United Kingdom (1943)
Half-Track Prototype – 6 Prototypes Built

The British Army, like other armies of the time, had a need for mobility in World War 2. The need to haul men and supplies across rugged terrain and roads and to tow field guns. Wheeled vehicles are well suited to roads, and tracked vehicles are well suited to off-road conditions. The German solution to this was the half-track or, more correctly, a ‘three-quarter track’. Tracks at the back of the vehicle extending well forwards for off road mobility, but wheels at the front for steering. For a vehicle, this combination uses a short track run to optimise travel over soft ground with the ease of steering using wheels with truck technology. If, when off road, the wheeled steering was insufficient, then track steering could also be used.

In a war of supply where quantities of materials such as rubber were in extremely short supply a means of making a truck with as little rubber as possible was also an advantage. The Vauxhall company had even gone as far as making a steel wheel for its wheeled vehicles for this very purpose and their own half-track design mixing elements of their Bedford QL military truck with the suspension and track of the ‘Bren Gun Carrier’. This lead the vehicle to be known as the ‘Bedford Bren’ as the firm of Bedford was at the time a subsidiary of Vauxhall Motors.

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‘Bedford Bren’ half-track. Photo: Vauxpedia

This vehicle was not a success but the British were nonetheless impressed by the maneuverability of the German ‘half-tracks’ and in particular its ability to haul heavy guns such as the 88mm across bad ground with relative ease, so they wanted their own version.

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One of the German Sd.Kfz.7s captured in North Africa and shipped back for examination. Photo: Vauxpedia

A number of German ‘half-tracks’ were captured during the North African campaign and were seen by the engineers who examined one at Vauxhall’s Luton factory as “the last word” in mobility. The military had shipped a small number of captured Sd.Kfz. 7 and 8-ton half-tracks and others to the factory in 1943 with instructions to strip them down in preparation for formal trials. The goals of the trials were to learn the lessons needed for a similar vehicle, specifically for towing 17pdr., 25pdr. and light anti-aircraft guns. Along with the vehicles, the engineers were provided with numerous documents and including captured reports detailing known deficiencies and other information on the German designs gleamed by the War Office.

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Wooden constructors model of the B.T. ¾ track Traclat vehicle. Photo: Vauxpedia

Design

After just a year of work, the engineers had developed their own vehicle. Much of the vehicle was roughly similar to the Sd.Kfz. 7, most obviously the overlapping wheel layout but some small changes such as a switch to right-hand drive were made. The manufacture of the tracks was a different matter as the German tracks were rather complex. Nonetheless the British produced their version, 12.6” (320mm) wide tracks with a total ground length of 80” (2032mm) on each side.

Six prototypes were ready for trials by the War Office. At the time, the UK was still using Imperial measurements and, to fit in with the needs of tooling and production, it was necessary to re-engineer all of the parts for imperial measurements down to the last nut and bolt. This would have the advantage of easing the production of standard parts and spares but meant there was effectively zero compatibility of parts from the original Sd.Kfz. 7 to this similar looking design. The suspension was by means of imperialised German pattern track bogies retaining only the look of the original German units. The distinctive overlapping wheels were a mix of designs from German vehicles although the holes in them are different.

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German 12 ton DB-10. Photo: As taken from Pinterest

The front wheels were standard Bedford Army truck wheels and were undriven and the body panels were standard truck items too. For the engine, the Army had not specified a new design for the vehicle so the engineering team simply took a pair of standard 3.5 litre 72hp six-cylinder Bedford truck engines already in Army use and put them together with the separate cooling radiators put on the sides of each to produce a combined, 7 litre 136hp unit capable of propelling it at up to 30 miles per hour. Drive to the tracks was delivered by a common driveshaft going into a coupling gearbox and steering was actually automatic turning both the wheel and adjusting drive to the track at the same time. This was unlike the German vehicle where the front wheels took all of the strain of the steering until they reached full lock after which the tracks were braked to assist.

The work on imperialising the parts and the choice of engine meant that the B.T had the significant advantage of being completely compatible with spares parts for the existing army Bedford trucks, greatly simplifying issues over repair. This new vehicle was simply known as the ‘B.T. meaning ‘Bedford Tractor’ and at some point received the name ‘Traclat’ as well, meaning ‘Tracked Light Artillery Tractor’. The six prototypes were assigned numbers H6264328 to H6264333 inclusive.

