XM104 Self-Propelled Artillery (USA)
By the mid-fifties, the US armed forces managed to master the helicopters and understand their high potential. Helicopter landings showed their best side, however, the existing aircraft technology allowed to transfer only personnel and light weapons. Tanks and self-propelled guns needed by the landing, did not fit into the limitations of military transport aircraft. In this regard, a program was launched to create promising aircraft transportable artillery installations.
One of the mockup XM104. Photo Ftr.wot-news.com
The study of the new issue was launched in 1955 year and was carried out by specialists of the US Army Ordnance Tank Automotive Command (OTAC). They had to determine the optimal technical appearance of the self-propelled artillery installation with minimal dimensions and weight, corresponding to the limitations of aviation, but capable of carrying an 105 caliber mm. It was planned to create a self-propelled howitzer self-propelled, capable of firing from closed positions, and this had a serious impact on the outcome of the program.
A promising project of air transportable and landed ACS received the working designation XM104. The number for the project was chosen "in order." The fact is that on this self-propelled one it was planned to use the XM103 gun - a modified version of the existing experienced towed XM102. Thus, the names of various modifications of the howitzer and self-propelled gun under it indicated a definite connection between several projects in the field of artillery.
The first theoretical and practical work on the XM104 project took several years. By the beginning of the sixties began technical design. In this case, the project was implemented in two stages. As part of the first plan to develop, build and test a simplified prototype model self-propelled guns. According to the results of his checks, it was necessary to modify the initial project and build improved machines. After the second stage, the XM104 had every chance to go into service.
One of the prototypes in full configuration. Photo "Sheridan. A history of the American Light Tank Volume 2"
In 1960-61, Ordnance Tank Automotive Command and the Detroit Arsenal built two prototypes with the common name Test Rig and different numbers. They were lightweight tracked chassis with a complete set of units of the power plant and chassis. Shells are simplified and built from structural steel. Instead of a full-fledged gun mount, a mass-dimensional mock-up was used imitating the XM103 product. In addition, some other aggregates were missing on the mockup samples. For example, they did not receive a full set of crew seats, a full-fledged ammunition, etc.
By the time the prototypes were built, OTAC decided on the main features of the future ACS. The XM104 machine was supposed to have a length of no more than 4-4,5 m and a combat weight of the order of 6400 pounds (2900 kg). She was supposed to reach speeds of about 35 miles per hour (about 56 km / h) and overcome various obstacles; water barriers should cross the water. Due to its small size and weight, the XM104 could be transported on modern and advanced military transport aircraft and helicopters of various types. Provided landing and parachute landing.
Model samples No.1 and No.2 passed the tests and showed the real possibilities of the new chassis. Taking into account the experience of their tests, OTAC engineers finalized the initial project, and soon a full-fledged prototype with the required configuration was built on it. This machine is very seriously different from the model products, both in terms of appearance, and its equipment.
In the project XM104, the reduction of mass and dimensions was put in the forefront. To achieve the desired weight reduction, the structure had to abandon any protection. The crew was asked to be in the open area of the hull, without any protection. However, the lack of booking was not considered a critical shortcoming. The self-propelled gun had to work in closed positions at a safe distance from the front edge, which reduced the risks of shelling and reduced the need for armor.
For SAU developed the original body of structural steel, characterized by a dense layout. The case was structurally divided into two volumes. The lower "bath" was intended for the installation of the power unit. She had a curved frontal sheet and vertical sides. In the center of this part of the body was the engine, in the front part - the transmission. On top of the bath was a box that formed a kind of habitable compartment. It differed a little more length and increased width. At the expense of the latter, fenders were formed, which provided additional volume for mounting various devices.
The basis of the power plant was the petrol engine Ford M151, borrowed from the car MUTT. Engine power 66 HP through a dry clutch, connected to a Model 540 gearbox, providing four forward speeds and one reverse. The front drive wheels received torque from the transmission type Model GS-100-3.
On each side of the hull on the torsion bar was installed on four track rollers. The rear pair of rollers served as guide wheels lying on the ground. The drive wheel of small diameter was located in the nose of the side and was raised above the ground. The entire upper part of the undercarriage and the caterpillar was covered with small metal shields and continuous long rubber screens. Each caterpillar included an 72 track 14 inch wide (355 mm).
According to calculations, the SAU suspension could not withstand the return of the 105-mm howitzer. In this regard, the machine is equipped with a lowered opener. Actually, the coulter was mounted on swinging longitudinal beams. Above on the beams and the opener, a site was provided that simplified access to the howitzer breech.
The machine is in a combat position. Photo Ftr.wot-news.com
For the XM104 ACS, an XM105 103-mm howitzer was offered. In the aft chassis there was a reinforced section with a seat for the upper machine tool. The gun mount was designed using existing ideas and solutions. Directly on the body there was a rotating device, on which was placed the swinging part with the barrel. The installation design provided horizontal guidance in a sector of width 45 °. Vertical guidance is from -5 ° to + 75 °.
The XM103 howitzer was created by the Rock Island arsenal based on the existing XM102 towed gun. A rifled 105-mm gun with a vertical wedge gate was offered. Different howitzer prototypes were tested with and without a muzzle brake. In the design of hydropneumatic recoil devices, some new solutions and components were used, which later became widespread. XM103 could use all standard 105 caliber mm projectiles and showed firing characteristics at the level of other weapons of its class. At the same time, it was noticeably lighter than its counterparts.
