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Tractor Heavy Breakdown 6 x 4 Scammell Pioneer Model SV1S

Tractor Heavy Breakdown 6 x 4 Scammell Pioneer Model SV1S
Tractor Heavy Breakdown 6 x 4 Scammell Pioneer Model SV1S

This vehicle is not currently on display at the Museum

The development of the Pioneer is covered in the section on the tank transporter tractor. Following the success of the original tank transporter the Pioneer chassis was selected as the basis for a series of heavy artillery tractors. In the 1930s, virtually all military trucks and most tanks used petrol engines. The high torque at low speeds which characterised diesel engines made them a good power source for towing vehicles and most of the subsequent Pioneers were fitted with Gardner diesel engines. Speed was not a consideration as the guns available then were modernised World War 1 types fitted with pneumatic tyred wheels, so high speed towing was not possible.

The two main types were the 60 pounder gun (ie firing a 60 pound shell) and the 6 inch howitzer firing a shell of that calibre. Howitzers were short barrelled guns designed to fire at relatively short ranges but at high angles so that shells could be landed vertically, clearing hills or other obstructions. Guns were fired at high velocities to greater a distance but with a shallower flight path for the shell. This made long range guns less suitable for hilly areas.

To move guns across rough ground where it was not possible to tow them, the tractor was fitted with a chassis winch. This chassis was therefore eminently suitable for use as a recovery vehicle, or breakdown tractor, to use the then current terminology. The breakdown tractor was put into production in 1939 a year or so after the gun tractor. The first 43 breakdown tractors, designated SV1S or SV1T, were fitted with folding cranes which, when not being used to lift a vehicle, folded down into the central well of the body. This was a method of reducing the height of the vehicle for carriage on trains or transportation overseas. One at least of the very early Pioneers was fitted with a canvas topped driver's cab. When the all steel cab was introduced, the height of the vehicle remained about the same, as the main jib of the folding crane did not lie completely horizontal. The mechanism for folding and unfolding the crane was complex and the operation time consuming, to run with the jib in the raised position resulted in an unwieldy vehicle. For these reasons a simpler jib was introduced in the design of the later breakdown tractors, designated SV2S.

The SV1S vehicle's body consisted of parallel lockers, a full length one on the right and two shorter ones on the left, divided by the access space to the well and jib winch controls. A drop down side door filled the space and was fitted with steps. The hand operated jib winch was located behind the vehicle's cab at the forward end of the body.

The lockers carried recovery gear, and towing bars were usually stowed on the top of the right hand locker. Early versions sometimes carried a towing ambulance, a long pole with towing eye at one end and a cross piece at the other to which small wheels could be fitted. These devices could support the front end weight of small vehicles when on tow.

An early problem when towing vehicles with one end suspended from the crane jib was that the casualty was free to bounce into the back of the recovery vehicle causing damage to both vehicles. This problem was resolved with the design of an ‘A' frame, its base secured to the casualty and the apex to the towing hook of the tractor. These and other items of recovery equipment were stowed wherever possible on the vehicle. In order to counter the weight of a suspended casualty the Scammell Pioneer breakdown tractors were fitted with ballast weights on a frame at the front of the vehicle's radiator.

Many of the Scammells built in 1939 and early 1940 were shipped to France with the RAOC(E) units of the British Expeditionary Force (BEF). Several were left behind on the evacuation of the BEF in June 1940. These were either destroyed or in some cases captured intact by the Germans. Some of these early models did remain in the UK. One at least was shipped out to the Far East after World War 2 and was in action during the Korean War, where it sustained mine damage but was later repaired. One SV1S became the unit recovery vehicle of 13 Command Workshop REME at Aldershot and was subsequently presented to the Museum.

This vehicle had undergone a modification in service. The main frame of the crane was locked into position and the horizontal jib and stays removed. A larger pulley was fitted in the fork of the main frame and this could take the cable of the hand winch. This winch provided the lifting force for the crane, or it could take the main chassis winch cable. To use this to lift a vehicle casualty placed a great strain on the cable, forcing it to bend in a sharp curve under the rear winch rope upper guide roller. It is intended to restore the Museum's Scammell SV1S to its original specification.

Length 6.09 m (20 ft 3 in)
Width 2.66 m (8 ft 9 in)
Height 2.87 m (9 ft 5 in)
Wheelbase 3.70 m (12 ft 2 in)
Winch 8 tons capacity
Crane lift 2½ tons (max)
Engine   Gardner 6 cylinder diesel

Further information on Scammells is available at http://freespace.virgin.net/scammell.man

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