Starting with the question of whether a bicycle can be faster than an engine-powered car, this article discusses the drag forces that affect the speed and performance of a bicycle. In particular, the design of bicycle wheels plays an important role in reducing drag, offering the possibility of developing a faster and more efficient means of transportation.
What is the top speed a bicycle can reach? Can a bicycle using human leg power be faster than a car using an engine? The short answer is that bicycles can be faster, depending on the conditions. Currently, the fastest speed ever recorded on a bicycle on flat terrain is 132 km/h, set by a Canadian cyclist at the WHPSC 2008. This speed was achieved on a velomobile, which is a type of bicycle that consists of a recumbent bike wrapped in a streamlined material. At first glance, it looks like a thumb, with only the head protruding upward for visibility. The wheels stick out just a little bit, minimizing the air resistance that a normal bicycle would experience from the front when riding.
However, it’s difficult to evaluate a bike’s performance by simply looking at its speed record. A bike’s true performance depends on how efficiently it can run in different conditions and how harmoniously man and machine work together. These factors play a particularly important role in bike racing. It’s not just a race for speed, it’s a multidisciplinary sport that requires strategy, endurance, and the ability to adapt to the situation. For example, in mountainous terrain with high gradients, stability and control are much more important than speed.
So, how fast can you go on a normal bike? If the same bike is used and the external factors are the same, the speed will be determined by the rider’s leg strength. So what if the same person rides the same bike? The answer is obviously the same, even if it’s a pointless question. But what if the same person is using the same bike, only the wheels are shaped differently? The results are enormous. If you’ve ever seen a racing bike, you’ve seen wheels without spokes. If you’re reading this, you’re probably thinking, “Why would anyone use such a skinny wheel? Do rims really have that much of an impact?” You might be asking yourself. The reason has to do with drag force.
Drag is one of the elements of aerodynamics, and it’s one of the biggest external resistances a bike faces. For example, when you’re running a 100 meters, the wind that you’re facing makes it difficult to move forward. The drag we’re talking about in this article is related to air resistance. On a bicycle, the wheels are one of the most important parts that use friction with the ground to propel you forward. When looking at the aerodynamics of a bicycle in motion, you might think that the wheels don’t have much of an impact because the area they occupy is so small. However, they’re the most moving part of the bike, and they have a special effect on the flow around them, unlike when it’s simply stationary. The numbers vary from bike to bike, but for a typical bicycle traveling at 48 km/h, the drag is measured to be around 35 N. This is 1020% of the drag of a bicycle, the second largest percentage of a bicycle after a person.
While the human portion can be reduced by correcting our posture, the wheel portion can only be reduced by designing aerodynamic rims. So how do we design them? G.S. Tew and A.T. Sayer (1997) published a paper on the effects of commercially available bicycle rims. They experimented with wheels with six different rims and found some very interesting results. He found that disk wheels (flat wheels with no rims) have a 30% reduction in drag compared to other wheels when the wind is blowing from the front, but the drag is greater when the wind is blowing from the side. This is because the nature of a disk wheel is such that it cannot pass wind from the side, but instead receives the force.
However, when a bicycle is traveling at 80 kilometers per hour, the effect of side winds is not as strong, which is why disc wheels are used in racing bicycles. This is the same reason why, for example, when we run a 100 meter race, even if there is a lot of wind blowing from the side, we only feel the wind in front of us. Here again, some readers may raise a question. Why do some race bikes use spoked wheels on the front wheel and disc wheels on the rear wheel? This is because the front wheel is responsible for changing direction. In bike racing, where you have to change direction frequently, the front wheel is more susceptible to crosswinds, which increases drag. To avoid this, the front wheel is usually a spoked wheel.
Efforts are still ongoing to design aerodynamic wheels to reduce drag. We believe that one day, wheels with minimal front and side drag will be researched and developed. This research is not limited to bicycles. Reducing drag is also essential for other modes of transportation, such as aircraft, cars, and yachts, as it will allow for faster and more efficient transportation.
The study of drag is not limited to bicycles, however, as it affects a wide range of mechanical devices used by humans. For example, minimizing drag is also important in the design of aircraft wings and car bodies. Not only does this allow us to travel farther with less fuel, but it also has a positive environmental impact. Ultimately, research and technological advancements are being made to reduce drag in all aspects of human life. One day, we may be able to overcome drag and enjoy perpetual motion.
