The Kettenkrad – is it a Motorcycle or a Tank?

The Kettenkrad is a truly unusual vehicle for the simple fact that no other vehicle like it has entered service, either before or after. It combines features of a motorbike with a tracked chassis, a combination that looks as weird as it sounds but actually became one of the most capable vehicles in existence over rough ground.

Measuring just 1 meter wide and capable of reaching 44 mph, the Kettenkrad was a mobile, nimble and fast little machine that could go anywhere and do anything.

And that is exactly what happened: the Kettenkrad would be used from laying cables across the battlefield, to towing German jet fighters.

Join us as we take a look at the fascinating German Kettenkrad.

Contents

Introduction

The creation of the Kettenkrad is credited to German engineer Heinrich Kniepkamp.

Kniepkamp is an intriguing and important character in German tracked vehicle design. Throughout the 1920s and 1930s he played a significant role in their development, and was a big advocate for the half-track concept Germany made famous. He would later join Wa Pruef 6, the office in charge of the development of new tanks, where he was involved in the projects like the Maus and E100.

In 1938 he came up with the idea of a very small half-track motorcycle that could be used for civilian and military purposes, such as logging or pulling loads through tight areas. The half-track concept had already been successfully explored on larger vehicles as a way of combining the mobility of fully tracked vehicles with the practicality of a truck.

He introduced the idea to motorcycle manufacturer NSU, which designated the vehicle HK 101 (“HK” likely stands for Heinrich Kniepkamp). The HK 101 had a small open-topped tracked chassis with a motorcycle-style front wheel and handlebar at the front and its engine in the center.

Kettenkrad with two passengers.
The tracks provided the vehicle’s propulsion, while the front wheel steered.

It is often argued that there was no need to make such a small half-track, but thanks to the traction provided by its tracks, Kniepkamp’s HK 101 would provide excellent mobility and transportation potential in areas larger vehicles simply could not navigate, such as up mountain trails and through forests.

However, the Wehrmacht took a look at the vehicle around the time war broke out in 1939 and was not impressed by its small size and load-pulling capabilities. Not long after this though, the vehicle received renewed interest, and a test batch of 70 HK 101s was ordered.

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A number of problems with the design were found, but these were soon eliminated and a further 500 were ordered in mid-1940.

The HK 101 officially entered service as the Sd.Kfz. 2 in 1941. It was better known as the Kettenkrad, a name derived from “ketten”, which is German for “tracks”, and “krad”, which is a shortened version of German word for “motorcycle”; “kraftrad”. Therefore, Kettenkrad means “tracked motorcycle”.

Kettenkrad in mud.
The Kettenkrad was popular because it was small yet powerful. Here, a Kettenkrad is carrying three passengers and pulling a loaded trailer with a person on top through thick mud. The wheels of this trailer could be used for the Kettenkrad’s front wheel.

This name was eventually used officially by the German military, but it was not actually considered a motorcycle. Technically it is a tractor or prime mover, as it was designed for moving equipment and supplies.

In reality, the Kettenkrad did not have a particular “role”, as German troops used it for just about everything. And, because it possessed exceptional off-road capabilities, it was taken just about everywhere.

The Kettenkrad’s Design

The Ketten is renowned for its complexity, but in reality the Kettenkrad doesn’t have any particularly revolutionary or advanced technologies. It is probably more accurate to describe the Kettenkrad as unreasonably complex for a vehicle of its size.

Its tracks and running gear are most responsible for its reputation. Each track link is connected to the next with lubricated needle bearings, and each link has its own lubrication reservoir. This reservoir is inside the track guide horns, which are hollow.

The links are protected by replaceable rubber pad on the outside. The road wheels are interleaved in three layers, with the outermost wheels being a different type to the rest.

Sd.Kfz. 2 running gear.
The Kettenkrad’s running gear was inspired by larger German half-tracks. Image by ChiemseeMan.

At the rear is an idler wheel, which can be adjusted to maintain the correct track tension.

The sprocket wheel is located at the front of the track run. Unlike most conventional track sprockets, which engage the track directly with teeth, the Kettenkrad’s sprocket teeth are actually metal rollers that rotate as they come into contact with the track links. This is the same type of sprocket used on other German half-tracks, and helps reduce wear on the tracks.

Interestingly, while these tracks are much more complex than conventional tracks, they can last the life of the vehicle if properly maintained. The problem for Germany was that in action, there’s a high chance vehicles will not receive their required maintenance, making what was once a clever idea into a burden.

Suspension was of the torsion bar type, mounted sideways on the bottom of the hull.

At the front of the Kettenkrad’s main body between the sprockets was the gearbox. It was a crash-type gearbox with three forward gears and one reverse gear, and incorporated an auxiliary gearbox for low-range and high-range options. This doubled the available gears and would be selected depending on whether the Kettenkrad was off-road or on-road.

