From the time it was formed in 1921 the Ashburton Electric Power Board, under the direction of its engineer-secretary H. G. Kemp, expanded its reticulation rapidly into the rural areas of the Ashburton District.
However, as the major depression of the 1930s began to bite the demand for electricity failed to keep pace with the network’s growth, bringing in insufficient revenue to meet costs. The board decided it needed to increase the load by promoting new uses for electricity. One initiative was the sale of heat storage ranges. However, it was also thought the increased application of electricity to agriculture could help the board out of its financial woes.
Mr Kemp felt electricity could be used to power tractors, which at that time were starting to win the battle against horses on farms. In 1932 he began designing electric tractors and building experimental models in the board’s workshops.
He used the chassis and drive equipment of internal combustion engine tractors that had worn out their original engines, experimenting first with British Wallis tractors before moving to American Hart Parr machines. His design consisted of a turntable at the front where the original engine had been, with a jib mounted on it, the jib carrying a large drum with the cable wound on it. The jib always pointed in the direction the cable was pulling it. A large electric drive motor was mounted low between the frames, driving to the original gearbox.
As the tractor drove away from the power source, the cable pulled the jib in that direction and the cable wound out. Driving in the other direction the jib would point towards the cable and a winding motor mounted above the cable drum would wind the cable in. This motor was controlled through a patented switching device at the top of the jib that was operated by the tension on the cable, switching on whenever the cable became slack.
About eight machines were built, although the ones on British Wallis chassis never got past the experimental stage as it was found their sheet metal frames cracked with the pull of the jib. Six tractors built on Hart Parr chassis, four on larger tractors and two more successful ones on smaller models. These were sold to farmers in different parts of the Ashburton county and proved to be remarkably efficient.
The tractors went into service between March 1934 and April 1937. They all did lengthy spells of work over an eight-year period, several working in excess of 4000 hours. They were used primarily for cultivation, although by adopting a different method of working it was found they could be used in standing crop without the cable damaging the crop. Some were also used to power stationary machinery, such as threshing mills. To increase the versatility of the tractors Mr Kemp also imported Howard rotary hoes from Australia, driven by the tractor’s power take off.
The tractors could not be powered while they moved from one workplace to another, but that was solved by towing them with the truck their transformer was mounted on. Some of these trucks were fitted with steel drive wheels to allow this to happen. Another invention was the way the transformer was connected to the mains. A lever pushed three spring-loaded hammers on to three large square plates mounted on the pole, meaning no great accuracy was required in positioning the truck.
In the mid-1930s Mr Kemp attempted to sell his ideas to overseas interests. He was in touch with a scientific institute in Russia and a research organisation in England. He even wrote on a number of occasions to the Italian fascist dictator Benito Mussolini, suggesting his tractors would be the ideal machine to develop Italian agricultural land.
In the late 1930s an English university surveyed every application of electricity to tractors in the world. Many were small machines, used in applications such as vineyards, often with their cable strung on wires above the work. The university published its findings, concluding that the Kemp tractor was the only one that showed promise for use in general agriculture.
As time went on it became harder to obtain parts such as gears for the original tractors, which were long out of production. This, coupled with the war effort taking supplies such as cables, and the fact the small number of tractors sold meant the business was not paying for the board and production did not continue. The last tractor ceased operation in September 1943.
This brought to an end New Zealand’s only serious attempt to build tractors, and the world’s most successful application at that time of electricity to agricultural motive power.