In times of peacekeeping operations and the fight against terrorism, partly carried out outside cities and towns, the most modern developments in caterpillar technology should be transferred to the troops without delay in order to make the combat mission successful and save the lives of soldiers.
Light and heavy tracked vehicles and main combat vehicles Tanks (MBT) play an important role, especially in difficult terrain. They demonstrate the highest performance and operational readiness, guaranteeing their own superiority and survival, which are the key to the success of a combat mission.
In order to describe the development trends of modern caterpillars for vehicles, it is best to start with the tracks for the LEOPARD 2 MBT. These tracks represent the current state of the technology level and are a good example for describing which considerations led to the further development of the tracks and what results were really achieved. The following observations will be limited to developments conducted by the German company Diehl Defense Holding GmbH.
570 FT track track: 1. 2 track connecting bracket. 3 coupling screw. 4 tubular body. Rubber shoe 5. 6 snow grip. Internal fitting 7. Internal fitting 8. Coupling screw
Main battle tanks
The standard tracks for the LEOPARD 2 tank are the Track Type 570 FT tracks from Diehl Defense. It is a link caterpillar (with a double finger), each link of which is a monoblock case with a central solid cast (ridge). The gaps between the bodies are curved grooves. This reduces the vertical shock load on the track rollers when rolling on an obstacle. There is no internal rubber coating here, since it does not provide the required properties at low temperatures, and this also increases the weight of the track link and adversely affects its operating life, in addition to increasing the production cost.
Constant forces acting through the support rollers when moving along inclined sections and when the machine is laterally accelerated, as well as when cornering, or impact loads when overcoming stationary obstacles, act on the body of the track itself, and not on the central guide (ridge), since it is part of it. Unlike the truck, whose central guide is located on the central coupling bracket, this solution significantly reduces the load on the track finger. In addition, the center guide — with its large bending moment of resistance — provides the ideal rigidity of the track body in its critical central section.
The principle of insertion was retained on the end surface of the rubber pad, but it has undergone modernization in the form of a bayonet fixation.
Quick Fit rubber liner
This reduces the length of the length required for installation and removal by about a third (Quick Fit system), and thus greatly facilitates any necessary replacement of the rubber lining.
The fingers have a new design: they are round along the entire length and do not have bald spots at their ends. In this case, the full cross-section of the round fingers is in the place where cracks and even fractures may appear, and which is really subjected to large transverse and bending loads. The constructive cut-out made for the transition from a circular section to a flat one and which was a stress concentrator in this place was thus eliminated. The high quality of the surface of the round billet is preserved; therefore, it became possible, without taking into account the shape of the finger, to select the optimum depth of hardness of the surface layer for real load conditions. At the end of the finger in the blind hole set pin. It centers the connecting bracket, thus ensuring the correct installation position. Due to the overlap of the axes and the finger, the axle brackets work in the same way as the additional locking element of the bracket, which is pushed out by the track’s fingers. This is especially important for tracks without central joining brackets, when in the event of any sudden shear force — for example, in the event of any accident or breakdown — detachment of adjacent track links may occur. The outer bracket has a rounding inside the sectional profile. Fixing the support surface of the bracket is achieved by friction in the seating surface.
Connecting brackets of round fingers and fingers
The Track Type 570 FT track weight from Diehl System is 185,6 kg / m. A complete set of tracks for the tank LEOPARD 2 has a length of approximately 30 meters and a mass of 5592 kg.
Further and more promising development tracks for the tank LEOPARD 2 were implemented in the model Track Type 570 PO from the company Diehl Defense. It implements all the advanced solutions and practical experience gained in recent years of research. The goal of this development was to achieve a significant weight reduction while maintaining the same useful life.
Tracks of the German tank Leopard 2A6
Unlike all previous tracks with connecting brackets, the engagement with the teeth of the drive wheel no longer occurs outside the brackets, but behind the track body itself. This provides a significant reduction in loads on the fingers, i.e., impact bending forces during engagement with the ridges. The crumbling rubber finger coating also becomes unloaded (absorbs less force) due to the uniform distribution of the total operating load arising from the tractive effort.
The external bracket is currently attached only to the left; its task is to connect adjacent tracks of the track. There is no longer any need for an additional amount of metal to compensate for the wear of the bracket when it engages with the teeth of the drive wheel and, thus, it is possible to design the bracket almost symmetrically. It works as a clamping clamp, which closes more balanced tangential and radial forces on the finger. Therefore, the bracket is already thinner and lighter than its predecessor. During operation, the caterpillars on the finger act less torque and force. As a result, lighter tools can be used, and greater safety is provided during repairs. Another advantage is that only rubber linings and track bodies are subject to wear. Here, additional wear is created on the contact surfaces of the drive wheels. Due to the design of the gearing interval, there is a zone with a very low tensile force, which, in principle, reduces wear on the rubber liner. Since there is enough material in this place to compensate for wear and local hardening to a greater depth, the life of this component is very large. Due to the gearing in the track body, the size of the track linings, however, must be reduced by 10%. This leads to a higher specific surface load on the lining, which in turn causes an increase in lining wear. This can be partially compensated by improving the rubber compound used. During the tests, it was found that the wear of the toothfoil on the drive wheels increased. However, perhaps this can be corrected by appropriate selection of materials and optimization of the shape of the tooth.
The main advantage of the Track Type 570 PO track is its low weight. A set of these tracks is more than a 650 kg lighter than a serial kit. This allows you to take measures to improve combat effectiveness and not to take into account further increase in the total mass of the machine.
Today, this principle has already been applied in two- and even three-stage tracks with connecting brackets, for example, in tracks of the 129 series for MLRS, ULAN and PIZARRO machines and for some M113 variants.
