What keeps an Atmos running

A wire thin­ner than a human hair keeps the Atmos running.

The tor­si­on pen­dulum – the slow­ly rota­ting disc that regu­la­tes every Atmos – hangs from a sus­pen­si­on wire made of Elin­var. That mate­ri­al was cho­sen for a spe­ci­fic reason: its ela­s­tic pro­per­ties remain sta­ble across a ran­ge of tem­pe­ra­tures, which mat­ters enorm­ously in a clock dri­ven by tem­pe­ra­tu­re chan­ge itself.

The pen­dulum oscil­la­tes at a very low fre­quen­cy. Becau­se so litt­le ener­gy is con­su­med with each swing, the main­spring needs to do very litt­le work. The move­men­t’s effi­ci­en­cy must be at least 95 % – a figu­re that lea­ves almost no mar­gin for fric­tion or wear.

That 95 % thres­hold is not a com­fort figu­re. It is the mini­mum the mecha­nism needs sim­ply to keep run­ning. When a clock comes in for over­haul, res­to­ring that effi­ci­en­cy is the cen­tral task.

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