Why choose aluminum as the material for electric bike frames?
Nov 22, 2022
As we all know, the frame of an electric bike retains the structure of a traditional bike. The bicycle was invented in the early 19th century. Inventors came up with a new concept − the bike which was a new modification on an existing design.
In 1790, a Frenchman named Sivrac invented the first bicycle. At that time, the frame material of the model was mainly made of heavy wood and it could only be pushed forward by using the legs. In fact, this was just a prototype of a bicycle that had no driving device and could not be steered.
Even so, the bicycle made by Sivrac was regarded as the prototype for modern bicycles and was the prelude to the era of bicycles.
In 1869, Reynolds of Britain used steel for the frame and wire spokes for the first time to tighten the rim of a wheel made from steel pipes. He was the first to install a solid rubber belt on the rim to reduce the weight of the bicycle.
In 1886, the British mechanical engineer Starley designed a new bicycle style from the perspective of kinematics and mechanics. The frame used a triangular structure made of metal and a diamond-shaped frame was made of steel pipes.
At this point, the bicycle was born in the true modern sense. The bicycle models designed by Starley are the same as today's bicycles.
The frame is the primary part of making a bicycle but when customers understand more about electric bikes, they often consider the importance of powerful motors, large-capacity batteries and sensitive disc brakes. But these high-end components require a safe and robust frame.
From 1790 to the present, the frame material has undergone significant development due to technological progress. In addition, people have had new demands for it.
The development direction of the frame material is lightweight, high strength, comfortable, and low cost. From wood at the beginning, then steel pipes, to the gradual development of material technology later, the weight-to-strength ratio of steel pipes has reached a specific limit.
Today's frame materials include steel, aluminum, titanium, carbon fiber and magnesium alloys. Density is the main factor affecting frame weight. In the case of the same volume, the lower the density of the material, the lighter the weight of the frame.
Due to the long history of steel, it has been widely used in the frame of electric bikes. With the development of new materials, the improvement of processing levels, the reduction of cost and the pursuit of lightweight materials for the future, the status of steel is gradually fading out.
Why is an aluminum alloy widely used in frame manufacturing? What is the reason why some materials cannot be commonly used in frame manufacturing? Let's compare how these materials differ.
Frame Material Comparison
Steel is the most widely used material in the bicycle industry. It has the most extended application history for the frame and the processing technology is also very mature. Steel has the advantages of high strength, good processing performance and good welding performance.
It has good elasticity, absorbing the body vibration caused by rough ground during riding and provides comfort. It is the lowest cost of all materials and has an unmatched price advantage over several other materials.
However, with the progress of industrial development steel also has apparent disadvantages in using it for the frame. Although modern processing technology and steel properties are improving compared with other materials, the thickness of the steel frame still needs to be improved.
And it is easy to cause metal fatigue, mainly concentrated in the weld. The fatigue phenomenon refers to a phenomenon in which metal materials are destroyed under alternating stress. When the object is subjected to repeated stress, tiny cracks will be formed in the local high-stress area, and the crack will gradually expand.
Once the crack reaches a critical point it will expand rapidly. Eventually, the object will break. This fatigue damage is often difficult to discover in time and easily causes accidents.
Carbon fiber is a new fiber composite material with high strength and modulus with a carbon content of more than 95%. It has the advantages of being lightweight, having high strength and having good rigidity.
But there is a fatal flaw − high manufacturing costs. This is a key factor restricting the widespread application of carbon fiber materials in frame production.
In addition, the carbon fiber frame needs to go through complex calculations to determine its alignment before processing. Polymer materials will age with the wind and sun, gradually affecting the vehicle's performance. Therefore, this material is not currently suitable for widespread use in manufacturing frames.
Compared with other materials, the obvious advantages of magnesium alloy are its lightweight, low density and lowest specific gravity among all materials. This can effectively reduce the weight of bicycles. In addition, it also has the advantages of particular strength, high specific stiffness, good shock absorption performance and processing performance.
