How does such a sensor work? Here, the physical laws of the transformation of mechanical pressure into electrical impulses come into force. The sensor is equipped with a piezocrystalline membrane, which, depending on the tire pressure, generates electrical signals. Then they are encrypted and sent to an antenna that transmits them to a receiver installed in the cockpit. Transmission is carried out at a frequency of 433 MHz, which minimizes information loss. The receiver transmits the received data to the control module, quite often they are duplicated on the built-in display. When the pressure drops below the critical level, the driver warning system is activated, which gives an audible and / or visual signal.
This system is battery operated. high power, allowing to monitor tires for 5-7 years. At the same time, the tire temperature values are taken, but they are rarely displayed and are not shown to the driver.
If your car is not equipped with such a system, you can order it additionally, many companies manufacture and install such devices.
Using Bluetooth technology to monitor tire pressure.
Recent developments in wireless communication systems allow them to be used to monitor tire pressure and take other parameters. So, in tandem of the Pirelli-Laserline companies, a system was developed and implemented that allows you to receive data on your mobile phone using Bluetooth technology. The order of signal transmission is quite simple: a microcircuit with a sewn bluetooth protocol mounted directly in the sensor, forms a data packet, connects to the phone and sends them.
Due to the low weight of the sensor, its installation does not require subsequent wheel balancing, it can be attached to any type of rubber. Today, almost all phones support this protocol, therefore, such a system is of particular interest to car owners.
Universal temperature and pressure monitoring systems.
Technological progress leads to the development of universal devices that can work in any conditions, on a rim of any size. In this case, the data is transmitted over a radio channel and received by the antenna on the control unit in the cab of the car. For correct temperature control, it is necessary to enter your nominal data into the system - tire pressure at “standard” (22 ° C) temperature. When the engine is turned on, the system self-tests, all the necessary information is displayed on the screen (moreover, each tire is displayed separately). On the onset emergency the display will show data indicating a problem in a specific wheel, at the same time the driver alert system will turn on.
A PURTURED TIRE IS A RISK FACTOR
The presence of safety equipment in the car is increasingly affecting its consumer qualities. The possibility of a tire puncture or burst is one of the constant sources of concern for drivers.
Complete or partial loss of pressure in a punctured tire increases rolling resistance, resulting deformations lead to friction of the sidewall of the tire against the roadway, which causes it to heat up and break down. Tires of a conventional design, when the pressure drops below a certain level, do not provide the car with the necessary handling and braking systems, they can fly off the wheel rim, cause wheel failure and cause an accident.
TIRES WITH SUPPORT INSERT
When such a tubeless tire loses pressure, the ring insert attached to the rim takes on the weight of the vehicle. Under normal pressure, the insert does not touch the tire, and when pressure is lost, it supports the tread, preventing the wheel rim from damaging the sidewalls of the tire.
Several options for supporting inserts have been proposed. The most widespread development of the Michelin company called PAX System (PAX). It requires the use of tires with a special lip, which prevents it from falling off the rim when driving after a loss of pressure, special wheel with asymmetric rim to simplify the installation of the plastic insert. With this in mind, it is required to install a tire pressure monitoring and indication system on the car, since drivers may not catch the moment of pressure loss and make maneuvers that are incompatible with the conditions that arise.
After a puncture, they can drive up to 200 km at a speed of 80 km / h, while maintaining control of the car. However, due to the original design of the tire and rim, you will have to go to a specialized service.
Currently, PAX has been chosen for the original equipment of Audi, Mercedes-Benz, BMW cars; it is also installed on various armored models. Compared to the standard, the tire does not lose any comfort level or rolling resistance; It has high index loads.
The disadvantages of the PAX system include: an increase in unsprung masses, manufacturing wheels according to new standards, and a high price.
Firm development Continental-CSR is a metal ring of a special profile with an elastic gasket-support, which is mounted directly on the rim of any regular wheel.
Due to the weight of the ring increases unsprung weight wheels, but this has little effect on dynamic properties while the car is moving. In the event of a sudden or gradual loss of air, the ring will support the tire, while the maneuverability of the car will remain almost the same. On a flat tire with CSR, you can drive up to 200 km at a speed of 80 km/h. This allows you to get to the car service, which has the necessary equipment. Just like with the PAX system, it is required to install a tire pressure monitoring and indication system. CSR rings do not require replacement unless the wheel has been damaged.
Four support rings weigh less than one complete spare tire and the tools to install it. Weight reduction vehicle, an increase in the useful volume of the trunk can also be attributed to the advantages of using this development. CSR is approved by Bridgestone and Yokohama for use in their products. Designed to equip cars, including all-wheel drive, with a tire profile height of 55–80%. Daimler-Chrysler, after testing, accepted the CSR as original equipment for the Maybach.
In developing RRS companies Rodgard Running on flat tires is ensured by a two-layer plastic ring design that fits onto the rim of standard 13" to 22.5" wheels. When punctured inner side the tires, leaning on the rings, begin to turn them relative to each other and around the rim. Due to this, it is possible to avoid overheating and loads that destroy and tear the flat tire off the wheel rim.
After a puncture, you can drive 15–50 km on the RRS. The rings are reusable devices, however, they require a mandatory assessment of the condition after driving in emergency mode.
SELF-SUPPORTING TIRES WITH REINFORCED SIDEWALL
In the sidewalls of self-supporting tires, united by the name "Run on Flat" or "Run Flat" (eng. - "Riding on a flat tire"), between the layers of the cord (carcass) there is an insert made of special rubber, which increases their rigidity. With a loss of pressure, such a tire holds its shape for a certain time and does not fly off the rim. Maintaining the high dynamic qualities of self-supporting tires makes it necessary to control the pressure in them, since the driver may not notice a puncture and commit dangerous maneuvers. At a speed of 80 km / h on such tires you can drive at least 80-150 km. At present, the technologies for manufacturing self-supporting tires have been mastered by many manufacturers, whose products can be purchased on the Russian market.
