Multifunctional army all-terrain vehicle M561

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Multifunctional army all-terrain vehicle M561

The success of modern combat is achieved not only by superiority over the enemy in forces and means, but also by the ability to maneuver troops and use the terrain during combat. The maneuverable nature of modern combat is a consequence of technical progress and equipping the army with special equipment, which makes it possible to quickly transfer the actions of the main forces from one direction to another.
M. G. Lazebnikov, 1958

The idea that it is possible to create an effective vehicle design for operation in complete off-road conditions based on road-type vehicles is wrong. An all-terrain vehicle must be built from scratch, abandoning many generally accepted designs. And American designers understood this well.



In 1960, in the United States, as part of the Detroit Arsenal project, a decision was made to develop a new model of a military cargo-passenger vehicle with high cross-country ability, which was supposed to expand the range of vehicles in the American army. Engineers from the American company Ling-Temco-Vought were involved in the design of the vehicle. It is interesting to note that the company never manufactured cars; it was engaged in the development of aerospace technology. Despite this circumstance, its talented engineers designed and built a magnificent three-axle all-terrain vehicle Gama-Goat with all-wheel drive, designed to transport people and cargo in severe off-road conditions.

Based on this, a prototype was designed to meet the requirements of the military customer (the US Army), and received the index XM561. With a length of 5620 mm, a width of 2135 mm and a height of 2700 mm (1585 mm with the awning removed), the vehicle weighed 2650 kg and could "take on board" 10 soldiers with full gear or a load of up to 1350 kg in total. In order to minimize its own weight, the all-terrain vehicle was made with the maximum use of aluminum alloys and with a load-bearing body. At the same time, the engineers managed to build such strength into the load-bearing system that the XM561 could retain functionality even after parachute landing with a payload of 1140 kg.

Ground clearance of 380 mm and the use of large low-pressure tires with a profile width of 300 mm and an external diameter (height) of about 1010 mm provided the vehicle with excellent cross-country ability. Moreover, the designers were able to achieve such a ratio of the vehicle weight to the area of ​​the supporting surface of the wheels, at which the specific pressure on the ground was (according to my calculations) only 0,6 kg / sq. cm. This is even less than the values ​​​​of the specific pressure of many tracked vehicles and ten (!!!) times less than that of some wheeled vehicles. For comparison: the specific pressure on the ground of the tires of the GAZ-63 trucks (front / rear) was 5,14 / 6,28; ZIL-151 - 6,24 / 5,22 kg / sq. cm. But the main highlight of the design was that the all-terrain vehicle consisted of two sections.


The first was a 4x4 tractor with an engine mounted behind the cabin. The second was a trailer with a power drive connected to the axle (the so-called "active trailer"). When driving on a good road with a small load, it was possible to disconnect the front and rear axles from the power drive, while the car moved due to the traction force of the wheels of the middle axle.

The trailer was connected to the tractor via a hinge of an original design, allowing a relative rotation angle of up to 30 degrees in each direction around the longitudinal axis (torsion) and up to 40 degrees around the transverse axis (bending). In addition, the middle axle of the vehicle (the rear axle of the tractor) could rotate relative to the longitudinal axis of the chassis at an angle of 15 degrees in each direction from the middle position. This technical solution brought several advantages at once:

a) all 6 wheels of the all-terrain vehicle, even in the most difficult conditions, constantly followed the terrain changes, rolled over uneven surfaces, maintained contact with the ground regardless of the terrain profile and, as a result, could develop the maximum possible traction under the conditions of adhesion to the supporting surface;

b) a good smooth ride was ensured, which increased the maximum possible speed off-road and reduced driver and crew fatigue;

c) the torsional stress acting on the body when passing over ridge obstacles was significantly reduced;

d) the threshold cross-country ability was increased; the all-terrain vehicle could overcome a threshold obstacle (barrier) up to 0,66 m high.

But the tricky hinge did not allow changing the position of the tractor relative to the trailer in the horizontal plane, since this would have caused the breakage of the intermediate cardan shaft, which supplied torque from the tractor to the trailer wheels. On the one hand, this was even good, since it eliminated the "folding" of the trailer on a slippery road, when braking and reversing. But it worsened the maneuverability of the car, since turning the car in the way usual for articulated vehicles became impossible.

Engineers addressed this issue by arranging the steering to act on both the front and rear axles, resulting in a minimum turning radius of 8,9 m. The rear wheel steering angle was 50% of the front steering angle.

