Military Review

Large wheels for the army: a tool for conquering transcendental off-road

Large wheels for the army: a tool for conquering transcendental off-road
FWD Terracruzer MM1. Source:

Unique crooks

Ultra-low pressure tires or pneumatic rollers are a real godsend for overcoming difficult road conditions. More precisely, not even road conditions, but directions over rough terrain. The most important advantage of huge tires is the low specific ground pressure (0,2 - 0,7 kgf / cm2) and, consequently, a sparing effect on the fragile soil layer of the tundra. Such machines do not bury themselves up to their ears in the snow and do not go into the depths of a swamp bog. Actually, that's why this technique is called snow and swamp-going vehicles. If the vehicle is equipped with standard systems of centralized tire inflation, the support cross-country ability increases multiple. Only equipment with non-traditional propellers - hovercraft or auger-rotor all-terrain vehicles - can argue with snow and swamp-going vehicles. The snow and swamp-going vehicle on flat tires literally hugs rather big obstacles with tires - stumps, logs and boulders. This is achieved, in addition to low pressure (0,2 - 1,0 kgf / cm2), due to the small landing diameter of the pneumatic roller, thin frame and large profile width. The prototypes of ultra-low pressure tires - arch tires behave in a similar way. They became especially popular in the second half of the last century. For example, the cross-country ability of the two-axle ZIL-164 with arched tires on the rear axle became equal to the cross-country ability of the three-axle ZIL-151.

Pneumatic roller experienced ET-8. Source:

The presence of huge wheels on the vehicle also causes a large displacement. In other words, cars on ultra-low pressure tires are often able to float - the wheels play the role of floats. By the way, tires on the water, due to their large diameter and developed lugs, do a good job with the role of propellers. On average, they allow you to accelerate on water up to 3 km / h; for high speeds, water cannons or propellers are already required.

In the 90s, one could find such semi-handicraft copies of snow and swamp-going vehicles. The picture shows the transport of Nara. Source:

The positive aspects of ultra-low pressure tires do not end there. The large wheel diameter naturally significantly increases the ground clearance - in some modern cars it can exceed 750 mm. Thanks to soft tires with a large profile, engineers in some cases do without a suspension on snow and swamp vehicles. Of course, at high speeds and in off-road conditions, the lack of shock absorbers can turn into a dangerous goat, but such a technique is not intended for rally-raids. Even on hard surfaces, the maximum speed does not exceed 70 km / h.

The most interesting thing is that due to the low pressure inside the tire, the air in the event of a puncture does not poison especially intensively, and this is easily compensated by the inflation system. A very good bonus for military vehicles. It is not for nothing that army drivers were among the first to try "super-rogues" on soft tires.

Historical background

In theory, it is not difficult to create a car on pneumatic rollers. For this, a motorcycle or passenger car is enough, in which standard wheels are replaced with used cameras from trucks, planes and tractors. The result is a kind of off-road vehicles, popularly called funny nicknames - caracats, tundrolets, dutik, etc. like a tire.

FWD Terracruzer MM1. Source:

On the industrial level, one of the first to use ultra-low pressure tires on its products was the automobile company FWD from the USA. In 1955, the company's engineers built an experienced XM357 Terracruzer conveyor with eight Goodyear pneumatic rollers with an internal pressure of 0,2 - 0,35 kgf / cm2... The transfer of torque and vertical load was carried out using rolls. A distinctive feature of the car was the actual lack of ground clearance - hefty pneumatic rollers took up almost the entire width of the truck. The total mass of the truck was 19 tons, of which nine were assigned to the payload. Originally developed for the needs of the US Army, an experienced all-terrain vehicle was sent for testing at the main duty station - in Greenland. In the harsh conditions of the Far North, the experimental car did not behave in the best way and constantly annoyed with excessive tire wear. In addition, the transmission of torque through the rolls showed severe power losses and, as a result, low efficiency. As a result, the engineers decided to go the traditional way - to transmit power to the propeller through the axle. The new Terracruzer MM-1 was also equipped with eight wheels with slightly narrower Rolligon tires, grouped into two bogies.

Civilian variations on the FWD Terracruzer theme. Source:

The four-wheel drive truck was assigned its main purpose - to carry American missiles on itself over difficult terrain. For this purpose, an air-cooled Continental eight-cylinder engine running on aviation gasoline with an octane rating of 145, and a 4-stage torque converter served. The off-road vehicle-snow and swamp-going vehicle had an adjustable suspension, which allows to overcome uplifts of 60%, and a centralized wheel inflation system with an adjustment range of 0,35 - 0,9 kgf / cm2... The giant's top speed reached 64 km / h. A symmetrical locking differential was installed between the bogies in the transmission, and the drive to the wheels was carried out using helical gears located inside the hollow balancers. The tractor was maneuvered by turning the front bogie using a hydraulic booster. The brakes were of the aircraft type with hydraulic actuator.

