A USB hub (or USB hub) is a device that can be used to extend a USB port to multiple available ports for connecting to a host system. The USB hub allows you to expand the possibilities of simultaneous use of various technologies when there is a lack of USB ports. It becomes possible to connect the maximum number of necessary devices, such as a computer mouse, scanner, keyboard, modem, external hard drive, coolers, lamps, etc.
The USB hub can be built-in or external, which determines the nature of the use of the hub. Most USB hubs are built-in and are part of a system device that connects any USB device to a USB PCI card (motherboard). In this case, the USB hub is installed in the PCI slot directly on the motherboard.
A built-in USB hub is used in laptops, which allows additional USB connections. This can be a built-in computer card, which is an alternative to a USB hub, or an external USB hub. If the laptop USB port is located in a hard-to-reach part of the system unit, then the USB hub is used with an extension cord.
An external USB hub can be unpowered (it is a regular splitter) and powered (equipped with a power supply from the mains, and capable of withstanding currents up to 500mA). The latter is more practical since most devices connected to USB ports require power, and a powered hub allows you to redistribute the voltage, which improves the performance of computers.
The principle of operation of a USB hub is quite simple. Depending on the distribution scheme from the exchange center, the hub allows the mechanisms included in it to work, both individually and in concert, depending on the access mode. The USB hub can expand the network up to 127 ports.
If the principle of operation of the hub chip has a physical "star" layout, then all USB connections will work autonomously from the center, without jumping each other. In the case of a serial connection from the center bus, the power supply can be bridged. There are also hubs designed according to the "octopus" and "squid" scheme, which allows you to connect various USB nodes that are close to each other. Such connections generally do not have the problems of blocking each other.
Modern USB hubs are represented by a variety of models: from classic functional hubs in the form of a box to stylish and original designer gadgets. All of them are characterized by a high data transfer rate, and also have additional features that allow you to improve the process of information transfer and the operation of the device itself.
These are end-of-frame timers, port controllers, PLL circuit, bit clock restorer, serial interface mechanism, MMU and embedded RAM, I2C slave interface, GoodLink indicator, SoftConnect, current overload detectors, voltage converters. All this makes it possible to facilitate the work of a PC user, as well as to secure the process of processing information, its transmission and storage.
Quite an interesting statistic: usually people start to get interested in hubs only in winter. Immediately questions like:
- what are hubs?
- how to turn on the freewheel?
- how to turn off the hub?
- How do you know if it's on or off?
Well, we, perhaps, will not torment you and still give answers to these questions.
What is a freewheel?
Firstly, the hub is the freewheel; secondly, it serves as an "intermediary" in the mechanical connection of the wheels to the drive. How useful is this item? For owners of SUVs with permanent drive - nothing. For those who have a switchable drive, the hub will be responsible for turning it off.
Of course, each model requires a certain type of coupling.
Hub types
The most common types of freewheels are automatic and manual. They are easily identified: in most cases, by inscriptions. Automatic hub - automatic; on manual you will see a switch - Lock and Free. Automatic clutches are used in the R20, R50 bodies, as well as in the WD 21 body. Domestic automatic machines differ from imported models in their production capacity.
Mechanical peculiarities
With manual clutches, everything is extremely simple: they have a mode switch that you need to turn on / off with handles before turning on / off the bridge. In order not to screw up, it is enough to know the following:
- Lock mode - the hub is turned off; Free mode - the hub is enabled;
- You can not drive a car with the clutches off, but the axle on;
- After prolonged braking, do not turn off the hubs with your bare hands: they get very hot, use gloves.
The principle of operation of automatic hubs is a little more complicated. If you believe the operating instructions, you can connect the front axle at speeds up to 40 km / h on Nissan Terrano with a WD 21 body and at speeds up to 80 km / h on R20 and R50 bodies. Reduced turns on and on those, and on those subject to a completely stopped car.
Connecting the coupling, even at low speed, causes a load in the form of a shock wave on its parts. And this is often not even accompanied by any rattling or tapping sounds. Therefore, many include the bridge only when the car is completely stopped. This extends the life of the clutches and friction rings in particular. In addition, off-road, you can stop and see which road you will take next. In the city for this there is a red color at the traffic lights.
We figured out when to turn on hubs. Now about how to start off: do it as smoothly as possible and in a section where you do not need to turn anywhere. Of course, follow these instructions only if you do not want to repair anything, and also if the condition of the friction rings is not very good.
