Anonim

“AWD gives less torque than 4WD.”

Opinion of one Internet "expert"

Image

The abundance of ingenious abbreviations such as AWD, 4WD, as well as Part-Time 4WD, Full-Time 4WD, 4x4, 4matic and other abbreviations is a good advertising move, inspiring the car owner that he was not mistaken when buying a car, choosing the "most-most." At the same time, unfortunately, such nameplates often do not have an unambiguous interpretation. Those who do not believe can type in the search bar, say, AWD and 4WD - you will be brought into such wilds from which you can’t even get out. About technical literacy is generally better not to stutter.

Meanwhile, by and large, the main types of cars, called all-wheel drive, are three (if you do not get deep into those very jungle with "chaldeks", asymmetric differentials, etc.). Typical representatives of the “trinity” are shown in the photo below.

УАЗ Patriot. Привод на заднюю ось - постоянный. Привод на переднюю ось - подключаемый; межосевого дифференциала нет. UAZ Patriot. The rear axle drive is permanent. Front axle drive - plug-in; There is no center differential. UAZ Patriot. The rear axle drive is permanent. Front axle drive - plug-in; There is no center differential.
Лада 4х4. Привод на обе оси - постоянный, есть межосевой дифференциал. Lada 4x4. The drive on both axes is permanent, there is an interaxle differential. Lada 4x4. The drive on both axes is permanent, there is an interaxle differential.
Renault Duster. Привод на переднюю ось - постоянный. Привод на заднюю - подключаемый через муфту. (Известны и обратные схемы, когда основной ведущей осью является задняя, а через муфту подключается передняя…) Renault Duster. The front axle drive is permanent. Drive to the rear - connected via a coupling. (Reverse schemes are also known when the main driving axle is the rear, and the front is connected through the clutch …) Renault Duster. The front axle drive is permanent. Drive to the rear - connected via a coupling. (Inverse schemes are also known, when the main driving axle is the rear, and the front is connected through the clutch …)
Related Materials Image All About Differentials: The Torque of Truth

And here is the first feature, for many - an unexpected one. From the point of view of the pedant, the title of an all-wheel drive car from the specified trinity is truly worthy only of the Togliatti car! After all, only her four-wheel drive works in 100% of cases, while for the rest it is, in general, a plug-in function: the UAZ often rides in the rear-wheel-drive Lada, and the Duster - like a front-wheel drive VAZ “eight”.

The second feature is also funny - few people know about it. Even with the axles off (the front on the UAZ and the rear on the Duster), a bunch of transmission elements on these cars are still constantly spinning! On the UAZ, the axles of the front axle and the universal joint will rotate, on Duster - the rear gearbox and rear wheel drives, as well as the universal joint. And this is noise and fuel consumption even in single-drive mode.

Now - about the trickiest: how the moments are distributed on these machines. Consider several situations. At the same time, we conventionally believe that friction and other losses are absent, the loads on the wheels are the same, the longitudinal and transverse weights are uniform, and the conditions for the adhesion of tires to the coating are the same, unless otherwise noted.

The car rides on a flat road in a circle

Related Materials Image Why Shniva is better than Duster, or Mechanical interlock against electromagnetic clutch

UAZ Patriot. If the front axle is not connected, then the moments on its rear wheels are distributed equally, and on the front moments are absent. If you connect the front axle, then on each axis the moments will be divided equally, but the distribution along the axes will depend on the loads and traction. On dry asphalt, this will lead to the fact that the front and rear wheels begin to slip relative to each other, since there are no one to align their moments: there is no center differential.

Lada 4x4. If the center differential is not locked, then the moments on all four wheels are equal. Accordingly, there will be no slippage. If you lock the center differential, then, like on an UAZ, when driving on a good road in a corner, relative slippage of the front and rear wheels will appear.

Renault Duster. When driving in Lock mode, the clutch rigidly connects the rear axle, which can lead to slippage on a good surface.

Drive wheel hanging in the air

UAZ Patriot. If the front axle is not connected, the machine will stop. When the bridge is connected, the entire moment from the engine will go to the "independent" axis, and the car will go further.

Lada 4x4. When the differential is unlocked, the machine will stop. If you block the center differential, then it will go further.

Renault Duster. When the 2WD selector is in position, the vehicle will stop. In the Auto or Lock position, the clutch will connect the rear axle and it will continue to move.

Common Truths

  • The symmetric differential always equalizes the moments: center - on the axles, cross-axle - on wheels.
  • The locked cross-axle differential actually turns the axle of the car into an analogue of the wheelset of a railway carriage. But even so, the moment on the posted wheel is zero.
  • On a posted wheel, the moment is always zero, regardless of the presence or absence of differentials.

What's in a name?

Related Materials Image Four-Wheel Drive Rating: Roller Testing

And where do all these AWDs and other 4WDs come from. I called my colleague at the car factory - he, to my pleasure, confirms what I came to myself. Say, such designations as a whole are not technically legislative, but purely marketing, conditional. Therefore, exceptions may occur in life. But basically AWDs are “mono drives” that have the ability to connect a second drive axis. And 4WD is, let’s say, machines with permanently connected axles with a predetermined initial distribution of torque between the axles (for example, 50 to 50, which have the ability to block the center differential).

In general, if you only need to get out of the snowdrift from time to time, then any of the above schemes with a hint of all-wheel drive will significantly surpass the usual “4 by 2”. And most need it. Well, those who are preparing for real off-road feats still live in a parallel universe, and therefore do not need any explanation.

Good luck to everyone on any road!

AWD, 4WD, 4x4 - ZR found the most four-wheel drive. The answer will surprise you
  • We are regularly asked the question of how many sets of snow chains you need to buy for an all-wheel drive car and how many bracelets you need for the car. The answer is simple - it doesn’t matter whether a car has all-wheel drive or not. One set of chains (2 pcs.) Per axis is sufficient. As for the bracelets, the more they are mounted, the better the car is “rowing”, each bracelet wears less. Recommended quantity - from 6 pcs.