The use of run flat tires is on the rise. Pirelli launches its models Eufori@, P Zero Nero, Winter Snowsport, Winter Sottozero with reinforced sidewalls (outwardly indistinguishable from regular tires) in more than 30 sizes from 16” to 20” bore. Goodyear manufactures 78 Run on Flat tire models and is involved in many OEM auto-support tire projects. Nokian Tires produces Nokian Hakkapeliitta 4, Nokian Hakkapeliitta RSi and Nokian WR winter tires in three sizes: 195/55 R16, 205/55 R16 and 225/45 R17.
On the other hand, car manufacturers BMW Group, Daimler-Chrysler, appreciated the benefits of "Run Flat" tires. BMW Group successfully applies them on wheels, including those with an increased hump (type EH2).
TIRE PRESSURE MONITORING SYSTEMS
Vehicles with puncture-safe tires must have a tire pressure monitoring system.
INDIRECT CONTROL BASED ON ANTI-BLOCKING SYSTEM (ABS) and STABILITY SYSTEMS (ESP)
With the help of such systems, the tire pressure is not measured, but calculated on the basis of signals from the ABS / ESP sensors. When air leaks, the tire diameter decreases and the wheel speed increases, which is recorded by the corresponding sensors. The signal is transmitted to the control module, after which the driver receives an acoustic and/or visual warning signal. The devices begin to operate at speeds over 15 km/h and with a loss of about 30% of the initial pressure (approximately 0.7 bar). Simultaneous loss of pressure in two or more tires is not monitored.
The undoubted advantage of systems based on ABS / ESP is the absence of additional sensors mounted on the wheels. This saves on these elements and eliminates the need to balance them.
DIRECT PRESSURE CONTROL USING SENSORS COMBINED WITH THE WHEEL VALVE
The piezocrystalline membrane of the sensor, when changing the internal pressure in the tire, converts mechanical influences on it into electrical signals, which, after frequency modulation, are transmitted using antennas (usually installed in the wheel arch) at a frequency of 433 MHz to the control module and then to the instrument panel or a special display. The result is a visual and/or acoustic signal. Non-replaceable batteries firmly built into the sensors last 5-7 years. The tire temperature is monitored in parallel and taken into account in the pressure assessment, but is rarely displayed on the instrument panel.
For owners of cars on which such pressure control systems were not installed in the primary configuration, companies of various profiles offer original devices.
PRESSURE CONTROL WITH BLUETOOTH TECHNOLOGY
Pirelli, together with Laserline, has developed a system for wirelessly connecting pressure sensors to Bluetooth-enabled mobile phones (see the article “Bluetooth Car Speakerphone” in this collection). The Bluetooth chip is built into the nipple/sensor (sensor) system and generates a signal perceived by a cellular telephone. The system automatically takes into account differences outdoor temperature and atmospheric pressure. Each sensor weighs 6g, making it easy to balance wheels and fits on any rim with a standard valve. Leading manufacturers mobile phones increase sales of the latest generation of devices with which you can control tire pressure.
UNIVERSAL PRESSURE AND TEMPERATURE CONTROL
On sale appeared universal devices, which show the pressure and temperature in tires of any design. The signal from the wheel sensor is sent to the display with antenna. Depending on the type of vehicle and tires, the user must set their own normal pressure value (maximum 2.8 bar at 22°C). When the ignition is turned on, the system performs a self-test, displaying information for each tire: pressure, temperature, condition. In case of deviation from the norm, the device will give sound signal, and the display will show which tire is flat.
GENERAL CONCLUSIONS
Tires capable of running at zero pressure have the following advantages::
- Significantly increases the level of safety in case of damage to the wheel;
- there is no need to replace the tire at the puncture site;
- there is additional space in the luggage compartment and the weight of the car is reduced due to the lack of a spare wheel, jack and wheel wrench;
The disadvantages of such tires include:
- some decrease in ride comfort due to increased wheel stiffness;
- increase in tire mass and rolling resistance;
- increased load on the suspension and wheel rim;
- the need for additional adjustment of the suspension during the initial installation on the car;
- the need for some systems to use a special rim;
- increase in the price of a tire by 15–25%;
- the need for tire fitting and installation of a pressure control system in specialized services.
A bit of history.
The cycling history of the Bohle family dates back to 1906. In 1922, the father of Schwalbe's founding father, Ralph Bohle, founded his first company for the production of bicycles and components. 1955 - In his 20s, already a well-known businessman, Ralf Bohle demonstrated his engineering talents by independently designing budget bikes that the Germans really liked. Some time later, the Bohle company began exporting its bicycles around the world.
Starting in the 70s, Ralf Bohle began to work closely with his Korean partners. This cooperation developed into the international corporation Schwalbe. The success of commercial decisions was not only in perseverance and courageous decisions, but also in the attitude towards his employees, whom he treated like his second family.
These relationships have borne fruit in the development of the company.
Ralf Bohle's success began immediately after the signing of a cooperation agreement with Swallow in 1973. From now on, two families (Bohle and Hunga)
merged into one large international corporation. Ralph Bohle knew that rubber manufacturers did not monitor the quality of their products, so he decided to focus on the reliability of their products. This rule is still in effect today. Every year, since 1973, the company has been developing new production technologies and producing more and more new models of bicycle rubber. Also, Schwalbe does not forget about its "hits", therefore it is always modernizing and improving its previous products. This pursuit of the perfect assortment has helped the corporation to retain and expand its customer base around the world.