Now let's talk a little about the pros and cons.
Advantages and disadvantages
Manual hubs.
- You can rely on manual clutches. They won't let you down on the road. They securely connect the wheel drive. If the car is unsuccessfully rocked on a not very good road or in mud, you can be 100% sure that the front end will not turn off. We can say that manual hubs are the choice of a real off-road pro.
- Against the background of such chic advantages, there is only one significant drawback: in order to turn the drive on or off, you have to get out of the car every time. This, perhaps, is not always convenient, given that you have to drive through the mud, and the weather conditions are not always good on the street.
Automatic hubs.
- Automatic freewheels have equally proportional differences from manual ones. Firstly, they do not force the driver to get out of a warm and comfortable car every time on the often cool, sometimes rainy and dirty street in order to switch the hubs from one mode to another. Secondly, and this already belongs to the disadvantages, with unsuccessful attempts to drive up a hill or conquer the countryside with mud and puddles, the car rolls down and the clutches almost always turn off at this moment.
- Nevertheless, those who have tried the machine rarely switch to manual hubs.
Vacuum hubs.
- Before, we did not remember them, because, unlike the above, they are much less common. But this is not a reason to ignore them, because the mechanism of their work is indeed worthy of attention.
- Advantages: full automatic. When you connect the four-wheel drive, a signal is sent to the electronic vacuum pump. He, in turn, sucks air from the coupling through a special system of tubes. Thus, the hub is blocked. Everything turns off exactly the opposite.
- Disadvantages: the performance of such a system depends on the degree of tightness of the tubes and the reliability of the glands. And as you know, they tend to wear out quickly.
Well, as you can see, each type of clutch has its own advantages and disadvantages, and it is quite easy to choose a car with one or another type of them: it is enough to know whether you are ready to periodically leave the car to turn them on / off or not.
Outcome
At the moment, the prices for hubs fluctuate quite well and depend on the manufacturer, the type of coupling (automatic / manual), and technological characteristics. You can still find relatively inexpensive hubs costing from 8 to 10 thousand rubles. More expensive ones start at 20 thousand rubles.
Given the instability of currencies and the auto parts market, freewheel prices will only increase, and it will not be possible to name the exact cost. Nevertheless, let the seeker find! Fortunately, there are sellers of used spare parts and the familiar Chinese market.
In cars like Kia Sportage-1, Opel Frontera, Nissan Patrol, etc. no center differential. Torque from the gearbox through the transfer case is transmitted in a 50/50 ratio to the rear and front axles only after the cardan shafts are rigidly engaged with each other. Further, the moment passes through the front driveshaft to the front cross-axle differential, which distributes the torque to the CV joints that rotate the wheel hub. In order for the wheels to rotate together with the CV joints, they are installed in the front axle hub freewheels (hubs). Hubs carry out rigid mechanical blocking of wheels with CV joints.
When driving a car on normal roads, it is advisable to turn off all-wheel drive and hubs so that the wheels rotate freely. As a result, the "rolling of the car" is significantly improved and fuel consumption is reduced.
Three types of hubs are usually installed on SUVs:
1) Manual;
2) Automatic;
3) Vacuum.
1 - Cars were rarely equipped with manual hubs from the factory, although today manual hubs are the most reliable. They are commercially available and the ability to replace their own is not a problem.
Currently, there are several manufacturers of freewheels (hubs) with manual engagement (disengagement). The most common are already well-known WARN (USA) and AVM (Brazil) branded couplings. And only recently on the market for the first time appeared products of the young, but already well-established trademark "AmicA" (Ukraine).
Why are AmicA wheel couplings interesting in comparison with existing brands, what makes the owner of an off-road vehicle make his final choice on the products of this company?
First, it is their undoubted reliability. The clutches feature a brand new patented design giving them a 100% on/off guarantee in harsh environments. Undemanding to the type of lubricant and its quantity, the clarity of on-off, the use of alloyed steels (in foreign products, the case is made of silumin, a light material, but mechanically unreliable), rolling bearings and full-fledged seals in the production of hubs make them worthy competitors with existing imported analogues. If necessary, these couplings, in contrast to the existing wheel hubs, allow them to be diagnosed and repaired in any field conditions, through the use of unified separate units (bearings, seals). The “AmicA” hub engagement unit is reliably protected from water ingress into the inner part, while this unit in manual clutches of other manufacturers is their most vulnerable point, contributing to the free penetration of water into the clutch housing, which drastically reduces the life of the clutch and wheel bearing car.
