Deployable Fabric Umbrella on a Folding Steel Frame

Project Overview

A large deployable shade umbrella: a steel mast carrying a set of folding radial arms, with a tensioned fabric canopy that opens and closes with the arms. Closed, it stands as a narrow column. Open, the canopy spans several metres in every direction.

The steel work here is the whole job. The fabric only holds its shape because the arms underneath put it into tension, so the frame had to be accurate before anything was cut in cloth.

What We Built

• A central steel mast with a head ring the radial arms pivot from
• Folding arms fabricated from welded steel sections, each pair linked so the set moves together
• Arm tips shaped and plated to take the canopy edge without cutting into the fabric
• A guided drive column inside the mast that raises and lowers the arm set
• Full trial assembly and cycling of the mechanism before the canopy was fitted

Why It Was Built This Way

A fixed canopy of this size is a simpler thing to fabricate, but it has to be engineered for the worst weather it will ever see and it is in the way the rest of the year. A folding frame lets the canopy be closed, so the structure only carries wind load on the fabric when someone chooses to open it.

Everything in a mechanism like this comes down to repeatability. Each arm has to travel the same distance every cycle or the canopy pulls uneven and the fabric wears at the tips. That is why the frame was assembled and cycled in the yard before the cloth went on.

The arms were kept as slender as the geometry allowed. From below the frame reads as ribs under the canopy rather than as structure, which is the point of the shape.

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