Schwerer Wehrmachtschlepper
Germany (1934-45) - Utility Half Track - 825 built
The Schwerer Wehrmachtschlepper (acronym sWS) for "Heavy Military Tractor" was a German WWII half-track manufactured between 1943 and 1945, but designed under orders from Hitler for mass production in May 1942. The present post is about the unprotected model were used to supply the eastern frontline and to haul artillery. However the shortage or armour meant many started to be later converted Armored versions for FLAK or as rocket launching vehicles (Nebelwerfer). Mass production remained a pipe dream and only less than a thousand were built before V-Day. Czechoslovakia designed an improved model, the Tatra T809, which became its early cold war standard APC.
Design development
Genesis 1926-30
In the summer of 1926, Heinrich Ernst Kniepkamp, from the Reich Ministry of Defence, was tasked with the fully motorization of the German artillery and he started testing agricultural tractors from Germany, Britain or the US over three years. In a 1932 trial, an half-track design proved superior and was adopted a baseline for future vehicles. So from 1933 several German companies designed half-tracked vehicles for this task at all towing capacities up to 18 tons. Leading to a range of powerful half-tracked prime movers, the "Sonderkraftfahrzeuge" (Special Purpose Vehicles) 10, 11, 6, 7, 8, and 9.
By late 1939, half-tracked vehicles performed well in Poland, offering better off-road mobility than trucks and higher speeds than fully tracked prime movers, a sweet spot added to the fact training was easy as a truck driver could make the transition easily. They provided versatility in a dynamic combat as part of the so called "Blitzkrieg". However, manufacture proved overly complex and expensive, added to the proliferation of different types. This was by 1938 already considered not efficient for production. The Army Ordnance Office (Grundgedanke) started working on a second generation of half-tracked prime movers and later with heavy attrition, and losses in 1914 with the growing aerial threat to supply units in rear areas on the Eastern Front led to an even more radical approach and development of a third generation, far more simplified and supposed to replace several vehicles at once.
Replacing several Items in park at Once
In 1941 the Half-Track park of the Wehmacht was impressive indeed. In addition to the armoured SdKfz 252 and 251 and all their derivative, there was a range of seven vehicles up to the Sd.Kfz.11 of all sizes, classes, as hauler, suppliers and usable for other roles. They were for the most designed well back from 1933 down to the the start of 1939, when production b several manufacturers took place. When the Eastern offensive started in the summer 1941, successes were so fast, that regular trucks could be used on roads up to Moskow.
However the offensive was bogged down in the Atumnal Resputista and stopped in the dead of winter and very cold temperatures that crippled the logistic train. It was clearly obvious that tracked vehicles were needed fast, especially since the bulk of roads encountered, aparts some exceptions, were no more than dirt tracks. Production of existing half-tracks was ramped up, but the models were complex and costly to produce and shortages started. One solution was to turn the standard Opel Blitz 3t supply truck into a half-track (Maultier) but this was never enough. One thing was clear, a new model that could replace several classes at once and being easier, cheaper to mass produce was urgently needed as the expected spring rasputitsa started to again block any further advance.
Program Start
On 7 May 1942 Hitler ordered development of a simple and low-speed "universal" half-track, with an average load for the Eastern Front. Büssing-NAG, relatively free at the time, at least on the standpoint of design, was selected to develop a new 5 tonnes (4.9 long tons; 5.5 short tons) tractor which took the name of "Zgkw. 5t neuer Art". The main role was to replace the existing, earlier 5 tonnes Sd.Kfz. 6 and 3 t Sd.Kfz. 11 half-tracks by a single model as other vehicles of the same class.
However this dragged on due to more urgent priorities and it was not before late 1942 that definitive specifications came out and final requirements drawn up, based on campaign experience. Büssing-NAG, was selecte to produce five prototypes. Four were for the cargo requirements and there was a slightly longer 5th prototype partially armoured that would become more prevalent after 1944. They were approved by the Heereswaffenamt.