At the same time, this solution improved cross-country ability, since the presence of steerable wheels on the outer axles ensures stable movement of the car on steep climbs, whereas in conventional cars, due to the redistribution of weight to the unsteerable wheels of the rear axle, controllability may be lost. And to improve the lateral stability of the car when turning corners on the highway at high speed, the rear steerable wheels were locked in a straight-ahead position, and only the front ones turned.

If necessary, the rear section could be quickly detached, resulting in a small two-seater 4x4 vehicle with a length of 3135 mm and a wheelbase of 2010 mm, which had excellent cross-country performance parameters and could be used as a reconnaissance, patrol, communications vehicle or a tractor for various purposes.


The XM561 powertrain was equipped with a transfer case with a 1,8 demultiplier, and the designers abandoned the mandatory for all-terrain vehicles forced locks of the interwheel differentials, using limited-slip differentials (self-locking) in all axles, having rightly decided that with the chosen type of design, wheel suspension is unlikely, and if so, then there is no particular sense in full differential locking. The axles were made split, power was supplied to the wheels by half-axles with constant-speed joints.

The XM561 suspension was independent with double wishbones. The elastic element of the front and rear axle wheels were springs, the wheels of the middle axle were suspended on a single-leaf transverse spring.


Note the monumentality of the lower arms of the 1st and 3rd axles.

Independent suspensions, compared to dependent ones, have the following advantages in terms of their impact on the vehicle's cross-country ability:

the possibility of obtaining a softer suspension with greater wheel travel without raising the vehicle's center of gravity;

lower unsprung masses and, therefore, lower probability of high-frequency resonance;

better adaptability of wheels to uneven roads;

the ability to eliminate self-oscillations and involuntary rotation of the steered wheels;

the possibility of obtaining a smooth bottom without protruding parts.

The disadvantages of independent suspension include its greater complexity and the presence of numerous rubber-metal connections that require frequent replacement.

The shafts that transmit rotation to the wheels are located on the outside of cars with independent suspension, not on the inside, like the axle shafts in solid axles, which increases the risk of damage and reduces their service life. It should also be borne in mind that the independent suspension must have a higher ground clearance than the dependent one, since it is significantly reduced by body vibrations and increased payload.

Therefore, in most mass-produced military vehicles with increased cross-country ability, intended for long-term operation off-road, as well as in all trucks with normal cross-country ability, solid axles are used. But in specialized all-terrain vehicles, such as the XM561, the presence of independent suspension is quite justified.

The interior space of the trailer was also carefully thought out. The free width of the body between the wheel arches was 1320 mm, which allowed for the placement of two standard containers, and its length of 2350 mm was chosen based on the requirements for army ambulances.

To enable self-extraction, the vehicle was equipped with a stationary winch.

The technical characteristics of the car did not include the column "maximum fordable depth", and this is not without reason. The fact is that the XM561 did not ford, it ... swam!


The height of the above-water part was at least 23 cm, and the wheels of the car were the propeller, which is why the speed afloat was low - 3,2 km/h. But if necessary, it would be possible to significantly increase the speed of movement on the water by installing a pair of screw propellers in the back in the form of ordinary easily removable boat motors.

The designers were absolutely right in thinking that the XM561 is a land vehicle, not an amphibious vehicle, it was not tasked with landing from a ship or swimming across wide water areas, therefore, it does not need high speed on water. And if so, then there is no need to complicate the design of the vehicle with additional stationary propellers (and their drive), which will remain unused for most of the operating time and will only add weight (and therefore reduce the load-carrying capacity), complicate the design and increase the cost.

The XM561 was equipped with a three-cylinder, two-stroke diesel engine with a power of 103 hp and a torque of 297 Nm at 1500 rpm. It was also possible to install a multi-fuel Lycoming AVM 310 engine with a power of 103 hp.

On hard roads the car could travel at speeds of up to 93 km/h.

In 1963, this magnificent all-terrain vehicle, along with other experimental and production vehicles, underwent lengthy military testing. It was the only one of the eight vehicles to successfully complete the entire testing program.

As a result, the experimental XM561 was accepted into service by the US Army as meeting all the requirements for vehicles of this class.

Exploitation


But when the M561, which had shown itself so remarkably in testing, went into production and entered service with the troops, American soldiers encountered the same problems when operating the vehicles as the soldiers of the former German army back in 1941, who had had enough of suffering with standard all-terrain passenger vehicles during the fighting on the Eastern Front.

