars (and boats) have proven their advantage over many years, but compared to mass-produced cars, their numbers are still small. Because of the urgent need to lower weight and fuel consumption, and thereby emission, modern cars utilize innovative materials, stronger and lighter than fiberglass, namely carbon fiber.

You may know that fiberglass takes hours to 'cure' or harden. Efforts are underway to 'bake' carbon fiber and resin combinations in autoclaves to reduce manufacturing times to less than six minutes. Under high pressure and temperature, resin is injected into the mold where a cloth-like weave of carbon and other fibers is placed. Variations of the chemical ingredients dictate whether a composite part is flexible or rigid – leaf springs are produced from fiberglass regularly.

After all the progress, wood still has a place in many motorists' mind: the eternal popularity of the 'Woodie'. Even recent engineering students are exploring the strengths of wood and others fibers when they built the 'Splinter' supercar. Long live the Woodie!

As newer fuel efficiency rules and CO2 restrictions are pending, many manufacturers prepare to mass-produce major components and complete unibody vehicles from carbon fiber composites. Stronger than steel, but less than half the weight, these new cars are 'paving the road' for zero emission electric vehicles.

New styles with good performance and efficiency are surpassing cars of the ICE (internal combustion engine) age; they will assure sustainable personal mobility for millions of future motorists in the current r EVolution of the automobile.

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