In the stern of the ACS XM104 managed to place a compact packing on 10 unitary shots. It is curious that the maximum rate of fire of the gun during the work of a trained calculation should have reached 10 rounds per minute. Thus, the entire portable ammunition could be spent in a minimum time, after which the self-propelled gun needed the help of the carrier carrier.
Any additional weapons were not provided. One of the reasons for this was the lack of a closed body suitable for mounting a machine-gun installation. The place to install the open turret also could not be found. As a result, the crew had to use personal weapon.
The crew of the self-propelled gun consisted of four people. When moving, they should have been located on their own seats at the sides of the hull. In front of the left was the driver; in front of his place were the instrument panel, the steering wheel, and the control levers. To the right of the gun was the second seat. Two more places for the crew were located directly behind the front; they were offered to ride backwards. On the sides of the seats were provided low shields, preventing falling overboard.
Side panels and four seats in pairs (two on each side) were mounted on folding panels. In the stowed position, these panels lay on the roof of the hull and allowed the crew to take their seats. When translating the self-propelled guns into the combat position, the panels folded back to the 180 °. Due to this, the seats were removed outside the sector of the gun guidance, and additional platforms were formed on the sides of the hull.
SAU XM104 turned out to be very compact and easy. The length of the machine, taking into account the implement and the opener, did not exceed 4,1 m. The width was 1,75 m, the height in the stowed position was 1,75 m. The combat weight was determined at the level of 8600 pounds (3,9 t). In the configuration for transportation by air - without fuel, ammunition and crew, but with some other devices - the weight was reduced to 7200 pounds (3270 kg). Driving characteristics consistent with the calculated. The car could move overland at speeds up to 35 miles per hour and swim water obstacles.
According to known data, the first full-scale prototype of the XM104 self-propelled gun with a full set of units was built and was put to the test in the 1962 year. Then five more cars were built with some differences. Due to this, from the beginning of 1963, six experimental machines were simultaneously tested at the Aberdeen Proving Ground. Thus, OTAC had the opportunity to evaluate different variants of equipment and choose the most successful one. First of all, the differences affected the gun installation and howitzer design.
The trials of the six experienced XM104 continued until the 1965 year and ended with mixed results. First of all, the desired opportunities were obtained in the context of strategic mobility. The presented vehicles met the limitations of military transport aviation; they could be transported without difficulty by existing and prospective aircraft and helicopters. In the future, it was necessary to develop a parachute system for landing such a technique. Thus, the main task of the project was successfully solved.
However, the possibility of transportation by air and landing had an unacceptably high price. The car had a number of drawbacks directly related to the reduction of its dimensions and mass. It was impossible to put up with some problems, since they directly influenced the fighting qualities and vitality on the battlefield. As a result, they did not allow the effective use of the proposed equipment in a real conflict.
First of all, the reason for criticism was the absence of any protection of the crew and its own machine units. Lightweight housing had to be built from relatively thin structural steel, which is why he could not withstand the shelling. The crew was located on the open top platform and was actually covered only with side flaps of a limited area. Moreover, their replacement by armor parts would hardly have significantly increased the level of protection. The open installation of the gun without shield cover also did not increase the survivability of the ACS. To all this, the car in the proposed configuration could not be equipped with even an awning covering people from the sun and rain. The cover was relied only on a howitzer.
A compact chassis with a relatively heavy 105-mm howitzer had an unsuccessful balance. The machine had a high center of gravity, due to the gun installation. This could hardly worsen the longitudinal stability, but worsened the transverse. A roll of more than 20-25 ° could result in the vehicle tipping over. The absence of a closed cabin at the same time could lead, at a minimum, to injuries among the crew.
Thus, the promising self-propelled artillery XM104 conformed to a number of requirements and could show the required fighting qualities. However, a number of characteristic features of this machine led to unjustified risks for the crew. In the proposed form self-propelled gun was not of interest to the army. The Army Command did not wish to continue the work, and the US Army Ordnance Tank Automotive Command closed the project due to lack of prospects.
Almost all of the prototype ACS built, including a couple of the first Test Rig machines, were disassembled as superfluous. Only one vehicle with the tail number 12T431 was saved. Now it is in the Fort Sill Armored Museum (Oklahoma) and is shown alongside other unique samples of its era.
The XM104 SAU project was based on the requirement to reduce the weight and size of the combat vehicle in accordance with the limitations of military transport aviation. This task was successfully solved, but the finished sample was not entirely successful. For some opportunities and qualities had to sacrifice others. The resulting sample had an unfavorable ratio of positive and negative qualities, which is why it did not leave the test stage.
Based on:
http://ftr.wot-news.com/
https://army.mil/
http://dtic.mil/
http://sill-www.army.mil/
Hunnicutt, RP Sheridan. A history of the American Light Tank Volume 2. Navato, CA: Presidio Press, 1995.
Chateau LA Lightweight 105-mm Howitzer // Artillery Trends, August 1961.
Howitzer, light, self-propelled, 105-mm, XM104. Aberdeen Proving Ground, Maryland. May 1963.
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