The fact is that in combat conditions, reliability and maintainability come to the fore, which is ensured by the simplicity of the design. The technically overcomplicated M561 often broke down, and its repair in field conditions by the crew was most often impossible. And this negated all the advantages in cross-country ability that were achieved by using load-bearing hulls, independent suspensions and an articulated design. Because the efficiency of a vehicle operating in off-road conditions is assessed by a set of operational properties, therefore, an insignificant increase in one operational property (cross-country ability) with a decrease in several others (reliability and ease of repair) is often unjustified.

The car's designers blamed numerous failures on third-party component manufacturers, who (in their opinion) were unable to ensure the proper quality of the supplied units.

It was not possible to establish who exactly was to blame, it is only known that the vehicles remained in service with the US Army until 1983, until they were replaced by the newly-introduced universal military vehicle "M998", better known by the abbreviation HMMWV.

Conclusions


It is well known that a significant increase in the reliability of complex structures requires the use of highly resistant materials, which entails a several-fold increase in the cost of the car. This explains the fact that, despite technical progress, most modern high- and high-cross-country vehicles of mass production still use many design solutions that came out of the early twentieth century.

However, already in the mid-60s of the last century, designers, having analyzed all the experience of the world automobile industry accumulated during this time, came to the conclusion that, while cars were created according to traditional schemes, their cross-country ability did not go beyond certain limits. A significant increase in the cross-country ability of wheeled vehicles can only be achieved by abandoning the usual design solutions.

It should also be taken into account that the optimal design solution cannot be universal, i.e. the most advantageous solution applied to some specific operating conditions may turn out to be erroneous in other conditions.

Acceptance of boundary conditions of operation also sometimes leads to uneconomical, and therefore incorrect decisions. The most economically feasible was considered to be the creation of specialized vehicles intended for a certain, relatively narrow range of operating conditions.

And sometimes, in the case of mass transportation, it is more economically advantageous not to develop and produce a new special vehicle, but to build a road and use ordinary road vehicles to transport goods.
These obvious conclusions have not lost their relevance to this day.

References
Ageikin Ya.S. Vehicle cross-country ability. Moscow, Mechanical Engineering, 1981.
Grinchenko I.V., Rozov R.A., Lazarev V.V., Volsky S.G. High-cross-country wheeled vehicles. M., Mashinostroenie, 1967.
Lazebnikov M.G. On the cross-country ability of vehicles on unpaved and snowy virgin soil. M., Military Publishing House of the USSR Ministry of Defense, 1958.
Laptev S.A. On the vehicle's cross-country ability. Motor, 1938, No. 8-9.
Selivanov I.I. Cars and transport tracked vehicles of high cross-country ability. M, publishing house "NAUKA", 1967.
34 comments
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  1. +3
    1 February 2025 10: 14
    A very unusual car. I'd like to see it in real life and how it goes off-road
  2. +4
    1 February 2025 10: 24
    Unfortunately, such well-written articles about interesting examples of foreign technology are not interesting to the general reader. But this is not the author's fault!
    1. +7
      1 February 2025 14: 19
      Good evening Olya, big hello to Sergey!!
      Unfortunately, such well-written articles about interesting examples of foreign technology are not interesting to the general reader. But this is not the author's fault!

      With the advanced reader on VO - a long-standing problem. If in essence you yourself know who is to blame, ... the only question is that no one knows how to fix it.
      My respects to the author of the article, thank you!!!
  3. -2
    1 February 2025 11: 39
    A pointless rip-off. Provides a conditional +25% to off-road capability with a significant complication of maintenance and deterioration of operational characteristics on the road. Perhaps for the preparation of some specific landing operations or long-term combat operations in swampy terrain.
    By the way, how are the LuAZs? They were purchased for the army, weren't they? We haven't heard anything about them in the SVO from either side.
  4. +6
    1 February 2025 12: 09
    Quote: MamboPoa
    By the way, how are the LuAZs?

    They have not been produced for a long time. The plant in Ukraine has long been re-profiled for passenger transport, and probably lost its expertise in SUVs. The motor plant is the same.
  5. +3
    1 February 2025 19: 02
    I wouldn't mind having one like this in the village (naturally with a mega discount and spare parts)
    1. 0
      1 February 2025 21: 23
      It will be cheaper to buy MTZ-80, and even better MTZ-82 with all-wheel drive, so that it would be easy to jump out of the rut. A cart will be attached to it and it will be a super all-terrain vehicle.
  6. 0
    1 February 2025 21: 30
    The dimensions of the body are modest. Now such a thing could be simply implemented on electric propulsion: the power and control cable goes into the body. All wheels with their own electric motor with individual control.
  7. +5
    1 February 2025 22: 52
    Quote: zyablik.olga
    Unfortunately, such well-written articles about interesting examples of foreign technology are not interesting to the general reader.
    I wouldn't say so.
    I just looked: it hasn’t even been 8000 hours since it was published, and there are already more than XNUMX views.