The name of the bicycle giant is taken from the small Korean brand "Swallow". "Swallow" in Korea symbolizes: speed, lightness, carelessness, freedom and confidence. These words resonated with Ralph Bohle, so he borrowed the brand name "Swallow" from his friends and translated it into German - so we got the current name of the corporation - Schwalbe.
In 1999, Ralf Bohle handed over the "wheel" of the company to his son Frank Bohle. This is the 3rd generation running the company. In 2010, at the age of 75, the founder of the company, Ralf Bohle, died.
Schwalbe from the first day was engaged only in bicycle tires and only for their company, hence the success was natural. Today Schwalbe is the most big producer bicycle tires in the world. In 1973, the company had 2 factories in Korea, but already in 1990, all production was transferred to Taiwan, to one of the largest enterprises in the region. The plant employs more than 3,000 people, and the scale of production capacity is impressive. However, like a hundred years ago, the headquarters is located in Germany, and commercial offices are located in 50 countries around the world. All development and testing takes place in Ralf Bohle's hometown of Bergneustadt.
Before getting on the assembly line, each tire is tested in all possible conditions and travels more than 10 thousand kilometers on various soils and roads. Only after positive evaluations of all doughs, the rubber is sent for testing to the company's pro-riders for an independent evaluation of the residual sample.
The assortment of the company today is 30 different models tires and tubes, a huge selection of equipment for tubeless wheels and all kinds of accessories for rubber care.
The company supports talented athletes and sponsors several cycling teams. Schwalbe also helps organize sports events. The corporation does charity work on behalf of its founder, Ralf Bohle, who created a youth tennis team and several sports facilities for athletic youth.
Schwalbe technologies.
Tire components: cord, carcass and tread. It depends on them how the bike will behave in various conditions on road.
The base of the tire is frame- textile fabric coated with rubber. Its quality is determined by the quantity O out and ut O threads per square inch (in English denoted by TPI) or the number of warp O out of fabric threads per inch (denoted by EPI). The denser the carcass, the less rubber can be used on the sidewalls (if there is a carcass there at all, of course) and the less the mass of the tire becomes. However, reducing the amount of rubber makes the tire slightly less strong even with a 100 TPI carcass, where the threads are thinner and more brittle.
Cord tires - this is the ring where the tire touches the inside of the wheel rim. The cord determines the fit diameter of the tire and prevents it from popping out of the rim. Traditionally, the cord is made from steel wire. Now a large number of tire models are made with Kevlar or other soft cord, so that the tires can be folded. Tires with a flexible cord are called folding. Obviously, they are lighter than their sisters with a metal ring inside.
Protector and boards tires are made from rubber with various additives - a compound. It must satisfy different qualities depending on the purpose of the tire. The composition of the rubber will determine how much the tire will weigh, how the bike will be controlled on wet pavement how fast the bike will roll, how well the wheels will cling to the ground and stones.
Schwalbe products are divided into quality levels to best meet the needs of their customers.
Evolution Line - an innovative level of tires optimized for specific use. All parameters are of the highest quality.
Performance Line - combines universal tread, low weight, no extra bells and whistles, affordable price
Sport Line - high quality competition tires
Base Line - basic Schwalbe quality level, used for inexpensive tires designed for the mass consumer
Puncture protection
All tires Schwalbe have puncture protection. The type of puncture protection ultimately affects tire weight, puncture resistance, rolling resistance and, of course, price. There are enough levels of protection and developments in this direction are constantly being carried out.
The most effective protection for bicycle tires. A significant advantage is the 5mm thick layer of special flexible rubber. Offers reliable protection. Even a pushpin will not damage this tire.
Level 5 - V-Guard
The extremely cut-resistant high-tech fiber allows even very light tires to provide an unusually high level of puncture resistance. Combined with SnakeSkin sidewall protection, Schwalbe calls it a double line of defense.
Level 5 - PunctureGuard
Same security as V-Guard but not as highly elastic.
Level 5 - GreenGuard
Principle Smart Guard, but the wall thickness is only about 3mm. One third of the high-elasticity rubber is made up of recycled latex products.
Level 4 - RaceGuard
The double layer of nylon fabric provides good protection for lightweight sports tires.
Level 3 - K-Guard
Minimum Standard Schwalbe for puncture protection. This technology has been in use for many years. Composed of natural rubber and reinforced with Kevlar fiber. Together with 50 EPI, all tire lines are puncture proof.
About the manufacture of boards
Schwalbe has three options for protecting the bead of the tire (in the nomenclature it is denoted by “skin”):
- Lite(also LiteSkin) - a thin lightweight version: the sides are made only of rubber, there is no frame fabric.
- twin(aka TwinSkin) - a double layer of rubber, respectively, better protects against damage.
- snake(already familiar SnakeSkin) protects the tire beads from troubles like sharp stones, branches and glass
Limited Slip Technology (L.S.T) prevents the tire from slipping in the rim and therefore damaging or tearing off the nipple.
About the composition of rubber
Consider the compounds that Schwalbe uses in production.
- Dual Compound- two grades of rubber in one tire: harder in the center for better rolling and greater wear resistance, on the shoulders - softer to improve grip in the turn. Used in most Performance models
- Endurance- wear-resistant compound for Marathon touring tyres.
- SBC- Schwalbe Basic Compound, a simple general purpose compound used in simple models Tires level Active.
- speed grip- sports rubber with low rolling resistance and good grip, as in a Kojak tire.
- Winter- rubber for winter tires like 28-inch Marathon Winter.
Triple Star Compound- a whole family of the best German triple compounds, divided by purpose into three groups.
