18.5 metre flagpole at South Crofty Tin Mine

The brief was to design and manufacture an 18.5m flagpole that could be mounted onto the gallows on the very top of the headframe at the South Crofty Mine and to fly a 6 yard (5.5m x 2.75m) Cornish flag. Our client was offered three flagpole options, a stainless steel, aluminium or glassfibre pole.

Once the client had selected a Glassfibre pole, the process involved a detailed study of the structure. It also included a series of wind loading calculations to refine the design of the flagpole. We needed to establish the correct wall thickness and diameter of the mast. This was to ensure that the pole will withstand the higher than normal windspeeds based on the exposed location and overall height of the frame. The site altitude was 113m above sea level and a further 30m up the framework to the fixing point for the base of the flagpole.

Other design considerations included identifying the loads transferring into the structure from the pole. Plus we needed to incorporate custom-made brackets to help transfer the load. As part of the design calculation we also look at the peak deflections on the pole at a SLS wind speed of almost 100mph. This is to understand how the pole will behave around the fixing points and its overall position within the frame structure.

The upper gallows of the mine frame are accessible to the public. Therefore the mast was provided with a secure cleat box. It also featured a double halyard and pulley system on the top of the finial. This will help increase the service life of the halyard used.

The client undertook their own installation of the mast. This took place whilst the gallow section of the headframe was on the ground. The overall structure was raised by crane into position. The final outcome is an impressive statement of Cornwall’s mining heritage. The 6yd Cross of Saint Piran, the patron saint of tin miners, flies high above Camborne and Pool.