During World War II, Nazi Germany made several attempts to create anti-aircraft self-propelled guns, but they all ended without much success - even the most successful examples of such equipment were not built in a series of more than several hundred units. At the same time, some projects in this area are of great interest due to certain technical or other features. For example, the ZSU 8.8cm FlaK auf Sonderfahrgestell was originally developed as a self-propelled vehicle to combat enemy tanks, but later radically changed its purpose.
The history of the 8.8cm FlaK auf Sonderfahrgestell project dates back to the initial period of the war in Europe, when German artillerymen established that 88-mm guns of the FlaK 18 family were capable of striking not only enemy aircraft, but also various armored vehicles. The large caliber and high muzzle energy of the shells made it possible to literally pierce the armor of most of the tanks of that time. In the future, there were several options for installing anti-aircraft guns on various chassis of the existing models, which made it possible to use them to combat enemy armored vehicles. Some of this equipment was able to reach operation in the army, but did not show noticeable results. The fact is that the 88 mm cannons were very heavy and had a high recoil momentum. These factors seriously reduced the list of potential carriers, and also negatively affected the design resource of the latter.
In 1942, Krupp proposed to develop a special chassis that could carry heavy powerful guns and effectively solve anti-tank defense tasks using FlaK 18 guns, etc. weapons. The proposal was approved by the potential customer and led to the start of the project. A promising chassis for self-propelled guns received the designation Sonderfahrgestell ("Special chassis") or Pz. Sfl. IV (c). To speed up development and simplify production, it was decided to ensure the maximum unification of the new chassis with existing and developing tanks of several types.
ZSU 8.8cm FlaK auf Sonderfahrgestell in firing position. The sides are lowered, the gun is raised. Photo Aviarmor.net
It was proposed to mount an armored wheelhouse on the chassis, inside which an 88-mm gun should be placed. Such a combat vehicle could become a relatively simple and effective means of dealing with enemy tanks and supplement other armored vehicles of the troops. However, soon after the completion of the preliminary work, the project of a promising anti-tank self-propelled gun changed its purpose.
Analysis of the proposed development showed that in its current form it no longer meets the requirements for such a technique. The observed and expected changes in enemy equipment did not allow hoping that the proposed self-propelled guns based on Sonderfahrgestell would be able to effectively deal with enemy tanks without significant risks to themselves. At the same time, the machine, with some special modifications, could well solve the problems of air defense. The use of guns of the FlaK 18 family gave a high efficiency of hitting targets, and the presence of a self-propelled chassis dramatically increased the mobility and overall performance of the vehicle.
In the fall of 1942, the Krupp company completed the redesign of the project of a new self-propelled gun, which was now intended to participate in air defense. Soon after that, a gun and a number of other additional equipment were mounted on one of the new chassis of the promising model. By the end of the year, the first sample of a promising self-propelled anti-aircraft gun was ready for testing. At this stage, the designation 8.8cm FlaK auf Sonderfahrgestell appeared. In addition, the more voluminous designation Versuchsflakwagen 8.8cm FlaK auf Sonderfahrgestell (Pz. Sfl. IVc) was used: “Experimental anti-aircraft gun with an 8.8 cm anti-aircraft gun based on the“Special chassis”.
88-mm cannon FlaK 18. Photo Wikimedia Commons
A promising chassis for new self-propelled artillery installations was developed with extensive use of developments in existing technology. In particular, the Sonderfahrgestell machine resembled the Pz. Kpfw. V Panther and Pz. Kpfw. VI Tiger tanks by the general contours of the hull and the design of the chassis. This similarity was due to both the use of similar ideas and the use of some finished products.
"Special chassis" was originally created as a special self-propelled platform for the installation of weapons, which affected its design. The body of the car had a low height, and the central part of the roof was a platform for the installation of the necessary systems. At the same time, in front of the gun platform, a small wheelhouse was provided with a control compartment, which had a multifaceted shape, and a large superstructure of the engine compartment was located in the stern. This design of the hull with a lowered roof allowed to some extent reduce the overall height of the vehicle in comparison with the chassis of the "tank" layout.
Inside the hull, only two workplaces were provided for the crew members. A driver and a radio operator were to be located under the front armored wheelhouse. To monitor the situation and the road, they had four viewing devices of a slotted design: two were located in the frontal leaf of the cabin, two more - in the cheekbones. In the roof of the cabin, it was proposed to install two hatches to get inside the machine. Between the hatches, a device for attaching the gun barrel in the stowed position was movably mounted.
Self-propelled gun in preparation for shooting. It can be seen that the cover of the engine compartment was used as a bench for the gunners. Photo Blog.tankpedia.org
The chassis hull was proposed to be assembled from armor plates of different thicknesses. The frontal projection of the vehicle received protection in the form of 50-mm sheets, while the protection of the sides and stern was carried out by 20 mm thick armor. The roof and bottom were twice as thin as the sides. Initially, it was assumed that such a booking would allow the anti-tank self-propelled gun to work at the forefront in the same battle formations with tanks and other armored vehicles. After changing the purpose of a promising vehicle, the design of the armored hull has not undergone any changes.