In addition, all manufactured AmicA freewheels are fully guaranteed for a period of 12 months, regardless of the vehicle's mileage. This means that if any problems arise during the operation of the couplings, they are repaired or replaced with new ones at the expense of the manufacturer with an extension of the warranty. This indicates the presence of a well-organized service department for technical support of products manufactured by AmicA. For foreign analogues, such a guarantee is not provided in Ukraine.
An important factor when choosing manual clutches for your "warhorse" is their cost. In this regard, AmisA manual couplings successfully compete with analogues, because their price is much less than foreign products (by about 30-35%).
All proposed clutch kits for different brands of SUVs contain a complete set of mounting bolts, which is far from always provided by their foreign counterparts.
Conducted field tests of manual couplings (hubs) in severe off-road conditions of the spring Carpathians showed their ability to work with large critical loads, not being afraid of either viscous clay or spring floods.
In conclusion, we can say with confidence that AmicA manual couplings not only are not inferior in terms of their performance to the products of foreign analogues, but in many cases surpass them.
In any case, choosing AmicA freewheels, you have a 100% guarantee of confident off-road driving, without fear of failure of this component, which is so important for all-wheel drive.
Consider classic hand hub device:
The CV joint shaft with the help of a splined connection enters the leading splined bushing (3) of the hub. In the disengaged state, the movable spline bushing (2) is on the left (according to the figure) and does not engage with the drive spline bushing, which allows the clutch body (1) to rotate freely around the drive spline bushing. Thus we have a disabled wheel drive.
When the clutch is engaged, the movable splined sleeve moves to the right (according to the figure) and connects the clutch body to the drive splined sleeve, making it possible to transmit torque to the wheel.
In hubs of Ukrainian production"AmisA" used a completely different, new design, protected utility model patent. The basic principle of operation is shown in the figure:
Here, the drive splined sleeve is connected to the coupling body by means of movable cylindrical keys. Due to the large contact area of the cylindrical surfaces of the keys and the use of alloyed hardened steels in the production of couplings, they allow them to transmit critical torques to the wheel without fear of damaging the mechanism. The large length of the key compared to its diameter, the independent movement of the keys under the action of powerful springs gives a guarantee of a clear on (and off) hub, undemanding to the type of lubricant and its quantity.
The leading splined sleeve rotates on a powerful ball bearing, the switch handle is protected by a reliable gland from water and dirt getting inside. Well, in order not to get your hands dirty when turning the hub on and off, there is a special key for the switch handle.
Coupling design AmisA"patented.
2 - Automatic hubs almost all cars were equipped from the factory. The principle of operation of automatic hubs is that when torque is applied to the front driveshaft (all-wheel drive is connected), the CV joints begin to rotate. This is where automatic hubs come into play that block. To disengage the hubs and CV joints, you must stop, turn off the four-wheel drive. Take back 3-5m. in order to finally disengage the hub and hub. Otherwise, the front propeller shaft will be disconnected from the rear. There will be no four-wheel drive, but the entire front axle will idle. At first glance, everything seems to be fine, you don’t even need to get out of the car. Unfortunately, there are more cons than pros:
In the hub, when driving on a rear-wheel drive, a silumin (on the Kia Sportage) three-stud ring and a plastic clip of the clutch engagement mechanism are ground together, and at the most crucial moment, when all-wheel drive is needed, it will not be because the hub ring will not have enough travel to ensure engagement of the CV-HUB-WHEEL.
Automatic hubs do not provide 100% blocking. If you fail to drive uphill, then roll back in neutral, the automatic hubs will be 100% disabled. Thus, in some cases, they can turn off, and there will be no four-wheel drive until the car drives forward or backward until the hub engages with the CV joint. If this happens in wet clay, then you can sit down hard and it is quite possible that you will not have those 1-2 meters needed to hook the hubs.
3 - Vacuum hubs"top of perfection". They were equipped with cars less often than automatic ones, but also quite often.
The mechanism of operation of vacuum hubs is actually advanced. When the driver turns on the four-wheel drive, an electronic signal is sent to the vacuum pump, which takes a vacuum from the intake manifold, and sucks air out of the hub through the tube system, which leads to its approaching the hub and, accordingly, blocking. When disconnected, the reverse process occurs - air is supplied and the hubs are disconnected from the hubs, the car goes into rear-wheel drive mode. Accordingly, everything is done automatically and there is no need to take it back after turning off the all-wheel drive.
