① Carbon fiber frame and its characteristics
Carbon fiber has been used in bicycles as a high-tech material in the last ten years. Strictly speaking, carbon fiber is not a pure carbon element, but a mixture of carbon elements bonded and reinforced with epoxy resin after weaving. Due to technical reasons in the early carbon fibers, the epoxy resin used would even decompose in sunlight. With the advancement of science and technology, various shortcomings of this excellent material are gradually being overcome. For example, the German K frame uses high-grade 16K carbon fiber. The strength of this carbon fiber even exceeds that of steel, and it has a quality promise of lifetime warranty.
Generally speaking, carbon fiber as a bicycle material has the following characteristics:
1. Extremely light weight: carbon fiber road frames of about 1200 grams have been seen everywhere. Since the quality of carbon is only 1.6 grams per cubic centimeter, it is no longer a dream to make a frame of about 1 kilogram.
2. Good impact absorption performance. Carbon fiber can effectively absorb shock and maintain good rigidity. This characteristic makes it a good competition grade material.
3. Various shapes of frames can be made. Unlike the general metal frame manufacturing process, the carbon fiber frame is generally made by making a mold first, then attaching carbon fiber sheets to the mold, and finally cementing it with epoxy resin. This manufacturing process can use aerodynamics to make a frame with minimal wind resistance.
At present, the shortcomings of this material are mainly the following two points:
1. Complicated stress calculation. The carbon fiber frame is composed of carbon fiber, which is characterized by strong tensile strength, but weak shear strength. Complex stress calculations (longitudinal rigidity and transverse rigidity) are required during processing, and carbon fiber sheets are overlapped and formed according to the calculation. Generally speaking, the impact resistance of carbon fiber is quite good, but the puncture resistance is very poor. That is to say, it doesn't matter if you fall horizontally or vertically, but you are afraid that you will encounter one or two sharp small stones in the process of horizontally falling and vertically shooting, which can't be solved by welding them.
2. The price is expensive. Compared with titanium alloy, the price of carbon fiber frame is even worse. The price of the top carbon fiber frame is tens of thousands, and the price of Konago’s C40 and C50 is even more than 20,000. Yuan. This is mainly because the production process of carbon fiber frame requires a lot of manual work, and the scrap rate is high, resulting in a large increase in cost.
②Titanium frame and features
Titanium is an emerging metal, this new material has very superior performance, and is one of the best materials for making top-level frames.
1. Titanium alloys can be used to make frames with light weight and high strength. As can be seen from the above table, the strength of titanium is similar to that of steel, but the weight is only a little more than half that of steel. Therefore, titanium alloy frames with the same strength Will be much lighter than a steel frame.
2. Titanium alloy has very good elasticity, which makes it play an important role in absorbing riding vibration. The frame made of titanium alloy has very good comfort, and titanium is a metal with memory, it has almost unlimited service life within its own deformation range, that is to say, buying a titanium alloy frame is a kind of One-and-done method. (laughs) Generally speaking, under professional use conditions, the service life of aluminum alloy frame is 2 years, that of steel frame is 8 years, and that of titanium frame can reach about 20 years.
3. Under normal conditions, titanium will hardly corrode.
There are advantages and disadvantages, and titanium alloys also have their inevitable disadvantages. At present, the most troublesome thing is one word: expensive!!
According to the content of the metal, titanium is not a rare metal. However, the titanium element in the natural state generally exists in the form of titanium dioxide, the refining process is complicated, the technical requirements are high, and it takes time and therefore the cost is high. Furthermore, welding processing is extremely difficult, because the affinity between titanium and oxygen is extremely strong, and it will immediately become titanium dioxide after contact with air, and titanium dioxide is hard and brittle, and the strength of this part will continue to decrease. Must be soldered carefully with inert gas. The so-called Tig welding is: (Tig: abbreviation for tungsten and inert gas) arc welding with tungsten electrodes and argon gas. The welding of titanium must be carried out under the isolation of air. Titanium frames are expensive for the above reasons. Generally, the price of a domestically made cruiser and a 3/2.5 titanium alloy frame of Baotai is about 3,000 yuan, and the price of a titanium frame like AIRBONE or LITESPEED is even tens of thousands. But if you consider the service life of the titanium frame, the price will not feel so outrageous.
③Aluminum frame and features
1. The metal fatigue of aluminum is very poor.
The Achilles' heel of the bicycle frame made of aluminum is that when riding a bicycle made of this material, the more times you ride, the higher the number of times the stress will occur, and the strength will change significantly. Recently, in order to achieve light weight, many frames are made of thin materials (the degree of thinness has reached the limit). These are all made of aluminum alloys with no fatigue limit, which is why an aluminum frame can only last for 2-3 years under professional use.
2. Aluminum has no elasticity and cannot absorb the vibration of riding.
A hardtail frame made of aluminum transmits most of the vibration directly to the rider's body. This makes the aluminum frame ride quite bumpy, and the ride comfort is poor.
Due to these two defects of aluminum, it is not suitable for general hard tail frames. However, most of the XC off-road frames for competition use aluminum alloy, because the weight of aluminum can be made very light, and great strength can also be obtained through heat treatment and pumping technology, which makes the racing performance of the aluminum frame very good. Good (of course the competition performance will not consider the player's comfort level and the service life of the product).
The full shock absorption car does not have these scruples. Since it has a completely independent shock-absorbing structure for absorbing shocks, plus thicker and softer handlebars and seat cushions, the shortcomings of aluminum's lack of elasticity have been completely neutralized. In addition, the lighter quality of aluminum allows it to be made into a larger cross-sectional area and to provide local reinforcement where strength is required. Therefore, aluminum is a relatively mature and reliable material, and it has more advantages when making a full shock absorber frame.
④Steel frame and characteristics
Steel is a material with a long history. From the most common civilian bicycles to high-end racing vehicles, steel is more or less used. In addition to the perfection of smelting technology, steel also has advantages that other materials cannot replace:
1. Good processing performance. Chromium-molybdenum steel is the oldest bicycle material, and its research time is also the longest, so its processing technology has developed to a fairly stable level.
2. High strength. From the above, we can see that the strength of steel under the same volume is far greater than that of aluminum alloy and titanium alloy, so the strength of a qualified steel frame can be reassuring.
3. The riding feeling is comfortable. Steel is a kind of metal with good elasticity. The frame made of steel can absorb the vibration brought by the riding process. Therefore, the steel frame will not feel uncomfortable like the aluminum frame, which is especially suitable for touring frames.
4. The metal fatigue of steel is much stronger than that of aluminum, so under the same conditions of use, the life of the steel frame will be much longer than that of the aluminum frame.
Of course, the steel frame also has its insurmountable shortcomings:
1. Weight: In today's extreme pursuit of lightweight equipment, the quality of steel 7.8/cubic centimeter makes everyone daunted by it. Although lightweight steel can be used, and the pipe wall is extremely thinned by pumped tube technology, it is still difficult to reduce the weight of the steel frame to less than 1600 grams. And many aluminum frames weigh only about 1400 grams. That's why steel frames are rarely seen in competition-level frames.
2. Rust: Compared with other materials, steel is relatively easy to rust. Rust will greatly reduce the strength of steel and reduce its service life. Therefore, various measures must be taken to prevent steel from rusting.
Therefore, if you are not pursuing competition-level weight and considering the durability of the frame, the steel frame is undoubtedly a good choice.
*But it should be pointed out that most good steel frames are harder to find than good aluminum frames these days. First of all, a good frame is not cheap. The high-grade steel frame of the Renault 853 series costs several thousand, while the steel frame of the Italian Konago costs tens of thousands. So what suits you is the best.