Which bike frame is better: steel or aluminum. Choosing a frame

Choosing metal products - heated towel rails and railings, dishes and fences, gratings or handrails - we choose, first of all, the material. Traditionally competing are stainless steel, aluminum and ordinary black steel (carbon steel). Although they have a number of similar characteristics, they nevertheless differ significantly from each other. It makes sense to compare them and figure out which is better: aluminum or stainless steel(black steel, due to low corrosion resistance, will not be considered).

Aluminum: characteristics, advantages, disadvantages

One of the lightest metals that is in principle used in industry. It conducts heat very well, is not subject to oxygen corrosion. Aluminum is produced in several dozen types: each with its own additives that increase strength, oxidation resistance, malleability. However, with the exception of very expensive aircraft-grade aluminum, they all have one drawback: excessive softness. Parts made of this metal are easily deformed. That is why it is impossible to use aluminum where, during operation, the product is subjected to high pressure (water hammer in water supply systems, for example).

Corrosion resistance of aluminum somewhat overpriced. Yes, the metal does not "rot". But only due to the protective layer of oxide, which forms on the product in air in a matter of hours.

Stainless steel

The alloy has practically no drawbacks - except for the high price. It is not afraid of corrosion, not theoretically, like aluminum, but practically: an oxide film does not appear on it, which means that over time " stainless steel» does not dim.

Slightly heavier than aluminium, stainless steel is excellent at handling impact, high pressure and abrasion (especially manganese grades). Its heat transfer is worse than that of aluminum: but thanks to this, the metal does not “sweat”, there is less condensate on it.

Based on the results of the comparison, it becomes clear - to perform tasks where low metal weight, strength and reliability are required, stainless steel is better than aluminum.

Currently, the most common illegal armed formations systems on the Russian market can be divided into three large groups:

• systems with a sub-facing structure made of aluminum alloys;
• systems with a substructure made of galvanized steel with a polymer coating;
• systems with stainless steel substructure.

The best strength and thermal performance, of course, have sub-facing structures made of stainless steel.

Comparative analysis of physical and mechanical properties of materials

*Properties of stainless steel and galvanized steel differ slightly.

Thermal and strength characteristics of stainless steel and aluminum

1. Given the 3 times lower load-bearing capacity and 5.5 times the thermal conductivity of aluminum, the aluminum alloy bracket is a stronger "cold bridge" than the stainless steel bracket. An indicator of this is the coefficient of thermal uniformity of the building envelope. According to research, the coefficient of thermal uniformity of the building envelope when using a stainless steel system was 0.86-0.92, and for aluminum systems it is 0.6-0.7, which makes it necessary to lay a large thickness of insulation and, accordingly, increase the cost of the facade .

For Moscow, the required resistance to heat transfer of walls, taking into account the coefficient of thermal uniformity, is 3.13/0.92=3.4 (m2.°C)/W for a stainless bracket, and 3.13/0.7= for an aluminum bracket 4.47 (m 2 .°C) / W, i.e. 1.07 (m 2 .°C) / W above. Hence, when using aluminum brackets, the thickness of the insulation (with a thermal conductivity coefficient of 0.045 W / (m. ° C) should be taken almost 5 cm more (1.07 * 0.045 = 0.048 m).

2. Due to the greater thickness and thermal conductivity of aluminum brackets, according to calculations carried out at the Research Institute of Building Physics, at an outdoor temperature of -27 ° C, the temperature on the anchor can drop to -3.5 ° C and even lower, because. in calculations, the cross-sectional area of ​​the aluminum bracket was assumed to be 1.8 cm 2 , whereas in reality it is 4-7 cm 2 . When using the stainless steel bracket, the temperature at the anchor was +8 °C. That is, when using aluminum brackets, the anchor works in the zone of alternating temperatures, where moisture condensation on the anchor is possible, followed by freezing. This will gradually destroy the material of the structural layer of the wall around the anchor and, accordingly, reduce its bearing capacity, which is especially important for walls made of material with low bearing capacity (foam concrete, hollow brick, etc.). At the same time, heat-insulating pads under the bracket, due to their small thickness (3-8 mm) and high (relative to the insulation) thermal conductivity, reduce heat losses by only 1-2%, i.e. practically do not break the "cold bridge" and have little effect on the temperature of the anchor.

