Just after WWI, the RAF found itself with a lot of surplus aircraft, amongst them number of Avro 504K biplanes. These were put up for sale as war surplus. A man named Juan de la Cierva had been doing some research into Autogyros, that proved quite interesting. The use of a free rotating, unpowered rotary wing and a conventional tractor airscrew gave a very short take off run requirement, and a low - speed agility that was extremely useful in certain circumstances. He hoped to save some major costing by using surplus 504 fuselages, engines and modified empennage and abbreviated wings. He widened the undercarraige track, but retained the central skid. A framework was built to mount the rotor, and the two-seat layout was retained. I decided to emulate the full-size production method, by starting with an SMER 1/48 Avro 504K biplane kit. I discarded the upper wing to the spares box, modified the planform of the lower wing and horizontal stabiliser, and then removed the awful raised lines that showed where the decals were to go - the worst feature of he SMER product. The engine was a bit ropey too, so I changed that for an Aeroclub cast white metal one, though the kit prop was better than the metal one supplied with the engine. I modified the u/c by spacing out the legs and mounting into holes I drilled in the wing, where the man spar would be, and fabricating a new axle and spreader bar from plasticard. I made a pylon for the rotor by drilling five holes n a piece of wood, like the pattern of spots on a playing card. The central one took a short length of aluminium rod, on which I threaded a length of brass tube to support another, shorter length that would form the housing for the rotor axle, pre-tinned. Then I made the support legs from STRUTZ streamlined brass rod, and laced them into position leaning inwards to touch the brass tube, and ran solder sparingly round the joint faces. when cool, I dressed the joint neatly by needle file. A short length of the aluminium rod was then epoxied into the tube mount, flush with the bottom and protruding at the top, to form the axle. The cage thus made was ready to fit into holes prepared on the upper shoulders of he fuselage. Thee cockpit was detailed with scratch made instrument panels, bent wire controls and etched throttle quadrants from an AIRWAVES set, after I had added some structure with Slaters plasticard strip. Seat belts from masking tape completed the inside, after painting. The fuselage and flying surfaces were painted with Humbrol 11 silver, and the cowl with Humbrol gloss black. The varnished wood items were painted with DULUX brushwood in Mahogany shade. After decals from the spares stocks and rigging the control cables from invisible mending thread, I tackled the rotor. This was based on a hub made from tin scavenged from a baked bean tin lid, with a brass tube soldered in the centre, and folded into four cruciform box sockets to take the blades, which were made from laminated plasticard shaped to an aerofoil section. Lengths of galvanised garden wire were shaped and added to form the blade bracing struts, and stripped cable filaments whipped around the tops to simulate the springing, the upper end soldered to the brass tube and cleaned up as before. The lower ends were epoxied into holes drilled in the blades, and I ensured the correct symmetry as went. A lick of paint after checking that the rotor spun freely, and all was done!
Posted on: Tue, 18 Nov 2014 18:26:17 +0000
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