But there are also disadvantages. The entire system of vacuum hubs depends on the tightness of the tubes and glands. They wear out quickly and begin to pump air, water, dirt, etc. The result affects immediately - the hubs stop blocking completely at first, and then there will not be enough vacuum at all, even to move them from their place.
As a result, the following conclusions can be drawn:
If you constantly need four-wheel drive, and you spend a lot of time off-road, then it is better to install manual hubs.
If you spend most of your time in the city, then automatic hubs are enough for you. They just need to be checked from time to time, and in case of critical wear, they should be replaced with new ones.
Vacuum hubs are installed on all new machines. It is not advisable to change them until they fail.
Text: Evgeny Konstantinov
Photo: Alexander Davidyuk, Andrey Khorkov, Alexander Ivanov
Having placed an advertisement for the hubs of the Brazilian company AVM in our magazine, we suddenly thought: what kind of South American beast is this, and is it really that good? What if we, without suspecting it, are deceiving readers? But this is all poetry... However, the "physical" side of the "obscene" question is also by no means idle. Especially for those who drive UAZs. After all, despite the fact that several types of hub couplings are produced for this brand today, they are not recognized as ideal by the “UAZ community”. Moreover, among the owners of Ulyanovsk all-terrain vehicles, hub locks are considered one of the most decent topics for small talk...
As a result of market research, five types of hubs for the UAZ car turned out to be in the center of our attention (we considered only options that can be found on free sale). One can be said to be historical. To turn it on and off, you need as many as two keys and a few minutes of time. The rest of the hubs are much easier to control: just turn the outer knob less than half a turn from 4x2 to 4x4, and everything should happen right there. It's in theory. And in life it all depends on how clearly the mechanism hidden out of sight works with a spring, two slotted bushings and two groups of guides. By the way, despite the fact that all four models are designed according to the same principle, they differ greatly in details and manufacturing features.
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The oldest hub produced by UAZ, leading the story from the GAZ-69. Such "switches" are still regularly installed on cars of the cargo family. Small sharp splines on the clutch body and on the inner sleeve enter into engagement. The latter is put on the axle shaft along the internal slots and screwed with a special bolt. Thanks to him, everything works. This version of the coupling is the most affordable both in terms of availability in stores and at a price (500 rubles per pair). |
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Nowadays, "Simbirs" and "Hunters" are equipped as standard with ELMO couplings made in Sterlitamak. They are most common among UAZ "quick switches" and are much more common than others in free sale. ELMO is produced in two versions: with a decorative metal cap and without it. There are no differences between them, with the exception of this cap itself and the price (920 and 960 rubles per pair, respectively). |
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Very similar in appearance to the previous version of the STED hubs, which are produced in Ufa, but if you look closely, it is easy to notice the differences in design and meticulous manufacturing. They are rarely found on sale, but they are a little cheaper - they ask for 850 rubles for a pair. |
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You can’t buy STELM couplings in any store either. They differ from all others in the conical shape of the body and light gray color. In addition, it is noticeably lighter than other subjects. They are produced, like the previous version, in Ufa, but at the same time they have a noticeable difference in price. For a couple, they asked us just an apocalyptic amount - 666 rubles. |
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The only foreign-made hubs in our collection are easy to recognize at a glance. It's not even about the letters AVM. "Foreignness" is visible on the polished lid and other pleasant little things. You can feel the meaningful work of the designer. Brazilian hubs are sold in a sealed cardboard box that contains two sleeves, instructions, a set of screws for the cover and two cardboard hub spacers. The price of the kit is $ 180, which in translation is a little more than 5 thousand rubles. |
"And all around aluminum, aluminum ..."
Having collected such a rich collection of hubs, it was impossible not to be interested in their internal structure ... First of all, we unscrewed the covers from the cases. And what? The mechanisms of the three Russian products turned out to be practically interchangeable (both in whole and in parts). And for the Ufa couple, everything turned out to be exactly the same. But the "Brazilian" and "Soviet veteran" demonstrated bright individualism and originality, which resulted in the absolute originality of the components.
