Rotor
Recently I bought the 8444 Air Enforcer helicopter set. While it's a neat little design, the rotor mechanism isn't very satisfying. It tilts the plane of the blades, rather than twisting each blade as it passes through a cycle. I'm sure this was a deliberate design decision to reduce the size and complexity of the model, and to give the controls a more visible effect. But a real helicopter rotor mechanism is much more interesting.Leo Dorst has a page with diagrams and beautiful drawings of his rotor design, which incorporates full cyclic and collective pitch controls. I wanted to start with something as small as possible that I could add to the 8444 model, and here is the result. I've reverted to two blades rather than four, and they can be much longer now that there is no danger of them striking the tail. The rotor shaft is elongated to accomodate the link rods between the ball joints that control the twisting of the blades.
The interesting part was keeping the blade pivots compact yet strong. The next photo is one of the two pivots, constructed with different coloured pieces to make the structure clear. The red piece sits atop the rotor shaft, and the black ball joint attaches to a dark grey link rod. The grey plate on the left is the blade. I dig macro shots of colourful Lego. :-)
The following photos show a grey rotor pivot assembly, but the "real" assembly is black. Black Lego just doesn't photograph very clearly, damnit, at least not without a lighting studio. Anyway, here you can see how moving the cyclic pitch control tilts the rotating plate which pushes the link rods up and down which twists the blades as they go around.
More photos of the rotor:
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Copyright © 1999 Ben Williamson