Based on existing ideas and units, the Sonderfahrgestell had a layout that was standard for German tanks of the time. In the front of the hull there was a compartment for accommodating transmission units, next to which there was a control compartment. The central part of the chassis was given for the placement of the gun, which was to be mounted on the roof of the hull. The engine and some related equipment were placed in the stern. The connection of the engine with the gearbox and other transmission units was provided by a cardan shaft passing through the entire body.
The "Special Chassis" received a power plant based on the Maybach HL90 12-cylinder petrol engine with 360 hp. The main transmission element was a six-speed manual transmission. Like the German tanks of the time, the transmission transmitted engine torque to the front drive wheels.
8.8cm FlaK auf Sonderfahrgestell in firing position. Photo Blog.tankpedia.org
The undercarriage of a promising combat vehicle was developed taking into account the developments in the projects of the Tiger and Panther tanks. On each side of the new chassis there were eight double road wheels, staggered and partially overlapping each other (the so-called G. Knipkamp's suspension). Also provided were the front drive wheels, raised relative to the rollers (this led to the appearance of the characteristic shape of the front of the caterpillar), as well as rear guides. Due to the large diameter of the track rollers, the undercarriage did not need support rollers. The caterpillar had a width of 520 mm and had a large-link structure.
The main weapon of the promising ZSU was to be the 88-mm FlaK 18 anti-aircraft gun (some sources indicate its later version FlaK 37). It was proposed to mount this gun on the upper platform of the hull using a slightly modified carriage of the basic design. For this, the carriage had to be deprived of the beds, intended for deployment on the ground, and rest its swivel block directly on the corresponding parts of the body. After revision, the carriage retained all guidance mechanisms with manual drives, an armored shield with an inclined front plate and small side plates, as well as a balancing mechanism and other units. Due to the use of ready-made units, the possibility of horizontal guidance in any direction and barrel lift from -3 ° to + 85 ° was retained.
The 88-mm cannon, proposed for use on the new ZSU, had a 56-caliber barrel and was equipped with a horizontal wedge breech. The semi-automatic mechanism provided the extraction of spent cartridges and the cocking of the gun before firing, thanks to which a trained crew could make up to 15-20 rounds per minute. With an initial projectile speed of up to 840 m / s, the FlaK 18 family cannons could hit air targets at altitudes up to 10 km and fire at ground targets at a distance of about 14-15 km. The ammunition consisted of several types of fragmentation and armor-piercing shells.
Self-propelled gun in a combat position from a different angle. Photo Blog.tankpedia.org
In the stowed position, the gun had to turn the barrel forward and stop in this position. At the same time, the barrel was fixed on a special frame mounted on the front wheelhouse. In preparation for firing, the calculation had to free the barrel and remove the stoppers of the guidance systems.
To work on the front edge of the ZSU 8.8 cm FlaK auf Sonderfahrgestell had to have additional protection for the gun and its crew. Together with the cannon, the vehicle was supposed to receive an armored shield of the existing design, covering the crew from bullets and shrapnel from the front hemisphere. The sheets of such a shield were 10 mm thick.
The side and rear of the gunners had to be protected by an armored wheelhouse, also assembled from 10-mm sheets. She had sides with a vertical bottom and an upper part piled inward. In front, small sheets were attached to the sides at an angle, covering the gap between the sides and the gun shield. Also, the wheelhouse received a stern sheet, the shape of which provided a tight fit with the rear of the sides. The roof of the cabin was not provided. In case of bad weather, the crew of the car had a tarpaulin awning. All elements of the cabin were hinged to the hull, so that the crew, if necessary, could tilt them at a certain angle. At the minimum angles of opening the sides, the horizontal guidance sector of the gun increased, and when fully lowered, they turned into a platform for calculation and made it possible to conduct a circular fire. The stern leaf of the cabin, like the sides, could be lowered to a horizontal position, after which it did not interfere with shooting into the rear hemisphere.
The FlaK 41 gun is the main armament of the modernized ZSU 8.8cm FlaK auf Sonderfahrgestell. Photo Wikimedia Commons
Inside the armored cabin there was a place for transporting ammunition, which consisted of unitary 88 mm caliber shells of various types and for different purposes. Also, the self-propelled gun could fire with the supply of ammunition from the ground. At the same time, however, it was necessary to lay out the sides for the convenience of transferring shells and supplement the calculation of the gun with several numbers.
The crew of the anti-aircraft self-propelled gun was supposed to consist of five or seven or eight people. When working as an anti-tank self-propelled gun or when using transportable ammunition laid in the wheelhouse, the work of the machine had to be controlled by a driver, radio operator, commander, gunner and loader. To supply shells from the ground, two or three carriers had to be included in the calculation of the gun.
The finished self-propelled gun of the new model was supposed to have a combat weight of 26 tons and in its dimensions correspond to most German tanks of that time. The length of the vehicle, excluding the cannon, did not exceed 8 m, the width reached 3 m, and the height was 2.8 m.