The development program started in 1942 with two basic types, the leichter Wehrmachtsschlepper (leWS) from Adler-Werke and schwerer Wehrmachtsschlepper (sWS) from Büssing-NAG and the new vehicles has been indeed the result largely of supply problems experienced during the winter of 1941/42. The heavy one was thus to be able to tow a 6-ton load and carry a 3-ton payload. The Army Ordnance Office made a decision in July 1942 to phase out production of the 5-ton half-track prime mover for the new Sws.
Thus, the Army Ordnance Office awarded Büssing-NAG a contract for five prototype s.W.S. assigned the chassis numbers 2016, 2017, 2018, 2020, and 2021. The light standard 3rd gen. half track however never progressed beyond prototype stage. Only the schwerer Wehrmachtsschlepper remained, eventually entering production at Büssing-NAG and Ringhoffer-Tatra from the autumn of 1943 (see below).
Production and Variants
Chassis, preserved.
Production started in December 1943 at Büssing-NAG and the earliest vehicle were outfitted with a truck-like, unarmored cabin like earlier half-tracks but with simplified shapes for mass production and sme equipments simplified or omitted. They were already much cheaper to manufacture compared to earlier models. However the rapid evolution of the front in 1944-45 imposed for the latter an armored cabin and engine compartment closer in shape to the Sd.Kfz. 251 armored personnel carrier but simplified and only for the cab. The flatbed was left unchange aparts folding panels with mesh.
Serial production started at Berlin-Oberschöneweide based on contracts 0213-1001/42, 625 vehicles were planned with cargo bodies and 375 with anti-aircraft mounts of either the Flakvierling and 3.7 cm FLAK type and 0213-1003/43 for a grand total of 1,725 units with cargo bed bodies and 575 units with anti-aircraft mounts, serial numbers in this series began with 150001. Another joint contract was awarded later for SS213-1001/43, to Ringhoffer-Tatra in Prague and Wagenfabrik AG in Kolin for an additional 500 cargo-bed vehicle startng with the serial number 250001.
Production planning called for an initial output of 50 vehicles in October 1943, and gradually go for a monthly output of 400 vehicles, by March 1945. Of course this was never achieved, despite Speer's best effort. There were massive delays due to allied bombings and some industrial bottlenecks. In fact the first five delivered, four prime movers, one self-propelled FLAK not delivered until December 1943... Peak production arrived in October 1944 (112 vehicles) and it later declined with a finl batch of 25 reportedly manufactured in March 1945.
At that stage when production ceassed due to the allied advance, in 1944 only 724 vehicles were delivered, 649 flatbed and 75 self-propelled FLAK vehicles and then in 1945 some 103 vehicles with about 73 of the flatbed cargo type and less than 5 self-propelled Flak vehicles in including the 97 vehicles from the Kolin plant.
This makes for a grand total of 830 units manufactured before the end of the war, way short of expectation, and thus, never able to replace the tow Half-track types as planned. However the never built and cancelled "light Wehrmacht tractor" was to contribute to parts standardization, sharing components with the sWS and with their cancellation thay could not take part in lowering their logistical burden.
Production in Germany was limited before 1943 at Büssing-Nag facility was historically located at Braunschweig. It had multiple factory sites across the city, such as on Böcklerstraße and Wörthstrasse and took over facilities of Neue Automobil Gesellschaft (NAG) in the early 1930s, manufacturig heavy trucks, buses, and armored vehicles but also used forced labor close to a satellite worker concentration camp system (Schillstraße camp). In 1945, Tatra joined in production, but together they were only capable of delivering 825 vehicles total on V-Day, a far cry to the 3,000+ envisioned. Tatra continued production of the improved T809 poswar (see below).
Design
Plans, from the blueprints
The basic engineering called for the same torsion bar suspension, and overlapping and interleaved double road wheels. So far, despite the maintenance nightmare, reports were still ignored and this system was imposed again for production. All the remainder aspects were worked out for the most simplified design and production was approved in Fabruary 1943.