Mountain bike group:
PaceStar is designed for cross-country, it has a “rolling” rubber in the main layer, a medium hard center, and moderately soft.
TrailStar is designed for enduro and freeride: "rolling" base layer, moderately soft grippy center, very grippy soft shoulders.
VertStar is used in downhill tires - a "rolling" base layer, a very soft center and even softer shoulders.
For road bikes:
racestar
Wet Star
One Star
For touring bikes:
roadstar
Travelstar
Balloon Bikes designates tires for fat bikes - bicycles with wide wheels. Such bikes have more cross-country ability, moreover, they have the same rolling and more comfort with less pressure in the chamber.
The number 27.5 ″ denotes models that are available for wheels with a bore diameter of 27.5 inches (in the international ETRTO system - 584 mm).
About durability Schwalbe
How long will a tire last Schwalbe
? It all depends on driving style and operating conditions. A standard tire will be able to roll from 2000 to 5000 km. Some models will withstand from 6000 to 12000 km.
The shelf life of the tire under appropriate conditions (cool, dry and dark) is at least 5 years.
Important indicators of tire reliability are maintainability and service life. According to forecasts in the near future, two hundred thousand km reach the mileage of truck tires, one hundred thousand km - car tires and 70-80% - their maintainability. Because the requirements for tire rubber increasingly tougher, we should expect an increase by 15–20% in their strength properties and wear resistance and a decrease in hysteresis losses by 10–15%. The durability of tires depends on the conditions of their operation, while more than 73% of the destruction is due to tread wear due to insufficient quality of tread rubber. The materials for the tire are selected depending on the operating modes of its elements, its design and operating conditions, and the main material is rubber-based rubber general purpose , capable of operating from -50 to +150 O C. Improving the formulation of tire rubber is in the direction of reducing the filling of carbon black and oil, increasing the degree of crosslinking, using multi-stage mixing methods, using mixtures of polymers and modified rubbers. The general requirements for them are high fatigue endurance and low heat generation.
Fatigue Endurance b (fatigue) is expressed in a change in the stiffness, strength, wear resistance and other properties of rubber when exposed to multiple cyclic loads on the tire, leading to a decrease in its service life. Multiple cyclic loading is distinguished by the type of deformation, the magnitude of the amplitude (maximum) stress, the frequency of loading, the shape of the cycles (dependence of stress on time) and the duration of the breaks between them. Fatigue endurance is evaluated by the number N cycles of periodic loading at a given amplitude stress y until the destruction of the material as a result of thermal fluctuation decay of chemical bonds activated by a mechanical field. Fatigue strength is the stress N , at which the destruction occurs after a given number of cycles. Relationship between N and at N in the mode y=const is expressed graphically as fatigue curves or analytically: N =y 1 N - 1/in, where at 1 - breaking stress during one loading cycle of the sample (initial strength of rubber), v=2-10 - empirical indicator of rubber endurance. The formula assumes a linear dependence of the fatigue endurance curve of multilayer rubbers and rubber-fabric materials before peeling in the lgу coordinates N -lg N.
Heat generation (temperature increase) is due to high internal friction in filled rubbers and manifests itself in the transition of a significant part of the mechanical deformation energy into heat, called hysteresis losses. Under repeated cyclic loading due to the low thermal conductivity of rubber, high hysteresis losses lead to its self-heating and thermal failure, which reduces fatigue endurance. At the same time, internal friction contributes to the damping of free vibrations in the rubber, the stronger, the greater the hysteresis loss. Therefore, rubbers with high internal friction dampen shocks and shocks, i.e. are good shock absorbers.
Tread rubber , in addition to the general requirements for tire rubber, must have high wear resistance and weather resistance, tensile strength and tear resistance. There are three types of rubber wear, which are easily determined visually and significantly affect the dependence of its intensity on the coefficient of friction:
- rolling (successive tearing off) of a thin surface layer;
- Abrasive scratching on hard protrusions of the abrasive surface;
- · fatigue failure due to mechanical losses and heat generation during sliding and rolling over uneven surfaces of a solid counterbody. The requirements for tread rubbers are controversial, and those listed above do not match the requirements for good processing properties, high coefficient of friction and fatigue endurance. In each case, these requirements are differentiated depending on the type and size of tires and their operating conditions. To improve durability radial tires To mechanical damage it is advisable to use harder rubbers. With an increase in the size of tires, the influence of heat generation on their performance and reliability increases, and in heavy-duty tires it becomes decisive. When working in mines, the tread must be resistant to punctures and cuts by the cutting edges of rocks, and in off-road conditions, wear resistance is determined by elastic and rigid properties.
A feature of the domestic tire industry is the use of 100% SC in production, therefore, their combinations are used to compensate for the shortcomings of individual rubbers and in some cases improve the properties of the compositions (Table 1.3). Rubbers SKI and SKD increase the fatigue endurance of the tread. BSK additives to SKI increase the resistance of the mixture to reversion, and rubber - to thermal-oxidative aging, and improve its adhesion to the road. Additives SKI-3 to BSK and SKD increase the confection stickiness of the mixtures, the strength of their bond with the breaker and the strength of the tread joint, and the additives up to 40 wt h SKD - wear resistance, cracking resistance and frost resistance of tread rubber. The plasticity of the mixtures is increased by the addition of ASMG-1 softener, a product of the oxidation of residues after direct distillation of oil, on the surface of which 6-8% of carbon black is applied. The content of carbon black and softeners is determined by the requirements for the processing of mixtures and the elastic-stiffness properties of vulcanizates.
Table 1.3.
