Kettenkrad

Kettenkrad winter 1943/44 in Russia

Kettenkrad with trailer, Russia 1943

Kettenkrad (1943)

Kettenkrad type HK 101 (1944)

View of the Kettenkrad transmission tunnel

The Kettenkrad (full name: Small chain motorbike type HK 101 ; military name in the Wehrmacht : Sonderkraftfahrzeug 2 ( Sd.Kfz. 2 )) is a half-track vehicle with a motorcycle-like front structure. It was developed by NSU and built for the Wehrmacht from 1940 to 1945. It was the smallest of the Wehrmacht's half-track tractors.

Ewald Praxl and Ernst Schmidt were instrumental in the construction .

construction

The Kettenkrad basically consists of a self-supporting, open-topped pan made of sheet steel. At the front a motorcycle-like parallelogram fork is attached to the front wheel. On both sides of the tub there is a caterpillar drive in a box arrangement, each with a drive wheel at the front, four running wheels and a guide wheel at the rear. The running wheels are sprung via rocker arms and torsion bar springs .

The drive motor sits in the middle of the vehicle. The gearbox is located in front of the engine in the direction of travel, the radiator behind the engine, under the rear seat bench.

The driver sits in front of the engine on a motorcycle saddle astride the gearbox. Behind the engine there is a bench for two more people who sit against the direction of travel. This was a tactical disadvantage in military use, as the passengers could not secure with the front.

As usual with half-track tractors, the drive has rubber bands on the wheels and rubber pads on the chain links. Furthermore, the chain links are provided with sealed needle bearings and lubricated with grease.

properties

The Kettenkrad far surpassed the cross-country mobility of the sidecar and all wheeled vehicles and could also be used as a tractor for a light gun. Kettenkrads were also used at airfields to move aircraft on the ground. However, it was much more complex to manufacture and maintain. The chains alone have 80 lubrication points, which have to be lubricated every 500 km.

The vehicles reached a maximum speed of around 70 km / h. The engine of the Kettenkrad comes from the car Opel Olympia , whereby the engine of the Kettenkrad differs from the engine of the car by a different oil pan , transmission bell housing and some other attachments.

The 1,250 kg heavy vehicle was steered with small steering angles (up to approx. 8 °) with the help of the parallelogram fork and the front wheel. The fork corresponded to the design common for motorcycles at the time, but was made much more stable. Early versions were mechanically friction-dampened; from mid-1944 a reinforced fork with hydraulic shock absorber was used. In the event of larger steering angles, a steering brake activated and braked the chain on the inside of the curve. By consuming Cletrac - steering gear has been prevented during cornering inner chain completely stopped. Nevertheless, the smallest turning circle diameter was only three meters (based on the center of the vehicle).

In difficult terrain it was also possible to drive without the front wheel, but then only relatively slowly.

Braking system

In the Kettenkrad, the steering brakes are used solely for steering. To brake the vehicle, there are special travel brakes in the drive wheels of the chain drive. These are drum brakes working according to the duo-servo principle with expanding wedge actuation and a 400 mm brake drum diameter. It is operated solely by the driver's muscular strength, as in a car with a pedal on the right. The transmission device is purely mechanical via rods.

Production numbers

At first, production took place exclusively at NSU Werke AG in Neckarsulm , which built around 7,500 units during the war, 500 of which were pre-series. From 1943, Stoewer also manufactured around 1,300 Kettenkrads under license in Stettin , which results in a total of 8,800 vehicles. The highest production figures were in 1944.

The information on the number of items varies depending on the source; even official documents and annual reports from NSU contain different information.

It was originally planned that Simca should also build Kettenkrads in occupied France. However, there was no production of complete vehicles, but parts were made. Many Kettenkrads from NSU production contain gearwheels manufactured by Simca, recognizable by the Simca logo.

variants

In addition to the usual Kleiner Kettenkrad Sd.Kfz.2, apart from prototypes and planned versions, two variants were built. Both variants were specially equipped for laying field telephone cables and were used in particular on the Eastern Front.

Sd.Kfz. 2/1: Small chain motorcycle for remote field cables
Sd.Kfz. 2/2: Small chain motorcycle for heavy field cables

Behind the driver, the vehicles were equipped with a large frame above the bonnet to hold cable drums of the respective cable type. Remote field cable (FFkb) is a shielded four-wire cable for remote connections. Heavy field cable (Fkb) is an unshielded two-wire cable (twisted pair) for shorter connections.

The cable drums for the remote field cable are significantly larger and heavier (approx. 45 kg) than the cable drums for the heavy field cable (approx. 14 kg).

