O. D. Alimov

ON THE CREATION OF LARGE-WHEELED ALL-TERRAIN VEHICLES

For the rapid development of the natural resources of the vast regions of Siberia and the North of our country, it is necessary to have means of transport capable of delivering various loads to any location.

In recent years there has increasingly arisen the need to deliver, to places remote from railways and waterways, large parts of drilling rigs, dredges, and turbines. Sometimes the dimensions of these machines are such that it is impossible to transport them on ordinary railway trains. Thus, for example, the delivery of turbines for the Krasnoyarsk Hydroelectric Power Station from Leningrad will be possible only by water transport via the Arctic Ocean. Great difficulties also arise in transporting parts of dredges and drilling rigs. These could be reduced if there were self-propelled installations which, without preliminary preparation of routes, could transport loads weighing up to 200–250 tons. One of the directions in the creation of heavy-duty all-terrain vehicles is the creation of amphibious all-terrain vehicles on large wheels. Below we shall dwell on certain questions of this problem.

The basic features of such machines should be a high load-carrying capacity and high cross-country ability under the conditions of Siberia, Central Asia, and the North of our country. All-terrain vehicles must, without preliminary preparation of routes, travel over sands, heavily swampy terrain with the crossing of water obstacles, through territories with deep snow, through brushwood and even forest.

Good cross-country ability under these conditions and high speeds can be ensured by large wheels, the diameters and widths of which must make it possible to overcome various obstacles with a small specific pressure on the ground.

The Americans began work on an all-terrain vehicle with large wheels long ago. About 15 years ago they created an amphibious automobile with wheels 3 m in diameter. All-terrain vehicles with such a wheel diameter were not competitive with amphibious all-terrain vehicles having ordinary wheels. Because of their large dimensions they had low maneuverability when operated on ordinary motor roads and did not possess particular advantages over other amphibians when moving over loose soil and through water obstacles. Therefore many specialists considered the creation of all-terrain vehicles with large wheels an unpromising direction and paid greater attention to tracked and multi-wheeled machines. The use of all-terrain vehicles with wheels 3 m in diameter made it possible,

apparently enabled American specialists to accumulate experience, as a result of which designs were created for all-terrain vehicles with wheel diameters of more than 15 m. Such an increase of wheels to unusual dimensions opens up new prospects. All-terrain vehicles with such wheels no longer need roads prepared in our usual sense; apparently, they can overcome any obstacles, including passing through forests, crushing under themselves trees 15–20 m high. The large dimensions of the wheels make it possible substantially to increase the load-carrying capacity of all-terrain vehicles and bring it up to the carrying capacity of river vessels.

From published data it is known that the load-carrying capacity of the “Big Wheel” all-terrain vehicle designed by the Americans is about 200 t, with the vehicle itself weighing 500 t.

The large dead weight of the all-terrain vehicle at first frightens some specialists, who hastily conclude that with such a weight all-terrain vehicles will be inapplicable for movement over weak soils, such as the soils of the West Siberian Lowland and swampy terrain. However, calculations show that with a wheel diameter of 15 m and a vehicle weight of 500 t, the specific pressure on the soil may be equal to and even less than the ground pressure of ordinary automobiles.

The Americans propose to install, for driving each wheel, an engine of 650 hp. The total engine power in this case will be 2600 hp.

If one proceeds from the practice of creating all-terrain vehicles with ordinary wheels, where for each ton of weight an engine power of 20 hp is recommended, then the required power of a large-wheeled all-terrain vehicle will be 10,000 hp. But even with such large power expenditures, with a load-carrying capacity of 200–250 t and a cruising speed of 30–40 km/h, large-wheeled all-terrain vehicles will be promising for the transportation of various cargoes and especially of large-sized installations without dismantling them (turbines, parts of bridges, and other special equipment).

Under favorable conditions, along a developed route, a large-wheeled all-terrain vehicle can make regular trips with large-wheeled trailers of high load-carrying capacity (200–300 t). In these cases, large-wheeled all-terrain vehicles may apparently be competitive with the river fleet and railway transport.

On the basis of heavy-duty all-terrain vehicles it will be possible to create self-propelled installations for drilling deep exploratory wells, powerful earth-moving machines for road construction and the development of mineral deposits, etc.

