Frequently used abbreviations and abbreviations in the article:
BTR - armored personnel carrier;
TBTR - heavy armored personnel carrier;
DBTR - two-link armored personnel carrier;
PU - launcher;
DU - remotely controlled installation;
MTO - engine-transmission department;
EMT - electromechanical transmission.
Photo 1. Russian heavy armored personnel carrier BTR-T
Photo 2. Russian two-link transporter DT-30PM
Inspired by the publications posted on the Courage website, I also decided to try my hand at proposing a concept for a promising armored vehicle. Since I am very interested in the two-link layout of armored vehicles (in particular, proposed by R. Ulanov), I tried to portray it as an alternative two-link heavy armored personnel carrier based on the chassis of the Russian T-55 (-54) tank. Please do not judge very harshly.
1. INTRODUCTION
The combat vehicle proposed by the author with the code name DBTR-T (Two-Link Armored Personnel Carrier - Heavy) can be considered as one of the promising alternative options for modernizing / converting old T-55 (-54) tanks into heavy tracked armored personnel carriers. (At one time, T-55 and T-54 tanks were produced in a fairly large number - about 95,000 units, so this chassis is the most affordable). An example of such a realized modernization is the Russian heavy armored personnel carrier BTR-T, which still exists in a single copy (photo 1).
BTR-T has clear advantages in armor protection over light armored personnel carriers. Its main disadvantages are the small number of troops and the inability to dismount the troops through the aft doors, which limits the use of the BTR-T.
It is theoretically possible to eliminate these shortcomings on the BTR-T due to the front placement of the MTO, but this will only solve the issue of the possibility of a safer dismounting of the landing force, the number of which will still be insufficient. And the conversion of a classic tank chassis into a platform with a front MTO position is more like creating a heavy armored personnel carrier practically from scratch.
On the one hand, the draft model of the DBTR-T proposed by the author is devoid of the main disadvantages of the BTR-T, on the other hand, it is incorrect to fully compare these machines because of their main difference - the number of links: the DBTR-T has two of them, the BTR-T has one.
The "relative" of the DBTR-T in terms of the number of links is the two-link all-terrain vehicle DT-30 "Vityaz" (photo 2), well-known for its super-cross-country ability, although its purpose is completely different.
Therefore, I will try to compare the characteristics of the DBTR-T with similar characteristics of the BTR-T, and also, in principle, justify the creation of such a machine, while its cost will be equal to the cost of three BTR-T, and maybe more …
Note
The two-link armored personnel carrier DBTR-T (pictures and text) proposed by the author is a sketch of the author's work, which does not claim any exact technical and tactical correspondence. The author is not a specialist in this field.
2. PURPOSE
DBTR-T is a highly protected off-road armored personnel carrier with armor protection that is not inferior to that of the BTR-T, but with almost twice the number of crew - 13 people. The landing party has the ability to leave flight number 2 of the vehicle through the rear doors and upper hatches.
Due to the two-link design, the DBT-T should significantly surpass all existing heavy tracked armored personnel carriers in terms of cross-country ability and functionality. The DBTR-T base is universal and can be used to create a whole family of two-link vehicles with increased security and cross-country ability.
Figure 1. Heavy two-link armored personnel carrier DBTR-T, appearance
3. COMPARISON OF BTR-T and DBTR-T
Comparative technical characteristics of the existing heavy armored personnel carrier BTR-T and the proposed by the author DBTR-T:
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4. COMPARISON OF DBTR-T WITH FOREIGN HEAVY APC Similar heavy armored personnel carriers have been actively used by the Israeli army since the late 1980s. The number of the first TBTR "Akhzarit", created on the basis of captured T-55 tanks, according to various sources, ranges from 500 to 1000 pieces. In addition to the Akhzarit, Israel has two more TBTR models in service: the 51-ton Puma based on the Centurion tank and the 60-ton Namer based on the Mk4 Merkava (photo 3). The creation by Israel of a new, more expensive and protected TBTR "Namer" based on their most modern tank, once again confirms both the value and effectiveness of these armored personnel carriers in the army, and the value of the lives of the crews of these vehicles for their leadership.