Technical specifications

Technical data NSU-Kettenkrad
Length: Width Height:	3000 mm 1000 mm 1200 mm
Seats:	3 (driver and two passengers)
Engine:	Four-cylinder OHV in - line engine , water-cooled, from the Opel Olympia car
Displacement:	1478 cm³ (old German tax formula ) 1488 cm³ (actually)
Bore × stroke:	80 mm × 74 mm
Compression:	1: 6
Power:	36 hp (26 kW) at 3400 rpm
Top speed:	70 km / h
Perm. Total weight:	1560 kg
Transmission:	3 forward / 1 reverse × 2-speed gearbox
Coupling:	Single-disc dry clutch
Fuel consumption: Tank capacity:	16–22 l / 100 km - depending on the terrain, more 2 × 21 liters
Carburetor:	SOLEX off- road carburetor type 32 FJ-II
Tires:	3.50-19

Large HK 102 chain motorcycle

At the same time as the well-known HK 101 small chain motorcycle , NSU developed the HK 102 large chain motorcycle . It was intended for the transport of six men (with driver), with emergency seats on the front fenders even for eight men (with driver). In order to carry the significantly higher weight compared to the HK101, an additional pair of impellers was required (three outer and two inner impellers per side instead of two outer and two inner impellers on the HK101).

The tub of the large Kettenkrad was basically the same as that of the small Kettenkrad. To accommodate the additional pair of wheels, however, it was extended by 30 cm; In order to accommodate the additional seats, it was also widened by 15 cm above the chains. The lower part of the tub and thus the track width of the drive remained unchanged. This leads to the overhang of the tub over the chains, which is visible in the factory pictures, while the tub on the HK101 ends with the chains at the side. This is a disadvantage in that the driver has to use the chain as a step when getting in.

A Ford V8 engine with a displacement of 2.2 l and an output of 48 kW (65 hp) served as the drive . There was a short cardan shaft between the engine and the gearbox. This created the foot space for the passengers sitting to the side of the driver.

About 30 prototypes were built. Only one of these vehicles still exists today. There was no series production.

Medium load carrier Springer, Sd.Kfz. 304

Attempts were made early on to build a remote-controlled load carrier based on the Kettenkrad. These vehicles were supposed to drive an explosive charge into a target by remote control and detonate it there.

The first vehicles were normal Kettenkrads HK 101, which were equipped with a radio remote control and a box at the rear to hold the explosive charge. The vehicles were used in the Crimea, among other places.

However, they did not do very well, as they often overturned when driving unmanned in the field and did not reach their destination.

In order to improve the driving characteristics during unmanned operation in the field, the medium load carrier Springer was developed from the Kettenkrad . The chassis was lengthened and now had six rollers on each side (three outer and three inner), but the front fork was omitted. The tried and tested Opel Olympia engine served as the drive again.

The jumper was able to pick up an explosive device weighing 330 kg and be guided into a target by remote control, where the explosive charge was detonated. The vehicle itself was destroyed.

Production continued after the end of the Second World War

After the end of the Second World War , NSU produced another 550 Kettenkrads from mostly still existing parts until 1948. Other sources speak of 1949 as the end of production. What is certain is that much later (verifiably in 1951) new Kettenkrads were sold from stock.

The Kettenkrads of post-war production were primarily intended for agriculture and forestry. Various fire departments in mountainous areas of southern Germany were also equipped with it. The production took place with the express permission of the American occupying power. This makes the Kettenkrad the only German military vehicle that continued to be produced in significant numbers even after the end of World War II.

The visible difference between a Kettenkrad from late war production and one from post-war production is the paintwork in the lighting system. On the chain wheels from post-war production, instead of the Notek camouflage headlight, there was a Bosch tractor headlight with a 130 mm light emission on the front fender . That is why the Notek multiple switch is missing from the dashboard. Instead of the Solex terrain carburetor with two float chambers, the normal Opel / Carter downdraft carburetor, which was already used in the pilot series, was installed again.

Babiole crawler tractor

Babiole tractor, Beltring (GB) 2002

In contrast to the post-war chain wheels built by NSU, which, except for the lighting, corresponded to the late war version , in France the Babiole establishments built caterpillar tractors for agriculture using chain wheel parts, which were constructed completely differently.

The most important difference was the reverse direction of travel. The Babiole caterpillar tractor drove ahead with the idler wheel. The driver's seat was at the back above the drive wheel, where the fork was on the Kettenkrad. As is customary with fully tracked vehicles, steering was carried out using two steering levers. Since the original engine and a slightly modified gearbox were used, the direction of rotation of the drive wheels had to be reversed. This was done by replacing the normal sprocket gears of the Kettenkrad with planetary gears. As a result, the drive wheel now turned the other way around, despite the same direction of rotation of the motor.

The structure was similar to the hoods of the other Babiole tractors. The radiator was in the front behind the radiator grille.

It is not clear whether the Babiole company converted used Kettenkrads for their crawler tractors or whether they only used remnants of Kettenkrad spare parts for the construction. The references are not clear in this regard.

The Babiole crawler tractor is not identical to the Kettenkrad except for the drive and parts of the drive.

Museum reception

Because of the unusual construction and the high level of awareness of the Kettenkrad, it is exhibited in many important technical and military history museums. These include For example, the Army History Museum in Vienna , the German Tank Museum in Munster , the Museum of Contemporary History in Stammheim am Main, the Auto and Technology Museum in Sinsheim , the Schleissheim aircraft yard , the Military History Museum of the Bundeswehr in Dresden and the PS store in Einbeck . One copy each has u. a. the Bovington Tank Museum in Bovington (GB) and the Musée des Blindés in Saumur (F).