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33-583: The Scammell Pioneer was a British 6×4 tractor unit used in World War II as an artillery tractor , recovery vehicle and tank transporter . Designed as a 6×4 off-road vehicle for use in Britain's colonies where metalled (sealed) roads were scarce, the Pioneer was first produced in 1927. Though lacking all-wheel drive , its combination of a suspension with great travel, excellent traction, and

66-529: A multi-ratio transmission (10, 13, or 18 gears) for maximum flexibility in gearing. The tractor–trailer combination distributes a load across multiple axles while being more maneuverable than an equivalently sized rigid truck . The most common trailer attachment system is a fifth-wheel coupling , allowing a rapid shift between trailers performing different functions, such as a bulk tipper and box trailer . Trailers containing differing cargos can be rapidly swapped between tractors, eliminating downtime while

99-567: A 12-short-ton (11 t) hard-cab 6×4 truck. Powered by a Hercules DFXE diesel engine developing 201  hp (150  kW ) and geared very low, it could pull a trailer of up to 115,000 lb (52 t) and proved capable of the task of moving the heaviest tanks then in service. The M20 used a Hercules DFXE , a 855 cu in (14.011 L) displacement naturally aspirated inline 6-cylinder diesel engine developing 201 bhp (150 kW) at 1,600  rpm and 685 ft⋅lbf (929 N⋅m) at 1150 rpm. Designed for

132-501: A British requirement, this was one of the few diesel engines used in US tactical trucks. A two plate dry disk diaphragm spring clutch drove Fuller four-speed main and three-speed auxiliary transmissions . The main transmission had a "low" first gear and three road gears, 4th being direct. The auxiliary had low, direct, and overdrive gears. The low gear allowed several very low gears for extreme off-road use. The direct and overdrive allowed

165-423: A certain amount of weight must be spread over driven axles, which led to heavier varieties having six-wheel drive , otherwise, another tractor unit would have to be used. Heavy haulage variants of tractor-units are often turned into a ballast tractor by fitting temporary ballast, which may require special permitting. M19 tank transporter The M19 tank transporter ( US supply catalog designation G159)

198-523: A few remained in tank transporter units up to 1971. Many of those sold off by the Army after the war were snapped up by heavy haulage and recovery specialists, notably Pickfords and Wynns , and were a familiar sight on Britain's roads, pulling heavy lowloaders and fairground trailers or parked on garage forecourts, in readiness for a heavy rescue operation equipped as wreckers (breakdown recovery trucks). They suffered from "very limited off-road performance" as

231-433: A longer wheelbase for an extended cab to accommodate the tank crew as passengers and larger rear wheels than the artillery tractor and recovery vehicle variants. It was designated Pioneer TRCU20 . 20- and 30-ton ( Pioneer TRMU30/TRCU30 ) tractor/trailer combinations were delivered. In both cases, the trailer was more-or-less fixed to the tractor, not demountable like modern semi-trailer trucks . Hinged ramps were used to get

264-478: A low-revving engine gave it impressive pulling power on rough ground at low speeds. Though not designed for military use, the British War Office purchased a single petrol engined example in 1932. Equipped as a tank transporter with a permanently coupled 18t semi-trailer , it was assigned to a training unit but did not initially catch on. Additional transporters were not purchased until 1937. With

297-517: A number of American truck manufacturers to assess their models. The Diamond T Company had a long history of building rugged, military vehicles for the U.S. Army Quartermaster Corps and had recently produced a prototype heavy vehicle for the US Army which, with a few slight modifications met British requirements and an initial order for 200 was very quickly filled. The result was the Diamond T 980,

330-624: A result of only the two rear axles being driven. Many of the 70-year-old Diamond Ts can still be found in private ownership in Britain and frequently appear at historic vehicle shows. This combination unit is referred to as the M19 tank transporter , consisting of the M20 tractor and M9 24-wheel trailer. In the nomenclature system used by the United States Army Ordnance Corps Supply Catalog this vehicle

363-500: A result of their tall profile the trailers proved undesirable postwar and most were scrapped; the tractors were retained for use with other trailers or sold into civilian use. Tractor unit It should not be confused with a tractor-trailer which is a combination of a tractor unit and semi-trailer , whereas a tractor unit describes only the tractor portion. Tractor units typically have large-displacement diesel engines for power, durability, and economy; several axles ; and