Like the Demag-designed Sd.Kfz. 10, the Büssing-Nag sWS had a Schachtellaufwerk suspension system: It was made of five double roadwheels per side, overlapping and interleaved in the, mounted on swing arms sprung by torsion bars. Lke a Tnank they had idler wheels mounted at the rear end of each track unit to control track tension and drive sprocket forward. The chassis was a ladder-type, wit the driving axle forward, two roadwheels. However as far as sharing assets, these vehicle had their own roadwheels, idlers and sprocket designs. The roadwheels, rubber-rimmed had their design changed also latter in the war from the spider type with 6 branches, to a simpler, flat, stamped, holed type.
Externally, the layout was the same as the vehicles they replaced, with an open cab forward (frames, forward tarpaulin), and instead of doors stowage bins over a flat, simple mudguard running over the forward driving axle. They carrier two standard lights. Notek (night) lights were omitted. The bonnet was a classic central spine hinge, with top louvres and two side panels with more louvres. The radiator and its forward case was flat, simple, without addition and at the bottom was a simple 3-sided stamped metal bumper. The was a towing hook below.
The entire aft part comprised the tracked chassis on which was located a flatbed with wooden sides (not hinging) and a back plate with simplified reflecting lights and convoy light, hinged. This utility flatbed was designed to receive frames for a tarpaulin, again simplified, with only two rear platic windows. This tarpauling rested on front and rear frames with longitudinal frames in between. The frame and tarpaulin, well folded, could be carried by the vehicle as well.
When used in troop/cargo configuration the flatbed was split, with the forward part, closed by a wooden face, having brackets for a spare tyre on the right, a supply area, then a separation with racks for stowed K98 rifles, and a transverse double bunk (fwd/rear) for 8 men like standard half tracks. If the forward aread was also modified that way, the vehicle could carry as much as 16 infantry. There was also a towing hook on the back plate.
Now,the power plant was a Maybach 4.2 litre HL42 TRKMS that developed 100 horsepower. The cargo variant was rated "only" for 5 tonnes but it showed improved weight carrying capacity over previous generation. So much so both the soft skinned and armoured variant could carry the 37mm flak 43/1 or 20mm quad Flak-vierling 38. Other tested anti-tank guns. And others, armoured carried rocket launchers (Panzerwerfer 42 auf sWS.). The vehicle was also planned for towing a 5t 2-axle trailer.
The vehicle was designed to be simple and straightforward with the running gear made of unlubricated tracks without rubber pads. It had cost-effective road wheel discs (from the stamped wheels) on. inside and outside the interleaved or overlapping wheel arrangement. Later in the war, the lack of self-propelled ordnance led to devise a self-propelled anti-aircraft 3.7 cm FlaK 43 positioned on the cargo bed with a gun shield which had side panels folding down to allow a 360-degree traverse.
With a base Payload of 4t and a towing capacity of 8t, it had an operational range of 300 km on road, 150 km cross-country, with a 240-liter fuel capacity. The vehicle's fording depth was one meter or 3.2 feet. The vehicle was normally unarmed, albeit its had racks in the cargo variant for sixteen K98 standard rifles. Of course later were developed two FLAK variants a 20mm Flakvierling and a 37mm version.
The base vehicle was also unarmored albeit there were some partially armored variants developed on the eastern front going from 6 to 15 mm plating (0.3 to 0.6 inches). Later the vehicle received a fully armoured cab forward.
Armament
The base vehicle was unarmed, apart personal weapons. It was also unprotected.
The FLAK versions (self propelled AA) were built alongside with a ratio of 1/5, and fitted either with a 3.7 cm or Flakvierling (4x 2cm).
However later in the war were developed armoured versions ("gepanzerte"):
There were Schwerer Wehrmachtschlepper with cargo bed configured as a self-propelled mounts for the 3.7 cm Flak 43/1 or 3.7 cm Flak 37 from the factory, but many individual vehicles were also converted in local workshops, fitted with anti-aircraft guns sometimes in ad-hoc or systematic basis in order to protect vehicle columns against allied low-level fighters or Soviet ground-attack aircraft like the Surmovik with a lot of photographic evidence to back this up.
The 3.7 cm was the most efficient for that weight class, it fired a Shell 37 × 263 mm B 623–659 g (1.373–1.453 lb) 1.5 in caliber from a gas-operated bolt with a mount elevating +85°, 360° traverse, 160 rpm (cyclic) rate of fire, 770–840 m/s (2,500–2,800 ft/s) muzzle velocity depending on the ammunition at 4,200 m (4,600 yd) range in AA fire and 7,995 m (8,743 yd) in ground range. It was reloaded by using 6-round clips.