As for the materials used, here we were most surprised by STELM, which hide a “strategic supply of silumin” under a neat gray paint. From an alloy, the "strength" of which is legendary, both the body (directly involved in the transmission of torque!), And the cover are cast. Here is the answer to why the “gray” (meaning the color) hub weighs only 800 grams. And this despite the fact that for the rest this parameter fluctuates around 1100 grams, and STED pulls at all 1200. However, we found silumin even in it - parts of the switching mechanism are made of it. In ELMO, a cover was added to the number of light-alloy parts. True, it does not bear any load. At AVM, the cover also turned out to be made of aluminum alloy, and the shift mechanism was made of plastic. However, splined bushings in all five cases turned out to be steel (as well as springs). The only hub lock made entirely of iron and its derivatives is the old-style UAZ hub.
According to the thoroughness of surface treatment and the general culture of manufacturing, the “Brazilians” turned out to be in the first place. However, remembering how much AVMs cost, there was no doubt about it. True, and here it was not without a small fly in the ointment. One of the screws for attaching the cover turned out to be ... without a thread. More precisely, instead of carving, its surface was covered with even annular grooves.
Oddly enough, the silumin STELMs distinguished themselves by the greatest accuracy of processing from Russian hubs. We were very surprised. Especially when you consider that exactly the same details inside the "steel Ufa man" turned out to be handled very badly. Burrs, rust, scale... Burrs and poorly polished surfaces were also found in Sterlitamak couplings (the most expensive Russian ones), but the quality of processing is still higher here. True, in one of the new couplings there was a stripped thread, because of which the cover could be screwed on five of the six screws.
It is difficult to spoil something in old-style couplings, as well as to surprise with high technologies. But we note that the inner sleeve of the copy that we got, it seems, was not processed on the machine, but some goblins gnawed with their teeth! Extraneous risks and dents on the working surfaces of the slots were also found. Against this background, a slightly knocked down thread on the cover was perceived simply as an innocent prank of the manufacturer.
But don’t think, we didn’t just disassemble and look at the internal structure of the “locks”, we constantly twisted something with playful little hands. Well, in the end they screwed it up... First, the splined bushing of one of the STEDs jammed in the seat on the case, and then a similar trouble happened to ELMO. In general, in order not to disrupt the end of the experiment, they had to be completely disassembled and, marveling at the “quality” of the rubbing surfaces, put back together. However, such a nuisance is not fatal. When working on a car, all rubbing surfaces will run in over time.
To the outgoing fields!
To identify the pros and cons of hubs in real operation, we take the entire collection and drive out into a snowy field. The program is simple: we install a couple of test hubs on the front axle, ride on virgin soil and try to turn them on after the rear wheels have stalled. Moreover, to collect statistics, we conduct a series of such inclusions.
And our work was not in vain: a lot of interesting things turned out. So, for example, to install AVM hubs, you need a 1/8-inch hex wrench (to first unscrew, and after tightening the hub bolts, screw back the shiny covers). This tool is not included in the kit, and it is not easy to find it on sale. But, on the other hand, non-standard screws of the cover partly perform the function of "secrets" for beautiful imported couplings. Otherwise, the "Brazilians" did not deliver any trouble. When installed, everything (including my own gaskets) fit perfectly. They showed exemplary clarity in their work. Thanks to the small slots with pronounced entries, Brazilian clutches turn on and off instantly, just turn the knob to the appropriate position. Of all the participants in the test, only they did not have a single misfire.
What does not turn on the hub look like? Yes, disgusting ... You drive into the snow and stop (the rear wheels start to slip). Get out, turn the knobs on the front hubs to the 4x4 position, get back behind the wheel, turn on the front axle with the lever and, having turned on the appropriate gear, step on the gas pedal. But instead of the expected movement, a crash is heard from somewhere in the area of the front wheel, and the car remains in place (the rear wheels are slipping). What to do in this case? In fact, nothing supernatural. Squeeze the clutch and try to start again. Usually everything works out. At least we always got out on the second try.
STED turned out to be the leader in failure on the first try. With him, extra gestures had to be made in more than half of the attempts. ELMO did not turn on on the first try a little less often, but also almost every other time. But cheap STELM, to everyone's amazement, almost caught up with the expensive "Brazilians". They did not deign to instantly turn on only two times out of several dozen attempts!
Analyzing the results, we concluded that, first of all, for the clarity of the inclusion, the shape of the splines involved in the engagement is important, and if the shape is the same, the surface finish is important. However, among the subjects there was also a model for which all this is completely unimportant. Old-style clutches always turn on, moreover, visibly. True, this process is rather dreary, but by turning the sleeve 13 turns, you can be sure that the clutch is tightly engaged. True, it is also possible that the tooth hits the tooth and no engagement occurs. It is useless to twist by force. As the experiment showed, the teeth will push into each other, but will not engage. It is much more effective to slightly loosen the puff and turn the sleeve into the desired position with your fingers. Or spin the front driveshaft. The only position in which it is impossible to turn on the ancient structure is under water or in liquid mud. The fact is that the unscrewed cap opens up free access of fluid to the inside of the coupling and further to the bearings and to the bridge.
