Linear chain proves a grand design

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Push-pull actuation of heavy loads using the Linear Chain Actuator from R. A. Rodriguez is gaining wide application appeal across all walks of engineering. Indeed, one of its main selling points is the compact nature of the drive which means it is often selected for tasks where technical performance and aesthetics are of equal importance. And it proved to be perfect for a project on the television programme, Grand Designs.

Linear chain proves a grand designThe new owners of the featured property wanted to replace the original Scandinavian-style chalet with a contemporary house. The site was also to remain a working farm, complete with its own meat supply business and micro-brewery. The design concept allowed the new building to nestle gently into the sloping landscape, resulting in a construction of changing levels and dramatic ceiling heights to accommodate specific items of furniture. Another key feature was a stunning, sliding glass door measuring 2.1m × 6m.

Architectural Glazing specialists, Cantifix, supplied this design highlight but the method by which the door was opened and closed required a non-standard approach. Whilst a cable mechanism is a common choice for concealed door actuation it was not suitable for this application. A standard cable would not meet the stroke length and a longer one would take up too much space. Linear Chain from R. A. Rodriguez provided the answer.

A special profile with interlocking fingers allows the Linear Chain to become a rigid thrust device for pushing the glass door along its track. The chain rolls up into a compact magazine and is therefore suited to this application whose stroke length is the full 6m of the door way. Linear Chain also provides a constant stroke speed of 50mm/sec allowing the door to be opened or closed in two minutes.

The Linear Chain housing is easily accommodated within a cavity in the flint-clad wall and the chain itself is unfurled through a gap measuring just 100mm square; this arrangement also eliminates any associated noise. The load capacity of the system easily covers the door weight of this application at 1500kg. Indeed, the maximum capacity of Linear Chain is 3.5 tonnes but higher loads can be accommodated simply by adding more chains.

Paul French from R. A. Rodriguez explains: “Although this is a relatively lightweight application for Linear Chain there were a number of special design considerations. The first requirement was to calculate the additional load caused by the door running at an incline of seven degrees. And we also had to balance the speed of door travel with the torque required from a 230V motor.”

As Linear Chain is electrically driven it is easy to control. Accordingly, R. A. Rodriguez provided a complementary, Framo Morat Compacta slip-on geared motor which has a maximum torque of 1600Nm and is suitable for most push-pull applications.

Paul French concludes: “We also had to make modifications to the linkage between the motor and chain drive. This allowed one to effectively sit behind the other in the wall cavity rather than the conventional arrangement of side-by-side. The result is an exceptionally streamlined solution given the arduous nature of this application.”

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