Unarmored Half-Tracks

Half-track vehicles have consistently captured the imagination of automotive engineers, and for good reason. Although they do have some of the inherent problems found in any tracked vehicle, they have generally exhibited characteristics that are the best of both worlds: good weight-carrying ability and cross-country capability combined with relatively high speed, and ease of maintenance.  Furthermore, most half-tracked vehicles used many components that were interchangeable with those found on similar wheeled vehicles, and this was a real advantage in maintaining a large fleet.

 The concept of a half-truck/half track vehicle appeared in the United States around 1916.  One of the earliest builders was the Holt Tractor Company, which marketed large commercial tractors and also made a track laying adapter which was to be attached to an ordinary 4x2 truck of about three tons' capacity, totally replacing the driving rear axle.

Coming late into WW1, The United States did not become as "geared up" as other nations already at war. Because of the late entry, the U.S. tended to purchase equipment from other nations. After the war, as typical for the U.S. in that period, extreme budget cutbacks where enacted on the military. Many of the vehicles below were simply presented to the Army for testing. Many were rejected because they were found wanting, others were rejected simply out of lack of funds. On the positive note, all the years of "tanklessness" and testing in the U.S. produced the finest automotive track/suspension/engine combinations used by any nation in WW2.


Photo provided by Dr. Andre Maurois
Holt 2.5 Ton Prime Mover

Details unknown


Photo provided by Dr. Andre Maurois
Holt 5 Ton Prime Mover

Details unknown


Holt 10ton Prime Mover - Photo provided by Dr. Andre Maurois
Holt 10 Ton Prime Mover

Details unknown


Holt 15ton 1917---Holt 15ton Prime Mover - Photo provided by Dr. Andre Maurois.
Holt 15ton 1917

The Holt Tractor Company was a pioneer in the development of industrial and tracked tractors, and the Army evaluated their 15-ton model during the early months of 1917. Although these monsters eventually evolved into full track-laying vehicles, the early models used a separate steering front wheel and were essentially halftracks. Holt made no effort to shroud the engine, and considering the massive size, almost straight-through exhaust, elaborate gear mechanisms and steel-on-steel track assemblies, they were slow and noisy. Despite its 20-foot length, it had a turning circle (inside diameter) of only 10 feet. A total of 232 of these 15-ton vehicles were shipped to the war in Europe before the Armistice; the Army's first order of 200 had been delivered between November 1917 and April 1920.  Weighing just over 25,000 pounds, they were employed primarily to pull field artillery weapons. They were replaced by the 20-ton version.


Holt 20ton---Holt 20ton - Photo provided by Dr. Andre Maurois.
Holt 20ton

The 20-ton version of the Holt half-track artillery tractor is seen here ready for issue to the Army. Although similar in appearance to the earlier 15-ton model, it was 21 feet long, weighed around 27,000 pounds, and had a 2,119 cubic inch, 120 horsepower six-cylinder engine which produced 15,500 pounds draw-bar pull in low range, 11,500 in high.  The maximum speed was the same as the 15-ton: 2.1 and 3.5 miles per hour.  These low road speeds were achieved by the use of a very large flywheel in the center at the extreme rear, which used small sprockets to drive large chains on either side, which in turn drove through a large sprocket and shaft to the large sprocket visible at the rear of the track assembly. The 71.5 gallon fuel tank was at the driver's left, while a massive water tank was mounted along the right side of the engine. Note that the six-cylinder engine has four straight-through vertical exhaust stacks. The front wheel was steered by means of open gears. These tractors could still be found in Artillery units in the early 1930s.


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Garfield-Holt 3 Ton 1918

The idea of using tracks or "Caterpillar treads" to assist in ground locomotion seems to have been applied both in full-and-half-tracked versions about the same time. One of the earliest attempts to add a track assembly to a truck to enhance mobility seems to have been this Garfield-Holt model. Photographed in June 1918, the original caption states that the vehicle was "specially designed for Quartermaster Corps." It must be remembered that the QMC was responsible for procurement of all motor vehicles from around 1912 until 1942 except those which were designated as Ordnance types (wreckers, ammo carriers, artillery prime movers, etc). Holt (later known as Caterpillar) offered such adaptations to private purchasers as well. This version, a 3-ton Garfield Model with non-driving front axle, is representative of the total concept: a standard production truck with the Holt unit replacing the rear axle.   The Garfield only achieved about 7 miles per hour with the Holt device. Normal maximum speed would have been around 20-25 miles per hour.