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396-534: A trailer is unloaded or loaded. Drawbar couplings are also found, particularly in dedicated exceptionally heavy-duty ballast tractors and as a means to connect intermediate fifth-wheel dollies for pulling multiple semi-trailers. Most tractor units are based on the chassis of a large truck (Class 8 in North America) minus the cargo body, with shorter frames used for cabovers and day-cab tractors, and longer frames used for Sleeper cab tractors, to accommodate

429-595: The M25 tank transporter , citing the fact that the M19 suffered from a wide turning radius, poor traction of the truck, and excessive rolling resistance . Five 1 short ton (910 kg) concrete blocks were routinely carried in the bed of the truck to improve traction; the conversion of an M20 truck and M9 trailer to a semi-trailer configuration rather than a trailed configuration alleviated some of these problems, and also improved fuel economy by approximately fifty percent. In general,

462-568: The Pioneer SV1S and the Pioneer SV1T both with a 3-ton folding crane and lockers for recovery equipment and towing bars. Most of these early Pioneer recovery vehicles were lost with the BEF. The Pioneer SV2S had a simpler redesigned extending crane that provided greater lifting height. It was Introduced in 1938 and remained in production throughout the war, with a total of 1,975 built by

495-629: The M19 was mechanically reliable, but "did not meet the overall requirements of this theater " and was relegated to duty in the rear areas of the combat zone and in the Communications Zone , with the M25 being used for frontline service. The British Army took delivery of around 1,000 during the war years and many continued in service afterwards, being replaced in the early 1950s with the Thornycroft Antar ("Mighty Antar"), although

528-817: The beam. A dual tire wheel was on both ends of both axles, with a beam on each side there were also four wheels per axle line. Twenty-four 8.25×15" tires on demountable rims were used, two on each wheel. Production began in 1941. The first batch was received in Britain in 1942 and very quickly demonstrated their rugged reliability in the British campaign in North Africa . Battle-damaged tanks needed to be quickly recovered, often under hostile fire, and returned to workshops for repair. 5,871 were eventually built by 1945 and were used by virtually every Allied army in every theatre of World War II. U.S. forces in Europe preferred

561-444: The centerline of rear bogie. A pintle hitch of 115,000 lb (52,000 kg) capacity was mounted on the rear frame crossmember; another pintle hitch was mounted on the front crossmember for positioning the trailer. All models had Budd split rim disc wheels with 12.20×20-20" tires. Dual rear mud and snow tires were used. Air powered drum brakes were used on all axles; the trailer brakes could be operated independently of

594-405: The driven axle. The 6×6 units have three axles, all can be driven, and 8×6 units have four axles, with either the rear three driven and the front axle not, or the front and rear-most two axles powered and an unpowered lifting center axle to spread the load when needed. The 8×8 units also have four axles, but with all of them driven, and 10×8 units have five axles with the rear four usually driven and

627-520: The end of the war. Among the Pioneer's equipment was a pair of tracks that could be fitted over the two rear wheels, converting it temporarily into a half-track and giving greater traction on soft ground. The last Pioneer recovery vehicle was not retired from the British Army until the 1980s in Belize . Delivery of a production tank transporter did not begin until 1937. This was equipped with

660-675: The evacuation of the British Expeditionary Force (BEF), either destroyed by the withdrawing troops or captured by the Germans. Scammell produced 980 Pioneer R100 heavy artillery tractors by the end of the war. As this quantity was insufficient to meet requirements, the Pioneer was supplemented by the Albion CX22S heavy artillery tractor from late 1943. From 1936, the British Army began to receive Pioneer heavy recovery vehicles. The first 43 delivered were designated

693-509: The exception of the single 1932 tank transporter, all Pioneers purchased by the British Army were equipped with a 102 bhp Gardner 6-cylinder diesel engine, driving the rear wheels through a constant-mesh gearbox and fitted with a power take-off driving a Scammell winch. Introduced in 1935, the Pioneer R100 heavy artillery tractor was used throughout World War II to tow medium and heavy artillery pieces. It had accommodation for

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726-440: The front axle for steering. All five axles of 10×10 units are driven. The front two axles are usually both steer axles. The axle configurations are usually based on axle load legislation, and maximum gross vehicle weight ratings (BDM). Heavier versions of tractor units, such as those used in heavy haulage and road trains , tend to have four or more axles, with more than two axles driven. In certain countries (such as Switzerland),