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Completed B.T. Prototype ¾-track Traclat with weather cover in place during testing. Photo: Nevington War Museum and Bart Vanderveen, respectively

Trials

These six vehicles were delivered and underwent very rigorous testing by the Army at the Fighting Vehicle Proving Establishment (FVPE) in a variety of conditions from very loose mud and freezing temperatures to desert heat and sand, and even in the sea. Overall, the vehicles were very impressive, with excellent mobility and “very good average speeds could be achieved by driving straight off the road, through ditches and over ploughed fields – just like that”.

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Completed B.T. ¾-track Traclat Prototype. Photo credit: Vauxpedia

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B.T. ¾-track Traclat towing a virtually submerged army field gun during testing showing the extreme mobility of this vehicle in appalling ground conditions. Photo: Vauxpedia

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Completed B.T. ¾-track Traclat Prototype No.6 showing minor differences in the arrangement of the sides. Photo: vauxpedia

The trials led to an order from the Army for large-scale production and arrangements for putting these vehicles into mass production were well underway when the war in Europe ended. Vauxhall, perhaps as an indication of the enormous time, manpower, and financial investment they made in the project, demanded substantial orders and with the trials completed successfully, they received those orders. 7,500 ordered in 1944 and 5,000 in 1945.

By June 1945 though, the cost and VE day killed the project, as Vauxhall were told to discontinue work on the project and orders were canceled.

Conclusion

The Bedford Tractor (B.T.) ¾-track, better known as ‘Traclat’, was inspired by the Sd.Kfz.7 and is viewed as a copy but was actually a superior vehicle. The primary advantages outside of production and supply being the advanced steering and improved stowage with externally accessible lockers. Tests of the Traclat in 1944 had shown that it “it is obvious that the Traclat with its ¾ track suspension and ample power is the answer to the Light Artillery Tractor question, as was realized by the German Army before the war.” For reasons unconnected with its design and abilities through the same report noted that “it is equally obvious that at the present rate of development and with the present engineering manpower and machine tool limitation the Traclat will not see service in any quantities in the British armies in less than 18 to 24 months time.”

Despite being canceled, the Traclat received some further testing in July 1946 against a Crusader artillery tractor and the tractor made from the Alecto self-propelled gun and beat both of them. Some further tests were carried out in Germany but the project was over and Traclat was no longer needed in a time for post-war austerity. For the post WW2 era, the army would have to make do with the existing stocks of trucks they already had. Trucks which in some cases stayed in service for decades afterward as the prime movers the B.T. would have been. All in all, the cancellation of the Traclat is a sad one, as a very capable and well-engineered vehicle capable of fulfilling the roles it was intended for was canceled and its full in-service potential was never realised. Sadly none are known to survive.

Vauxhall B.T. ‘Traclat’ Specifications

Dimensions L-W-H 21’ 1.5” (6.439m) x 7’ 6” (2.286m) x 8’ 11” (2.718m)
Total weight, unloaded 6.81 tons with 1.89 ton payload
Total weight, loaded 8.7 tons
Crew 1 (Driver) plus gun crew – Crew capacity with seating up to 8 men
Propulsion Two 3.5 litre 72hp 6 cylinder Bedford, 136hp
Top speed 30 mph (48.2 km/h)
Production 6

Links, Resources & Further Reading

Vauxpedia
Nevington War Museum
German Military Vehicles of World War II, Jean-Denis G.G. Lepage
Report 38/Lorries 3-ton/22 DDEM from DCGS to CMHQ dated 21st of September 1944 courtesy of Trevor Menard
Classic Military Vehicle Magazine Issue 46 March 2005
www.mafva.net – pre 1948 vehicle Census
Source Book Military Tracked Vehicles, Bart Vanderveen

40RBL78 MA Field Gun
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One Response to Vauxhall B.T. Three-Quarter track ‘Traclat’

  1. Jack Luz says:

    Sd.Kfz.7 that have survived the war would later be used in such movies as “The Dirty Dozen” and “A Bridge Too Far”.

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