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McKeen FWD Model B

Any design, which enhanced cross-country mobility, would be sure to attract the attention of the military, and one of the earliest pure military applications of the half-track was this balloon winch version by the McKeen Motor Car Co., based on the ubiquitous FWD Model B, which had been introduced in 1913. Of course the FWD had all-wheel drive, which means that while the Holt unit gave the rear of this very heavy unit good flotation over soft soils, the driving front axle also did its part. The FWD was powered by a 389 cubic inch four-cylinder engine which produced 36 horsepower, and drove through a three-speed transmission which was mounted in the center of the chassis. A five inch wide belt-type chain then drove a side-mounted differential just ahead of the left track device, and drive shafts went along the left side of the chassis to the axles. A pair of radius rods were also mounted on each end of the differential and served to keep the axles aligned. The large engine at the rear was strictly to power the winch.


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McKeen Balloon Support Vehicle 1919

The use of observation balloons for directing artillery fire was a worldwide practice during the Great War and for many years thereafter. It required that the balloon be taken on the ground to a position near enough to the enemy to make a visual observation, and the balloon then inflated. Once airborne, the balloon, with the observer's gondola hanging underneath, was quickly allowed to rise while tethered to a steel cable. The observer stood in the gondola with a pair of binoculars and as soon as he had made note of the enemy positions, he used wire communications to call the information back down to the artillery units. Rapid ascent and descent were obviously critical, and could help add to the fife span of the observer. This view shows the Holt-adapted FWD with all of the shrouding in place. The McKeen Motor Car Co. of Omaha, Neb., built this unit around 1919. Note that a second FWD radiator was mounted at the rear to provide cooling for the big six-cylinder engine that powered the balloon winch assembly.  The McKeen Company usually built railroad cars.


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Nash Quad 1919

A half-track with a driving front axle was this artillery caisson-bodied Nash Quad of about 1919.  The Nash Quad achieved about as much fame in WW I as did the FWD Model B, and both were reasonably versatile and reliable, considering the era of manufacture.


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Packard 3-Ton 1918

A 3-ton Packard truck chassis of 1918 was the basis for this Classed as a two-ton model, the Nash (and later Jeffery) half-track vehicle being put through some mobility tests prior to delivery to the Army's Quartermaster Corps. The unit had a 349 cubic inch, 32.4 horsepower Packard engine and a four speed transmission.


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Hadfield-Penfield / Fordson 1922

One of the simplest concepts was to take one of the best small farm tractors of the day, the Fordson, and try to give it more mobility by adding a half-track device. Sadly, the tilt of the engine, caused by the new rear tracks being lower than the original big rear wheel, gave it poor lubrication. Engines in that era used the “splash” system of lubrication unlike engines today that use an oil pump. Even so, 4 were purchased at $945 apiece ($395 for the tractor and the rest for the Hadfield-Penfield conversion). The Fordson tractor used a 251 cubic inch, 4-cylinder engine. The engine, whose top revolutions being 1000rpm, produced 21.5hp. The total weight was 4120lbs.


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Hadfield-Penfield / McCormich-Deering 1926

Another Hadfield-Penfield conversion. This time it was applied to a McCormich-Deering tractor (later known as International). An engineering redesign allowed this model to at least sit vertical as compared to the Fordson conversion. The conversion was of a McCormich-Deering model 10-20. This unit had a 19hp, 4 cylinder engine with a 4 speed transmission. Although the vehicle performed better than the Fordson, it was still considered lacking. The test report stated "... possesses all the disadvantages of both wheeled and full tracklaying types and none of the advantages of each." The report also recommended that this vehicle be given to the Ordnance Museum. It is not known if this actually occurred.


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Mack-Christie Wheel-Caterpillar 1922

J. Walter Christie designed a track device to enhance a truck's ability to move across unimproved terrain. Applied to a Mack AC chassis of 5.5 tons capacity, it was evaluated in Aberdeen in May, 1922.  It consisted of a Christie-designed final drive ahead of the front axle with chains driving all four wheels, with a track device fitted tightly over the solid rubber tire wheels.  Known as the Mack-Christie Wheel-Caterpillar, it claimed to be a "four wheel drive" system. The front axle, however, was non-powered. The Mack AC used a water-cooled 471 cubic inch displacement engine with four cylinders and 40 horsepower, and utilized a three-speed transmission.  According to an Aberdeen letter of May, 1922, the track itself failed, the vehicle was almost totally immobilized without the track, the engine overheated constantly, and the transmission had heat-producing friction, a grinding noise, and oil leakage. The truck was returned to Mr. Christie.