And a few more observations. Steel Ufa clutches are the easiest to switch, whose rotary handle allows you to take it with your bare hand in a 15-degree frost without experiencing discomfort. Exactly the same switches on the silumin ones turned noticeably tighter, and on one of the hubs there was no clear fixation in the 4x4 position. The most "unpleasant" switches are equipped with ELMO: their silumin knobs with sharp edges require the greatest force to turn. As for the AVM, they have the most accurate fixation of the handle in the extreme positions, while it itself is convenient and requires a little more effort than the STED.
As I already said, with the installation of all types of hubs on the axle, except for the fact that the gaskets bought in the store slightly did not match the size of the hub flange, and we needed a special key for AVM, we had no difficulties. But when removing the problem, they threw STELM: the centering belt on their flange, apparently, turned out to be thicker than necessary, and it got stuck in the hub.
chilling horrors
Hubs are not only valuable fur... In the sense that, among other things, they must serve as reliable end caps for the bridge, preventing water from entering when fording. Are our test subjects up to the task? As a water barrier, we took ... a bucket and, adjusting the level in it with a mug, lowered the hub couplings into the font one by one up to the very flange. Then they switched them several times without taking them out of the water, and finally left them alone for 10 minutes. It is worth mentioning that we did not carry out any additional lubrication treatment.
I will say right away that only STED came out of the water absolutely dry. No matter how we twisted it, in 10 minutes he did not gain a drop. This, fortunately, compensates for one of its design features: it, like the “veteran”, has an internal space that freely communicates with the bridge. In the rest of the hubs, the water flow will still have to overcome a narrow gap between the housing and the rotating inner sleeve. By the way, the “military switch” can also be considered 100% waterproof: with the lid screwed on by hand along a dry thread, it began to let water through (drop by drop) only by the end of the tenth minute. Obviously, with a lubricated thread and tightening with a wrench, water does not get inside at all.
The remaining three types of hubs draw water through the switch handle. The STELM started leaking after nine minutes. But the results of AVM and ELMO were unpleasantly surprised. These hubs start leaking when switched underwater. At first glance, they do it slowly, but after 10 minutes the “Brazilian” was half filled, and ours was almost completely. If the hubs are not switched, then the leakage at the Sterlitamakets begins after 2 minutes, and at AVM - after 2 and a half. And one more observation. Unlike Russian products, the Brazilian one has through holes in the case for cover screws. Therefore, it is very important that all these screws are fully screwed in and well tightened. Otherwise - the flood!
After water procedures, we sent the test subjects for several hours in the freezer. And what? You will not believe, but all the switches are covered with ice crust! They didn't want to turn at all. The ice had to be chipped, but even then, of all the switches, only AVM turned by hand. True, its icy mechanism did not work instantly - it had to make several turns of the inner sleeve before a characteristic closing click was heard. Domestic hubs froze inside, apparently, not so much and turned on immediately. It’s just that in all cases it was necessary to turn the knobs with pliers. They just didn't give in. ELMO and at all had to twist together.
hub model
Outer sleeve
Inner sleeve
Knowledge is power
Well, almost everything is clear. It remains only with the help of special devices to determine the strength of the hubs and the hardness of the working surfaces of the splined bushings.
We started with a hardness tester. Of course, we expected that the metal of the splined bushings would be different, but to such an extent ... The hardest steel was found in the Brazilian product. STED splined bushings have almost the same hardness. The ELMO bushings are slightly inferior to them. But the steel of the old-style couplings turned out to be raw. But STELM's metal turned out to be the worst. Nails and those harder! So, with a standard measurement of Rockwell hardness, the device showed a solid zero on the splines of the inner sleeve! To get at least some result, I had to measure it according to Brinell. Meanwhile, this method is usually used for soft non-ferrous metals. However, in this case, we had iron in front of us, unless, of course, the magnet lied ...
The strength test required the development and manufacture of a special device, in general terms resembling a massive lathe with a lever. In the device, they fixed the axle shaft with a hub put on it, fixed it with a special drum, and began to spin the resulting system, watching how the load on the dynamometer grew ...