3. Low thermal expansion of guides. Temperature deformation of aluminum alloy is 2.5 times greater than that of stainless steel. Stainless steel has a lower coefficient of thermal expansion (10 10 -6 °C -1) compared to aluminum (25 10 -6 °C -1). Accordingly, the elongation of 3-meter guides with a temperature difference from -15 ° C to +50 ° C will be 2 mm for steel and 5 mm for aluminum. Therefore, to compensate for the thermal expansion of the aluminum guide, a number of measures are necessary:

namely, the introduction of additional elements into the subsystem - movable slides (for U-shaped brackets) or oval holes with bushings for rivets - not rigid fixation (for L-shaped brackets).

This inevitably leads to the complexity and cost of the subsystem or incorrect installation (as it often happens that the installers do not use bushings or incorrectly fix the assembly with additional elements).

As a result of these measures, the weight load falls only on the bearing brackets (upper and lower), while the others serve only as a support, which means that the anchors are not loaded evenly and this must be taken into account when developing project documentation, which is often simply not done. In steel systems, the entire load is distributed evenly - all nodes are rigidly fixed - slight thermal expansions are compensated by the work of all elements in the stage of elastic deformation.

The design of the clamp allows you to make a gap between the plates in stainless steel systems from 4 mm, while in aluminum systems it is at least 7 mm, which, moreover, does not suit many customers and spoils the appearance of the building. In addition, the clamp must ensure free movement of the cladding plates by the amount of elongation of the guides, otherwise the plates will be destroyed (especially at the junction of the guides) or the clamp will unbend (both of which can lead to the falling of the cladding plates). In a steel system, there is no danger of unbending the clamp legs, which can occur over time in aluminum systems due to large thermal deformations.

Fire properties of stainless steel and aluminum

The melting point of stainless steel is 1800°C and aluminum 630/670°C (depending on the alloy). The temperature during a fire on the inner surface of the tile (according to the test results of the Regional Certification Center “OPYTNOE”) reaches 750 °C. Thus, when using aluminum structures, melting of the substructure and collapse of a part of the facade (in the area of ​​the window opening) can occur, and at a temperature of 800-900 ° C, aluminum itself supports combustion. Stainless steel, on the other hand, does not melt in a fire, therefore it is most preferable for fire safety requirements. For example, in Moscow, when building high-rise buildings, aluminum substructures are not allowed to be used at all.

Corrosion properties

To date, the only reliable source on the corrosion resistance of a particular subfacing structure, and, accordingly, durability, is the expert opinion of ExpertCorr-MISiS.

The most durable are stainless steel structures. The service life of such systems is at least 40 years in an urban industrial atmosphere of medium aggressiveness, and at least 50 years in a conditionally clean atmosphere of low aggressiveness.

Aluminum alloys, due to the oxide film, have high corrosion resistance, but under conditions of high content of chlorides and sulfur in the atmosphere, rapid intergranular corrosion may occur, which leads to a significant decrease in the strength of structural elements and their destruction. Thus, the service life of an aluminum alloy structure in an urban industrial atmosphere of medium aggressiveness does not exceed 15 years. However, according to the requirements of Rosstroy, in the case of the use of aluminum alloys for the manufacture of elements of the substructure of the illegal armed formations, all elements must necessarily have an anodized coating. The presence of anodic coating increases the service life of the aluminum alloy substructure. But during the installation of the substructure, its various elements are connected with rivets, for which holes are drilled, which causes a violation of the anode coating in the fastening area, i.e., areas without anodizing are inevitably created. In addition, the steel core of an aluminum rivet, together with the aluminum medium of the element, forms a galvanic couple, which also leads to the development of active processes of intercrystalline corrosion at the points of fastening of the substructure elements. It should be noted that often the cheapness of one or another IAF system with an aluminum alloy substructure is due precisely to the lack of a protective anode coating on the system elements. Unscrupulous manufacturers of such substructures save on expensive electrochemical processes for anodizing products.