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Various Christie conversions of Mack trucks 1923-28


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Mack Roadless

This view of the 11,500lbs AB-based Mack Roadless clearly shows the clean design of the AB-series, with its traditional placement of the radiator ahead of the engine instead of at the firewall as with the larger AC. The engine was a 4-cylinder, 28 horsepower model which displaced 251 cubic inches. Unlike the model AC that was usually fitted with an open "C" cab; the AB was of often fitted with a closed cab similar to the one seen here. The front tires were of solid rubber, 36 x 5, and since the AB did not have front wheel drive, hollow drums were fitted to the outsides of the wheels to assist in flotation over soft soils. It carried 30 gallons of gas, enough to drive the vehicle only 50 miles, at 3 to 8 miles per hour. The Ordnance officials liked the Roadless; especially the very serviceable track mechanism, although they felt a larger 6-cylinder engine would have been better.


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Nash Quad 1923

The Nash Quad was also a prime candidate for the application of any traction-enhancing device such as a halftrack assembly, as it used a driving front axle as did the FWD. Essentially a 2-ton 4 x 4 known to Jeffery (later Nash) as the Model 4017, it relied on a 288 cubic inch displacement Buda gasoline engine of 32 horsepower, driving through a four-speed transmission. The body seen mounted on the Nash had a very explicit goal in life. Referred to as a caisson body, it was designed to carry artillery ammunition, and to follow the big guns wherever they were to be emplaced.  The photo was taken at Aberdeen Proving Ground in December 1923, and shows a Holt device that did not have return rollers to keep the track taunt.


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Nash Quad/Holt 1924

A quick comparison with the photo of the Nash Quad/Holt vehicle taken at Aberdeen will show the addition of track return rollers to help maintain tension on the track.  Although many early track development authorities tended to feel the weight of the steel track would keep it in place on the sprockets, they rapidly found that turns in substandard soils would run the tracks right off and onto the ground. Modifications were introduced to assure that track tension remained sufficient to keep the track on the sprocket and idlers. This photograph, perhaps taken in 1924, clearly shows the unusual "cab" found on the Quad. Although appearing to be a cab-over-engine layout due to the forward placement of the cowl, in fact the driver sat in essentially a conventional location: to the rear and left of the engine, while the engine itself occupied the majority of the "cab" floor, covered by a sheet metal housing. Hudson, National, and Paige also built quads during the Great War under license.


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Class BBW

The Army wanted to test a half-track with a driving front axle. They acquired the components and assembled it all at the Quartermaster shops of Fort Holabird Maryland. It used 40 x 8 tires on the front and a 64.5” track using a Coleman axle. The vehicle weighed 24,000 pounds gross weight. The truck was evaluated during 1929 and had angles of approach and departure of almost 45 degrees. It could ford 18” of still water and required 64 feet to make a turn. Unfortunately, this vehicle only got 3 miles per gallon of gas.


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French Citroen-Kegresse P17 1931

The Citroen-Kegresse P17, it was most assuredly the state-of-the art half- track at the time, and it certainly warranted a close look by the Ordnance Corps. The P17 and its predecessors had been highly successful in service with the French military, and had seen thousands of hours of desert service. A relative lightweight at 4,300 pounds, it could pull 3,500 pounds cross-country and carry close to 1,000 pounds.  During tests it pulled a 75mm field gun, and the 27 horsepower four-cylinder, 100 cubic inch Citroen engine allowed a speed of 18 miles per hour.  It was 167.5 inches long, 62.5 inches wide and 78.5 inches high.  The steering was quite advanced in that along with normal steer of the front wheels, a mechanism also activated the brakes on the respective track. The vehicle was not adopted by the U.S. Military.


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Ford Cunningham 1933

This early Cunningham half-track has been mated to a 1932 Ford 1.5 ton, 4 x 2 truck, and was photographed at Aberdeen in August, 1933. It used Ford's 50 horsepower four-cylinder flat head engine and 4 speed transmission. Although not accepted into service, it did test well and good remarks were written about it's performance.


