In 1942, the DUKW amphibious transporter entered the supply of the US Army. This machine performed well during World War II and was used by several countries. By the beginning of the fifties, this sample was outdated and required replacement. The result of the subsequent design work was several prototypes. Experienced amphibian XM-158 Drake is of the greatest historical and technical interest.
Needs and suggestions
The existing amphibian DUKW with a curb weight of 6, 2 tons could take on board 2250 kg of cargo. The car kept well on the water and developed a speed of about 8-10 km / h. However, by the end of the forties, the US Army was no longer satisfied with such characteristics. Initially, this problem was solved by reworking the hull and a more powerful engine. The resulting amphibian XM-147 Super Duck could take 4 tons of cargo, and on water it accelerated to 10-12 km / h. However, this was considered insufficient, which is why the XM-147 did not go to the troops.
In the mid-fifties, General Motors Canada (GMC), which had previously created DUKW and its modernized version, proposed a new project for an amphibious transporter. It proposed to radically revise the existing design and introduce a whole set of new technical solutions. All this made it possible to raise the carrying capacity up to 8 tons and increase mobility.
The new sample received the working designation GMC XM-158 (in some sources, there is an erroneous spelling of XM-157). The name Drake ("Drake") was also used - it was an allusion to the nickname of the serial DUKW, which was called "Duck" by consonance.
To increase the carrying capacity, the promising "Drake" needed a whole set of innovations. GMC developed a boat hull practically from scratch, created a new version of the power plant and transmission, as well as a chassis and a propeller group that meet the new requirements. As a result, Drake had only minimal external resemblance to its predecessors, but at the same time had to show advantages over them.
Design features
The XM-158 amphibian was built on the basis of a new boat hull with characteristic contours. The body was made of steel and aluminum parts, joined by welding and riveting; all seams were sealed with a special paste. The hull received a curved lower frontal part, above which an almost horizontal "deck" was placed. There were vertical sides with reinforcement and a vertical stern sheet. In the sides there were niches for wheels. The central part of the bottom formed a tunnel for the units.
The layout of the XM-158 resembled previous amphibians. The power plant was placed in front of the hull. Various transmission units were located next to the engine, under the cab floor and under the cargo area. Behind the engine compartment, the crew and control post were located. Almost all the rest of the body was given under the "side body". Behind it there was a small platform for various devices.
Calculations showed that "Drake" needs an increased power plant. This issue was solved with the help of two diesel engines GMC-302-55 with a capacity of 145 hp each. with their own transmissions. The power flows were not combined, which simplified the design. Each engine was mated to Alisson's own 12-speed automatic transmission. Behind it was a transfer case with two gears, as well as a two-speed power take-off.
The left engine drove the wheels of the first and third axles, the right one - the second and fourth. Also, the engines were responsible for the operation of two propellers. On a good road, it was proposed to use only the right engine and have an 8x4 wheel arrangement. On soft ground, the left engine should also be started, getting the 8x8 formula. Both engines, driving two propellers, had to work on the water.
The special power plant was distinguished by high fuel consumption - about 90 liters per 100 km. The hull housed four tanks with a total capacity of 636 liters, combined into a common fuel system.
The chassis included four axles with independent air suspension of wheels. A reinforced rubber cylinder with compressed air was used as an elastic element. By changing the pressure in the cylinder, it was possible to adjust the ground clearance and suspension stiffness. In addition, this suspension allowed the wheels to be pulled up when driving on the water, slightly reducing drag. The chassis included eight single wheels of size 14.75-20.
A block with two propellers was placed under the stern of the hull. On land, he rose, protecting the screws from damage. On the water, the block was lowered to the operating position. There was no separate steering wheel. Control on the water was carried out with the help of the front swivel wheels and due to the differential change in the revolutions of the two propellers. A wave-reflecting shield was provided on the nose of the hull.
The cockpit for the XM-158 was similar to that of previous vehicles. In front, the driver and commander were covered by a sloping windshield with a narrow roof and side glazing. The driver was on the left and had all the necessary controls. The helm was a steering wheel, pedals to control the two engines, as well as a whole set of levers from all transmissions and propeller controls.
The main part of the "deck" was occupied by a flat cargo area. In its flooring, hatches were provided for access to the internal units of the machine. A platform with a length of about 7 m and a width of less than 2 m could take up to 8 tons of cargo (on land). Carrying capacity when driving on water was reduced in accordance with weather conditions.
In front of the cockpit and behind the "deck" there were numerous mounts for various equipment. The amphibian carried an entrenching tool, spare parts and accessories and various property. At the stern, according to the DUKW model, the winch was retained. With the help of additional arcs, the car could be equipped with a removable awning to protect the crew and cargo.
Initially, the XM-158 Drake transporter did not have its own armament. Later, after being adopted by the army, he could get a machine gun for self-defense. The crew and the landing force also had to have personal weapons.
The total length of the amphibian was 12.8 m - almost 3.5 m more than that of the DUKW. Width - 3.05 m, height along the rudimentary roof - 3.3 m. The curb weight was determined at 14 tons. With a maximum load of 8 tons, the total mass reached 22 tons. On the highway, the amphibian accelerated to 70 km / h, on water - up to 14 km / h. The in store overland is 700 km.
Drake failure
In 1956, GMC built a prototype of a new amphibious transporter. Some sources mention that the Drake car remained in one copy. According to other materials, several such prototypes were built. One way or another, the number of Drakes was minimal, but sufficient for testing.
During the tests, the prototype (samples) confirmed the main running characteristics. The car moved briskly over land, both along the highway and over rough terrain, overcoming various obstacles. Comparisons with the serial amphibian DUKW clearly showed the advantages of the new model. "Drake" successfully overcame obstacles on which the lighter, but less powerful "Duck" simply got stuck.
The payload characteristics were fully confirmed, and in this respect the XM-158 was ahead of all existing American-made amphibians. She carried as much cargo as two Super Duck or four production DUKWs.
However, not all the features of the new XM-158 suited the army. First of all, they criticized the overly complex power plant and transmission, as well as extremely inconvenient control systems. So, the lack of a mechanical connection between the engines did not allow the speed synchronization. This was not a problem on land, but made it difficult to move on water. The difference in turnovers made it difficult to maintain the course; the driver had to constantly steer and monitor the operation of the engines. The control of the power plant and transmission in all modes was hampered by the ergonomics of the cab: next to the driver there was a whole battery of levers for various purposes.
Thus, the resulting amphibian had rather high characteristics and was superior to similar designs. However, the cost of this was an overly complex and expensive design of key units, as well as various operational difficulties. Probably, the GMC designers could have rid their development of the identified problems, but it was too difficult. In fact, a radical overhaul of the power plant and transmission was required, which could affect other systems.
Such a revision of the project was considered inappropriate. The amphibious XM-158 Drake did not enter service with the United States. The unfinished car with a lot of problems was not offered to foreign customers. Thus, the prototype (or prototypes) was left alone.
After the tests
According to various sources, in the future, the experienced "Drake" was used as a platform for testing new solutions. It was later sold to a commercial company. For several years, a unique car took tourists somewhere on the West Coast of the United States. Apparently, in this role, she worked out the remnants of the resource, after which she went for recycling. Unlike the XM-147 Super Duck, no XM-158 specimen has survived.
In the fifties, GMC made two attempts to create an amphibious transporter to replace the outdated DUKW, none of which were successful. The XM-158 Drake project stopped due to the excessive complexity of the design and the inappropriateness of its improvement. However, the US Army was not left without amphibians. In parallel with GMC, other companies were developing new samples, and their projects turned out to be more successful.
