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Bumax screws hold world’s largest telescope together ❍ The ELT uses a 39m-wide curved mirror

The high strength Bumax 109 fasteners prevent costly damage to the mirror segments. Their corrosion resistance is also essential, as the fasteners are sometimes open to the elements. The bolts are a customised product that required special tools to manufacture. At the customer’s request, the bolts were coated with a special surface treatment commonly used for fasteners used in telescopes. Bumax managing director Patrik Lundström Törnquist said, “This order is yet another testament to Bumax being able to provide the very best fasteners for the most demanding applications. We have also been trusted with supplying fasteners for the CERN accelerator in Switzerland, satellites, submarines, etc.” Bumax AB www.bumax-fasteners.com European Southern Observatory www.eso.org/public/teles-instr/elt

The segments will work together as a single huge mirror to collect 100 million times more light than the human eye. The Bumax fasteners will be used to fix the nearly 800 telescope mirrors to the segment supports. Twelve 10mm-long Bumax 109 M6 bolts per segment will be used for more than 900 segments in total (798 support segments plus an additional 133 segments for a continuous swapping process to allow the mirrors to be cleaned and coated while the ELT stays operational). The ELT is presently under con- struction by the Dutch company VDL ETG Projects in the Netherlands. That company’s project manager, Michael Evers, commented, “Standard stain- less steel bolts lack the strength required for the ELT. We required a 10.9 strength bolt, and with the corrosion resistance of stainless steel. Bumax offered us the perfect solution.”

SPECIALIST stainless steel fasteners manufacturer Bumax has been chosen to supply thousands of high-strength and corrosion-resistant fasteners for the ELT – the Extremely Large Telescope – presently under construction. The Swedish company received the order for 11,000+ Bumax 109 fasteners for the construction of the ELT by the European Southern Observatory (ESO). The €1bn ELT will be the world’s largest telescope when it becomes operational in the dry Atacama Desert in northern Chile in 2024. The ELT is a reflector telescope, collecting universal light using a massive curved mirror that is 39m across – three times the area of the next largest telescope. Such a large mirror cannot be made from a single piece of glass, so it will consist of 798 individual hexagonal segments, each measuring 1.4m across and driven by electrical motors for fine tuning.

Graphics bigstockphoto.com/Artist Kumruen Pakom

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Fasteners ASIA – September/October 2020