JAZZ

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Sweden looked at a number of MBT concepts in the 1980's as a replacement for the stridsvagn-103. Key ones were UDES-11, UDES-17, UDES-19 and Stridsvagne 2000. A UDES-3 has been mentioned and appears to be a prof of concept vehcile based on the marder - with a bofors external mounted gun. not to be confused with the Greman VTS-1 (which was to lead to teh Leopard 3SL, Leopard 3SLD, Leopard 3SLB configurations.

Anyway here is the UDES-11 casement tank
 

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Swedens FMV did some concept definition studies to look for a replacement for the strv-103. By 1978 five concepts each crewed by 3 and of 35-40 tonnes were being considered. Favoured concept was UDES-19.

A joint company between Bofors, Hagglund and Soner to devlop proposals was begun in 1981, short listing of the solutions by 1984.

UDES-19 had a 120mm gun fed from an external mouted magazine at the rear of the hull, holding 34 rounds, a further 17 rounds could be added if necessary.

Loading mechanism has a laoding arm, witha armoured barrel at one end to take the ammunition. The loading arm is mounted on a rail concentric to the gun mount to permit reloading of the gun, what ever its position. Reloading cyle taking just 2 seconds.

Other armament included a 7.62mm coaxial MG and two 7.62mm MG's mounted eitherside of the front hull.
 
Photos of UDES series and model of UDES-19
 

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1981 Bofors, Hagglund and Soner looked to develop a tank destroyer, it was not seen as a replacement for the Strv-103 or Sweden's Centurions. The concept had a 3-man crew in the front unit and 120mm Rheinmetall gun with Bofors muzzel brake. The rear unit contained ammunition, fuel and engine. loading cycle took 6 seconds.

Two other versions were looked at ATGW and APC, in the latter case the engine was in the front unit and rear unit contained crew of 2 and 8 infantry and armed with a 20mm gun.
 

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UDES-19 drawing
 

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Yet again, what was old is new again: http://www.militaryphotos.net/forums/showthread.php?210223-Future-tank-of-the-Russian-military
 
H/t pr0 over at MilitaryPhotos:
 

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JAZZ said:
1981 Bofors, Hagglund and Soner looked to develop a tank destroyer, it was not seen as a replacement for the Strv-103 or Sweden's Centurions. The concept had a 3-man crew in the front unit and 120mm Rheinmetall gun with Bofors muzzel brake. The rear unit contained ammunition, fuel and engine. loading cycle took 6 seconds.

Two other versions were looked at ATGW and APC, in the latter case the engine was in the front unit and rear unit contained crew of 2 and 8 infantry and armed with a 20mm gun.

Question...if the ammunition for the gun in the tank destroyer version was carried in the rear unit, how did it reload, especially on the move?
 
cluttonfred said:
Question...if the ammunition for the gun in the tank destroyer version was carried in the rear unit, how did it reload, especially on the move?

I would suspect a kind of belted ammo.Works well for eleconic components to be installed via automatic production machines,
even for quite big and heavy parts.
 
In the experimental rig the gun was loaded manually during testing, but an autoloader was to be developed. I think it would not be unlike certain SP artillery vehicles which can be supplied with ammunition from a limber vehicle (such as the FAASV), i.e. by conveyor. I assume the front end of the conveyor would be fixed to one half of the articulated vehicle and would use a rotating base to align a round either with the conveyor (in the rear half) or with the loading arm (in the front half). It would be a bit complex, but certainly doable.
Some links:
http://www.sphf.se/Axvall/XX20.htm
http://strangernn.livejournal.com/860041.html
http://www.ointres.se/udes.htm
http://forums.spacebattles.com/threads/most-favorite-mbt.207405/page-4
 
The automatic loading system was to be a swinging arm as in the Swedish mono-hull vehicles with the external turret. This arm was mounted on a ring around the base of the turret and would lift a round from the magazine and swing it around to the rear of the turret to load it. The same thing was proposed for the Soviet T-74. The movement of the aft hull in relation to the forward hull would not be so great to preclude the swinging arm from finding the top of the magazine.
 