Insufficient corrosion resistance, in terms of durability of the structure, galvanized steel has. But after applying a polymer coating, the service life of a substructure made of galvanized steel with a polymer coating will be 30 years in an urban industrial atmosphere of medium aggressiveness, and 40 years in a conditionally clean atmosphere of low aggressiveness.

Comparing the above indicators of aluminum and steel substructures, we can conclude that steel substructures are significantly superior to aluminum ones in all respects.

• Steel is a well-known material. Aluminum is a modern, light, but at the same time whimsical material. When using facade subsystems made of aluminum alloy, it is necessary to clearly fulfill a number of requirements put forward by aluminum. In the conditions of the harsh Russian realities of construction, which became even more severe with the crisis, when the installers are cheaper, the fasteners are simpler, and it is necessary to build faster, it is difficult to fulfill these requirements. Consider what aluminum subsystem vendors are silent about, but what is described in their catalogs of technical solutions.

  1. Steel has a lower coefficient of thermal expansion than aluminum. With a temperature difference from -20 to +50 degrees, a stainless 3-meter guide lengthens by 2mm, while an aluminum one by 5-6mm. Therefore, aluminum systems provide a number of movable joints and thermal seams. In steel systems, all connections are fixed, simpler and more reliable. The elements of the system operate in the zone of elastic deformations.

  2. In the steel system, all brackets are load-bearing. Therefore, the weight of the cladding is evenly distributed over all the brackets on the rail (in a two-circuit system - over the array of brackets). All attachment points are rigid, with the help of rivets or self-tapping screws.
  Recall that in aluminum facade systems, the brackets are necessarily divided into load-bearing and wind. Moreover, the entire weight of a 3-meter rail with a lining must be carried by one supporting bracket.

  3. The rest - work only on wind loads. For movable fastening of the guide to the wind bracket, the latter has elongated holes. To create a movable connection, it is supposed to use rivets (not self-tapping screws!). In addition, the fixing point of the rivet must change depending on the ambient temperature at which the installation takes place.

  In real construction conditions, how many installers study catalogs of technical solutions? How many orders are followed? (drawings - wind-bearing brackets, attachment point, temperature).

• In steel systems of ventilated facades, inexpensive, uniform fasteners are used with the facade system. These are galvanized steel rivets and self-tapping screws for galvanized steel systems and stainless steel rivets for stainless steel systems. The kleimer is always fastened with stainless rivets.
  Aluminum subsystems should theoretically use stainless steel fasteners or aluminum blind rivets. Stainless rivets have, from the installer's point of view, three major drawbacks. A stainless rivet costs four times more than a self-tapping screw, installation of a rivet takes three times more time than a self-tapping screw, and an expensive tool (800 euros) is required to install a stainless rivet. Therefore, very often, blind rivets are replaced with ... galvanized self-tapping screws. The electrolytic pair metal-aluminum speaks for itself.
• The tensile strength of aluminum alloy AD31 is 20kg/mm.kv., against 54kg/mm.kv. at steel. Steel has 2.5 times the load-bearing capacity of aluminum. Therefore, in steel systems, parts are used that are 2 times thinner than in aluminum ones. This saves weight.
• Steel facades are fire resistant. The melting point of steel is 1800 degrees. Extruded aluminum 600-700 degrees. As tests show, the temperature during a fire can reach 900 degrees in some parts of the facade, which can lead to aluminum melting. To counteract this, aluminum systems are required to have fire cut-offs. This leads to an increase in the cost of an aluminum ventilated facade.
• Steel has a thermal conductivity 4 times lower than aluminum. Thermal conductivity of aluminum 220 W/(mºС), stainless and galvanized steel 40 and 45 W/(mºС) respectively. Thus, brackets in aluminum systems of ventilated facades are great cold bridges. Russian colleagues calculated that for equal insulation of the facade, when using an aluminum subsystem, it is necessary to lay a heater 20 mm thicker.

• The thermal conductivity of aluminum alloys is 5.5 times higher than that of stainless steel. Therefore, to exclude the possibility of formation of cold bridges in the places where the brackets are attached to the wall, thermal breaks 10 mm thick are used in aluminum subsystems (in steel 2 mm), which negatively affects the reliability of the bracket-wall attachment point, since the anchor head operates in alternating temperatures, which leads to to corrosion of the most loaded element of the illegal armed formation - the anchor. Also, the presence of a thick plastic element in such a critical unit does not increase the overall reliability of the system.
• The cost of a steel facade system is an important factor for the customer. Galvanized steel facade systems are a good compromise between price and quality. A double-circuit steel system for hanging a ventilated facade is cheaper than an aluminum single-circuit one already initially, when calculating for a blank wall. Considering the advantages that bypass provides, the difference in price can be double.

Edited: 02/02/2017

We continue our series of articles on the different materials used in the manufacture of bicycle frames. In the last article, we talked about bikes based on steel frames.

In the modern world, the following materials are used to make bicycle frames:

• (regular, carbon, chromoly).
• Aluminum alloys ( Alloy)
• (Titanium)
• (carbon fiber, Carbon fiber)
• Various rare, experimental and materials (magnesium (Magnesiumc), aluminium-scandium, beryllium alloys, bamboo, etc.)

In this article, we will look at the properties of a frame made of aluminum alloys.

The term aluminum frame itself is not entirely correct. Aluminum in its pure form is not used - it is too soft. This term refers to alloys with other metals: zinc, copper, magnesium, manganese, etc.

One of the big pluses of aluminum frames is their light weight. That is why bikes with such frames pick up speed faster, it is easier to climb uphill on them. However, this also gives a negative effect in the form of a loss of overrun, i.e. when the cyclist stops pedaling, the bike stops faster.

Advantages of aluminum bicycle frame:

• Less weight, compared to steel frames, and as a result, good acceleration characteristics.
• Almost absolute corrosion resistance- such frames do not rust from the word "generally".
• High speed characteristics: Easier to pick up speed and drive uphill.

Disadvantages of aluminum alloy bicycle frame:

• Rigidity. The aluminum frame practically does not dampen vibrations, and all the bumps in the road are transmitted to the hands and through the fifth point to the spine, especially if the fork is also rigid and not shock-absorbing.
• Fast coastdown. Due to the lighter weight, as soon as the biker stops pedaling, the bike quickly loses its speed, unlike a steel frame bike.
• fragility. If the bike is actively used, then after a few years the probability of getting a crack increases sharply. And after 10 years of normal riding, it is recommended to regularly inspect the bike before the trip for their presence. Manufacturers most often give guarantees for frames made of aluminum alloys within 5-10 years.
• More sensitive to bumps and drops than steel and titanium frames. Still, aluminum is softer than steel and a blow that steel will not even notice - it can leave a dent on aluminum.
• Non-repairability. It is too difficult to weld an aluminum frame, and this, in fact, will not add confidence in its strength - it is more reliable to buy yourself a new one.
• High price.

Types of aluminum alloys used in the manufacture of bicycle frames.

Let's dwell a little on the types of aluminum alloys used for the manufacture of bicycle frames.

There are quite a few brands of aluminum alloys (2014, 7000, 7005T6, 7009T6, 7010T6, 6061T6, 6065, etc.), but the most commonly used brands in bicycle construction are 7005T6 and 6061T6 (an analogue of the domestic alloy AD33 according to GOST 4784-97).

They are also called alloys of the six- or seven-thousandth series.

The use of the letters "T6" in the name indicates that the material has undergone heat treatment.

For example, during the heat treatment of alloy 6061, a product made from it is heated to 530 ° C, then it is intensively cooled with water. Then it is artificially aged for 8 hours at a temperature of about 180 ° C. After such processing, the 6061 alloy is already designated 6061-T6.

Alloy 7005 during heat treatment is not cooled with water, but with air.

For example, the table below shows the composition of metals in alloys and how their physical characteristics change after heat treatment.

