Page 1. Shelvoke & Drewry Enthusiasts' Club Magazine - Spring 2010.
War Production of Trailers and Submarines.
At the beginning of the Second World War the British army was desperately short of the Scammell 30 ton Pioneer semi-trailer tank transporter and Scammell were unable to increase production. The Wheeled Vehicles Experimental Establishment turned to Shelvoke & Drewry in late 1942 to investigate the possibility of converting the American Diamond T tractor for use with a semi-trailer and to design a suitable trailer.
By December 1942 S&D had a converted Diamond T tractor coupled to a un-modified Scammell 30 ton semi-trailer. This was tested against the Scammell powered unit and acquitted itself well, and also had the potential for an increase in road speed. As a result Shelvokes received a contract for 100 'trailers, 30 ton. 8 wheel recovery' plus 100 coupling conversion kits.
Close up view of the trailer coupling.
Full length heavy steel trackways supported the load with wedge-shaped stops at the nose end. Clearly the design of the semi-trailer followed the lines of the Scammell but also had some of the characteristics of the Dyson 40 ton drawbar trailer.
But the greatest innovation of C.K. Edwards' design for S&D was to be found in the loading ramps. The Scammell trailer employed a pair of long fixed ramps which were raised and lowered by means of a hand operated winch. It is easy to imagine the amazement of the army staff who witnessed the demonstration of the first S&D trailer. The folding spring-loaded counterbalanced ramps could easily be placed in position by one man! Vic Negus has recalled that scene to me. "They could hardly believe it!" he told me.
Loading ramp details.
First the ballast box had to be removed from the Diamond T tractor, which was designed for towing a drawbar trailer. The coupling was then bolted across the chassis just ahead of the centre line of the bogie. Trailers were provided with jack screws as it was fairly simple to uncouple the trailer from the tractor unit by unbolting the coupling unit.
Between 1942 and 1945 444 units were produced with 120 from SMT, 104 from RA Dyson and 220 from S&D. Trials were conducted which showed the trailer to be capable of carrying 41 tons so that in an emergency it was cleared to move a 40 ton Churchill tank.
Each trailer proudly displayed the SD logo on those ingenious loading ramps.Meanwhile the Machine Shop was kept busy on a variety of contracts which included sprockets and wheels for Churchill tanks.
I am indebted to Classic Military Magazine of April 2002 for some of the information provided above.
The Machine Shop at Icknield Way during War Production.
As well as working long hours in production to assist the war effort, many S&D employees were also members of the Home Guard.
This photo was supplied by Roy French.
Possibly the most remarkable of the Shelvoke & Drewry War production was the Welfreighter submarine. The following article is re-printed from a 'Citizen' article published shortly after the end of the war.
The Citizen Friday November 9 1945
MYSTERY SHIPS IN LETCHWORTH. War secret now revealed SUBMARINES ON SHOW ON THE CAR PARK Residents in Letchworth will probably be surprised to learn that for a considerable time vessels for the Royal Navy have been built in their midst - but it is nevertheless a fact. For reasons of security it was necessary that the strictest secrecy should be observed, and it was not until a few days ago that the Admiralty gave permission for disclosure. We are, however, now able to reproduce on this page photographs of one of the vessels in question. As readers will see, this is a submarine of a special type, considerably larger than those craft which are known as "midgets" and capable of a greater range of action. Local residents will have an opportunity of inspecting the "Mystery Ships" which have been made in their midst, on the Car Park, Letchworth, on Saturday and Sunday next. There will be a small charge for admission to the enclosure and the proceeds will go to the British Legion "Poppy Day" Fund. Despite the distance from their works to salt water, Shelvoke and Drewry Ltd., were selected by the Admiralty to build the vessels and are the only contractors who produced craft of this type.
MADE IN LETCHWORTH With the exception of the main engines, which were issued by the Admiralty, the whole of the submarine was built entirely in Shelvoke and Drewry's works. The hulls, which are an excellent example of welded marine construction are of steel plate. To meet the demand of early delivery, the craft were dealt with in sections and special jigs and fixtures were designed in which these were welded up complete. Subsequently, the different sections were assembled and welded together as complete hulls ready to receive the machinery. In addition to the main engines the craft contain a mass of mechanism, including batteries and motors for running submerged, air-conditioning, refrigeration and lighting plants, with the usual gear for surface and underwater navigation; in short, they embody practically every feature of an ordinary submarine, although, of course, on a scale of dimensions necessarily dictated by the limited space available. DIFFICULT PROBLEMS Anyone who has examined one of these craft will realise the difficulties which the builders had to overcome in installing the machinery and electrical apparatus in so confined a space, and this was one of the most difficult problems in view of the need to produce the craft speedily enough to satisfy the Admiralty demand. This was overcome by building the various electrical, high-pressure air, water, oil and other circuits with their motors, pumps, meters etc., and subjecting them to rigorous tests before being finally built into the craft. The workmen responsible for the different installations were then able to follow each other in quick succession until the whole was complete. The man who was responsible for the planning and production of this important and unusual undertaking was Mr. Huskisson and he had the assistance of a highly efficient and enthusiastic staff. It says volumes for the organisation that at the time hostilities ceased the company were producing these submarines at the rate of one every seven days. SWORN TO SECRECY The company's employees who were engaged upon this work were sworn to secrecy, and it is gratifying testimony to their sense of duty that despite the temptation to refer outside to such an interesting topic, no whisper of their activities reached the public. The need for secrecy dictated that the transit of the craft from Shelvoke and Drewry's works to their destination should be carried out in a way which still remains a mystery. |
Subsequent research has shown some of the information in 'The Citizen' from 1945 to be incorrect. You can read the full story of the Welfreighter on Tom Colville's excellent and comprehensive website www.welfreighter.info
It pays to know what you're doing!
C.F. Clapper tells the story of a young man serving in the R.A.F. who did some un-authorised driving of an SD Freighter. After an overhaul the usual precaution of blanking off top gear in reverse had not yet been taken. The young man drove the vehicle forwards without any difficulty. Then reversing back into the hangar he turned round as he'd seen other drivers do. He put his heel on the accelerator but unfortunately forgot that as he was standing with his back to his original position the control tillers were reversed. Simultaneously he changed gear into reverse top and steered sharply into the hangar door! A kindly C.O. took no further action beyond advising the aircraftsman to do a welding job on the straightened out door.
[British Lorries 1900 - 1945 C.F. Clapper pub: Ian Allan 1973]
|