Figure 2. Modifications of the DBTR-T All of the above machines differ from each other only in link # 2. Link # 1 remains practically unchanged in all modifications, which increases the unification of these alternative machines. In the versions of DBTR-TR, BREM and KShM course 7, 62-mm machine guns are removed from the fenders of chassis No. 1, instead of them one or two 12, 7-mm NSVT machine guns are installed (standard commander's ZPU tanks T-64 and T-80) … The replacement of machine guns is due to the impossibility of course machine guns to provide all-round protection of the machine, which can be provided by tank ZPUs with fully circular rotation. Next, we will briefly consider two options for possible power plants. The proposed transmission is electromechanical (EMT), however, realizing its complexity and high cost, the DBTR-T layout is drawn in such a way that both purely mechanical and electromechanical transmissions can be used. 6. WEAPON Link No. 1 in the variant DBTR-T / T1 and T2. The armament of link number 1 in the combat models of the DBTR consists of two course 7, 62-mm PKT machine guns, they are remotely controlled by two operators. An important issue will be the angles of horizontal guidance of machine guns, so that they provide a good firing zone, protecting to the maximum not only the frontal projection, but also the side one. Ammunition approximately consists of two tapes of 1000 rounds each. The location of the machine guns on above the tracked shelves is due to the location of the armament of link number 2, which has a circular rotation. Theoretically, it would be correct to create universal remote-controlled installations that can be armed with both 7.62-mm PKT and 30-mm AGS-17D, as done on the Terminator-1 BMPT, only with large guidance angles. The advantages of such weapons: large ammunition load in the 1st tape (1000 rounds); Disadvantages: limited aiming angles. 
Photo 4. Anti-aircraft machine gun caliber 12, 7-mm Link # 1 in other versions. Link number 1 in the "auxiliary" modifications of the DBTR-T is armed with a standard tank anti-aircraft machine gun (ZPU) of 12, 7-mm caliber (photo 4). It is supposed to use standard machine-gun installations from T-64A and T-80 tanks, since they allow the operator to fire from a machine gun without sticking out of the car. The machine gun mount has an electromechanical drive and provides horizontal circular guidance in the sector of 360 degrees and horizontal guidance in the range from -15 to +85 degrees. The installation has day and night sights, there is no two-plane stabilizer. The firing range of the machine gun is 1500 m, the ammunition load is 3 boxes of 150 rounds for each machine gun. The author chose the ZPU machine gun for reasons of crew security, since to fire from the anti-aircraft machine gun of the T-72 tank, the shooter must protrude from the hatch. On link number 1, one or two ZPUs can be installed above the gunners' hatches. The advantages of such weapons: excellent aiming angles; disadvantages: limited ammunition of 150 rounds. Link No. 2 is the basic model of DBTR-T. This modification of the link can be used both as an armored personnel carrier and as a combat vehicle for flamethrowers. Given the absence of loopholes in the side armor of the second link of the vehicle, two commander's turrets of T-64/80 tanks are mounted on its roof, which rotate in a circular manner. The turrets are equipped with standard NSVT-12, 7 machine guns. The estimated ammunition load is 4 boxes per machine gun (1 on the machine gun, 3 in the troop compartment). DBTR-T in the basic configuration provides simultaneous destruction of 4 different targets. According to this indicator, it surpasses the BMP-3, BMD-3/4 and BMPT Terminator-1. In the rear doors of the troop compartment, there are loopholes covered with a lid for firing from personal weapons in the direction of the stern. 
Photo 5. One of the BMPT prototypes with two cannon mounts Link # 2 combat model DBTR-T1. The flight has more powerful armament, consisting of two independent 30-mm cannon installations with paired 7, 62-mm PKT machine guns. On the right (in the direction of travel) gun mount mounted launcher for two ATGM. The cannon mounts are completely borrowed from the BMPT prototype of the 2nd modification (photo 5). Why was this weapon chosen? The compact dimensions of the links required to increase the maneuverability of the vehicle (the total length of each link is 5000 mm) does not allow, simultaneously with the landing, to place in link No. 2 the fighting compartment of a two-man turret with more powerful weapons, for example, with a 57-mm S-60 cannon or "twin" from 100 mm 2A70 and 30 mm 2A72. In addition, a two-man turret should have powerful armor protection at the level of hull protection, which will inevitably weigh down the turret itself and the vehicle as a whole. Unlike the two-man manned turret, the armament complex of the experienced BMPT with the code name No. 2 can provide several advantages at once: + additional protection for the roof of the troop compartment at the location of the weapons; + two different targets hit at the same time, for example, if the DBTR-T comes under simultaneous fire from two opposite sides; + the ability to hit one target (or a cluster of targets) from 2 cannons and 2 machine guns at the same time; + in case of failure of one weapon, there is a second; + the armament taken out to the outside reduces the gas contamination of the troop compartment. Disadvantages of this option: - cannons overlap each other at certain angles of rotation, - the lack of a modern LMS and limited capabilities in the fight against highly protected targets (tanks, bunkers, bunkers, etc.). 