Typical recipes for tread rubber compounds (wt h)
|
Name of components |
Heavy duty tires |
Freight |
Cars |
sidewalls tires type P |
|
|
NK or SKI-3 |
|
||||
|
Vulcanization accelerators |
|||||
|
zinc oxide |
|||||
|
Stearin technical |
|||||
|
Scorch retarders |
|||||
|
Modifying group |
|||||
|
Antioxidants |
|||||
|
Microcrystalline wax |
|||||
|
Softeners |
|||||
|
Softener ASMG-1 or ICS |
|||||
|
Active carbon black |
|||||
|
semi-active carbon black |
rubber for carcass should have the highest elasticity, which is achieved by using carbon black of medium activity and structure and reducing its amount. Rubber for breaker should have low hysteresis losses and good heat resistance, since in this zone the busbar temperature reaches its maximum values. Cover rubber compounds must have high adhesive contact between duplicated elements in the manufacture of semi-finished products, assembly and vulcanization of tires, and also have high plasticity, adhesiveness, cohesive strength and stay in a viscous state for a long time at the beginning of vulcanization. Rubbers should have high strength and low hysteresis loss, and isoprene rubbers are better suited for them (Table 1.4). Carcass tires for diagonal tires are made from a combination of SKI-3 with SKS-30ARKM-15 in a 1:1 ratio or combinations of isoprene rubbers with SKD to increase frost resistance and dynamic endurance of rubber cord systems or with BSK to reduce their cost. Technological properties of mixtures are improved by introducing up to 5 wt h aromatic softeners (plastor 37), and adhesive properties - thermoplastic softeners (rosin, hydrocarbon resins). To protect rubber from aging, combinations of diaphene FP with naphtham-2 or acetonanil R in a ratio of 1:1 are used.
Table 1.4.
Typical recipe for lining rubber compounds (wt h)
|
Name of components |
Heavy duty tires |
P type truck tires |
Passenger tires type P |
|||
|
Rubbers NK, SKI-3 or SKI-3-01 |
||||||
|
Vulcanization accelerators |
||||||
|
zinc oxide |
||||||
|
Stearin technical |
||||||
|
Modifiers |
||||||
|
Scorch retarders |
||||||
|
Rosin |
||||||
|
Softener ASMG or IKS |
||||||
|
Antioxidants, anti-fatigue |
||||||
|
Active carbon black |
||||||
|
semi-active carbon black |
||||||
|
white soot |
Insulating rubbers are semi-ebonites with a hardness of 65-70 s.u. and go to the manufacture of a filling cord and insulation of a wire or braid, therefore they must provide good grip rubber with metal and firmly connect the wires to each other. Rubber compounds are prepared on the basis of combinations of SKI-3 and SKMS-30ARKM-15 (3:1) with the addition of up to 40 wt.h regenerate with increased sulfur content (up to 6 wt h) and carbon black (up to 70 wt h). The high filling of rubbers determines the need to increase the content of softeners, and the adhesive properties of the mixture are increased by introducing a modifying system from a combination of RU-1 and hexol ZV in a ratio of 1:1 (Table 1.5). Lubrication rubber compounds for rubberizing fabrics of wing and side tapes (chafer and coarse calico) they must have high plasticity and good adhesiveness, they do not require high rubber strength, and heat resistance must be high. Rubber compounds prepared on the basis of cis-1,4-polyisoprenes (usually NK) or a combination of NK with SKMS-30ARKM-15 meet these requirements. The hydrocarbon of rubbers is reduced by introducing up to 60 wt h regenerate, and the features of filling the mixture - up to 40 wt h mineral fillers with a small addition of semi-active carbon black and a large amount (up to 30 wt h) softeners.
Table 1.5.
Typical formulation of insulating and lubricating rubber compounds (wt h)
|
Name of components |
Insulating compound |
Probing mix |
|
|
Regenerate |
|||
|
Accelerators |
|||
|
zinc oxide |
|||
|
Stearin technical |
|||
|
Scorch retarder |
|||
|
Antioxidants |
|||
|
Modifiers |
|||
|
Liquid softeners |
|||
|
Oil bitumen |
|||
|
Rosin |
|||
|
mineral fillers |
|||
|
Active carbon black |
|||
|
semi-active carbon black |
Rubbers for driving chambers and sealing layer of tubeless tires must have low gas permeability to maintain the tire's internal pressure and be resistant to tear and heat aging. Chamber rubbers must have high elasticity and low modulus and permanent deformation to reduce wear, as well as high values of joint strength, resistance to puncture and crack propagation. Chamber mixtures should be well injected and have a slight shrinkage. Abroad, cargo chambers are produced from BC (Table 1.6). Domestic mixtures for profiling passenger and cargo chambers of a mass assortment, for the manufacture of a valve heel and adhesives are prepared on the basis of combinations of SKI-3 with SKMS-30ARK or 100% BK-1675T with the addition of two wt h HBK. For tires with adjustable pressure and frost-resistant, a chamber rubber compound based on SKI-3, SKMS-30ARK and SKD is recommended. The cohesive strength of mixtures is increased by the introduction of promoters, and the technological properties are improved by a wide range of technological additives. The sealing layer of tubeless tires is made using halogenated BC, for example: HBC - 75, epichlorohydrin rubber - 25, carbon black N762 - 50, stearic acid - 1, alkylphenol-formaldehyde resin - 3.3; nickel dibutyl dithiocarbamate - 1, magnesium oxide - 0.625; zinc oxide - 2.25; di-(2-benzthiazo-lyl) disulfide - 2, sulfur - 0.375; 2-mercapto-1,3,4-thiodiazole-5-benzoate - 0.7. A rubber based on a combination of KhBK and SKI-3 in a ratio of 1:1 has been developed.
Table 1.6.