For each of these cases the optimal parameters of the all-terrain-vehicle chassis must be specified.

Preliminarily, it may be assumed that the largest wheeled all-terrain vehicles should have the following parameters: wheel diameter—10–15 m, drive power—2000–5000 hp, load-carrying capacity—200–300 t, specific ground pressure on the order of 0.5–3.5 kg/cm², travel speed—up to 50–60 km/h. All wheels must be driven.

The operability of a heavy-duty all-terrain vehicle and its field of application will depend to a considerable extent on how successful its general layout and the design of the principal assemblies are: the frame, wheels, their suspension, and drive. Considering that heavy-duty all-terrain vehicles will have to be used for transporting various loads and for mounting various units (drilling rigs, excavators, etc.), we believe that their design should consist of a large-wheeled chassis with all wheels driven.

One of the variants of the large-wheeled chassis proposed by us consists of four large-diameter wheels 1 (Fig. 1), two equalizing beams 2, and a three-tier platform 3. All four wheels are driving wheels. Control of the large-wheeled chassis is carried out in such a way that, when turning, the wheels on one side are braked or are given opposite rotation.

Fig. 1. Diagram of a large-wheeled all-terrain vehicle with wheels 15–20 m in diameter.
1 — wheels; 2 — equalizing beams; 3 — platform; 4 — axles; 5 — shock absorbers; 6, 7, 8 — lower, middle, and upper tiers of the platform; 9 — control cabins.

Each pair of wheels on one side is connected by equalizing beams 2. The equalizing beams are connected to the chassis platform by two axles 4. Such a connection of the wheels to the platform should provide the all-terrain vehicle with good obstacle-negotiating capability and good distribution of the load over all the wheels of the all-terrain vehicle.

To stabilize the position of the platform, the equalizing beams are additionally connected to the platform by four shock absorbers 5 with damping devices. The travel of the shock absorbers should be 3–4 m. This will allow the all-terrain vehicle to move over uneven terrain at high speed and to overcome obstacles 3–4 m high without significant oscillations of the platform.

The equalizing beams can be used to accommodate the wheel-drive transmissions, and possibly also power units. It is advisable to consider a variant in which the engines are located in the wheels of the all-terrain vehicles. The main engine may be located in the lower tier of the chassis platform 6. The second tier 7 of the chassis may be used for small-sized cargo and as a compartment for transporting people. The upper tier 8—the deck of the all-terrain vehicle—should be intended for transporting large-sized cargo. On the same upper deck are also located two cabins 9 for controlling the movement of the all-terrain vehicle in different directions. The lower and middle tiers of the platform may, during move—

the all-terrain vehicle’s cabins are isolated against the ingress of water. In this case the all-terrain vehicle can be used as an amphibian for crossing large rivers, lakes, bays, and straits.

To increase its speed of movement on water, the all-terrain vehicle can be equipped with propellers. The greatest technical difficulties in creating such all-terrain vehicles will apparently arise in developing the design of the wheel tires and wheel suspension. In our opinion, the wheels of all-terrain vehicles should be sectional, low-pressure, with chain or cable armor.

To solve the problems that will arise in creating such all-terrain vehicles, it is expedient to build several reduced-scale models of all-terrain vehicles on which the mobility, stability, and maneuverability of large-wheeled all-terrain vehicles can be studied. Fig. 2 shows—

Fig. 2. Diagram of a large-wheeled all-terrain vehicle with wheels 1.5–1.8 m in diameter. 1 — wheels; 2 — balance beams; 3 — body; 4 — shock absorbers; 5 — axle connecting the body and the balance beams; 6 — propeller.

—the principal scheme of a reduced model of a large-load, large-wheeled all-terrain vehicle, in which the driving wheels of a “Belarus” type tractor are used as the wheels. In our opinion, apart from experimental purposes, machines built according to the scheme in Fig. 2 can be used in the national economy as small amphibians. Amphibians built according to the “large-wheeled” scheme will have greater mobility in marshy terrain than GAZ-46 type amphibians, and a higher speed of travel on roads in comparison with tracked amphibians. A larger model of a large-wheeled all-terrain vehicle can be built on the basis, for example, of a “Kirovets” tractor. The wheel diameter of this model may be on the order of 3–5 m.