UK composites company creates hands for world’s largest mechanical clock

Staff at epm: technology, based in Draycott, have made 12 carbon fibre hands for a clock destined for the top of the Harmony Tower, in Ganzhou, South west China. The tower has four clock faces, each with a diameter of 12.8m – over twice the size of Big Ben's. Each minute hand measures 7.8m long, while the hour hands are 6.2m long. Each dial also has a third 4.4m hand, which will point to a series of animals to indicate the Chinese lunar month. The clock has been designed by Smith of Derby, one of the city's oldest companies, which won the contract after beating off competition from firms across the globe. While it set about making the movement, it contacted epm: technology asking it to make the hands. As carbon fibre was used for the construction, the minute hands weigh 60kg each, compared to a ton if they were cast in traditional steel. This makes them easier to install and also means that they are maintenance-free. The clock is designed to operate for 100 years between major overhauls and the hands have been specified to offer similar durability and performance. The hands were made by applying layer after layer of carbon fibre material around an aluminium honeycomb core placed inside a mould. They were then put into an autoclave oven, which cooked them at a high temperature while applying intense air pressure to create a smooth moulded finish. They were then removed from the autoclave and the mould was taken away, leaving the hands. The hour hands were made in one piece, while the minute hands were made from two components bonded together. All four sets will now be painted and shipped to China, where the clock will be installed in the tower at the end of June. Graham Mulholland, managing director of epm: technology, said: "At the moment, carbon composites are regarded as niche materials, primarily used by our customers in Formula 1, but they have a huge potential for the future, including the construction industry and wind turbines."