Recipes for chamber rubber compounds based on BR from foreign companies (wt h)
|
Name of components |
||||
|
Esso Butyl 268 |
||||
|
Polisar-butyl 301 |
||||
|
Carbon black N762 / N550 |
||||
|
Carbon black N660 |
||||
|
Carbon black N330 |
||||
|
Paraffin oil |
||||
|
Paraffin-naphthenic oil |
||||
|
Stearin technical |
||||
|
Alloy Amberol ST-137X with stearin (60:40) |
||||
|
zinc oxide |
||||
|
Sulfur / thiuram |
||||
|
Altax / Captax |
Adhesive rubber compounds are used to prepare 20% gasoline glue, which, when lubricating the rubber flange of the valve, forms a film with high adhesiveness and low shrinkage, capable of reliably connecting it to the surface of the chamber and covulcanizing with the duplicated rubber. Domestic adhesive mixture is prepared on the basis of 100 wt h brombutyl rubber BK-2244 with an effective vulcanizing group of sulfur, thiazole and thiuram D and 60 wt h semi-active carbon black. The company "Esso" recommends a similar composition of the mixture for glue based on BR ( wt h): butyl 218 - 100, carbon black N762 - 40, carbon black N550 - 20, paraffin oil - 20, zinc oxide-5, ST-137X resin - 20, sulfur - 2, thiuram D - 2, mercaptobenzthiazole - 0.5. Resin ST-137X improves adhesive autohesion.
Valve rubbers - high-modulus with increased hardness, used to isolate the valve heel, providing a strong bond with the brass body of the valve and covulcanization of duplicated rubbers with an adhesive rubber compound. Domestic valve rubber is prepared on the basis of SKI-3 and chlorobutyl rubber in a ratio of 3: 1, and foreign ones are based on BK (Table 1.7).
Table 1.7.
Recipes for valve rubber compounds (mass h)
Diaphragm rubbers must have high tensile strength and tear strength at high temperatures, elasticity, thermal conductivity and fatigue properties. For them, take BK with low viscosity and increased unsaturation (BK-2045, BK-2055) with the introduction of 10 wt h chloroprene rubber (nairit A) as a vulcanization activator with alkylphenol-formaldehyde resin (SP-1045, USA). Rubber compounds for rim tapes are made on the basis of 100 wt h rubber SKMS-30ARKM-27, and to reduce the cost, waste tire processing products are introduced: reclaimed rubber and elastic fillers - crumb rubber and dispor.
Technological properties of tire rubber compounds include rheological , which should also include their vulcanizability, and adhesive properties, and their behavior during molding is evaluated by the ratio of the plastic and highly elastic parts of the total deformation. Plastic characterizes the ease of deformation of rubber compounds and their ability to retain their shape after removing the deforming load, and elastic recovery (reversible part of deformation) - resistance to irreversible change due to their viscosity. The change in the plasticity of a material depending on temperature determines its thermoplasticity and shaping ability. A complete picture of plastoelastic properties mixtures are obtained from their dependences on temperature and strain rate.
When vulcanizing rubber compounds plastic properties decrease and highly elastic properties increase, therefore vulcanizability and evaluated by their change on heating. During processing on technological equipment and storage, an undesirable change in their plastoelastic properties may occur, called scorching or premature vulcanization . The tendency to scorch is characterized by the time during which the mixture at 100 O C does not change the plastoelastic properties, and evaluate:
- · by changing the height of the sample during compression between plane-parallel plates under test conditions on a compressive plastometer;
- by the resistance of the sample to shear between the movable and fixed surfaces when tested on a Mooney viscometer at 100 or 120 O WITH;
- by the rate of flow under pressure through calibrated holes;
- by the speed of indentation under the load of the hard tip.
Rheological properties of rubber compounds evaluated during scientific research their viscosity at various temperatures, stresses and shear rates. For this use capillary viscometry method and determine the rate of flow under pressure through the calibrated holes. Melt flow index (MFR) characterizes the mass of polymeric material in grams, which is squeezed out in 10 min through a capillary hole with a diameter of 2.095 mm and length 8 mm standard instrument at a given temperature (170-300 O C) and load (from 300 G up to 21.6 kg). To assess the tendency of rubber compounds to scorch, use Mooney rotational viscometers , and for rheokinetic studies - vibrating rheometers . Highly elastic properties before, during and after vulcanization of one sample of the mixture are studied on rubber processing analyzer RPA-2000 developed by ALPHA Technologies.
Stickiness of rubber compounds - adhesive property characterizing the ability to firmly connect two samples, which is necessary in the manufacture of products from separate unvulcanized parts ( product confections ). External bonding ability, due to the forces through which dissimilar bodies adhere, is called adhesion . With a different nature of the contacting surfaces, they speak of autohesion , and the adhesion of macromolecules of the same nature under the action of attractive forces - about cohesion . Adhesion is evaluated by the force required to delaminate samples duplicated under a certain load for a given time.
An important feature of the mechanical properties of rubber is stress relaxation , which manifests itself in a decrease in stress in the sample over time at a constant strain value to a final value - equilibrium voltage at ? , which is determined by the density of the vulcanization network. The rate of stress relaxation is determined by the ratio of the energy of intermolecular interaction in rubber and the energy of thermal motion of segments of macromolecules. The higher the temperature, the more energetic the thermal motion of the segments of macromolecules and the faster the relaxation processes in the deformed rubber. Since the equilibrium between strain and stress is established slowly, rubber usually works in non-equilibrium state , and the stresses during its deformation at a constant rate will depend on the strain rate.
