Greeting all! I have been asked to do a little something on half-tracks. They are a supposedly a great idea. They
provide additional traction and reduced ground pressure. However, their one main moment of
triumph was World War Two. Where did they come from, and why did they go away? Stay
with us, and we’ll give you a quick breakdown. The first vehicle we would recognize as using
half-track principles today would have been the Lombard log haulers originally built in
the 1890s. These were steam locomotives, intended to drag a ‘train’ of about 100 tons of
logs cross-country, primarily across snow, and the front bogies at first ran skids instead
of wheels. However, useful though perhaps the Army corps
of Engineers might find the things, it would fall to a Frenchman named Adolphe Kegresse
to apply such a design to a more practical vehicle... Like Rolls Royces and other such
luxury vehicles which the Tsar had, and which he wanted to use to get around his lands when
it was snowing. He invented the Kegresse Track, which was basically a single piece rubber
track which ran around an idler and sprocket wheel, and was suspended on a bogie. The track
could be mounted onto the regular drive axles of the vehicle in question. They worked quite
well, and indeed, the Kegresse system became the most common half-track type built. The
design would have first seen combat in the Austin-Putilov half-tracked armored car of
the Russian Army, the Bullock-Lombard half-tracked armored car arriving shortly afterwards.
Though the Kegresse would be the design of choice in the future, it was not the first
such system to be used by the military, nor, indeed, to be used in the US. Enter a man
named H. H. Linn. Looking nothing as much as like a streetcar with strange running gear,
his traveling circus “The Linns and their Wonderful Educated Dogs and Monkeys”, I
guess folks were hard up for entertainment back then, Linn had Lombard create in 1909
a 26-foot long rectangular vehicle which ran on tracks where the rear truck on a streetcar
might be expected, and a four-wheel, two-axle bogie at the far front for steering. At 50hp,
this was something of a road locomotive, hauling a train of wagons at about 4mph. The tracks
provided additional traction. By 1915, Linn had parted ways with Lombard
and created his own tractor company, using half-track designs as their basis. He would
eventually build some 2,500 of these vehicles, the configuration would become familiar to
operators of heavy vehicles in particular. Meanwhile, over on the other side of the ocean,
a Holt 75 artillery tractor was in service with the French Army. A set of tracks at the
rear and a single wheel up front for steering. And, if you think about it, the first tanks
were also half-tracks, though the wheels on the Mk I were at the back. They were also
found to be all but useless and quickly discarded, a similar result happened with some of the
artillery tractors which could be made to steer with tracks alone.
However, by the end of the war, there was certainly more interest in the concept. The
US Army in particular took a serious look at the design, and a number of trucks from
Garford, Packard, Ford, Nash, and Mack were converted between 1918 and 1923, some more
successfully than others. In the meantime, Kegresse had returned on
the scene. Leaving the Bolshevik paradise of the new Soviet Union, he returned to France
and linked up with Citroen. The Citroen-Kegresse half-tracks turned into a resounding success.
Kegresse-bogie half-tracks were operated by the French, Belgian, British and Polish Armies
in numbers. Well, the British not so much in numbers, their Burford-Kegresse armored
personnel carriers were just too heavy and broke down a lot, the hundred or so built
being withdrawn from service in the early 1930s. A few Crossley Kegresse soft-skins
were also used as staff cars and scout vehicles. During WW2, the British attempted some conversions
like the Bedford Bren, which replaced the rear axle of Bedford truck with the running
gear of a Bren carrier, or even one copy of a German system, but they were not successful.
And then there were the Americans. In 1922, Virgil White invented the Snowmobile, a half-track
and skids conversion for the Model T, selling 25,000 of the things, and some users found
that keeping the front wheels in combination with the tracks made the Model T very suitable
on sand and mud. Then Citroen Kegresse sold two vehicles to the Army’s artillery branch
to haul 75mm field guns in 1925, and in 1931, tried to sell the US Army the P17 as used
in other European countries. It had all of 28 horsepower and ran at 18 miles an hour.