Figure 3. Modification of the DBTR-T1 with two combat modules from the BMPT prototype Due to its powerful armor, the DBTR-T1, if necessary, can be used as a full-fledged BMPT, or accompany tanks while simultaneously performing the tasks of an armored personnel carrier and an BMPT. According to its armament, the DBTR-T1 can fully replace two BMP-2 infantry vehicles or two BMD-2 infantry vehicles. Link # 2 combat model DBTR-T2. A promising weapon system. In this case, the author provides for the installation of a fully automatic turret, which will not "eat up" the useful volume of the troop compartment. The tower is controlled by the commander and the operator, who sit “permanently” under the tower and receive information on the monitors. The armament of such a module consists of a 37-mm 2A11 anti-aircraft gun from the Yenisei ZSU with an air-cooled barrel and, accordingly, a lower rate of fire (200-300 rounds / min). The cannon is fed by two bands. The 7, 62-mm PKT machine gun and the 40-mm AGS grenade launcher are paired with the cannon. Why 37mm caliber? It is believed that for promising artillery systems 30-mm is no longer enough, for 57-mm you need a voluminous turret compartment. The author considers the 37-mm "golden mean", or rather the "temporary" middle, while there is no automatic cannon of 40-45-mm caliber. Even in its present form, a 37 mm HE shell has almost twice the mass of a 30 mm HE shell. In addition, according to various information - 35 … 37-mm minimum caliber, which is already advisable to equip with a remote fuse. The gain of a 37-mm BPS in front of a 30-mm projectile in the thickness of penetrated armor is noticeable only at a distance of up to 1000 m. A complex of guided weapons BMPT "Terminator-2" of four missiles "Attack-T" is used as a guided weapon. 
Figure 4. Modification of the DBTR-T2 with a promising combat module The advantages of such weapons are: a modern weapon system and control system, fully automatic ammunition, the ability to hit more complex targets such as enemy tanks and combat helicopters; Disadvantages: bulky turret, which cannot be given a level of armor protection similar to the body of the armored personnel carrier itself. The tower would theoretically be highly vulnerable even to small-caliber automatic cannons. 7. TRANSMISSION DBTR-T The considered type of transmission for DBTR-T is an electromechanical transmission. On the one hand, the use of such a transmission contradicts the basic concept of the DBTR-T - a budget and simple machine made on the basis of old T-55 tanks. On the other hand, its presence significantly expands the capabilities of the DBTR-T, as a result of which it should significantly surpass all existing heavy armored personnel carriers in cross-country ability, functionality and other performance indicators. 
Figure 5. DBTR-T transmission diagram 
Figure 6. Scheme of disassembly of the DBTR-T transmission The transmission shown in the sketch is the same for links # 1 and # 2. On link number 1, it is installed "classically" in the rear of the MTO, instead of the old mechanical transmission of the T-55 tank. Link number 2 - a similar unit is installed in the front part, since there are two doors in the stern for dismounting the landing. What advantages can an expensive EMT give to a two-link armored personnel carrier: + The ability to quickly uncouple the links for loading / unloading DBTR on road or rail transport. The length of each disengaged link is no more than 6,000 mm. The decoupling is done by the crew. Both links independently enter platforms / tractors / wagons, etc. using a special power cable 10-15 m long, through which electricity is supplied from the leading link (No. 1) to the slave link (No. 2). To control the driven link, the driver-mechanic goes to link # 2, to the commander's place, where there are direct controls for the transmission of link # 2. At the moment of the maneuvers of the link No. 2, the link No. 1 works motionlessly in the mode of an electric power generator. 
Figure 7. Loading links of DBTR-T on the railway platform + Evacuation of damaged links separately from difficult sections of the road (mountain roads, narrow streets, forest, etc.) due to the possibility of separating the links and the possibility of towing these links using an external generator or other DBTR-T. + Application of various types of engines without changing the transmission. The author proposed two versions of the DBTR-T with diesel engines of the "B" series of the T-90 tank and with gas turbines (GTE) of the T-80 tank. In the future, in the course of the development and availability of alternative fuels and energy sources, it is possible to integrate a power unit based on fuel cells that generate electricity due to the chemical reaction of the fuel. 