Deforming rubber at an infinitesimal rate , at which relaxation processes have time to take place, is described by a linear dependence of the true stress on the strain value. The coefficient of proportionality between true stress and relative strain is called equilibrium module (modulus of high elasticity), which does not depend on time: E ? =P. e O /S O (e -e O- initial cross-sectional area of the sample; e O- initial length of the sample; e - length of the deformed sample. The equilibrium modulus of rubber characterizes the density of the vulcanization network: E ? =3sRT/M c, Where M c- molecular weight of a segment of a macromolecule enclosed between the nodes of a spatial grid; With- polymer density; R- gas constant; T - absolute temperature. It takes a long time to establish true equilibrium in rubber. Therefore, determine conditionally equilibrium module by measuring the stress at a given degree of deformation after the completion of the main relaxation processes (after 1 h at 70 O C) or measuring the deformation of the specimen under a given load after the completion of creep (after 15 min after loading).
Rubber tear test carry out standard single stretch method samples in the form of double-sided blades with a constant speed (500 mm/min) to rupture at a given temperature for a visual assessment of its specific properties. The dependence of stress on deformation at a constant rate is complex and decreases with repeated deformation, showing its peculiar "softening" - the Patrikeev-Mullins effect. Tensile strength of rubber f p calculated as load ratio R R, which caused the rupture of the sample, to the initial area S o cross section in the fracture area: f p =P R /S o . Elongation at break l R expressed by the ratio of the increment of the length of the working section at the moment of rupture ( e R -e O) to the original length e O : l R =[(e R -e O )/e O ] . 100% , A relative permanent elongation after the break - the ratio of the change in the length of the working section of the sample after rupture to the original length.
Nominal stress at a given elongation f e, which characterizes the tensile stiffness of rubber, is expressed by the value of the load at this elongation R e per unit area S o initial section of the sample: f e =P e /S o. Usually, conditional stresses are calculated at deformations of 100, 200, 300 and 500% and are called rubber modules at given elongations. Additional characteristics of rubber - true tensile strength , calculated taking into account the change in the cross-sectional area of the sample by the moment of rupture, provided that the deformed sample remains unchanged. The influence of temperature is estimated ratio of indicators strength at elevated or reduced and at room temperature, which are called respectively heat resistance coefficient And frost resistance . The coefficient of heat resistance is determined by the ratio of tensile strength and relative elongation, and frost resistance - by the ratio of stretching at the same load.
Work of deformation is measured by the area under the loading curve of the sample and is converted into the energy of rubber elasticity, part of which relaxes and irreversibly dissipates in the form of heat of internal friction. Therefore, the work during unloading the sample will be less than the work spent on its deformation. The ratio of the work returned by the deformed sample to the work expended on its deformation determines useful elasticity of rubber , and the ratio of the scattered energy to the work of deformation is energy loss due to hysteresis , which are proportional to the area of the hysteresis loop. For different rubbers hysteresis losses can range from 20 to 95%. The ability to absorb and return mechanical energy is one of the distinctive properties of rubber. Hysteresis losses are more often estimated by the value rebound elasticity , which is the ratio of the energy returned by the sample after hitting it with a special striker, to the energy expended on the hit. The expended energy is determined by the mass and installation height of the pendulum striker relative to the sample, and the returned energy is measured by the height of the rebound of the striker after impact.
Rubber tear resistance characterizes the effect of local damage on its destruction and represents the breaking load at a strain rate of 500 mm/min, referred to the thickness of the notched sample of standardized thickness, shape and depth of notches.
Rubber hardness characterizes its ability to resist the penetration of a solid indenter under the action of a given force. The most common method is to press a standard needle Shore hardness tester A into a rubber sample with a thickness of at least 6 mm under the action of a spring designed for a certain force. The test results are expressed on a scale in arbitrary units from zero to 100. At high hardness (value 100), the needle does not plunge into the sample, and the hardness of the rubber varies widely: 15-30 - very soft, 30-50 - soft, 50-70 - medium, 70-90 - hard and more than 90 - very hard rubber. The International Organization for Standardization (ISO) recommends a method that takes into account relaxation processes and friction, according to which hardness is assessed by the difference in depths of immersion in a sample of a ball with a diameter of 2.5 mm under the action of contact (0.3 H) and main (5.5 H) loads. Immersion depth is measured in international units IRHD or hundredths mm from zero, which corresponds to the hardness of rubber with Young's modulus (a value close to the equilibrium modulus) equal to zero, and up to 100 - with Young's modulus equal to infinity. Hardness indicators are close to conventional units of Shore hardness A. Hardness is measured quickly, and its performance is very sensitive to changes in both composition and rubber manufacturing technology.
Dynamic properties of rubbers determine their behavior under variable external mechanical influences. An important indicator of rubber stiffness under periodic harmonic loading is dynamic module E din- voltage amplitude ratio f O to the deformation amplitude e O (E din =f O /e O). They also define relative hysteresis G- share of total energy W for deformation q per cycle, dissipated in the form of mechanical losses: G= q/W=2 q/E din e O 2 . Hysteresis losses of rubber under conditions of harmonic periodic deformations characterize modulus of internal friction TO. This is the doubled value of mechanical losses per cycle at a dynamic deformation amplitude equal to unity, i.e. K=2 q/e O 2 , Then G=K/E din .
fatigue (dynamic fatigue ) are called irreversible changes in the structure and properties of rubber under the action of mechanical deformations together with non-mechanical factors (light, heat, oxygen), leading to their destruction. In rubbers subjected to constant static deformation or load, accumulates permanent deformation e ost. It is determined by compressing cylindrical specimens by 20% and holding in a compressed state at normal or elevated temperature set time: e ost =(h o -h 2 /h o -h 1 ) . 100% , Where h o- initial sample height; h 1 - height of the compressed sample; h 2 - height after removal of the load or deformation and rest.
fatigue (dynamic) endurance N is characterized by the number of cycles of repeated deformations of the samples until their destruction. Variable test conditions can be strain amplitude, load amplitude and strain frequency. A large number of methods for testing rubbers for fatigue endurance have been developed. Widely used tests for multiple stretching until the destruction of rubber samples in the form of double-sided blades. Standardized test method for multiple compression until the destruction of samples in the form of massive cylinders, inside which the temperature is measured, which characterizes heat generation due to hysteresis losses and difficulties in heat removal to the environment. Often, rubber is tested for resistance to the formation and propagation of cracks in samples subjected to repeated bending and having zones of increased stress concentration, in which they are destroyed. When tested for crack growth resistance observe the growth to a certain limit of damage, which is applied to the test sample by puncture or incision, and when tested on crack resistance determine the number of deformation cycles before the start of sample destruction - the appearance of primary cracks on it.