But it also has more obvious disadvantages − magnesium alloy welding performance is poor, it easily deforms and cracks and easily reacts with oxygen and nitrogen in the process. The corrosion resistance is poor. It has vigorous chemical activity with quick chemical reaction to substances in the air and no protection for the base metal. It needs electroplating, anodic oxidation and other processes to enhance corrosion resistance.
Its most prominent advantages are high strength and low density. In addition, it also has the advantages of being lightweight, having good toughness, being corrosion resistance and having a long life. Although the performance of titanium alloy material is very suitable for frame production, it is difficult to refine and expensive because it is in the form of titanium dioxide in nature.
And, it isn't easy to process. Due to the material's high strength, it easily reacts chemically with other substances at high temperatures to form titanium compounds with high hardness. This complicates the processing process.
Why does an aluminum alloy successfully break through among many high-quality materials? What are the characteristics of an aluminum alloy frame?
Design teams like Cyrusher chose to use 6061 aluminum alloy instead of other materials. As a company specializing in the production and sales of high-performance electric fat tire bicycles, the reasons for choosing this material are as follows:
It has low density, good plasticity and high corrosion resistance. It is widely used as the frame material of lightweight electric bicycles. Its usage is second only to steel. There are mainly two high-quality alloys, 6061 and 7005. Three elements of frame design: lightweight, low cost, and beautiful appearance.
The density of aluminum is low. Although its rigidity and strength are not as good as steel, heat treatment technology or an appropriate increase of the wall thickness of aluminum tubes can also meet the strength requirements of the frame, but the weight is much lower than that of steel frames. With a weight like the Cyrusher Rider with batteries of only 61 lbs, customers can easily move it.
In fact, the cost of using an aluminum alloy frame is not high although it is not as cheap as a steel frame. Cyrusher has been shipping high-quality attractive electric bikes to customers for eight years and the use of aluminum makes perfect sense.
They are machined for superior strength, are lighter and the aluminum frame is easy to mass-produce. The combination of low cost and high strength is fully in line with the development trend of lightweight electric bicycles.
After the aluminum alloy is oxidized, a dense oxide film will be formed. This can protect the base metal and prevent further corrosion when it reaches a certain thickness. In addition,, the oxide film is almost colorless and the material is dense and defect-free. It is easy to polish and can increase the aesthetics of the surface.
Compared with other materials, 6061 aluminum alloy has excellent processing performance, welding characteristics and electroplating properties. Furthermore, it is not easily deformed after processing so it can be molded into beautiful and smooth aerodynamic lines in frame design which is very satisfying to customer. At the same time, aerodynamics can increase a bike's ride speed under certain conditions.
Designed to be aesthetically pleasing while also incorporating safety and strength. Cyrusher's bikes have been tested for international quality and comply with CE, UL, Rhos and FCC standards.The frames are strong and beautiful and customer response has been overwhelmingly positive, leaving many positive reviews.
The brand has opened its own factory which means that they have absolute supervision over the quality of each vehicle and it will undergo strict testing before leaving the factory.
The design team took the unexpected choice of producing and manufacturing frames with bright paint colors. These brightly-colored frames are different from the black and white ones on the market and will be the center of attention wherever you go. If the bright frame doesn't catch your attention, what about the colorful rims that are the same color as the frame?
Although the elastic coefficient of aluminum alloy is small, the design team added full suspension to the frame design so that the vehicle can absorb ground vibrations well and improve riding comfort. The tire selection uses fat puncture-resistant fat tires and they can handle any terrain.
Not only do they increase traction and stability, they also provide a lot of comfort for the rider. Cyrusher owners often rave about the high quality of their electric fat bikes and their ability to comfortably ride long distances without getting tired.
Aluminum alloy is currently the most suitable material to be widely used in frame manufacturing, and the dominant position of steel will eventually withdraw. Since the cost of using titanium alloy, magnesium alloy and carbon fiber will be difficult to reduce in the future, it is difficult to mass-produce the corresponding frame.