Figure 8. Three degrees of freedom of a two-link machine + "Flexibility" DBTR-T. As you know, two-link articulated machines have three degrees of freedom of movement relative to each other, respectively, and three ranges of restrictions on this movement. For example, a two-link conveyor DT-30P "Vityaz" (with a mechanical transmission - cardan shaft) has the following range of degrees of freedom of movement: - angles of rotation of the links relative to the longitudinal axis: +/– 38 degrees; - lifting angles of the links relative to each other: 35 degrees; - angle of "twisting" of the links relative to each other: 8 degrees. The absence of a rigid mechanical transmission of torque (cardan shaft) of the DBTR-T engine from link No. 1 to the transmission of link No. 2 may allow increasing the range of these limitations. Taking into account the functional purpose of the DBTR-T, the most important thing will be to increase the ranges of the angles of rotation of the links relative to the longitudinal axis (No. 1 in the diagram), in this case, the flexible power cable EMT will not be any limitation of this degree of freedom of movement. The sketch layout of the DBTR-T is drawn taking into account the maximum range of the link rotation angles: ± 45… 50 degrees. + Movement in reverse. The long length of the DBTR-T (11,000 mm) significantly limits its mobility in a combat situation in comparison with other combat vehicles (TBTR, BMPT, BMP), the hull length of which does not exceed 6,500-7,500 mm. Thus, the DBTR-T is almost completely deprived of the possibility of turning on mountain roads or on the streets of cities and towns. This design flaw can be partially compensated for by increasing the maximum reverse speed to the maximum forward speed of 50 km / h (for comparison, the reverse speed of the BTR-T based on the T-55 is only 5 km / h). Increasing the reverse speed for EMT DBTR-T does not present any particular difficulties. In the machine control department, a rear-view video monitor and a reverse video camera are provided, installed on the aft armor plate of link No. 2. + Traction characteristics. The main unique advantage of the DBTR-T is its increased cross-country ability with “heavy armor”. Considering that all the most difficult obstacles (trenches, anti-tank ditches, walls, steep climbs, forest belt, off-road, soils with low bearing capacity, etc.) DBTR-T will overcome at low speed, it needs the highest torque at these low speeds. It is known that EMT provides high torque at low speeds, which is its main advantage. From the history. Even during the Great Patriotic War, EMT was used on the heaviest tanks and self-propelled guns: it was serially installed on the German heavy self-propelled gun Ferdinand, weighing 68 tons, the prototype of the super-heavy Maus tank, weighing 180 tons, on the Soviet experimental heavy tank EKV (KV version -1) and the post-war heavy tank IS-6 + Towing equipment. Taking into account the expected high cross-country characteristics of the DBTR-T, it will be entrusted with the task of towing damaged equipment or simply stuck combat vehicles in difficult terrain. In any case, towing will be done at low speed, which will also require high torque. + Possibility of connecting the 3rd link. For some modifications of the DBTR-T, it is theoretically possible to connect the 3rd lightweight link (similar to the DT-30P transporter). If the DBTR-T will be used as a repair and recovery vehicle or a highly passable vehicle for transporting infantry and weapons / ammunition, it is possible to add link # 3 (with a similar transmission), which will be located between link # 1 and # 2. 8. POWER PLANT DBTR-T The promising DBTR-T author proposes to create on the basis of the chassis of T-55 tanks with diesel engines of the "B" series, as a result, a power plant based on the engine of the "B" series is also assumed as a base power unit, only models: V-92S2F2, with a capacity 1130 hp, T-90SM tank. 
Figure 9. Engine "standard" modification DBTR-T The use of the most "top-end" version of the engine of this series increases the cost of the potential production of the DBTR-T, but it is this power that is necessary to ensure the high mobility of the rather heavy DBTR-T, the armor of which is equivalent to the tank one. As an alternative power unit without a fundamental change in the transmission (in the case of using EMT), a gas turbine GTE, tank T-80 can be used. It is quite obvious that the use of a more expensive gas turbine can be justified only for special machines, for example, intended for permanent service in colder regions, where the "winter" advantages of a gas turbine engine are needed. You can consider two modifications of the DBTR-T by type of power plant: - "Standard" modification of the DBTR-T with the V-92 tank engine, with a capacity of 1130 hp; - "Northern" modification with a gas turbine tank engine with a capacity of 1250-1400 hp. Some engine parameters for comparison:
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