FWD Terracruzer Prototype. 1956 year. Source:

FWD Terracruzer MM1. Source:

In the future, the Americans built for the military, as well as for geologists, agricultural workers and builders, many super-passable pneumatic equipment. Probably the most curious unit was the FWD trailer, equipped with four pneumatic rollers with a diameter of 1625 mm and a width of 1070 mm. In these tires, engineers proposed to transport 1900 liters of liquid cargo - fuel, oils and other technical fluids. In addition, the trailer had a platform with a carrying capacity of 2,72 tons.

Soviet experience

The Soviet Union, possessing endless expanses, completely devoid of a roadbed, also found itself among the pioneers of snow and swamp transport. The leading developer was the specialized institute NAMI, which in 1958 built an experienced NAMI-044e with a 4x4 wheel arrangement. Initially, arched tires were installed on a small truck resembling a tractor, and in 1959, wide pneumatic rollers with a pressure control system appeared.

US-044e. An early prototype still had arched tires. Source:

Obviously, under the impression of the overseas Terracruzer MM-1, NAMI created an ET-8 all-terrain vehicle of the 1961 model, very similar to it. The prototype had an inter-carriage and two inter-bead differentials, as well as a drive gear guitar in a hollow balance bar. The ET-8 did not have a suspension as such. The front bogie was turned by a hydraulic booster from MAZ-525, installed on a running device. ET-8 was developed with a carrying capacity of 8 tons, and the specific pressure on the ground was 0,4 - 0,9 kg / cm, which is comparable to tracked propellers. Each I-245 wheel provided contact with the ground with an area of ​​about one square meter. An experienced 8x8 truck was equipped with a tire pressure regulation system.

ET-8. Source:

To reduce the cost of production of the machine, some units were borrowed from serial equipment. So, the cabin came from an average artillery tractor ATS, and the engine was taken from a carburetor ZIL-375 with a capacity of 180 hp. from. - later it will appear on Ural cars. Tests ET-8 showed that the SUV copes well with sticky soils, swampy meadows and swamps, while maintaining traction on the hook up to 9 tons! For the 50-60s, no wheeled vehicle could boast of such cross-country ability - the ET-8 could only be compared with tracked vehicles. At the same time, the resource of the caterpillar propeller did not exceed 4-7 thousand kilometers, while pneumatic rollers could work even 30 thousand.

Despite the obvious advantages, the experienced snow and swamp vehicle from NAMI did not interest the military, although in the West such FWD vehicles became the founders of a whole family.

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  1. Vladimir_2U
    Vladimir_2U 20 February 2021 05: 53
    Regarding the specific pressure on the ground, I remember a comic problem: "Mom weighs 65 kg, and the son weighs 30 kg, which of them will fall into the swamp earlier, provided that the mother is in heels and the son is in flippers?" laughing
    1. Free wind
      Free wind 20 February 2021 08: 00
      Surely my son, my mother will not trample into the swamp, and this is all the boy needs. wassat
    2. The leader of the Redskins
      The leader of the Redskins 20 February 2021 11: 08
      At the school they used to say something different to us:
      The pressure of the tank on the ground is 0.92 kg / cm, the pressure of the female heel is 1.05.
      Output. Better to be under a tank than under a woman's heel! laughing
      1. Mister X
        Mister X 20 February 2021 16: 26
        Quote: Leader of the Redskins
        Better to be under a tank than under a woman's heel!

        And how did it carry over? wink
        1. The leader of the Redskins
          The leader of the Redskins 20 February 2021 17: 49
          Not really ... Married twenty-two years. Not henpecked, but ... The opinion of the wife has to be reckoned with.
          1. Mister X
            Mister X 20 February 2021 18: 17
            Quote: Leader of the Redskins
            The opinion of the spouse must be taken into account.

            How else?
        2. Proxima
          Proxima 20 February 2021 18: 32
          Regarding an elephant, if he steps with the ball of his foot on a person's feet, it will feel as if a bag of grain has been placed on the foot. And if the front part, then the fracture. Such are the metamorphoses of specific pressure. request
          1. Mister X
            Mister X 20 February 2021 19: 21
            Quote: Proxima
            if he steps on a person's feet with the ball of his foot, it will feel as if a bag of grain has been placed on the foot.

            If only the elephant does not want to dance wink
      2. Andrei Nikolaevich
        Andrei Nikolaevich 20 February 2021 17: 16
        Original! And intelligibly.)
    3. max702
      max702 April 11 2021 21: 32
      All the devices presented have one problem - a poorly developed tread profile, and therefore a quick salting of it and the loss of adhesion on weak soils .. This problem was less successfully solved by Gargashyan on Sherpa and on the new AG-20 tires

