Bumper (car)
Vehicle structure absorbing impact in minor collisions.
A bumper is a structure attached to or integrated with the front and rear ends of a motor vehicle, designed to absorb impact in a minor collision and ideally minimize repair costs. Early stiff metal bumpers appeared on automobiles as early as 1904, serving a mainly ornamental function. Over time, developments in materials and technologies, along with a greater focus on functionality for protecting vehicle components and improving safety, have transformed bumpers.
Quick Facts
- Earliest car bumper installed
- 1897
- First impact-absorbing bumper material
- rubber
- Year of that patent
- 1905
Facts from the source article.
History
George Albert Lyon invented the earliest car bumper, which first appeared on a vehicle in 1897, installed by the Austrian carmaker Nesselsdorfer Wagenbau-Fabriksgesellschaft. These early bumpers were unreliable, serving only a cosmetic function. Early car owners replaced the front spring hanger bolt with longer ones to attach a metal bar. G.D. Fisher patented a bumper bracket to simplify attachment. The first bumper designed to absorb impacts, made of rubber, appeared in 1901, and Frederick Simms gained a patent for it in 1905. Automakers added bumpers in the mid-1910s, typically a steel strip across front and back, often as an optional accessory. Bumpers became more common in the 1920s as designers made them more complex and substantial. Chrome-plated bumpers grew heavy and elaborately decorative until the late 1950s, when US automakers began establishing new trends. The 1960s saw lighter chrome-plated blade-like bumpers with painted metal valances. Multi-piece construction became normal as grilles, lighting, and rear exhaust were incorporated. In 1968, General Motors introduced the 'Endura' body-colored plastic front bumper on the Pontiac GTO, designed to absorb low-speed impact without permanent deformation. Similar elastomeric bumpers appeared on the 1970-71 Plymouth Barracuda. In 1971, Renault introduced a plastic bumper made of sheet moulding compound on the Renault 5. Modern bumpers typically consist of a plastic cover over a reinforcement bar of steel, aluminum, fiberglass composite, or plastic, often made of PC/ABS.
Physics
Bumpers protect other vehicle components by dissipating the kinetic energy generated by an impact, which is a function of vehicle mass and velocity squared. The force and energy loads multiply exponentially as speed increases; a bumper protecting at 5 mph must be four times as tough as one protecting at 2.5 mph. Until 1959, rigidity was considered beneficial to occupant safety, but modern theories favor vehicles that crumple progressively. A completely rigid vehicle might protect components well but would offer poor occupant safety.
Height mismatches
For passenger cars, bumper height and placement are legally specified under US and EU regulations. During emergency braking, suspension changes the pitch of each vehicle, allowing bumpers to bypass each other in moderate-speed collisions. Preventing override and underride can be accomplished by extremely tall bumper surfaces or active suspension. Bumper height from the roadway is essential for engaging other protective systems; airbag deployment sensors typically trigger only upon contact with an obstruction, so front bumpers must be the first parts to make contact in a frontal collision to allow time for airbag inflation. Energy-absorbing crush zones are ineffective if bypassed, as when a tractor-trailer's elevated platform misses a passenger car's front bumper and contact occurs with the windshield. Aftermarket lift kits are legal in most of the United States, but many jurisdictions restrict bumper height to protect pedestrians. New Hampshire requires any vehicle other than a private passenger car to have a horizontal bumper height between 16 and 30 inches. Modifications raising the front while keeping the rear low have caused fatalities; states such as Georgia, North Carolina, South Carolina, and Tennessee have banned the practice, and making a front bumper four or more inches higher than the rear is illegal in Virginia. Underride collisions, where a smaller vehicle slides under a larger one, often cause severe injuries or fatalities; around 500 people are killed this way annually in the United States.
Regulation
Most places require cars to have bumpers by law. These rules exist for two reasons that often clash: letting a car handle slow-speed hits without breaking safety gear, and keeping pedestrians safer. A bumper that holds up well and keeps repair bills low is more likely to hurt a pedestrian, while one that’s kinder to pedestrians usually costs more to fix. Most bumpers are built to just barely meet the legal minimum. International rules, first created as European standards through the United Nations, are now used in most countries outside North America. They say a car’s safety systems must still work after a straight-on hit from a pendulum or moving barrier at 4 km/h to the front and rear, and after corner impacts at 2.5 km/h from 45.5 cm off the ground, whether the car is loaded or empty. Europe has put in place rules to tackle the 270,000 pedestrian deaths that happen worldwide each year in car accidents. Special bumpers called bull bars or roo bars help protect vehicles in rural areas from big animals, but studies show these rigid bars make death and serious injury more likely for pedestrians in cities, since they don’t crumple or absorb force like a normal bumper. The European Union has banned selling rigid metal bull bars that don’t meet pedestrian-safety standards.
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