Wear resistance of rubber characterize abrasion , which is the volume loss due to friction on a solid surface due to wear by separating small particles of material per unit of friction work under a given test mode. Abrasion is a complex process, the mechanism of which significantly depends on the properties of rubber, friction surfaces and the conditions of their interaction. At the points of contact of surface irregularities of materials, local stresses and deformations occur. When rubber rubs against surfaces that have very sharp and hard edges, abrasive wear (abrasion "micro cutting " ). When sliding rubber on a rough abrasive surface without sharp cutting protrusions, the contact zones are repeatedly loaded, which leads to fatigue wear most characteristic of rubber products. When rubbing on relatively smooth surfaces with a high coefficient of friction between the rubber and the abrasive surface, when the contact stresses reach the values of the rubber strength, there is an intense cohesive wear (abrasion "rolling"). To assess the abrasion of rubber, various instruments are used, in which samples of a strictly defined shape are tested under conditions of sliding or rolling friction with slipping. The samples are subjected to abrasion on an abrasive abrasive paper (abrasive wear) or on a metal mesh (fatigue wear). The constants during the test are the sliding speed and the load on the specimen. The change in the volume of the samples is estimated from the loss of mass, and the work of friction is calculated knowing the friction force and the length of the path traveled by the sample during the test. There are other more specific laboratory and bench test methods.
Laboratory tests make it possible to strictly regulate and simplify deformation conditions and obtain well-reproducible results, in contrast to the results of operational tests. Therefore, they are the first and main stage in the process of developing new or quality control of existing types of rubber products.
Hello brain cyclists! In this project, I will be using used tires from an old bike to create a puncture resistant tire for my bike.
Background: After puncturing a couple of tires due to thorns, which are abundant in our area, I decided to make a tire that would have effective puncture protection.
In this project, I use the usual materials at hand and items from household. This means that anyone can handle the manufacture of this tire!
Step 1: Required Tools and Materials
To complete the project, use:
- 15mm wrench
- 2 flathead screwdrivers (you can use a knife)
- Knife for cutting drywall sheets
- New camera
- An old tire (I have a couple of such tires accumulated lately).
— New or used tire
Step 2: Removing the wheel from the bike
Start by removing the wheel from the bike; use a 15mm wrench to remove the nuts holding the wheel in place. Also make sure to disconnect the brakes - this will make it easier to remove the wheel (as shown in the photo).
Step 3: Removing the camera from the wheel
Now you should remove the camera.
Proceed as follows: Pry off the bar using two screwdrivers, i.e. insert a screwdriver into the gap between the tire and rim, and then pull down. Next, insert another screwdriver about 5cm from the location of the first screwdriver, and run the screwdriver around the tire to remove it.
Step 4: Shaping the Old Tire to Fit
In this step, you should minimize the size of the old tire so that it can fit in the new or used tire. For this procedure, I used a sharp knife - I cut and removed the edges of the tire (as shown in the photo). You should make sure that the only part of the old tire that should be used is the flat section of the tire. As you can see in the second photo, I made a mistake when cutting off the tire - it turned out to be too big and did not fit into a new tire. So I trimmed the used tire to fit perfectly.
Step 5: Inserting the Cut Bar
In this step, you will need to insert the cut tire into the new or used tire, which should be installed back on the bike. This is simple to do by inserting the cut tire into the tire to be used on the bike. However, when inserting the tire, you will run into the problem that the tire does not fully fit into the tire that you will be reusing on the bike. Therefore, the bar to be inserted must be cut off. To cut the tire, I used a drywall cutter; I first measured the overlapping parts and then cut so that the tire fits perfectly!
Step 6: Replacing the Camera
Step 7: Fitting the Tire to the Wheel Rim
First, make sure that the air vent of the chamber is in line with the vent hole in the wheel rim. Next, insert the valve into the hole and secure the tire to the rim. During this process, first press down one side of the tire, and then the other. To facilitate this procedure, you can use a screwdriver. But be careful not to puncture the tire.
Step 8: Inflate the Tire
After installing the tube in the tire, it must be inflated.
Step 9: Installing the wheel on the bike
After inflating the wheel, install it back onto the bike using a 15mm wrench to tighten the nuts. Don't forget to reattach the brakes!
Step 10: Conclusion
Finally you have a bike with puncture resistant tires. Now your bike can not be afraid of thorns, broken glass and other sharp objects. Even in the event that the tire is punctured, the wheel will remain "hard", and this will allow you to somehow get to your destination. In addition, such a wheel requires less pressure to fully inflate, since the cut tire inserted inside occupies part of the internal volume of the wheel.
This design can be improved as follows:
- Insert more layers of the tire - this will ensure additional stability to punctures.
- Use lighter materials to reduce bike weight.
- Make a tubeless tire using only used tires.
- Install the converted tires on both wheels of the bike.
Good luck riding bicycle, and forget about punctures!