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Cunningham T1

The military half-track for the U.S. Army finally reached the serious stage in the form of the Tl.  Photographed at Aberdeen the third day of January 1933, it had just been completed by the James A. Cunningham Company in Rochester, N.Y. The Army told Cunningham what it wanted, and the private firm to designed and built the vehicle.  The Tl was the first of a series of Cunningham-built half-tracks, and they helped the Army establish just what it was they needed. Initially intended as prime movers for light artillery, by the mid thirties they were pretty well established as reconnaissance vehicles as well. No top was fitted to the Tl, a deficiency corrected in subsequent models.



T1E1

The advent of the TlEl brought about several improvements. As photographed in June 1933, it featured a heavy C-section non chromed front bumper a radiator brush guard, no cab doors, a wider seat, equipment storage boxes and fuel tanks over the rear fenders, and a framework supporting a tarpaulin top. A solid rail in the track assembly supported the rear idler wheel.  The Army’s Rock Island Arsenal in Illinois carried out the modifications that created the TlEl.



T1 Series Engine

Cadillac's V-8 engine was the source of power for the Tl series half-track cars. It was a 353 cubic inch model that developed 115 horsepower at 3,200 rpm. It was known for its reliability and durability. The Cadillac allowed the Tl to travel only 144 miles on the 40 gallons of gas it carried, or about 3.6 miles to the gallon. Top speed in fifth gear (overdrive) was 42 miles per hour.



T1E2

Combat loaded and ready, this TlE2 posed at Fort Knox, probably around 1937. Now displaying an authentic USA registration number, it also has a tow cable wrapped around the bumper and, most important, three pedestal mounts for Browning caliber.30 machine guns (Ml9l9 series): one to the right of the cowl, and one on each rear fender. Sometimes known as the M1, it had no rail going to the idler wheel, and a simpler roadwheel support assembly is also evident.  The eight-pointed star insignia with eagle in flight indicates the TlE2 belonged to the 1st Cavalry Regiment Mechanized, and the insignia below refers to the 1st Machine Gun Company.



T1E3

The original T1 Half Track Car seems to have been use as a basis for creating the TlE3. The narrow body of th T1 is evident, along with frontal features of the earlier types. The goal of the E3 was apparently to develop a more satisfactory track system.


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Linn

Manufactured commercially by the Linn Mfg.  Co. of Morris, N.Y., especially for extremely heavy-duty off-highway work, the Army thought they might make good cross-country vehicles.  Seen here carrying a TlE6 Light Tank (weight: 19,900 pounds), it was being evaluated in Aberdeen in June 1933.


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GMC T4

GMC continued their development of half-tracks in cooperation with the James Cunningham Co. In April, 1934.


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GMC T5

The third variation of the GMC-Cunningham half-track truck was known as the T5, and debuted in early 1935.  The engine size was now up to 401 cubic inches, and it’s 125 horsepower (at 2,800 rpm) allowed speeds up to 40 miles per hour on hard roads and 17 miles per hour over unimproved terrain.  The T5 was designed to tow the 75mm pack howitzer MlAl seen here. The vehicle on the left belonged to Batt B, 68th Field Artillery Battalion, and was participating the 3rd Army maneuvers in 1940. The picture on the right is a rare version that used a canvas top. The canvas top was not considered satisfactory.


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Linn T3 Half Track

The Linn half-track appeared in limited numbers in the Army inventory in two models during the mid-1930s. This 1933 version, designated T3, had the same basic specifications as the earlier model, but featured a cab complete with weather protection, a winch, and a steel cargo body with top bows and tarpaulin. The American La France V-12 was still fitted, and it was expected to pull field artillery guns weighing up to 15 tons. The T3 weighed 17 tons itself with fully loaded. The speed of this 22-foot long vehicle was a respectable 20 miles per hour on firm roads, but only 2 miles per hour off the road. The average fuel consumption was a 1.7 miles per gallon. The pneumatic tires were 9.75x2O. The wheelbase was 192 inches measured at the center of the track mechanism. The T3 required almost 66 feet to turn around under good conditions, as it did not have the capability of braking the inside track to assist in turning.