    I am surprised that so many people now read such specific articles on the history of technology, intended more for specialists than for the general reader.
    1. 0
      1 February 2025 23: 07
      The cabover configuration performed poorly when exposed to mines. This is especially important at the moment.
      1. 0
        3 February 2025 03: 34
        Quote: Sergey Alexandrovich
        The cabover configuration performed poorly when exposed to mines. This is especially important at the moment.

        With such a low weight and an open cabin, this is practically irrelevant.
        1. 0
          3 February 2025 10: 42
          It certainly does. There are two big differences when a mine explodes right under you or two or one and a half meters away from you.
          1. +1
            3 February 2025 11: 40
            Quote: Sergey Alexandrovich
            It certainly does. There are two big differences when a mine explodes right under you or two or one and a half meters away from you.

            This is if the mine is anti-personnel. But with an anti-tank mine, these one and a half to two meters will not solve anything, if there is no armor. And where are you going to get one and a half to two meters? At least look at the picture, it is clearly not a Ural or a Kamaz, but a little larger than a UAZ, and only in length.
            By the way, for anti-personnel weapons even a motorcycle wheel is an obstacle, and this is clearly not a motorcycle.
            1. -1
              3 February 2025 14: 09
              The "Tiger" has about 1,5 meters from the wheel to the driver. Your arguments and approach as a whole are amazing, to say the least.
              1. 0
                3 February 2025 16: 06
                Quote: Sergey Alexandrovich
                The "Tiger" has about 1,5 meters from the wheel to the driver. Your arguments and approach as a whole are amazing, to say the least.

                And I am amazed at you. The Tiger is an armored car with anti-mine protection and a mass of 9 tons, and here we have one and a half not even UAZ, but LUAZ with an open cabin.
                Will the bonnet configuration help LuAZ much in case of TM explosion?
                1. 0
                  3 February 2025 16: 10
                  The GAZ-66 had many shortcomings. One of the main ones was the driver's position on the wheel, which had a negative effect on the driver and passengers in the event of an explosion.
                  For this reason, GAZ-66 and KamAZ trucks were used less frequently in Afghanistan.
                  1. 0
                    3 February 2025 16: 11
                    Quote: Sergey Alexandrovich
                    For this reason, GAZ-66 and KamAZ trucks were used less frequently in Afghanistan.

                    Now with the weight and dimensions of a Kamaz and even a Shishiga the layout is already starting to work. But not with a Luazik.
    2. +1
      2 February 2025 00: 12
      It also seems to me that our people love all sorts of iron gadgets. A certain group of readers is eager to touch the "exclusive" - ​​the process of creation, the solution of engineering problems, the path of the struggle of ideas and their implementation. And all-terrain vehicles simply turn them into children. And in general, cars are beautiful and brutal.
    3. +1
      2 February 2025 03: 49
      Quote: Lewww
      I wouldn't say so.
      I just looked: it hasn’t even been 8000 hours since it was published, and there are already more than XNUMX views.

      Against the backdrop of publications with loud headlines, the authors of which often do not understand what they are talking about - this is not so much. My forecast: Your article will be read by no more than 10 people in a week.
      In any case, your publication is well-deserved.+" good
      1. +3
        2 February 2025 12: 41
        Quote: Bongo
        Compared to publications with loud headlines, the authors of which often do not understand what they are talking about, this is not so much.

        I agree, to get mass appeal you need to write speculative articles like "Were Stalin's repressions as massive as they sometimes write?" or "Did the repressions really cause as much harm to the Red Army as is commonly believed?" and something similar - 100 views and 000 comments are guaranteed.

        But I'm not chasing mass appeal - I write for pleasure and therefore try to produce high-quality materials.
        Now I'm thinking about making a review of the design features of the M-151, also an interesting topic
        1. +1
          2 February 2025 12: 45
          Quote: Lewww
          But I'm not chasing mass appeal - I write for pleasure and therefore try to produce high-quality materials.