Alloy	Compound metals	Limit strength to break (in thousand PSI)	Limit fluidity (in thousand PSI)	Percent elongation	Hardness according to Brinell
2014	4.5% Copper 0.8% Carbon 0.8% Manganese 0.5% Magnesium	27	14	18%	45
2014T6		70	60	13%	135
6061	1% Magnesium 0.6% Silicon 0.2% Chrome 0.3% Copper up to 0.7% Iron	18	8	25%	30
6061T6		45	40	17%	95
7005T6	4.5% Zinc 1.4% Magnesium 0.45% Manganese 0.13% Chrome	51	42	13%	n/a
7075T6	5.6% Zinc 2.4% Magnesium 1.6% Copper 0.23% Chrome 0.15% Manganese	83	73	11%	150

In the table:

Tensile strength- is the load, above which the destruction of the product occurs.

The disadvantages traditionally include corrosion of steel. However, in the case of a children's bike, this is not so relevant. After all, children grow up, and an age-appropriate model will be needed faster than the first spots of rust appear. If you look at the offers of the XXX store, you can see that most of the children's models have a steel frame.

Aluminum frame: pros and cons

The first and foremost advantage that any salesman will name is that aluminum is much lighter than steel. When a bike needs to be lifted and carried a distance, weight matters. Well, every student knows that aluminum alloys are less afraid of corrosion than steel ones. It is easy to manage such a great one, he is obedient and dynamic.

For all its attractiveness, the child will feel the nuances of a bicycle with an aluminum frame on the first attempt to ride. The slightest roughness of the road is felt by the whole body, especially with a small weight of the baby. Some manufacturers supply the front fork with a shock absorber, which solves the vibration problem. Bad rolling is the second minus, relevant for children who have already mastered this transport well. Accelerating and driving for a long time due to inertia, without pedaling, is unlikely to succeed.

Aluminum alloys are strong, but tend to accumulate "fatigue". Well, if a breakdown happened to the frame, it is not so easy to fix it. Argon welding will have to be looked for, and it will cost a lot. Butting is used to increase reliability - a technology in which the tube has thickened walls in some places. Visually, the aluminum frame is always thicker.

In alloys, in addition to aluminum itself, there are zinc, silicon, cadmium, and copper. They are marked with four-digit numbers, in which the composition of the alloy is encrypted (for example, 7005 contains zinc). Advanced riders will recommend a titanium or carbon fiber frame, but children's models with such frames are not made.

So what to choose? There is no single answer. A list of your priorities and a small test drive will help you decide.

• "bed iron" mild steel
• alloy steel
• aluminum alloys
• titanium
• composite alloys
• exotic materials

Let's take a closer look at each material and talk about their pros and cons.

The cheapest material is the so-called "bed iron", in fact, it is not even pure iron, but low-grade steel. This is the main material for touring bikes, and it is also mostly used to make fakes of major mountain bike brands. A distinctive feature of bicycles made of this material is the large frame weight, the most popular manufacturers are from India and China. Although we talked about iron here, this is the first material from which bicycles were made. So seamless iron frames began to be made back in the 19th century. And pipes with a variable section according to technology, the higher the load, the thicker the walls will be, they were first produced in 1935, and in our time this technology is called "butting". A lot of good manufacturers make alloy steel frames - this material is better, more expensive and not as heavy.

Consider the main advantages of steel frames

• Extensive experience with steel greatly improved the technology of working with it. From it you can make any shape of pipes for the frame and achieve high-quality welding or soldering. And so many manufacturers give a lifetime warranty on steel frames, while aluminum frames often come with a 5-year warranty.
• Alloy steel has very high fatigue strength. And they can withstand millions of cycles under load. And it is easier to notice the wear of a steel frame, it does not burst like aluminum, but gradually hints at its replacement through cracks.
• The high modulus of elasticity makes it possible to design frames thinner than aluminum while maintaining tighter rigidity.
• A high vibration damping rate made it possible to make a bike without shock absorption, and design errors are not particularly noticeable, while in aluminum frames there is such a thing as "goat", when the wrong geometry leads to large jumps even with the slightest obstacles (small pebble, etc.). e.)

Well, steel is a good option for long, grueling rides, but steel-framed bikes are mostly in the lower price range and choosing a good iron horse is very difficult. All eyes on aluminum and why read on.

