Rodless cylinders make sculpture dance

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Rodless pneumatic cylinders from Hoerbiger-Origa have give ten years of service on a moving sculpture outside a dance studio in Leeds. Now they are to be refurbished to extend their life still further.

Rodless pneumatic cylinders that have operated continually for over a decade are to be refurbished so that they will carry on for years to come. Back in 1995 the Yorkshire Dance Studio in Leeds commissioned engineer-turned-sculptor Johnny White to create an artistic installation to enhance the main entrance. His piece, created in stainless steel, consisted of profiles of several dancers attached to the building at first, second and third floor levels above the entrance.

But they held a surprise in that every 30 minutes the dancers would begin to move and keep up a routine for the next five minutes. Some pivot on their toes; others leap effortlessly upward and yet more glide elegantly across the faccedil;ade.

For all of the linear movements Johnny used Hoerbiger-Origa rodless cylinders and these have performed faultlessly, twice an hour, for ten years, enthralling passers-by and becoming a firm favourite with the local people.

Pneumatics provided the most elegant solution to the technical aspects of the design, with little visible engineering and avoiding the reliability questions associated with outdoor electrical installations.

"Hoerbiger-Origa gave us a one-step engineering solution, discreet actuation design and freedom from worry about corrosion, short circuiting and differential thermal expansion," says Johnny. "Ten years on I can also say they gave us reliability in spades."

He also explains that the rotary actuators used to pirouette some of the dancers have failed and been replaced twice during the life of the rodless cylinders. "One had its bearings eaten away by rust when the desiccant dryer failed and no one noticed for months that wet air was being squirted all over the moving parts."

The dryer and compressor are actually located in the Studio's lift service room and are now checked regularly. "The Hoerbiger-Origa units are 14 metres above street level: it is such a job to access them that they have never yet been serviced - they weren't broke so we didn't fix 'em!"

The cylinders are 3.5m stroke versions of Hoerbiger-Origa's workhorse P320 actuators, controlled by P9 valves on a P manifold. They are mounted on a north-facing wall where the mirco-climate can be relatively harsh. These represented the 'state of the art' 10 years ago and many are still in service today, in a wide variety of industrial and non-industrial applications around the world.

Another element of the sculpture that has been reliable beyond all imagining is the tiny industrial PLC (programmable logic controller) controlling the dance sequence. This was installed, programmed and set running at the time of the original installation in the mid-1990s and has not missed a beat yet. The PLC, a Mitsubishi FX industrial controller normally used in factories to control plant and machinery, is a solid-state device with no moving parts. It has been the world's best selling PLC for over 25 years, with many units proving the long-term reliability claims of the manufacturer.

The Director General at the Yorkshire Dance Studio asked Johnny to overhaul his artistic sculpture, as part of a major 'spring-cleaning' programme. "We have repolished the stainless steel dancers back to their original mirror finish so that we get all sorts of exciting reflections at different times of the day. While we had the scaffolding up, it made sense to check over the moving parts. Frankly I am stunned at how new the cylinders and valves still look despite 10 years of constant hard work. If only I could say the same about myself. "

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