          I really like this position! Yes
          Quote: Lewww
          Now I'm thinking about making a review of the design features of the M-151, also an interesting topic

          Are you talking about M151 MUTT? Very interesting machine, I'll read about it with pleasure!
  8. 0
    2 February 2025 21: 45
    Moreover, the designers were able to achieve such a ratio between the weight of the vehicle and the area of ​​the supporting surface of the wheels, at which the specific pressure on the ground was (according to my calculations) only 0,6 kg/sq. cm.
    Actually, there is nothing technically new. From the description, I understood that the principle is like that of the K-700 tractor, which has two half-frames with articulation through an intermediate support and a disconnectable drive to the rear axle going through an intermediate support. Only the XM561 has two frames, unlike the Kirovets half-frames. Even low ground pressure, like the Kirovets, due to the use of low-pressure tires. The disadvantages of the XM561 are the lack of high speeds on good roads due to the two-frame and articulation. A very narrowly targeted truck for off-road use. Probably difficult to maintain.
    1. +3
      2 February 2025 23: 56
      Only the XM561 has two frames
      then there will be two bodies laughing
      One of the disadvantages of the XM561 is the lack of high speeds on good roads.
      Naturally, as with any all-terrain vehicle.
      But a high-cross-country military vehicle does not require high speeds, it is not a sports car. It is enough to maintain the usual speed of the column.
      Well, you can't really accelerate off-road either.
      1. -1
        3 February 2025 02: 46
        then there are already two bodies
        Judging by the diagram in Fig. 154, it has a chassis with an engine on the first frame and a body on the second frame. And about the speed. It doesn't need the speed of a sports car. But this ashcan definitely won't be able to handle movement in a marching column with other equipment. With such a two-frame configuration, this ashcan will only go 40 km/h.
        1. 0
          3 February 2025 09: 59
          Judging by the diagram in Fig. 154, it has a chassis with an engine on the first frame.
          I don't see any chassis, and even if the engine is mounted on a subframe (which you can't tell from the picture), this doesn't mean that the first section had a frame support system
          With such a two-frame configuration, this jeep will only reach 40 km per hour.
          Not a two-frame, but a two-section one.
          And I don’t see any reason why it will give 40 km/h at most if the maximum declared is 93 km/h
          1. 0
            3 February 2025 22: 03
            I don't see any chassis, and even if the engine is mounted on a subframe

            If you are hinting at the lack of a rigid frame and the stamped sheet metal body structure like a passenger car, then a single-axle trailer does not fit into such a structure. A single-axle trailer will simply tear off the sheet metal part of the body when fully loaded. And regarding the declared speed of 93 km/h. The maximum permitted speed for modern trucks with trailers and semi-trailers is 80 km/h. And this strange ashcan on low-pressure tires can do 95 km/h? If you coast it down a mountain at that speed, it will simply fall apart from the vibration.
            1. 0
              3 February 2025 22: 15
              A single-axle trailer, when fully loaded, will simply tear off the sheet metal part of the body.
              I told you what is written in the source, I don't see any point in arguing with you
              And this strange car with low-pressure tires goes 95 km/h?
              Colleague, I don’t see any point in discussing your speculations.
              This is stated in its technical characteristics, if you don’t believe it, it’s your right
              1. 0
                4 February 2025 01: 29
                colleague, I don't see the point in discussing your speculations
                I also don't understand why I got involved in this discussion. This is a 1960s ashcan. Now it is neither seen nor heard in service. It was obviously an unsuccessful project and was abandoned. There is nothing to discuss here.
                1. 0
                  4 February 2025 18: 47
                  They refused it not because it was unsuccessful (although it may have been), but because the US Army periodically changes its vehicle fleet - they change models.
                  Personally, I liked their M715 better - a solid and practical vehicle, just right for war.
  9. +3
    2 February 2025 23: 40
    Thank you!
    An example of a good presentation of complex and little-known material in simple words, but without simplification.
    This is the opinion of a VO reader.
  10. +1
    2 February 2025 23: 49
    Quote: Bongo
    My prediction: Your article will be read by no more than 10 people in a week.

    Your forecast did not come true, the second day has not yet passed, and there are already 15600 views.
    Apparently, in our country there are still many people who have not lost interest in historical and technical articles about all-wheel drive vehicles.
  11. 0
    3 February 2025 03: 53
    It would be interesting to read about other compact off-road vehicles of the 20th century of the US Army, the Bundeswehr, and NATO in general.
    1. 0
      4 February 2025 18: 48
      If you are interested, check out my account, I published several articles about all-wheel drive cars last year.
      https://topwar.ru/user/Lewww/
  12. 0
    6 February 2025 15: 29
    Judging by the pictures, the driver's workplace did not encourage a comfortable position.