759-616: The gun's crew, tools, equipment, and ammunition. Typical early war use included towing such medium pieces as the 60-pounder , 6-inch howitzer , 4.5-inch gun and 5.5-inch howitzer , until the AEC Matador medium gun tractor was issued in sufficient numbers. Heavy artillery pieces towed included the 6-inch gun , 8-inch howitzer , 155 mm Long Tom and the 7.2-inch howitzer . Many Pioneer gun tractors were lost in France in June 1940 with

792-418: The longer cabin. There have been three common cab configurations used in tractors, two are still widely used. A tractor unit can have many axles depending on axle load legislation . The most common varieties are those of 4×2, 6×2, and 6×4 types . However, some manufacturers offer 4×4, 6×6, 8x4, 8×6, 8×8, 10×8, and 10×10 axle configurations. A 6×4 has three axles, normally an undriven front steer axle and

825-478: The service brakes. A single disk transmission brake parking brake was also provided. This used four brake pads with a cable clasp mechanism onto a 16 in (41 cm) disk, mounted behind the auxiliary transmission. A Garwood winch of 40,000 lb (18,000 kg) capacity, with 300 ft (91 m) of cable, was mounted behind the cab. In the Model 980 it was intended mainly for hauling damaged tanks aboard

858-488: The tank onto the trailer; if the tank was immobilised, it could be pulled onto the trailer with the tractor unit's winch. Pioneer tractor/trailer combinations proved too tall to carry higher profile US tanks under some British bridges, resulting in their being superseded by the American Diamond T tank transporter from 1941 on. Despite this, it remained in production throughout the war, with 459 being produced. As

891-407: The three road gears to be split, making six road gears. Spicer driveshafts drove two Timken double-reduction axles with an 11.66:1 final drive ratio. The M20 truck had a riveted ladder frame with three beam axles , the front on leaf springs , the rear tandem on leaf springs with locating arms. The wheelbase was 179 in (455 cm), measured from the centerline of the front axle to

924-485: The trailer. Cable rollers and sheaves let the winch from the M20 truck pull tanks onto the trailer, chocks and chains were used to secure the load. The front axle suspension system was trailing beam assemblies on coil springs, with a dual tire wheel on each side of the beam. With an assembly on each side there were four wheels on the axle line. The rear tandem beam assembly was a center pivot type, with axles on both ends of

957-443: The trailers. The Model 981, introduced in 1942, had a winch with 500 ft (150 m) of cable, which could be used from both the front and rear. This allowed tank recovery, in addition to loading. Early trucks used a standard Diamond T commercial cab, also used by the four-ton G509 trucks. In August 1943 it was replaced with an open military cab. A long butterfly hood had vertical louvres along both sides. A short ballast body

990-542: The two rear axles driven. 6×4 units are more common in long-distance haulage in larger countries such as the United States and Australia. In Europe , the 4×2 and 6×2 variants are more commonplace. Tractors with three axles or more can have more than one steering axle, which can also be driven. Most 6×2 units allow the undriven rear axle to be raised when lightly loaded, or running without a trailer, to save tire wear, save toll road fees, and increase traction on

1023-400: Was a heavy tank transporter system used in World War II and into the 1950s. It consisted of a 12-ton 6×4 M20 Diamond T model 980 truck and companion 12-wheel M9 trailer. Over 5,000 were produced, and employed by Allied armies throughout all theaters of war. It was superseded in the U.S. military by the M25 tank transporter during the war, but usefully redeployed in other tasks. It

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1056-413: Was mounted behind the winch. There were closed tool compartments along both sides, two open containers in the front, and a bottom-hinged tailgate. The spare tire was mounted in the front. The box could hold 18,000 lb (8,200 kg) of ballast to increase traction on the rear tandem axles. The M9 had tandem rear axles and a single front axle on a rotating dolly. Ramps hinged down at the rear end of

1089-744: Was superseded by the Thornycroft Antar in British service by the early 1950s, though a few remained operational in units through 1971. Designed as a heavy prime mover for tank transporting, the hard-cab Diamond T 980 was the product of the Diamond T Company in Chicago . In 1940 the British Purchasing Commission , looking to equip the British Army with a vehicle capable of transporting larger and heavier tanks, approached

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