Kettenkraftrad rear bench.
The rear of the Kettenkrad had space for two passengers. The vents on the rear panel are for the radiator.

Behind the gearbox, in the center of the vehicle was its engine, a four cylinder, 1.5 liter Olympia model 38 that produced 36 hp.

At the rear of the Kettenkrad was the engine’s radiator.

The gearbox engine and radiator were covered by an unarmored steel body. At the rear of this body was a small bench large enough for two passengers and a tow hook for attaching equipment and trailers.

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The operator sat on a sprung seat at the front of the Kettenkrad inside a “tub” that surrounded his lower half. It contained the gear selector, dials, clutch pedal, brake pedal and the steering handlebar. This handlebar connected to a single un-powered front wheel, reminiscent of the type used on motorbikes.

This wheel and handlebar steering made the Kettenkrad much easier to drive at high speeds compared to tracked vehicles, and enabled the driver to more comfortably counter the natural tendency of tracked vehicles to slide down the camber of roads. In some circumstances, the large-diameter front wheel allowed the Kettenkrad to climb taller obstacles than it ordinarily should be able to, as the front wheel can roll up the obstacle while the tracks push it forward.

Kettenkraftrad front wheel.
The front wheel was used for shallow turns. Image by Rama CC BY-SA 2.0 fr.

However in particularly rough conditions such as deep snow or mud, it was officially recommended to remove the front wheel and rely entirely on the tracks.

All-in the Kettenkrad measured just 3 meters long (9 ft 10 in) and 1 meter wide (3 ft 4 in), and weighed 1,235 kg (2,700 lbs) empty. The Kettenkrad’s maximum weight was 1,560 kg (3,400 lbs), which includes a crew of three people.

Although it only had 36 hp, the Kettenkrad was still a rapid little machine with a top speed of 44 mph.

How Does it Steer?

One of the most common confusions surrounding the Kettenkrad is its steering. Does the operator have to lean like on a motorcycle? Does it have tillers like a tank? Do the tracks bend like the Bren Gun Carrier?

The Kettenkrad has two means of steering; its front wheel and track braking.

For shallow turns, or when steering at high speeds, steering is done entirely with the front wheel.

Once the handlebars have turned past 5 degrees, a track-braking system takes over.

Kettenkrad driver's position.
The operator’s position. Note the handlebars on the left. Image by Zandcee CC BY-SA 3.0.

This is achieved by the front steering column above the wheel. When the column rotates past 5 degrees left or right, it engages with a tab around the column that then starts pulling on a rod. This rod connects to a lever, which when pulled actives the brake on the corresponding side. For example, if you turn the handlebars far enough left, the left track brake will be applied.

Then, the path of least resistance through the differential becomes the unbraked side, so more power is sent through further aiding the steering effort.

This system is mechanical and not hydraulic, as is often erroneously stated.

Service

The Sd.Kfz. 2 Kettenkrad was one of the most unusual vehicles to see service during the war, with few other vehicles that can even be considered contemporaries. The closest thing to it is perhaps the British Bren Gun Carrier or tankettes like the Carden-Loyd, although both of those vehicles had some form of armor.

As mentioned near the start, the Germans did not have one exact “role” for the Kettenkrad, and it found use in many different activities. It was first used on the island of Crete, where it was flown in inside JU-52 transport aircraft.

Throughout the war they would be used as simple modes of transport, reconnaissance vehicles, gun tractors and cable-layers. Some Kettenkrads were famously used as tugs to pull German aircraft around airfields.

Kettenkrad pulling a truck in mud.
Here, a Kettenkrad is being used to pull a stuck truck in deep mud.

They were very practical vehicles, useful for quick trips or pulling something through thick mud or up a winding trail. It is said that their off-road capabilities were so good that they were last vehicles to be stopped by Russian winters. Even Allied troops would use them where possible.

A few different iterations of Kettenkrad were produced during the war, mostly relating to updates to improve its practicality and ease of production. There was an attempt to create a version with increased passenger capacity known as the HK 102, but this version would not enter production.

The production run of the Kettenkrad (including pilot vehicles) lasted from 1940 to 1945. When the war ended, the desperate conditions within the devastated Germany meant many Kettenkrads found themselves in civilian agricultural use to help feed the nation.

Kettenkrad tractor variant.
One of the post-war variants of the Kettenkrad was this, the French Babiole Crawler Tractor. It was chassis was reversed, and used as an agricultural tractor. Image by Andreas Mehlhorn CC BY-SA 4.0.

The Allies even allowed NSU to restart production, which lasted until around 1948 or 1949. Some of the vehicles produced during this time were rebuilt examples.

As a result the total number of Kettenkrads is unknown, although the number is somewhere around 7,500 to 9,500.

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Today, due to its rarity and small size the Kettenkrad is a popular vehicle among collectors, and many are still operational or are in the process of being restored. They can be seen at military shows, museums and enthusiast gatherings.