The US Army decided that the basic concept had merit, but that the pansy French engine
was insufficient. They contracted with James Cunningham and Son Company of Rochester New
York, and basically said “give us a half-track car on the Kegresse principle, but put a proper
engine into it”. So they did. The T1 was built later in 1931 and was armed with a Cadillac
V8 putting out 115hp. The half-track topped out at over 40mph, and the US Army was off
to the half-track races. By 1934, trials had started with replacing the leaf springs of
the Kegresse system with vertical volute springs, and this now became the pilot for the half-tracks
the US would produce in WW2. Eventually a couple dozen half-track trucks
T5 were fielded, these were softskin General Motors trucks. But in 1938, someone had ‘an
idea’: Convert a Scout Car M3 to a half-track configuration. The test worked, and White
was asked to build a half-track APC, to be called T14. This was the daddy of all the
65,000 or so US half-tracks which would be built through the war.
The design was simplicity itself. Take a regular truck, and just make the rear wheels bigger.
The driveline under the vehicle was identical to that of the M3 Scout Car from which it
was based. From the engine, the power went to a manual transmission, and from the transmission
a power shaft went aft to a regular differential on a straight rear axle. On that axle would
be found one sprocket wheel on each side. Thus, power would be applied to both tracks
at all times, including during turns – just like a regular car. Steering was performed
by turning the front wheels, and the effect was that overall driving was just like driving
a car which a lot of Americans knew how to do anyway. The tracks themselves were simple
8-wheel bogies with a pair of volute springs and continuous rubber track. Driving them
was a 6-cylinder inline putting out about 148hp.
In order to increase traction, and to help a bit with steering on really soft going,
the front axle could be engaged as on a regular 4x4. Some half-tracks had a winch on the front
to help either recover itself or other vehicles, the others had unditching rollers. Almost
all US halftracks came with a calibre 50 machinegun, many had one or two calibre 30s as well.
The American half-track was perfectly suited for mass production, and the half-track engineering
committee which consisted of Ordnance Branch and three manufacturers (Diamond T, White
and Autocar) created standards so that every part of the halftracks from every manufacturer,
excluding the armor plate, was interchangeable. Eventually International Harvester would join
the production fray, those half-tracks mainly being intended for lend-lease and running
a different engine. The US continued its experiments with half-tracks,
to include some three-quarter track designs intended to further reduce ground pressure
and using different bogies, but the move to full-tracked high-speed tractors removed the
requirements for them. Thus, that one design derived from T14 was the focus of the US mass
production effort. Though originally intended for scouting and
to be an armored personnel carrier, American half-tracks soon moved to other roles. 81mm
mortar carriers, a variety of anti-aircraft vehicles, 105mm howitzer carriers, gun tractors,
and sonic deception. More visible were the 75mm assault guns, which were found in the
tank battalions before being replaced by M8 HMCs, and the tank destroyers, which used
the French M1897 75mm gun, a slightly older version of the 75mm found on M3 and M4 medium
tanks, before themselves being replaced by M10s. A second tank destroyer, T48, was developed
to use the 6pr gun, 57mm in US terminology, but Tank Destroyer branch didn’t like it
due to the perception that the 75mm would be better at long range. As a result, the
T48s were shipped to the UK, and from there, on to the Soviet Union as Lend Lease where
it was known as an SU-57. The Soviets themselves took a good crack at
the half-track design, understandably given the things were basically invented there.
However, they didn’t find as much favour. Ten ZD-5s were purchased from Daimler Benz
in 1931. The BA-30 armored car was used only in the Winter War, and the ZiS-22 and 22M
wasn’t much better. The ZiS 42, however, was built in numbers, some 6,000 of the vehicles
being built and used as an artillery tractor, transport and anti-aircraft gun. The tracks
were Kegresse style, but the bogies sported near ground level idler and sprocket wheels,
making them a bit unwieldy over rough terrain. They weren’t as good as the 6x6 trucks the
US would eventually deliver, being very thirsty and underpowered, but they were still better
than the domestic truck offerings of the time. And so we move to the Germans. Where the American
design stressed simplicity and producibility, the Germans put the emphasis on capability.
Their half-tracks were very good at what they did, but they paid for it in a number of ways.
As would be typical for a German vehicle, the half-tracks came in a bewildering number
of variants from a number of manufacturers. Unlike the Americans, the Germans tailored
their half-tracks for use, with some being smaller and lighter than others. The fundamental
design features were developed by the German military in the early 1930s, and production
of the stereotypical German half-track started in 1934. By the time Germany kicked off WWII,
the half-track was a commonly found asset, particularly in artillery units as a tractor.