The second variant carried the 2 cm Flakvierling 38, most common ad hoc field conversion for individual vehicles weighting 450 kg (992 lbs) for the towed mount and 4.08 meters (13 ft) long, with a Cyclic Rate of Fire: Up to 1,400 to 1,800 rounds per minute combined across all four barrels. Practical Rate of Fire: Around 800 rounds per minute because each gun used a 20-round box magazine that required frequent reloading. Muzzle Velocity: Between 780 and 900 meters per second depending on the type of ammunition used. Maximum Range: 2,200 meters. A seated gunner aimed the weapon and used two foot pedals to fire diagonal pairs of barrels (top-left/bottom-right and top-right/bottom-left) in semi-automatic or fully automatic modes. It was also on self-propelled half-tracks like the Sd.Kfz. 7/1.
Variants
- Early (alte) Schwerer Wehrmachtschlepper cargo/flatbed type (1943): "Spider" roadwheels.
- Late (1944/neu) SwS cargo/flatbed type (1944-45): "disc" simplified roadwheels
- AA Vehicle (Flak-Sfl): 3.7 cm FLAK
- AA Vehicle (Flak-Sfl): 2cm Flakvierling
- Schwerer Wehrmachtschlepper mit Behelfspanzerung: Several sub-types. To be covered in tank afv.com*
*In some sources some 770 schweren Wehrmachtsschlepper mit Pritschenaufbau were built until March 1945.
The Schwerer Wehrmachtschlepper in combat
A typical cargo load, model kit
Due to compromises regarding mobility, deployment with armored units or other fast-moving troops was out of the question; its low speed limited its use to infantry support. This limitation also contributed to losses during retreats on the Eastern Front, leading troops to use the available vehicles primarily for transporting supplies rather than as prime movers. Operational capability and troop confidence were similarly hampered in the case of the self-propelled anti-aircraft variants. Photographic evidence documents various guns towed by the sWS, revealing some of the vehicle allocations. Other allocations can be identified from unit inventory reports. Examples include (without claiming to be exhaustive):
-5t standard trailer:
Heavy Tank Destroyer Battalion 657 – 8.8 cm Pak 43 – (Report dated 8 February 1945 – 14 vehicles)
Heavy Tank Destroyer Battalion 668 – 8.8 cm Pak 43 – (Report dated 8 February 1945 – 22 vehicles)
Vehicle usually towing the 8.8 cm Pak 43/41 and 21 cm Mörser 18.
With only about 81 vehicles delivered with the improvised armored superstructure, just a small fraction was originally intended to serve as self-propelled anti-aircraft vehicles. However, photographic evidence confirms that light anti-aircraft guns were also mounted on a number of unarmored chassis, while vehicles with improvised armor were simultaneously employed as artillery tractors.
Two vehicles were documented in reports by US Army Technical Intelligence teams after falling into the hands of the 3rd US Army following the Allied advance. Chassis 150636 – Unarmored version (Report No. 175) – the vehicle bore American markings – photos of another destroyed vehicle are included in the report Chassis 150560 – Armored version (Report No. 217).
Specifications |
| Dimensions | 6.92 x 2.5 x 2.07 (22 ft 8 in x 8 ft 2 in x 6 ft 9 in) |
| Total weight | 13.3 to 13.5 tons |
| Crew | 2 +up to 12 troop |
| Propulsion | 4.198 L (256.2 cu in) gas. inline 6 cyl. WC Maybach HL42 TRKMS: 100 hp (75 kW) |
| Top speed | c30-50 kph |
| Payload | 4,000 kg (8,800 lb) |
| Transmission | ZF kb 40D |
| Suspension | Transverse leaf-spring and torsion bar |
| Fuel & range | 240 L (53 imp gal; 63 US gal), 300 km (190 mi) |
| Armament | See variants. |
| Armor | Late versions, see notes |
| Production | 825 |