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Click to view large map Coordinates: | INTRODUCTION Searchlights were an essential component of the Gun Batteries constructed on Robben Island for Coast Artillery during World War II. Two searchlights provided night-time support to the Robben Island Battery and these were supplied with power from the Searchlight Engine Room (today also known as a Generator Room or Power House). The Searchlight Engine Room (Building T225) comprises of a substantial rectangular concrete building and was designed to protect and camouflage the Generator installation. This Searchlight Engine Room is one of two such buildings on Robben Island. It is situated a short distance to the northeast of No. 1 Searchlight Emplacement Building, a similar distance to the north of No. 2 Searchlight Emplacement Building and a reasonable distance to the southwest of the Robben Island Battery itself. ARCHITECTURAL DESCRIPTION The Searchlight Engine Room is rectangular, single-storey, reinforced concrete structure with a flat concrete roof with a nominal cantilevered overhang on all four sides. Remnants of painted camouflage patterns exist on the external face of the concrete walls - more particularly on the better protected landward side of the building. The fragmentary remains of a timber framed hipped corrugated iron roof survive on the flat concrete roof. The hipped roof was probably added at a later stage in an attempt to camouflage the building as a residential structure. A notable feature of this building is the faded 'memory' of the rectangular painted military signage above the door recording the original Building Number 'T225', still just visible in black paint on a white painted surface. Entry into the building is through a double outward opening door (on the northwest side) made of steel plates, rivetted to a heavy welded angle iron frame. Each door leaf was provided with two diagonal braces internally for structural support. Each door leaf was hung on three heavy duty metal pintle hinges. A rotating bar and staple was used externally to secure the doors in a closed position. The doors could be secured from within using sliding bolts. The Searchlight Engine Room was provided with five pairs of inward-opening steel cottage pane casement windows, each with a pair of outward-opening steel plate shutters. The doors and the window shutters are all badly affected by rust due to the exposed position of the building. The concrete walls, the underside of the flat concrete roof and the surfaces of the two down-stand concrete beams supporting the roof bear the clear 'witness marks' of the timber planks that were used for temporary shuttering during construction. The steel reinforcing within the concrete walls has rusted in places and has caused localised spalling of the concrete on the exterior facades. Fresh cool air was drawn over each of the Engine radiators through five separate low-level square openings on the east wall. These openings were provided with double sided fixed louvres made of heavy steel plate to direct and control the air flow. Ten sets of four small, simple rectangular openings at close centres were provided at high level through the internal face of the concrete wall to allow warm air to exit the building. Another ten sets of similar rectangular openings - but in groups of five openings - were provided on the external face of the wall at high level. These were not aligned with the internal openings and therefore did not permit a direct line of sight into the building. The staggered arrangement of each opposing group of rectangular openings was presumably intended to minimise light exiting the building at night under emergency conditions. Each of the external rectangular openings was originally provided with a fine woven wire mesh screen - close to the external face of the wall - to prevent the ingress of birds and insects. The four engine exhaust pipes were each directed though a separate rectangular covered floor duct, adjacent to the left hand side of each engine plinth. The four ducts each passed through the east wall and allowed the exhaust pipes to rise vertically up the external face of the wall. The flat concrete roof was cantilevered an additional distance on the eastern side and was provided with four cast in circular penetrations - at positions matching the exhaust pipes - which permitted the exhaust pipes to pass through and discharge at high level. The four electrical generators and other equipment were presumably removed when the military ceased to have a presence on the Island in 1960. Clear 'witness marks' visible on the interior walls of the building provide interesting evidence of the original layout of the generator control panels, conduiting, pipework, fuel lines, electrical switchgear and signage. These items - if not removed by the military - have all been removed in the intervening years - presumably as memorabilia or by scrap metal collectors. GENERATOR EQUIPMENT The generating equipment installed in the Engine Room comprised three large diesel driven DC generators; presumably one for each searchlight and the third either as a standby or to power ancillary buildings. A fourth, smaller generator was provided for auxiliary services when the large generators were shut down. In order to start the diesel engines it was apparently standard practise to lift all the valves to the cylinders to decompress the engine. The engine was then 'swung' using a manual crank handle; a single cylinder's valves were closed to start on one cylinder after which the others would be progressively brought in. Regarding the fuel supply to the generators, it has not yet been determined where the main diesel tank was originally accommodated. Possibly the diesel tank was housed in an underground concrete chamber on the north side of the building. However four rectangular witness marks (or paint shadows) are visible on the internal face of the wall at high level above each generator providing clear evidence of the size and position of a daily, or ready use, fuel tank. These tanks were mounted on the wall through which the air intakes and exhausts passed. Each generator unit was mounted as a single unit on a steel frame on a low linear concrete plinth to permit secure mounting and levelling of the electrical generator and in-line engine. Each generator unit comprised of a large diesel engine linked to an electrical generator and each unit was carefully 'shimmed' - with thin metal shims - to ensure it was perfectly level. The unit could obviously be split and dismantled to replace defective or damaged major components if required. A series of narrow covered floor ducts - the metal chequer-plate covers now mostly removed - provided covered electrical cable routes from each generator. HERITAGE VALUE The Searchlight Engine Room's heritage value lies in its historical associations with World War II, as an example of a building designed for a particular purpose and function and as an architectural landmark on the coastline of Robben Island. STATEMENT OF SIGNIFICANCE The Searchlight Engine Room is closely associated with the defence of Table Bay (and Cape Town) during World War II (1939-45), and during the immediate post-war period when the Island was used as a military Training Base. The building accommodated, protected and camouflaged the generators which enabled night-time operation of the two nearby Robben Island Battery searchlights. The Searchlight Engine Room is a good example of specialised coastal defence architecture. The scale and volume of the machine room, the cantilevered roof overhang, the in-situ off-shutter cast concrete finish, the heavy steel shutters all create a distinctive visual impact. The Searchlight Engine Room reinforces the character of the historically important WWII layer present on Robben Island. The choice of construction materials and the robust detailing relate closely to the other concrete structures built for the military on Robben Island. CHARACTER DEFINING ELEMENTS The heritage character of the Searchlight Engine Room resides in the following character-defining elements: The one-storey, box-like, concrete construction, the heavy duty steel window shutters, the louvred fresh air intakes on the east side of the building, the memory of the exhaust pipe discharge through the cantilevered concrete roof, the memory of the engine coolant pipelines, the remnants of a large metal tank externally for accommodating the coolant, the low linear concrete plinths for secure mounting and levelling of the Electrical Generators and in-line Engines, the witness marks of interior fittings (now removed), the recessed floor ducts for the reticulation of the electrical cables and exhaust pipes; the steel plate doors and the vestiges of a painted camouflage pattern on the external wall. Text compiled by William Martinson, Osmond Lange Architects, with invaluable input and advise from Chris Dooner; October 2019. |
