Started June 27, 2005
The flap handle assembly is actually very similar to the brake handle on my old '73 VW bug. A very simple, yet effective design.
As you pull up on the handle it it rotates around a arc shaped piece of 1/8" aluminum plate with notches in it. A spring pushes a pin on the inner flap rod (pushbutton tube) into notches in the aluminum arc at various degrees of flap settings.
Here is the finished arc piece after cutting it out and smoothing all
The flap handle assembly is a tube inside a tube design. The inside tube is actually the pushbutton part of the handle. The pushbutton (inside tube) and the flap handle tube, each must have a 3/16" wide notch cut in them. The notch in the pushbutton tube is longer than the one in the flap handle tube. The aluminum arc that we just made, will ride inside these notches.
The pushbutton tube has a 1/4" steel rod pin in it going across the aft end
of the notch:
The pin in the pushbutton tube will fit in the notches that were cut in the aluminum arc. The pin will be trimmed flush with the tube sides and welded in place.
The flap handle tube is fitted, on its bottom end, with the flap cable drive arm. The drive arm is made from a couple of pieces .062" thick, 4130n steel plate. The plans have full sized drawings of the flap drive arm pieces. These were cut using a template made from the full size drawing and then bent using the bending block and vice until they perfectly matched the drawings.
The two halves of the flap drive arm are held together with piece of 1/2" tube. This tube is left long on one end. This 1/2" tube will slip into a bearing welded to the fuselage and will serve as the rotational part (axle) of the flap handle. After cutting them out, the drive arms were bent to exactly match the drawings in the plans and the 1/2" tube was inserted and welded in place. The drive arm assembly was then clamped to either side of the flap handle for welding.
The end of the flap tube is fitted to, and butts up against, the 1/2" tube in the drive arm and is welded to it. The steel plates are cut to a shape that allows them to slightly wrap around the handle end, giving it more strength and weld area. To shape the ends to the flap handle, they were 1st tack welded to the flap handle, then heated and shaped with a hammer around the flap handle tube.
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