The standard German half-track design was what the US would consider a ¾ track, with
a long track length in contact with the ground giving great traction and low ground pressure.
To further increase cross-country capability, they were designed with Schactellaufwerk suspension,
the interleaved roadwheels. These provided excellent ride qualities, though of course
at the cost of increased maintenance time and the possibility of getting clogged with
mud. The tracks themselves were heavy duty, with individual links unlike the rubber-band
of the Kegresse track, each link having a good sized block to run on for traction. Presumably
annoyingly for the crew, each and every track link was needle bearing and individually lubricated,
meaning every link had a bolt which had to be removed, oil topped up, and placed back
in. Very easy running resulted. The US in 1946 replaced the running gear of an M24 tank
with that of an Sdkfz 8, and at low speed running resistance of the German track was
40-55% less than that of the American track. Of course, this came at a cost of man-hours
for the crews and mechanics. Probably manufacturers, too.
Also unlike the American half-track, the German half-track’s running gear came with a track
steering system. Though smaller changes of direction were applied in the normal car manner
by turning the front wheels with a steering wheel to allow normal turns without losing
speed, after a certain point the vehicle’s track system would be engaged, slowing one
track in order to assist the turn. Of course, this added to the complexity and cost of the
vehicle. About the only major concession to simplicity in the design was the fact that
the front axle was not driven, although given the size of the tracks behind, it’s not
quite as big a drawback as one might think. Though initially developed for towing purposes,
the possibilities of speed made it the prime candidate for German tank destroyer designs
of the 1930s, although in the end only two PzSfl II saw service in North Africa.
At the bottom end of the scale, no pun intended, was the 1-tonner, originally intended to tow
light loads like the 37mm anti-tank gun or the 2cm anti-aircraft gun. Tonnage in German
half-track descriptions was for towing force, not cargo capacity. These 1-tonners were mainly
made by Demag, but Adler, Bussing-NAG, MIAG, M.N.H, Mechanische Werke Cottbus and Saurer
all got involved. The Sdkfz 10 was the vehicle in unarmored form of which 13,000 were made
and named Sdkfz 250 if armored, 7,500 or so of those were made. The armored half-tracks
were designed with excellent armor protection for the weight, with good quality steel and
slopes. However, there were never enough of those, or the larger 251s, to meet the establishment
requirements. Though we associate the Panzergenadiers with leaping out of their half-tracks into
battle, they were often lucky to have a company per regiment. Indeed, 251s were almost unheard
of in the North African campaign. Still, with good armour and a shielded machinegun, the
vehicle was a useful support asset to the troops.
The 251 itself, of which some 15,500 were made was the armored variant of the 3-ton
Sdkfz 11, the chassis differing in detail. Manufactured by Hansa Lloyd and Hanomag, the
3-tonner was developed to haul the 10.5cm howitzer, but eventually the series came to
perform almost any tactical role the German army could think up. Artillery and ammunition
hauler, engineer vehicle, anti-aircraft vehicle, anti-tank vehicle, assault gun, rocket launcher,
poison gas dispenser, decontamination vehicle, radio vehicle, artillery observation vehicle,
flamethrower, command track, ambulance, counterbattery acquisition, infra-red illuminator… Think
of a task, a 3-tonner was probably doing it. The 5-tonner, SdKfz 6 was mainly a Bussing-NAG
product, 3,820 being built, of which about 800 were actually made by Daimler Benz and
BMM. Mainly used by engineering units, they found a secondary use as an artillery hauler.
200 were equipped with a 3.7cm flak gun. Built mainly by Krauss Maffei and Hansa Lloyd,
11,000 the 8-ton SdKfz 7 were mainly artillery towing vehicles, either for indirect fire
pieces or, in the early war, hauling 8.8cm guns to deal with bunkers and heavy French
tanks. Some 2,000 were equipped for anti-aircraft purposes, with a quad 2cm or single 3.7cm
gun. The Sdkfz 8 was the 12-tonner, and the oldest
of the family. Daimler Benz had the headstart on experience from the ZD-5 sold to the USSR.