      1. Vladimir_2U
        Vladimir_2U April 12 2021 03: 15
        If this tire is big, how is it doing side slip resistance on the same slope?
        1. max702
          max702 April 12 2021 08: 25
          But Gargashyan is now solving this problem in the new tires.
  2. andrewkor
    andrewkor 20 February 2021 06: 11
    Now, if a tank turret with a cannon were installed on the ET-8, this would interest the military!
    1. Cowbra
      Cowbra 20 February 2021 06: 59
      And when fired, the platform shakes like a jelly ...
    2. Hunter 2
      Hunter 2 20 February 2021 07: 55
      Indeed, it is strange that this technique did not interest the military, in my opinion - for rear services, under certain conditions, it would fit perfectly. Actually, at the present time, such equipment is not on the balance sheet of the Ministry of Defense (as far as I know), the Ministry of Emergency Situations does.
  3. Lech from Android.
    Lech from Android. 20 February 2021 06: 15
    An interesting topic ... I'm looking forward to continuing. hi
    1. mirag2
      mirag2 20 February 2021 10: 22
      Here is almost the same as in the article:
  4. SovAr238A
    SovAr238A 20 February 2021 07: 40
    All swamp vehicles on low-pressure pneumatics have one huge drawback - pneumatics often break against any small "junkies", which are abundant in the Far North. Fragments of small tundra trees, which are scattered across the tundra. The stones are small too.
    Not work, but eternal repairs.
    There are several swamp vehicles in the works.
    Got tired with them.
    And the price of a tire in the central part of the Russian Federation is from 35 thousand.
    And to deliver it to Novy Urengoy is "priceless" ...

    So every plus has its minus.
    1. ycuce234-san
      ycuce234-san 20 February 2021 16: 28
      They can probably only be used on ready-made routes that have been "swept" by a tractor with a disc lifter or a bulldozer knife, as well as on ready-made primers. For example, such a car should walk well on a timber road; along a highway swept by a blizzard or a ready winter road.
    2. kamakama
      kamakama 20 February 2021 18: 51
      Augers ... There is nothing to break
      1. abrakadabre
        abrakadabre 20 February 2021 19: 19
        Augers ... There is nothing to break
        Oh yeah ... This is the topic. Just a racing car. With proper camouflage, you can make movable points out of them ... Tfu you, movable bumps. The enemy, even after an hour of observation, will not notice that it is moving.
      2. SovAr238A
        SovAr238A 25 February 2021 19: 21
        Quote: kamakama
        Augers ... There is nothing to break

        And 100% irreversible damage to the surface layer of the soil ...
        In tundra conditions - hundreds of years ahead.
        In black soil conditions - for a couple of years.

        Any road surface becomes completely unusable immediately after the first application.
        This is what augers are in fact.
        1. kamakama
          kamakama 26 February 2021 10: 55
          Alas, yes. This does not go on the roads in principle. But with the off-road ... In fact, no matter what the tire pressure, the surface layer of the soil deteriorates for years after 10-15 drives along the same track. I judge by a very rarely used road in a pine forest on sandy soils. Drives 1-2 cars per MONTH
  5. Ros 56
    Ros 56 20 February 2021 07: 47
    I still remember ZiLs with wide rear wheels instead of the usual twin single ones.
    1. Konnick
      Konnick 20 February 2021 08: 50
      Arch tires were used on the ZIL-130 widely in agriculture. In terms of cross-country ability on soggy arable land when harvesting sugar beets and cabbage in the fall, they were not inferior to the all-wheel drive ZIL-131 and Ural-375.
    2. Dym71
      Dym71 20 February 2021 10: 17
      Quote: Ros 56
      I still remember ZiLs with wide rear wheels instead of the usual twin single ones.

      1. Uncle lee
        Uncle lee 20 February 2021 13: 53
        I did not find a photo of the ZIL-150, but I saw it at the autodrome.
  6. mr.ZinGer
    mr.ZinGer 20 February 2021 08: 52
    I understood from the title, Evgeny Fyodorov, so you need to read the case when it is not the topic that is interesting, but the author.
    1. Mister X
      Mister X 20 February 2021 16: 28
      Quote: mr.ZinGer
      Understood by the title, Evgeny Fedorov, so you need to read

      And I'm on the first lines smile
    2. Alien From
      Alien From 20 February 2021 19: 42
      But the author, as always, leaves a reserve for the future. I liked the article, we look forward to continuing)
  7. Victorio
    Victorio 20 February 2021 09: 56
    US-044e. An early prototype still had arched tires. Source:
    I remember how at the end of the 80s something similar was installed in the port on Japanese Komatsu bucket loaders so as not to spend currency on the purchase of new rubber. took / bought from the military written off and unused from warehouses nz.
  8. Free wind
    Free wind 20 February 2021 10: 03
    I thought that these were our developments, all sorts of motorized dogs, walk-behind tractors, snowmobiles. But it turned out that all this was done for a long time. It was a shame.
  9. Alien From
    Alien From 20 February 2021 11: 26
    Thanks Eugene!
  10. iouris
    iouris 20 February 2021 12: 08
    not only and not so much for the army. we have had many such developments. now it is not relevant.
  11. kamakama
    kamakama 20 February 2021 18: 54
    The augers. "Blue Bird" and related equipment. Or a very ancient "Fordson"

    1. ycuce234-san
      ycuce234-san 22 February 2021 00: 06
      It is strange that such special tractors are not made for Antarctic expeditions. They would be there to the place. It would even be possible to make a helicopter for polar explorers with an auger chassis - this is both a supply of fuel in the augers and a chassis for self-propulsion along the ice airfield.
  12. Outsider V.
    Outsider V. 22 February 2021 13: 26
    Extant MM1 Terracruzer: