In Part one we learned the Ancient history(BC) of Vehicle frame. Now We will be talking about modern history(AD) of vehicle frames. One of the reasons for almost negligible improvement in Vehicle design in ancient times was lack of roads. Throughout the Middle Ages, when roads were little more than tracks, wheeled vehicles were used only for the laborious process of carting goods from place to place. When going on a journey, the able-bodied ride(horses) and the infirm were carried in a litter.
It was around 13-15th century that something exciting started happening. If we talk in technical terms then these first wave of new vehicle designs were base on body on frame and primarily pulled by horses till the first instances of modern engines happened in late 19th century in Europe.
So what is Body on Frame or Ladder Frame as commonly known
In this practice an automotive body is placed atop a separate frame evolved directly from the design very first buggy/cart of ancient times. Starting with horse-drawn carriages/coaches I would say it get refined. In fact, the earliest horseless variety even looked like their predecessors. Shared techniques of classic carriage fabrication employed wood and fabric coachwork that called for a high level of craftsmanship. The first example were the coaches.
By the 13th century the chariot had evolved into a four-wheeled form, unlike the earlier two-wheeled version most often associated with the Romans. In the 14th century the passenger coach form of vehicle began to evolve. Coaches featured a rear set of wheels much larger than the front set and, therefore, a shaped body. This provided greater passenger comfort despite its lighter construction and made it possible for it to be pulled by a single horse. These vehicles were first made in Hungary and by the 16th century were in use around the world.
Further Evolution of Design
Coaches gradually become more comfortable. The most common design, developed in Germany in about 1660, is known as the Berlin. In this design, compartment for the travelers has the shape of a shallow U, with a protective roof above. There is a door on each side and the coach can seat four people, in pairs facing each other. The coachman, driving the horses, sits above the front wheels.
Further development of coaches continued including the omnibus, to be pulled by teams of horses over long distances and lighter vehicles designed for style and speed. Some of these carriages were further improved by being enclosed with wood, glass, and cloth.
In the 18th and 19th centuries a wide variety of carriage types were in common use. Wood remain the prominent in vehicle frame until early 20th century. That’s why much of the construction and form of the carriage could be seen in the automobiles that came into use in the early part of the 20th century like Ford’s Model T.
The Modern Chassis
Unlike the first engine and chassis builders, who had no precedents to follow, the first auto body engineers represented an old established craft. It mattered little to them whether vehicles were to be propelled by a gasoline engine, electric power, or steam. Their task was the same as in the days of chariots: to construct a conveyance that would carry people.
The body builders contended that if carriages were good enough for horses, they were good enough for engines. They were even given carriage names — phaeton, brougham, tonneau, landaulet, and wagonette.
The Innovative bunch
Don’t get the idea that early body engineers were a stodgy conservative bunch. When it came to trying new structural concepts and materials, they were as radical as the engine and chassis guys. So much so, in fact, that practically every body structural technique in use today had been tried by 1920, even gluing bodies together.
For example in 1984 Volvo announced the use of epoxy to tack-weld body parts together, thus reducing the number of conventional spot welds from 4000 to 500. But this thing was inspired by early body engineers who used casein to hold early wooden body members together on the Cadillac, Columbia, Loco-mobile, and Peerless of 1898 to 1904 among others.
Wood to Metal
First real revolution in vehicle frame came from the transition from wood to metal. As wooden body panels of those early cars restricted body designers. Wood can only be steamed and bent into simple curves. When applied to wooden frames, the body panels of one make of car looked pretty much like those of any other make. First metal used for the body panels and then for chassis.
Wood Frame-Metal panel
In late 19th and early 20th century most of the vehicles looked similar. But this sameness in appearance was going to change soon. Aluminum and steel started vying to replace wood body panels as early as 1900. At the time, sheet aluminum was more expensive than steel, and cast aluminum brackets more expensive still. Thus was born the first car caste system. Cars having sheet steel body panels were manufactured for the masses, while those with aluminum body panels were made for the rich.
As new metal working techniques such as drop-hammering and power-hammering were perfected in the 1900 to 1910 era, hydraulic stretching around 1920, and drawing and stamping around 1935. As each occurred, metal panels began taking on new, novel shapes. The first U.S.-built auto to sport a steel body was the 1901 Eastman Steamer, the first to have an aluminum body was the 1902 Marmon. Both were built with all-wood frames to which metal panels were pinned.
The wood frame/metal panel arrangement lasted about 10 years. Then, wood frames reinforced with steel to give the car body greater rigidity came along. Called armored wood, it saw its first use as framing to hold the steel body panels of the 1911 Hupmobile. Built by Edward Budd, the Hupp body was the traditional design for the day — a touring (open) car. This design choice was favored one as fully close car were 20% more expansive.
In 1914, Dodge was the first automaker to offer a vehicle with an all-steel body ,The dodge brothers car. Meaning it was the first car that offer both chassis and body panels made of steel. With new ways of forging metal made auto bodies stronger and more durable than ever, in turn making all-steel car bodies the standard by the end of the 1930s. The use of wood in auto construction gradually diminished, with American automakers phasing out their classic “woodie” wagons in the 1950s.
Uni-body (monocoque structure)
After the use of metal which freed the designers and revolutionized the auto-making, next big thing was a completely new approach on making cars. That was uni-body design where vehicle frame is build as one rather that two separate parts. I.e chassis and body.
How it is made
‘Uni-body’ is also known as ‘monocoque’; (from the Greek mono (single) and the French coque, meaning shell.). Monocoque is a one-piece structure which defines the overall shape of the car. Made by welding several pieces together.. The floor pan, which is the largest piece, and other pieces are press- made by big stamping machines. Then they are spot welded together by robot arms (some even use laser welding) in a stream production line. After that, some accessories like doors, bonnet, boot lid, side panels and roof are added.
First instance was 1922 the Lancia Lambda which was a revolution in the evolution of chassis design.at that time. Inspired by ship building it had all steel body monocoque structure. In 1934 Chrysler and Citroën built the first mass-produced monocoque vehicles, Chrysler Airflow and the Traction Avant.
But it didn’t really take off until Nash Motors released their 600 in 1941. Because the body was constructed as a single unit, Nash produced a vehicle that was not only stronger, but about 500 pounds lighter than a traditional body-on-frame automobile. From 1960’s most of the small passenger cars switched to uni-body construction, leaving trucks and large cars using conventional frames. And that still the case.
The base concept of uni-body design have remained true till now. But this does not mean any sense that no progress have been made in last 7 decades. Number of improvement have been introduced in manufacturing, modular design approach and material choices.
Tubular Space Frame
From 1960s many high-end sports cars also adopted tubular space frame to enhance the rigidity / weight ratio . As High performance cars require higher strength. And tubular space frame chassis usually incorporate a strong structure. A slight variation also used in which space frames for the front and rear structure and made the cabin out of monocoque is used to cut cost. .
All Ferrari before the 360M, Lamborghini Diablo, Jaguar XJ220, Caterham, TVR used tubular space frame. And First tubular space frame road car, 300SLGullwing.
Colin Chapman, the founder of Lotus, invented backbone chassis in his original Elan roadster. A strong tubular backbone (usually in rectangular section) connects the front and rear axle and provides nearly all the mechanical strength. Inside which there is space for the drive shaft in case of front-engine, rear-wheel drive layout like the Elan. The body is built on the backbone, usually made of glass-fibre.
The Chevrolet Corvette (1953) was the first production car with a fiberglass body (46 components in total). But it was 1957 Lotus Elite that pioneered Glass-Fiber Monocoque chassis. Engine, transmission and suspensions were bolted onto the glass-fiber body. The stressed chassis are usually backbone, tubular space-frame, aluminium space-frame or even monocoque. Whole car weighed as light as 660 kg.
In the early 80s, FIA established Group B racing category, which allowed the use of any technology available as long as a minimum of 200 road cars are made. As a result, road cars featuring Carbon-Fiber body panels started to appear, such as Ferrari 288GTO and Porsche 959.
What future holds
I think basic design will remain uni-body only. With industry moving towards simplicity with EV revolution. All you need is electric motor and battery and some suspension parts. This is a similar transitions that took place in early 20th century, when car body were inspired by horse driven carriages. So even with no bonnet or boot required on EV Tesla Model S for it to run its design is more or less same with any other sports sedan. But it will change as EV’s goes mainstream. May be cars will be 3D printed in small garage and no big manufacturing plants required.
What the future holds is even more thrilling than what history had. keep up with history and future with us here.