BTW
two-unit.jpg
 
6.4. Sweden
6.4.1. Some of the best examples of the effective use of test beds are
provided by the development of combat vehicles in Sweden and in particular, j
the development of the S-tank. The novel concepts embodied in that tank
were first explored in a series of low-cost test beds. This greatly
reduced the technical risks involved in the development of the S-tank and
helped to keep its cost down.
6.4.2. The low-cost, stage-by-stage approach to new concepts is now being
repeated in the development of a novel articulated tank destroyer armed
with a 120 mm gun, the UDES XX 20. The development of this vehicle started
with the construction of a reduced scale test bed, based on the chassis of
the light, articulated BV 206 carrier, which proved the new automotive
features of the concept. This was accompanied by the construction of
another test bed, which consisted of a 105 mm tank with an enlarged chamber
mounted on the chassis of a Marder mechanized infantry combat vehicle,
which proved the feasibility of firing a 120 mm tank gun from a relatively
light vehicle of about 20 metric tons. After these basic issues were
resolved with the two test beds, the tank destroyer program advanced to the
construction of the UDES XX 20 test bed, which is close in several respects
to the vehicle that might be fielded. However, the primary purpose of the
UDES XX 20 is to develop the installation of the 120 mm gun and its control
system, and also to develop the elaborate automatic loading system
associated with this concept. Only when all this has been successfully
accomplished will the decision be made, whether or not to proceed with the
articulated tank destroyer.
http://www.dtic.mil/dtic/tr/fulltext/u2/a131652.pdf
 
cluttonfred said:
What was the primary rationale for this sort of two-part vehicle vs. a larger single hull?

Crossing rough terrain while keeping as much track in contact with the ground. Because you can pivot around the x axis. Plus ease of steering. With differential steering the longer the length of track in contact with the ground the more energy needed to pivot around the z axis. Plus the two hull vehicle can use articulated steering if the joint between the two includes a powered pivot ( z axis again). Another advantge is the potential for a modular family of vehicles.
 
cluttonfred said:
What was the primary rationale for this sort of two-part vehicle vs. a larger single hull?

1. Lower ground pressure.
2. Greater off-road mobility (in the same class of weight).
3. If in rear unit - better crew survivability.
4. More space for payload.
 
eshelon said:
1. Lower ground pressure.
2. Greater off-road mobility (in the same class of weight).
3. If in rear unit - better crew survivability.
4. More space for payload.
It might have to do with the Arctic landscape being spectacularly unfriendly to land vehicles.
- Soviet Vityaz
- Swedish Bv202 - Bv 206 - BvS 10
- Finnish Nasu
... all of them articulated tracked vehicles, were developed to tackle the Arctic's rocks and bogs.
 
cluttonfred said:
Thanks, but it does seem like an awful lot of complexity for limited gain.

Complexity of UDES-XX20 (or Twister)? Yes. Complexity of articulated vehicles? No.
See the case of two connected M113s as articulated vehicle (1970s).

In the 1970s, TARDEC experimented further with vertical modularity using articulated vehicles; the goal was less toward modularity and more toward improvements in off-road mobility. Two M113s were connected through a cybernetically controlled articulation joint invented by TARDEC, which featured positive pitch and yaw control with roll freedom that provided force feedback to the operator. Two hydraulic cylinders mounted on the vehicles provided the force to control the relative pitch and yaw between the two coupled M113s. A single M113 could climb an 18-inch high obstacle, but the two articulated M113s could climb a 5-foot wall.

The articulated vehicle could also cross open trenches up to 10 feet wide; climb a 60 percent slope; enter, cross, and exit a waterway; and be controlled from either the front or back vehicle by means of a joystick (Beck & Kamm, 1974; 1975).


(from "The TARDEC Story: Sixty-five Years of Innovation 1946-2010", page 52)

http://www.dtic.mil/dtic/tr/fulltext/u2/777799.pdf
http://www.slideshare.net/ISTVS/tardec-50-years-slides
 

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