Bespoke decorative bronze tree grilles, NOMA development

Challenge

The NOMA project is a 20-acre mixed-use redevelopment scheme in the centre of Manchester – one of Britain’s busiest and vibrant urban environments. It incorporaties innovative urban design, structures and spaces, and designed as a location to live in and to be creative, as well as a destination to visit for shopping, eating and entertainment.

ASF had already manufactured stainless steel tree grilles for NOMA, and as such were approached by Planit Design and The Casey Group to develop and manufacture bespoke and highly decorative bronze tree grilles.

Brief

Based on drawings supplied by Planit Design, ASF was tasked with specifying the manufacturing process for the grilles and the grade of bronze that would be most suited for the project.

Solution

ASF has been manufacturing tree grilles for decades, and used its experience to solve the practical issues presented by bronze – a material that doesn’t readily lend itself to use in a tree grille application.

Bronze is a relatively ‘soft’ alloy that has a high resistance to corrosion but will also continually patina and change in physical appearance – starting out as a medium bright metal of red / pink colour in its raw state, the surface will oxidise over time creating weathered colours that range from lime green to deep dark browns.

The rate and colour variant of this oxidisation depends on a number of factors, partly the composition and grade of the bronze, but largely as a response to local climatic, geographical and environmental conditions.

After some consideration, ASF eventually proposed PB102/EW541K, a grade of bronze known for high fatigue strength and ductility.

Whilst the ductility makes the bronze very durable, it also means it can bend out of shape relatively easily so the next challenge was to design a sub-frame that would offer the necessary support. It was decided that a simple ladder frame be manufactured – consisting of heavy duty box section supports seated in an angle outer support frame.

Additional support was needed for the delicate areas of the design, so the bronze was mounted on a sheet of black coated steel that was then laser profiled to match the intricate design of the visible bronze tree grille.

To fix the whole structure together, ASF had security fixings bespoke manufactured in the same grade of bronze as the grille tops, meaning that the fixings themselves would oxidise at the same rate and in the same colour pattern as the grilles.

Outcome

ASF supplied three bronze tree grilles on time and on budget to grace one of the most exciting urban developments in Britain.

Due to the nature of the material the grilles will evolve, oxidise and patina as the development matures, and indeed as the trees they protect also grow, flourish and change.