We started with a gray "Ufimian" (obviously a weak link). The fact that this clutch will break, no one doubted. But how did she do it! Until the very last moment, she did not give herself away. The load grew evenly and confidently, but as soon as the dynamometer readings reached 3500 Nm, there was an ... explosion (smoke even stretched from the hub). Imagine our surprise when, having disassembled the system, we took out the clutch with the body falling apart. The material turned out to be not just silumin, but low-quality silumin (chips exposed an abundance of shells of various sizes).
We “filled” the Brazilian hub into the machine with approximately the same feeling with which the Siberian men put the rail under the Japanese chainsaw. But the result was completely unexpected. We knew something was going to fail. But a hub or half shaft? At a load of 4100 Nm, the first light “crunch” was heard. We turn further. And at around 4250 there is a crackling, whistling and the sound of broken glass. She cut off 8 hardened M8 bolts holding ... the hub on the stand drum! Their fragments were fired, causing light destruction in the room. The axle shaft remained intact, the hub was not damaged either, but there was nothing to carry out “destructive” tests of the remaining samples ...
Tsar Bell and others
Are you sure you are waiting for conclusions and results? This time it's clear. For the gray hub, apparently, it will be necessary to allocate a special shelf so that it stands there like the Tsar Bell. In vain you laugh, STELM is by and large not good for anything else - it will let you down at the most crucial moment.
The old-style coupling, despite the quality of the material and workmanship, is reliable. But at the same time, it is very inconvenient to switch. Its installation on a car makes sense only for very hardworking people (or if this UAZ constantly drives with a bridge connected).
As for the rest of the couplings, they all require improvement, however, to varying degrees. Closest to the ideal were AVM. Everything is simple with them: check all the screws for threads, purchase a hex key and, having disassembled the switch, lubricate its parts with a thin layer of waterproof grease.
ELMO requires the same waterproofing. In addition, in order to achieve a clearer inclusion, this clutch will have to be completely disassembled into separate parts and the working surfaces should be sanded with a velvet file and sandpaper. True, the model will still have one fatal inconvenience - a tight and unpleasant to the touch switch.
STED needs sanding even more (this process will take longer than sanding along with waterproofing in the previous case). In addition, you will have to tidy up the internal landing belt under the spring on the large sleeve. Due to its chipped surface, we were not able to properly assemble the disassembled clutch and make it work.
If you become the owner of an SUV, then you definitely need hubs. In literal translation into Russian, a hub is a hub, that is, the central part of a wheel with a hole for fitting onto an axle. In our time, for short, hubs are called freewheels, they are also hub couplings with the wheel connected to the axle shaft. Any admirer of off-road understands that when returning from mud to smooth asphalt, his all-wheel drive car remains all-wheel drive, although there is no longer any need for all-wheel drive.
Happy owners of switchable all-wheel drive may be outraged. However, they can be reminded that when all-wheel drive is turned off, the front axle, gearbox, axle shafts, propeller shaft and gears in the transfer case rotate unnecessarily. They are rotated by front wheels that run on asphalt. And this leads to loss of speed, wear of parts and increased fuel consumption. That is, it is inconvenient and not free.
Wheel hub design
What are hubs for? In order to avoid wear of car parts and reduce fuel consumption. Wheel hubs disconnect the front wheels of the car from the transmission and from the front axle drives. It is logical to assume that disconnecting the hub from the axle shaft when driving on a flat road should be somehow technically implemented on many generations of cars. And indeed it is. Until 1948, this operation was carried out with a wrench.
After the Second World War, one American company set out to return to active civilian life thousands of off-road vehicles decommissioned from the army. For this, the invention of the notorious Albert Varna came in handy - a clutch with an overrunning locking mechanism, where overtaking eccentrics were actuated by slightly turning the clutch cover with a hand. This is the classic hub. An inexpensive and reliable mechanism then made it possible to turn an outdated SUV model into a useful work vehicle.
Types of hubs in a car and their principle of operation
All wheel hubs must be divided according to the principle of their work and consider how they differ. Hubs are: manual, automatic(electric, hydraulic, vacuum) and mechanical automatic.
Let's see how the hub works. It consists of a leading splined bushing, a movable splined bushing, and a clutch housing. The CV joint shaft enters the drive splined bushing. If the hub is disabled, then the movable spline does not engage with the drive spline. This allows the clutch body to rotate freely around the drive spline. That is, the drive is disabled. If we turn the hub knob and engage the clutch, then the movable splined bushing moves and connects the clutch body to the drive splined bushing. As a result of such actions, it is possible to transmit torque to the wheel.
