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Old Jul 18, 2006, 09:45 AM
JochenK is offline
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Next we come to the bottom plate (drawing bottomplate). My own gyro has a one-piece bottom plate - again made out of my favourite sandwich conbination. of course. But I strongly recommenf building the two-part solution shown in the plans. The rear part of the bottom plate is made of 1.5 mm to 2 mm cf or gf and is epoxied and taped to the main airframe - a pretty unbreakable connection. The front part of the bottom plate is made of lighter material such as 3 mm beech plywood or similar and is just bolted to the rear part with 3 mm nylon screws. In case of a crash the nylon screws will sheer off or the front bottom plate will break, but the airframe and the rear bottom plate will stay intact. And it's much easier to make a new front bottom plate than to rebuild the airframe (remember the slanting holes?).

Now cut out the rear bottom plate using the plan as a template. Drill the holes for the rotor mast and support strut and enlarge them slightly till the airframe fits int the holes. Drill the 3 mm holes for the nylon screws and drill a cluster of 4 mm holes around the mast and strut positions. Use epoxy to glue the bottom plate to the airframe (first picture) and when that is done, use cf rovings or similar to tape all the joints marked in the airframe plan. Use the holes in the bottom plate to tape the lower 8 mm cf tube tightly to the plate, and don't forget to tape the rear end of the bottom plate (second and third picture).

While the epoxy is curing, cut out the front bottom plate. Drill 3 mm holes for the nylon screws and for the screws holding the wheel collars of the landing gear. Make a cut-out around the support strut. Now slip some thin heat shrink tube over the 3 mm cf rod of the landing gear to protect the cf rod in the wheel collars. Slip two 4 mm wheel collars over the heat shrink tube. Using a washer at the top and bottom of the front bottom plate put two 8 mm long M3 screws through their holes and tighten them lightly into the wheel collars. Now you have a bit of adjustment to do. If the M3 screws can move up and down in their holes, shorten them until a) the screws sit tight in their holes and b) the axle of the landing gear is still held in place by the pressure of the screws on the heat shrink tube. Put your favourite wheels on the landing gear axle.

Bolt the front bottom plate the rear bottom plate with nylon screws and epoxy the last remaing 8 mm wheel collar over the end of the tail boom support and repeat the drillng and thread-cutting procedure (fourth and fifth picture).

To be continued.

Jochen
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