570 PO Track Track
Track Track Type 622 for WIESEL: 1. 2 bracket. 3 connecting bolt. Tubular casing with vulcanized rubber pad
Lightweight caterpillar design
As its first light track, Diehl developed the track for the WIESEL weapon transporter. This caterpillar has replaced the Clouth rubber track. The disadvantage of these rubber tracks was the fatigue wear of steel cables caused by bending forces in the transverse connecting elements. After running more than 3000 km, this caused a break in the tracks without any previous external signs. Since other measures to eliminate the cliffs did not lead to anything, these tracks eventually were replaced with new link tracks with Diehl Track Type 622 end brackets. For the first time, successful development of a steel casting track with vulcanized rubber linings, which is slightly heavier than the rubber track used before, has become possible. The caterpillar is driven by the center guide rollers. The track width is 20 cm; linear weight - 17,4 kg / m. The rubber pad can be replaced in the event of a resource.
Extreme requirements for the American high-tech expeditionary combat vehicles EFV (project is closed) for the Marine Corps initially led to the development of light tracks made of aluminum. However, it was found that aluminum is an unsuitable material for tracks, since only steel has a reliable safe margin for peak loads and forces in the boundary region. With a mass of approximately 82 kg / m, the newly developed light steel caterpillar is close to an aluminum caterpillar, whose running weight is approximately 75 kg / m. Each caterpillar track consists of two tubular bodies with very thin walls, in which rubberized hollow fingers are installed. They are interconnected by two end brackets and a central bracket bolted to the central guide (ridge). All parts are optimized for weight. Rubber linings are inserted using the Quick Fit system.
The experience gained in testing this track for the EFV expeditionary combat vehicle has influenced the similar development of the track for the new PUMA BMP. It consists of two light steel tubular bodies with two hollow steel fingers with rubber bushings. They are interconnected by two end brackets and a central steel bracket, combined in one piece with a central guide (ridge). As a result, parts optimized for mass turned out to be lighter by 40% compared to similar standard tracks. Rubber linings are inserted using the Quick Fit system and fixed in place by the snap-fit axle. This reduces the likelihood of loss of rubber linings, and when they are replaced very significantly reduces the time for maintenance and repair compared to the time required for loosening the bolted lining.
Even with regard to rubber for running linings, significant improvements can be realized. For the first time, Diehl has succeeded in developing an elastomeric material that has excellent characteristics for fast driving on roads (the problem of heating), as well as on difficult terrain (destruction from sharp stones). WIESEL was the first machine in the German army equipped with a new type of lining. This can significantly increase mileage, for example in Afghanistan.
This rubber compound is also intended for use in a PUMA machine. With a running mass of significantly less than 100 kg / m, the Track Type 464 caterpillar is currently unparalleled in performance.
Diehl Defense Products
Continuous (continuous) tracked belts
Until now, continuous tracked belts were used only on light machines that have a correspondingly small engine power. So, the heavy version of the Hagglunds BV 206S, has a total weight of 7,1 tons and engine power 130 kW / 177 hp. In this car, the drive power is theoretically divided into four tracks. There are several manufacturers of this type of solid track. All these caterpillars have steel transverse ties, to which a thrust force from a driving wheel is applied. The transverse forces from the caterpillar act on the support rollers due to its guide teeth (crests).
Traction force is perceived rods of aramid-nylon fiberglass or steel cord, enclosed in a rubber casing. Along with rods, steel ropes (WIESEL 1) can be used. Rubberizing protects the loaded elements from corrosion and any damage, while the profiled running work surface transfers all the effort to the ground, and wear out over time. As a rule, belt tracks are continuous (continuous), which makes their replacement more laborious, as in this case one of the sides of the machine must be raised or even the undercarriage must be partially disassembled. It is hardly possible to perform such work under operating conditions. The main advantage of these tracks is a small mass and in a quiet course, the disadvantage is the low maintainability. In the event of any damage, the entire caterpillar must be replaced, repairs on the machine, replacing only a separate link, is impossible.
Track for Track Type 464 BMP PUMA: Width - 500 mm, Link size - 183,5 mm, Weight - 95 kg / m, Resource - 6000-7000 km (38 tons), 4000 – 5000 km (43 tons); tubular body with steel inner working surface of cast iron or stamped; steel bracket; working rubber pad (quick fit quick installation system)
Place of separation, caterpillar from Diehl
The demountable directing wheel and a caterpillar from the Soucy company by M113 car
An exception is made for Diehl's tracks on the BV206. It can consist of two, three, or four segments that are connected at proprietary endpoints with special brackets. This greatly facilitates any installation and installation of the track on the machine, its transportation and storage. Individual segments can be stacked and transported in a compact form.
Recently, the Canadian company Soucy group also began to offer potential customers a complete track belt for M113. Thus, this company ventured to enter the sector in which steel caterpillars still reigned. This solid track is significantly lighter than a tandem caterpillar (approximately 26 kg / m instead of 64 kg / m on a caterpillar track). It is also liked by the consumer in its quiet course. Thus, for example, a decrease in noise was measured at approximately 10 decibels (A); during measurements of the external noise of the machine, the sound level was more than 10 decibels (A) lower than the standard machine used for comparison. Installing the tracks on a raised machine is relatively time consuming. In order to accomplish this task, the guide wheel is made of two parts.
Currently, the Soucy group has developed a solid track for the BRADLEY infantry fighting vehicle, and in this regard also has the courage to enter the field, which until now has been the exclusive privilege of track-type tracks. The results of these developments, of course, are of great interest.