This is the most common frame material. One of the factors behind this is the low cost of production, as there are aluminum frames that leave the factory for $25 each. Despite the fact that the characteristics of aluminum are much worse than steel, it is still more popular. And it's in his weight. So steel has a specific gravity of 7.85 grams per cubic centimeter, while aluminum has only 2.7 grams. If we recall the lessons of physics, then the larger the diameter of the pipe, the higher its rigidity, and more precisely, there is a cubic dependence, an increase in diameter by 2 times will give an increase in rigidity by 8 times. With wall thickness, everything is simpler here, a linear dependence - a double increase in thickness will give a double increase in stiffness. But since the wall thickness cannot be reduced indefinitely, aluminum outperforms iron. The minimum wall thickness of the steel frame is 0.4 mm, aluminum 0.8 mm, while the steel is much heavier.

The shapes of aluminum frames are very different, and thanks to the hydroforming technology, it is possible to make various thickenings in pipes of a single design without resorting to welding. That increases reliability (no seams from welding) and simplifies the production technology.

The advantages of aluminum frames include: low cost, high rigidity, lower price and weight. Disadvantages: short life, break without visible warnings, shaking is well felt.

Titanium combines the best advantages of steel and aluminum. About 40% less weight than steel. Corrosion resistance. But there is one thing, the rigidity of titanium is lower than steel and this is compensated by the large diameter of the pipes, but even this option makes these frames lighter than steel ones. Among titanium frames, the 2 most popular alloys with aluminum and vanadium are distinguished: 3Al / 2.5V and 6Al / 4V. The first is less durable and heavier, but its price is much less. Titanium frames, like steel frames, dampen vibration well. True, these frames are not entirely suitable for beginners, firstly, the high price due to the complex production process (it is very difficult to create a frame with the indicated properties) and the high cost of the material, and secondly, they will not be able to feel the difference without trying frames from other materials. For this, I advise beginners to lean towards aluminum.

Recently, the popularity of carbon frames has been on the rise. In stores, you can even find components from aluminum and carbon. It is the lightest material for frames with a specific gravity of only 1.76 grams per cubic centimeter. High strength (7 times more than steel) and high rigidity (3 times more than steel), good vibration absorption make carbon frames the best choice for bicycle production. The production technology is based on a reinforced composite: a carbon matrix reinforced with carbon fabric. Production requires a lot of energy and time. The entire structure is ultimately carbonized in a vacuum furnace at high temperatures (1200°C - 2500°C). The only minus carbon does not hold loads well in all directions except the direction of the fibers, so side impacts are not desirable, but if you fall less, everything is fine, and the durability is less than that of aluminum or steel. But they are working on this issue and perhaps soon carbon will overtake steel.

To the question of which frame to choose, we will not give a definite answer. Given the high price of carbon and titanium frames for beginners, we would advise taking an aluminum frame first. And already having gained experience and realizing that you need to choose more expensive solutions from a bicycle, depending on your requirements.

Aluminum frame bikes are among the most common on the market today. This is due to the lightness of the material, combined with low cost. If steel has a specific gravity of 7.8 grams per cubic centimeter, then aluminum has a specific gravity of about 2.7 grams. In terms of wall thickening, this material also outperforms iron, since the minimum parameter is 0.8 mm, while the product will weigh less than a 0.4 mm thick steel frame. Reliability is further enhanced by the absence of welded seams. In addition, they can be performed in various configurations. Consider their features, advantages and disadvantages.

Description

Aluminum-framed bikes are lighter in weight and gain speed faster and are easier to climb. For the same reason, the bike stops faster after the rider stops pedaling. Aluminum in its pure form is not used, this material means its alloy with zinc, manganese, nickel, copper or magnesium.

These bikes are more difficult to get into tight turns, because they are stiffer than their steel counterparts, they can not bend as well. Due to the rigidity of the frame, the energy from the efforts of the cyclist is transferred to the wheels with less loss. Such subtleties play a role for professionals, for amateurs this is not a critical indicator. A stiffer and less comfortable ride becomes noticeable. Bicycles with an aluminum frame practically do not dampen the vibrations transmitted to the saddle and handlebars on uneven surfaces and bumps. A bike like this requires a good suspension unit and a comfortable saddle. This will allow part of the blows to be leveled, which will favorably affect the movement.

pros

Let's start with the advantages of the product in question. These include:

• Light weight for improved speed and acceleration.
• Maximum resistance to corrosive processes.
• High driving performance even when driving uphill.

Minuses

Bicycles with an aluminum frame have a number of disadvantages, namely:

• High rigidity, which is especially felt on models without a suspension fork.
• Rapid roll loss. Due to its light weight, the bike stops faster than its steel frame counterpart after the rider stops pedaling.
• A small working resource during active operation. After a few years, cracks may appear. Manufacturers give a guarantee of 5 to 10 years, but after this period it is recommended to lubricate the part to check for possible deformations.
• When dropped on an aluminum frame, there is a higher chance of dents.
• Poor maintainability. It is very problematic to weld such a part, it is better to purchase a new one.
• Pretty high price.

Folding bikes with aluminum frame

Below we list several popular brands of this type and name their brief characteristics:

1. The expensive city bike Strida SX has an original exterior. It folds down to the size of a compact cart that can be transported on its own. The steering wheel can also be transformed. The advantages of the bike include the fact that the cables and wires are hidden in the cavity of the frame, it is easy to assemble, there is a trunk, disc brakes. With good maneuverability, the device weighs only 11.6 kg. Among the minuses are a small carrying capacity, narrow wheels, poor depreciation.
2. Smart 20. Stylish city bike, considered one of the best in its price category. Can be used by women without any problems. Among the advantages are a solid frame, a convenient transformation mechanism, the presence of reflectors and other accessories. The disadvantages include the lack of a handbrake and the quality of centering of the wings.
3. Stealth bike. The aluminum frame of the Pilot-710 model does not interfere with the softness of the ride. The transport picks up speed well on coast, has a discreet design, fits into the luggage compartment of any car in the folded position, is equipped as standard with a luggage rack and chain protection. The disadvantages are the presence of a wide steering wheel and an uncomfortable fit for tall people. The intended purpose of the modification is city trips.

Children's bicycles with an aluminum frame

Below is a brief description of some children's and teenage models:

• Mars. This bike is designed for children aged 3 and up. Comes with extra polyurethane wheels. The frame and fork are made of aluminum alloy, there is a handlebar height adjuster. Wheel diameter - 12 inches, model weight - 4.5 kg.
• Forward Timba‏. One of the best for kids 6-9 years old. It has a beautiful design, affordable price, chain protection and removable safety wheels. The disadvantages include a decent weight (almost 14 kg), as well as the need to adjust some moving parts.
• Shulz Max. These children's aluminum frame bikes are in the middle price range. The weight of the bike is 14.3 kg. It is aimed at adolescents 12-16 years old, has a load capacity of up to 110 kg. The advantages of the model are the ease of assembly / disassembly, a good set of speeds, equipment with 20-inch wheels and quality. Among the minuses are incorrect factory adjustment, brake pads of dubious quality.

Peculiarities

When choosing a bike, the question often arises of whether to choose an aluminum or steel bike frame. The final decision depends on the financial capabilities of the buyer, the purpose of the machine and the subjective requirements of the user. It should be noted that thick-walled pipes of large diameter are used in the manufacture of aluminum structures.

This is due to the fact that, according to the laws of physics, if the pipe size is doubled, its rigidity will increase by eight times, and if the wall thickness is doubled, the stiffness index increases by the same amount. Therefore, of the available options, increasing the diameter is preferable.

As a rule, the minimum wall thickness of a pipe on an aluminum frame is 0.8 mm. Often manufacturers make pipes by butting or using different sections, which also makes it possible to strengthen the product.

Used alloys

There are many aluminum alloys that are used to make bicycle frames. The most common are the brands 7005T6 and 6061T6. The T index indicates that the material has undergone heat treatment. For example, a 6061 alloy product is heated to 530 degrees Celsius, then actively cooled by a liquid. Further, for 8 hours, the material is artificially aged at a temperature of 180 degrees. The output is 6061-T6. Analog number 7007 is air-cooled, not water-cooled.

Below are the comparative characteristics of the materials before and after heat treatment (in parentheses):

• Alloy 2014 (2014T6) - tensile strength is 27 (70) thousand PSL, yield strength - 14 (60), elongation percentage - 18 (13), Brinell hardness - 45 (135).
• Similar indicators of material 6061 (6061T6) - 18 (45), 8 (40), 25 (17), 30 (95).

The first alloy uses 4.5% copper, 0.8% carbon and manganese, 0.5% magnesium. The second material includes 1% magnesium, 0.6% silicon, 0.3% copper, 0.2% chromium, about 0.7% iron.

Finally

The strongest bike is 16 ”, the aluminum frame of which is made of 70005 or 7005 alloy. Nevertheless, the 6061 analog is more technologically advanced, which makes it possible to make pipes with a complex section from it, and this increases the strength of the product. In addition, such aluminum lends itself better to welding. When choosing a type, consider the financial possibilities and the intended use of the bike. With proper maintenance, a bike with a frame made of any material, including steel, aluminum or carbon, will last quite a long time.

For many years, steel has been the most common material for bicycle frames. For almost a hundred years, production technologies have been improved and the most suitable steel grades for a bicycle frame have been selected. The most common steel grades for frame production are those containing chromium and molybdenum alloying elements. Accordingly, they are called chromomolybdenum. In some cases, other less expensive steel grades are used to produce frames.

Advantages of steel frames

1. The steel frame, due to the springy properties of the metal, dampens shocks and vibrations well on a bad road.
2. Maintainability. In case of breakage, the steel frame can always be repaired and even individual elements can be replaced using a welding machine.

Disadvantages of steel frames

1. Heavy weight is the main disadvantage of a steel frame due to the high specific gravity of iron.
2. Susceptibility to corrosion. During the operation of the bicycle, the protective paint coating of the frame is damaged and rust appears in these places. Corrosion can also appear on the inside of the frame tubes, so it requires regular inspection and tinting.

Aluminum alloy frames

The most common material for the production of bicycle frames today. Pure aluminum is not used. There are a large number of different alloys containing silicon, magnesium, zinc and copper in various percentages.

Advantages of aluminum alloy frames

1. Weight is the main advantage. Aluminum alloy frames are made from heavier tubes to match their strength with steel, but still they are much lighter than steel.
2. Due to the properties of aluminum to resist oxidation, the frames made of it are practically not subject to corrosion. The exception is cycling in winter, when roads are treated with various chemicals that can interact with aluminum.
3. Rigidity. The aluminum frame has a high rigidity, which makes it easier to control the bike.

Flaws

1. High price. Aluminum has always been more expensive than steel, plus its welding requires a complex process, which drives up the price.
2. Difficult repair. For welding aluminum, an argon welding machine is required - an expensive pleasure and not a fact that the weld will withstand subsequent loads.
3. The rigidity of the frame is also its disadvantage: all potholes and bumps in the road are transferred to the body parts of the cyclist.

Magnesium Alloy Frames

Advantages

1. Light weight, even lighter than aluminum and titanium.
2. High strength. With less weight they have good strength.
3. They dampen vibration well, like steel frames.

Flaws

1. Price.
2. The main disadvantage of magnesium is its ability to easily interact with other chemical elements, which reduces their corrosion resistance.

Titanium alloy frames

Frames made of this material are usually not mass-produced, although they are widely used, especially in professional cycling.

Advantages

1. High strength.
2. With the same strength as steel, titanium is twice as light.
3. Not subject to corrosion.
4. They dampen vibration from road bumps well.

Flaws

1. The price is the main drawback that holds back the demand for bicycles with such frames.

Frames made of composite materials

Composite materials began to be used in bicycle construction to reduce the weight of the bicycle without losing strength. The development of the chemical industry in the field of polymers contributed to the emergence of carbon frames.

Benefits of carbon frames

1. Light weight.
2. Strength.
3. They dampen vibration well.
4. Not subject to corrosion.

Flaws

1. They are afraid of blows, due to the fragility of the material.
2. high price.

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