David Tozer
David Tozer
Michael Adams

Part twelve
Michael L. Roach.
British Railways rated the Great Western Railway's 4-6-0 Counties as 6MT; this put them between the Hall class at 5MT and the Castle class at 7P. With their relatively high tractive effort of 32,580 (later reduced to 29,090) and 6 feet 3 inch wheels they were particularly useful on hilly routes such as the Cornish main line. The year 1962 started with the class of 30 engines intact. Withdrawals started in September 1962 and ended in November 1964 with the withdrawal of the last one; and all 30 were cut up for scrap. The Great Western Society are now constructing a replica County class loco from scratch using some donated parts from other classes. At the start of 1962 there were a total of five Counties at Laira (2) and Penzance Sheds (3); but by the end of the year there were none with all five locos withdrawn or transferred to other steam sheds. In the first four photos attached are shown three different Counties from three different sheds: Swindon, Penzance and Laira
INTERNATIONAL HARVESTER BTD 20
The final three photos being shown today were taken on the Forder Valley Link Road in the spring of 1962 and show another crawler tractor. This time it is a BTD 20 the big brother of the BTD 6 seen in Part 9 on 10 March. The tractor was made in the Doncaster factory of International Harvester and was normally equipped with a blade for bulldozing. The blade was so long that it was removed and travelled separately to the next site. Some 3,000 BTD 20s were manufactured in Britain from 1959 to 1974. I think many must have been exported as it is doubtful the British market could have absorbed that number.
In these views of the BTD 20 at work the tractor is towing a Le Tourneau 9 cubic yard scraper and is lowering the formation to the requisite level to build the road. A scraper was used to scrape, lift, transport and spread the material being excavated either into a fill area or as here into a stockpile to be removed later. The scraper was operated by a winch on the back of the tractor through a friction clutch and cables which meant that the driver spent some time sat at an angle pulling levers during loading and unloading; the spoil being ejected slowly in a thin layer (for compaction) by a door at the rear of the scraper which could be moved forward. In 1950 Caterpillar had invented the integral motor scraper on wheels where the tractor and scraper units were permanently coupled together and operated by hydraulics rather than wires. The motor scraper would become universal on large construction sites in the 1960s rendering the combination the tractor and separate scraper redundant except for smaller sites where the large capital cost of a motor scraper could not be justified. During World War Two dozens, if not hundreds, of new airfields were built for the Royal Air Force and the Royal Naval Air Service. Contemporary views of construction of these airfields usually show the bulk of earth moving being done by a large crawler tractor and a towed scraper as in the photographs shown blow. There were a number of manufactures of large crawler tractors at the time but many of the photos will show the ubiquitous Caterpillar D6 crawler first introduced in 1935 and still in production today. Caterpillar use their own diesel engines which are made in Britain at a factory in Peterborough. These engines have also been used in diesel multiple units and many other applications. The BTD 20 featured in the photograph was powered by a 12 litre 6-cylinder Rolls Royce diesel engine, which like the Cat engines were available for many different applications. At the time many of these tractors and excavators also had hidden in the engine bay (although it was not obvious) a small petrol engine whose sole purpose was to run for a short time and get the big diesel engine started. It was called a donkey engine.
The crawler tractor on steel tracks had been popular as a farm tractor for decades in the USA but in Britain it was only in a few counties that they were used as farm tractors in any number, and those counties were Lincolnshire, Cambridgeshire, Norfolk and Suffolk. The crawler is still being bought by farmers in those counties because they cause less compaction to the soil and they have better grip on heavy soils but these days they are on rubber tracks, with the first one produced in 1986. There is still a place for crawler tractors on steel tracks and Lilac Farm at Orwell, 7 miles south west of Cambridge is still using an International crawler tractor for harrowing that the farm bought new in 1959. It looks like a BTD 6 to me.
International Harvester was formed in 1902 as a merger between two US companies; one was McCormick which could trace its history back to 1830. McCormick tractors were made at the Doncaster plant for many years but the last one rolled off the production line in December 2007. The tractors are now made in Italy and still sold in Britain through a network of dealers, of which one is located at Stoke Canon. The current range of McCormick tractors have horse powers up to 310. For comparison the BTD 20s Rolls Royce engine gave out 135 hp net. Finally a story about the machine from 1963 when I was setting out a new estate at Deer Park Road, Eggbuckland about half a mile up the same valley to most of the FVLR. The same BTD 20, scraper and driver were stripping and stockpiling the topsoil. On this particular morning, after a night of rain, the tractor was making its way into and across a new field of long grass with a steep side-slope of about 1 in 10 when suddenly it started sliding sideways on the wet grass and travelled some 10 to 15 metres before the grousers finally dug in and stopped the machine. I suppose it proved just how a 14 ton machine could be quite light on its feet. The steel tracks of the BTD 20 were 20 inches (500 mm) wide.
MLR / 30 March 2023

Martin Scane