Production started in 1934, but by the time WW2 began, the vehicle had improved to a 14-ton
pull capacity. About 4,000 of the vehicles were made. Two dozen were converted before
the war to become self-propelled mounts for the 8.8cm Flak. Placed in Panzerjaeger units,
they were primarily to be used as assault guns to destroy bunkers, but they had a role
in destroying any heavy armor which might have gotten into their way. In addition to
hauling large artillery, it was also used as a tank recovery vehicle. They also came
with a 5-ton winch as standard. Finally, Big Daddy was the FAMO SdKfz9, the
18-tonner. This very capable half-track was developed to haul the heaviest artillery such
as the 24cm gun, the 35.5cm howitzer and the 12.8cm FlaK. It was also used as a tank recovery
vehicle, though at an 18-ton haul provided by the 12.8 litre, 250hp V12, it still required
three of them combined to haul a Tiger I. 6-ton and 10-ton crane variants were also
made to aid the mechanics. The catch was that the vehicle was about as difficult to make
as a Panther, but they still made about two and a half thousand of them.
There was an attempt to simplify the system with the creation of the Schwerer Wehrmachtsschlepper,
a 8-ton half-track designed by Bussing-NAG. It wasn’t particularly successful. The heavy,
dry-pin tracks and the 100hp engine resulted in it having great traction, but low speed.
Too slow to do the intended job of hauling artillery, the 850 or so made mainly ended
up in the supply trains. The one major type of German half-track not
mentioned thus far is the Maultier, or Mule. These were conversions of standard trucks,
a bit like the American halftrack in that context, which had their rear axles replaced
with the suspension systems of, mainly, older Carden Lloyd designs. They were developed
primarily for the poor conditions found on the Eastern Front. Somewhere over 22,000 vehicles
were produced, of which about 5,000 were based on the Opel Blitz, and 14,000 on the Ford
V 3000 S. Maultiers were designated SdKfz 3 and 4.
Lastly, there’s the SdKfz 2, the kettenkrad, which was more of a half-track motorcycle.
Originally designed for the Luftwaffe as a tractor for paratroopers and as an aircraft
tug, the Army started using them to haul small trailers and as an off-road runabout. They
maintained the complex lubricated links and the track steering systems of their larger
cousins, but after the war became popular as agricultural vehicles, and arguably the
first recreational ATV. There is one more country to visit.
After seeing the success of the German mechanized units in 1940, the Japanese decided that this
whole tank division business had some merit, and it was obvious that the troops needed
to have transport similar to that provided to the Panzergrenadiers. Hino Motors took
on the challenge in 1941, and by 1944, the Type 1 Ho-Ha had entered production. Pretty
obviously influenced by the 251, the vehicle was also a ¾ track design, but the suspension
was domestically designed instead of using the german interleaved system. As with the
rest of the Japanese plans for armored divisions, production wasn’t even close to meeting
establishment requirements, and it had a curious failing in that none of the three machineguns
would fire to the front. Despite over 100,000 half-tracks being used
through World War II, the design suddenly fell out of favour. The only notable post-war
producer was Czechoslovakia. Skoda and Tatra had been involved in SdKfz 251 production,
so to equip the Czech Army, they dusted off the plans, put in a better engine, added overhead
cover, and replaced the maintenance-intensive wet-lubricated needle bearing track with a
much simpler dry pin system. Tatra also built the Schwerer Wehrmachtsschepper after the
war as the T809. Though WW2 American half-tracks would continue
to see a long service life abroad, particularly with Israel, with less of a stress on time
production moved to full-track vehicles. That move had already started by the end of WW2.
There is currently one vestige of the half-track still in military use, and that’s the attachable
band which can be fitted to dual-rear-axle vehicles. Similar to the original track found
on the Ford Model T Snowmobile, by World War Two, a track was developed to be fitted around
the rear wheels of the CCKW deuce-and-a-half truck. They didn’t replace the wheels, they
were quite simply a track which went around them, and as such lacked the sprocket drive
and risked some slippage. Some Soviet truck designs could have them fitted as well. However,
though these days over-the-tyre tracks are mainly found in civilian applications, if
necessary, they can still be fitted to the military trucks
of today. And that brings us to pretty much
the end of the story of the half-tracks. Hope you find it interesting and informative. And we return you now to your
regularly scheduled host.