Manual hub - what is it
Manual freewheels are more reliable. Their resource is comparable to the resource of the transmission itself. In addition, they completely exclude the possibility of spontaneous shutdown. The driver operates the manual hubs. To do this, he needs to switch the flags on the hub to the position of all-wheel drive or rear-wheel drive. Their only drawback is the need to leave the car to turn them on or off. All subsequent improvements are aimed at overcoming this particular inconvenience and are essentially attempts to turn a manual hub into an automatic one.
The principle of operation of the automatic hub is quite clear: to control the connection of the wheel to the axle shaft from the cab using some kind of drive. Therefore, electric, hydraulic and vacuum drives were invented to control the hubs. Automatic hubs turn on and off themselves at the moment when the driver turns on the front axle in the cabin either with a button (in modern cars) or a lever (in classic cars).
To turn on such an automatic hub, you must activate the all-wheel drive of the car and move off. To turn off - turn off the front-wheel drive and drive a little in the opposite direction. Everything is very simple and convenient, and you do not need to get out into the street in order to switch, possibly dirty switches. But the machines, due to their complex structure, are much less reliable than manual hubs. And this is understandable. Widely spread pneumatic automatic hubs. The thin point of this hub is the rubbing pair of axle shaft-oil seal. When the axle shaft and oil seal are worn out, this connection ceases to be tight, and a situation arises when the hub does not turn on.
Mechanical automatic hub - what is it
Separately, it is worth considering how mechanical automatic hubs work. They also turn on automatically, but without the intervention of an external drive, but under the influence of the laws of classical mechanics. They begin to act when a torque is applied to the axle shaft. These devices are very complex structurally, although they are quite reliable in Japanese and Brazilian designs.
The most successful such systems are installed on cars of the brand Nissan. The disadvantage of such couplings is the need to turn off the all-wheel drive to drive a few meters in the opposite direction to the previous one, so that the wheel and axle shaft disengage. However, such mechanisms also wear out. The classic automatic hub engages in engagement mode while the vehicle is in motion. There is some play in the transmission. At the moment when this backlash is selected, a blow occurs on the transmission, and this affects the reliability of the hub itself.
As for restoring the performance of automatic hubs on SUVs, this procedure is equal in price to installing a new manual hub. For all cars on which the manufacturer puts automatic hubs, manual hubs are produced by third manufacturers. Therefore, at the service station you will be offered to replace broken automatic hubs with reliable manual ones.
How to choose the right hub (Hub) for your car
How to choose the right hub? Hubs are installed on cars with plug-in all-wheel drive of various brands. The choice of drivers should be based on the operating conditions of the vehicle. If the main movement will take place off-road, then you should give preference to manual hubs. If you mainly drive around the city, then automatic will do. Installing the hub on your own SUV is within the power of anyone, if you act in order:
1. After parking the car and fixing it securely, we dismantle the hubs installed on it. To do this, unscrew the six bolts that secure the hub, or remove it in parts.
Note! Some cars have a retaining ring on the axle shaft, which can prevent the hub from being removed. Then it must be dismantled.
2. At the new hub, we unscrew the two screws on which it is assembled and disassemble it into two halves;
3.
We put the gasket and the base of the hub on the hub. We return the retaining ring to its original place.
4.
We fix this part of the hub on the hub with bolts and install the control part on the hub body.
In practice, turning hubs on and off is not necessary as often as it seems. They need to be turned on when we are going to leave the asphalt on the road, and turn off as soon as we left the asphalt. Thus, a simple and reliable device called a manual wheel hub will allow the wheel of your SUV to rotate freely on a wheel bearing, without loading either the axle shaft, or the gearbox, or the differential, thereby significantly adding dynamics to the car while saving fuel.
Attention!It is impossible to use thick lubricants in the design of the hub at all. Use liquid engine oil to lubricate moving parts.
Pros and cons of using wheel couplings
Consider pros hub usage:
The resource of car parts switched off by hubs is increased;
Improves car acceleration and rollover;
Saves fuel up to 1 liter per 100 km.
Consider minuses this procedure:
The impossibility at the right time to connect the car to all-wheel drive when driving from asphalt to dirt, when driving onto a high curb, when alternating the route (dry asphalt - snow marks).
After weighing all the pros and cons, you yourself must decide whether you need hubs or not.
