“You can’t reinvent the wheel but you can put your own spin on it.” – Lauren Beukes
From the round slice of a log ancient people relied on some 5500 years ago — to the ultra-light high-tech magnesium alloy wheel deployed for modern Formula One cars, the wheels of yesteryear have certainly come a long way. Although no one has yet managed to invent anything better than a wheel for purposes of moving vehicles along ground surface, other than actually lifting vehicles up in the air, some of the world’s greatest engineers and technologists have over time achieved serious improvements in the wheels’ performance. The story of a wheel is the story of evolution backed by science and some great discoveries it brought about. So let’s analyze how the first wheels were made, how they are made today and how they might possibly be made in the future.
Invention of a wheel
If we knew the name of the person who invented the wheel, he would be one of the most famous innovators in history. But in reality archeologists are not even sure whether it was invented in Mesopotamia, Northern Caucasus or Central Europe. All we know so far is that the first transportation-oriented wheels were simply slices of log with a hole for the axle to fit through it. There is plenty of evidence to confirm that people in Europe and Asia were using four-wheeled vehicles back in the 4th millennium before Christ (around 3500 BC). However, this simple and powerful transportation mode was barely used, if at all, by African tribes and American cultures.
The need for a faster and more cost-effective transport led to the invention of a wooden spoked wheel by 2000 BC, which had barely changed during the 3800 years that followed (up until the invention of wired spokes and pneumatic tires in 19th century). Long before that happened, Celtic chariots had apparently tried using iron rims back in 1000 BC.
Wire spokes and tires
Wire spokes that we still use on bicycles and on some motorcycle wheels were invented in the beginning of the 19th century. In 1802 G. F. Bauer had first patented wire tension spokes, but wooden spoked wheels still remained largely in use. Some 40 years later, a 23-year-old Scottish engineer R. W. Thompson has come up with the idea of a pneumatic tire. The invention of an air-pumped tire has immediately made the ride smoother – the wheels without such were quite uncomfortable on bumpy unpaved roads.
First cars and steel wheels
The first European autos had wire wheels and hard rubber tires, which were very similar to bicycle wheels. The famous Ford Model T that was produced in the US from 1908 to 1927 was still equipped with wooden artillery wheels. Only in 1926-1927 they were replaced with steel-welded spoked wheels. In 1910 B. F. Goodrich started adding carbon to rubber tires, which made them significantly more durable, but those tires still needed repairs every 35 miles or so. As cars were becoming more and more popular, active competition between wheel and tire manufacturers became tougher – thus leading to faster rate of development in this field.
Magnesium and aluminum alloy rims
In the middle of the 20th century aluminum alloy and magnesium alloy wheels started to gain popularity. In a comparative test conducted by Korea’s biggest bus company, Kyonggi Bus, which provides transport to millions of people all over Korea for the past 80 years (its bus fleet consisting of over 5,000 vehicles), a 10% increase in tire life and a 16% increase in brakes longevity were noticed after switching to aluminum wheels from steel ones. These constitute significant economic and environmental advantages a lighter wheel delivers, in addition to important safety considerations and some reduction in carbon emissions.
Light-weight magnesium rims were originally invented for racing applications, as they provide a further 20% reduction in weight, and eventually made their way into mainstream market. Today most car dealerships offer aluminum alloy wheel packages to buyers, and only some specialize in magnesium rims, which are somewhat more pricey and do possess higher characteristics and provide for better performance on the road. Manufacturing process also results in significant differences in wheels’ performance even if they are made of the same metal. Formula 1 teams and Moto GP racers currently prefer forged magnesium wheels over cast predecessors or other alternatives, such as aluminum wheels, since forged mags are the lightest and also prove to be more durable at impact do a much better job tackling shocks and vibrations. Forged magnesium wheels are not offered by low- and middle-priced automakers due to their higher cost basis; but they do remain the choice of some sports and luxury car owners keen on improving their ride’s safety and performance. Tests confirm that forged magnesium rims prolong the lifecycle of tires, suspension and braking systems, as an effect of reducing the un-sprung mass. A car accelerates and stops faster, with less kinetic energy expended.
In 2006 Michelin announced that it was testing a completely new Tweel technology, which would replace regular rims and tires we use today. Tweels are airless hybrids of wheel and tire that rely on the polyurethane spokes for absorbing shocks. The biggest problem of Tweels is their vibration at the speed over 80 km/h (50 miles per hour). Although Michelin experiments have gathered a lot of attention, the concept of an airless tyre is not new, and scientists were working on it from the beginning of the 20st century. Today a lot of companies are trying to develop a polyurethane analog of Tweel, but there are still too many problems with this material such as traction and thread wear resistance and shock absorbance.
Will the airless polyurethane tire and wheel hybrids eventually replace the pneumatic tires? Well, it may happen some day in a distant future, but it might also be the case of scientists working in the wrong direction. Another likely alternative is that forging technologies may advance to become cheaper, opening the door for forged wheels into lower-priced automotive segment. Engineers have already made great technological progress, including new-generation surface treatment, which allowed manufacturers of forged magnesium wheels to reduce prices, to extend warrantee to ten years and to offer custom designs and colors meeting the needs of even the most sophisticated enthusiasts.
The latest study into economic effects of lightweighting wheels, along with other benefits, is underway – and the results will be published upon availability. It is already clear that the fuel savings alone make up for the difference in price in less than three years, and the reduction of the stopping distance will save an impressive number of lives and will decrease the number of accident-related injuries.