Updated self-propelled gun in the stowed position. Photo Aviarmor.net
According to reports, the design of a promising 8.8 cm FlaK auf Sonderfahrgestell ZSU with an 88-mm gun was completed in the fall of 1942. Soon after that, at one of the factories of the Krupp company, the first chassis of a new type was assembled, which received an anti-aircraft gun of the FlaK 18 type. The first tests showed that the "Special chassis" turned out to be a fairly successful basis for promising equipment for various purposes. With a power-to-weight ratio of just under 14 hp per ton, the armored vehicle could reach speeds of up to 35 km / h on the highway. The power reserve was determined at 200 km. In terms of firepower, the ZSU did not differ from the corresponding guns in the original towed form.
The new anti-aircraft self-propelled gun has been tested and showed fairly high performance. Such a technique could be of great interest to the troops, but the military decided otherwise. By the time the tests were completed in early 1943, the potential customer decided that the existing version of the ZSU 8.8 cm FlaK auf Sonderfahrgestell did not fully meet the requirements of the time. The main complaints were about the used FlaK 18 cannon, which was already considered obsolete. It was proposed to create a new version of the armored vehicle with a newer weapon of a similar purpose and caliber, but with improved characteristics.
In 1943, the Krupp design bureau began to modernize its development in order to use new weapons. Now on the "Special chassis" it was proposed to install the FlaK 41 cannon, which was a further development of the guns of the previous models. Due to a number of innovations, including a new projectile with improved characteristics and a 72 or 74 caliber barrel (depending on the series), the FlaK 41 cannon could fire at a long range. In particular, the maximum firing height reached 15 km. The new gun was equipped with a different carriage with different characteristics. Thus, the elevation angles of FlaK 41 varied from -3 ° to + 90 °.
The sides are not completely lowered, but the FlaK 41 cannon has the ability to fire at air targets. Photo Blog.tanlpedia.org
The use of the new weapon made it possible to maintain the existing mobility of the ZSU, but at the same time significantly increase its combat effectiveness due to the increase in the range and height of target destruction. However, the production of the FlaK 41 guns faced noticeable problems, which left much to be desired in the pace of production. Due to the complexity of the technological nature and high cost, a little more than 550 FlaK 41 guns were assembled before the end of the war. These weapons were immediately sent to the troops, which made it difficult to work on the self-propelled gun project. According to some reports, it was only in 1944 that the development company was still able to obtain the required weapon of a new type and install it on the existing "Special chassis" already used in the project. Together with the gun, a carriage of an updated design with a new shield was also installed on the vehicle.
The most noticeable difference between the upgraded 8.8cm FlaK auf Sonderfahrgestell armored vehicle from the first version was the armor shield of the new design. It differed from the previous one by wide side plates with a curved top and aiming hatches, as well as narrow side plates. In addition, along with the new shield, a movable gun mantlet was used, which included protection for the front of the recoil devices. Due to the larger area, the new shield provided better cover for the gunners from possible threats on the battlefield.
Inspections of the updated self-propelled gun, which took place in 1944, showed a noticeable increase in the main characteristics and overall efficiency. Nevertheless, in this case, the combat vehicle could not interest the army command. Probably, this time, the failure of the military was caused by the insufficient rate of release of guns, as well as the specifics of the situation at the front, because of which the industry had to focus on other projects and reduce the cost of developing new weapons.
The gun is brought to the maximum elevation angle. Photo Blog.tankpedia.org
Due to the lack of prospects, the 8.8cm FlaK auf Sonderfahrgestell project was closed after testing an updated prototype. Subsequently, the weapon was removed from it, and the chassis was used in the development of some new projects. On the basis of the "Special chassis" it was proposed to build anti-tank and howitzer self-propelled guns, as well as anti-aircraft systems with small-caliber artillery systems. It is known that during one of the projects, the Sonderfahrgestell machine received an installation with a 37-mm automatic cannon. Also considered was the option of an arms transporter with a gun mount for the leFH43 howitzer, lowered to the ground for firing. Other options for various artillery systems on the existing chassis were also proposed.
Despite all the efforts and expenditures of time, effort and resources, the project of a promising anti-aircraft self-propelled gun with an 88-mm cannon did not give noticeable results. Only one prototype was built, which at a certain stage underwent modernization and received a new weapon. In both cases, the proposed armored vehicle did not suit the potential customer, who refused it for one reason or another. As a result, the army did not receive new ZSU with powerful weapons, and the promising chassis could not get out of the construction stage and test various new types of equipment.
In parallel with the 8.8cm FlaK auf Sonderfahrgestell in Germany, several other projects were developed for installing guns of the FlaK 18 family on a tracked chassis, but they also did not achieve serious success. With all its advantages, this technique had a lot of disadvantages that led to failures on the part of potential customers. Thus, the project ZSU 8.8cm FlaK auf Sonderfahrgestell, which ended in failure, was not the only example of such an outcome of work in a promising area.