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Linn T6 Half Track

Linn's T6 is shown here prior to delivery to Aberdeen Proving Ground in July, 1934. It was just as ponderous and massive as its predecessors had been.    The extra-wide frame that encompassed the entire track assembly can be seen in this view. Although it was a very heavy and noisy vehicle, it was also extremely rugged and capable of carrying heavy loads for sustained periods. The T6 had a road speed of 15 miles per hour (off-road was 10 miles per hour), and a five-speed transmission carried the 174 horsepower of the big 935 cubic inch Hercules model HXE engine back to the 14 inch wide rear tracks.  Weighing 35,000 pounds loaded, it needed 35 feet to turn its 20.5 foot length and 156 inch wheelbase. Only one T6 was built.


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Ford-Marmon-Herrington T9E1

One of two unarmored half track vehicles to ever go into full production. From Left to right shows the metamorphosis of the pilot version to the full production vehicle.

The pilot model of the Ford-Marmon-Herrington T9El half-track truck used only two roadwheels, probably in an effort to reduce weight and complexity. A volute spring was encased in the housing in the center of the assembly, and provided the suspension, while two small return rollers were mounted on the top of the housing.  The differential-axle assembly was mounted about 18 inches behind the cab, and the rear idler is identical, probably in an effort to standardize components. The pilot was 19 feet 1 inch long, and weighed 11,585 pounds.  It had 8.5 inch wide tracks which were 71 inches long.  The turning circle was 55 feet, while the wheelbase was 131.5 inches long.  At 3.7 miles per gallon average, the 85 gallons carried by the T9El allowed a range of only 300 miles.

The production versions of the Ford-Marmon-Herrington half-track truck were known as the T9 or T9El. The T9 pictured here still used the four roadwheel rear bogie, with a volute spring in the center housing providing the basic suspension. Despite the redesign of several components to lighten them, this early T9 still weighed 11,430 pounds gross, 3,000 pounds of which was payload. It could climb a 25' slope, assisted at the bottom by the roller assembly out front that was expected to keep the front frame from digging in. A Warner four-speed transmission was matched up to a two speed transfer giving eight forward speeds and two in reverse, with power provided by a 221 cubic inch Ford V-8.

The Ford-Marmon-Herrington T9EI was one of only two half-track trucks to actually go into series production for the U.S. military. Neither type was produced in any quantity. The production model of t T9El varied from the pilot primarily in the size and weight of the track device. A full six inches shorter at 65 inches, the shorter track assembly resulted in a wheelbase of only 127 inches and a reduction in gross weight. Much of the reduction in weight was achieved by replacing the cast metal drive, idler, and roadwheels with stamped components. The turning circle was also slightly less at 53 feet.  A practical metal body with tarpaulin, front roller, and brushguard, and driving front axle completed the conversion. The 221 cubic inch Ford V-8 and eight-speed transmission/auxiliary were still used.


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Linn C5 1939

An odd vehicle that combined both a half track and wheels. The Army evaluated it as a potential to haul the 155mm howitzer.


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Linn B29 Carrier

These vehicles were to be used in pairs to lift disabled B29 Superfortress planes and carry them to a repair center. A total of 40 (20 pair) were ordered but only 2 were built before the end of WW2 which resulted in a cancellation of the remaining units.


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Autocar T17

One of two unarmored half track vehicles to ever go into full production. Mechanically the T17 was fairly identical to the M-series armored half-tracks of WW II: White 160 AX, six-cylinder, 386 cubic inch engine with four speed transmission and two-speed transfer. Front tires we 8.25x2O mounted on combat rims, and the rear steel-cable and-rubber track was 121/4 inches wide. The wheelbase was 135.5 inches. Although the T17 Radio Carrier seen here has U.S. military markings on it (the Desert Training Center Indio, Cal.), the majority of these Autocars went to the USSR under the Lend-Lease program. A normal Autocar commercial cab was fitted, and the hood and radiator shell were modified to suit the vehicle, while retaining the Autocar identity. The fenders and headlamp assemblies appear to be the same as those used on the armored versions.

On the right is a picture of an Autocar conversion by the Heil Company of Milwaukee. Heil installed an aircraft refueler body on the chassis of the Autocar T17, probably making this variation the rarest model.  Obviously intended for use at remote and primitive airfields. The tanker versions probably went to the USSR under the Lend-Lease program.


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Last Update: Thursday, February 13, 2003

Samuel Adams

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