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Helicopter Rotor Bell 4 Blade Articulated 51 Studs
Helicopter Rotor Bell 4 Blade Articulated 51 Studs
About this creation
Visit my Lego helicopters blog

This model contains some ideas about creating realistic light helicopter in Technic at 1:20 scale.

- Fully articulated 4-blade Bell-type main rotor:

Creating fully articulated rotor requires flapping hinges and yaw hinges/dampers besides pitchable blades. In more modern rotors, flapping and yaw hinges are replaced with torque tube and elastomer joint of blade allowing flapping/yaw movement. In Technic, building pitchable blade with flapping and yaw hinges would result in a very bulky and complicated rotor, not suitable for Lego tech figure-scaled models (1:18..1:20). Torque tube with elastic part inside it is even more troubleful.

However, if we combine parts "4 stud hub" and "rubber tie" parts carefully, we can create reasonably small articulated rotor. Blades have spar-and-ribs construction and covered by decals. Blade spars are connected to upper arms fixed to hub through rubber tie: it allows flapping/yaw movement of the blade, and also alows pitching it. In pitching the blade, rubber tie acts as a torsion spring, gently forcing blade to zero pitch. Blade pitch arm and pushrod can slide in a driving plate placed beneath of rotor hub, and can pitch blade against the force of torsion spring. This way, swashplate can be just a flat, tiltable and liftable plate with a hole in the middle letting through main rotor mast.

- Compact collective-cyclic mixer linkage under main rotor mast:

5 studs long × 4 studs wide × 5 studs tall. The trick is that collective lever (yellow) pushes swashplate upward against the force of rotor torsion springs.

- Huey-type angled tail with universal joint, 2-blade variable pitch tail rotor and very thin cross-section: 3 × 1 studs.

The trick here is that there are 3 long cross-axles in the tail above each other:
1.The upper crossaxle of is the tail rotor transmission shaft and can rotate accordingly
2.The middle one is fixed, this is the tail boom
3.The lower one can slide forward and back, this is the yaw control rod

Another trick is that there are rubber ties integrated in tail rotor blades, gently focing tail rotor blade pitch to zero. So it is enough that a lever pushes pitch rod hub aside against the force of rubber ties to increase pitch for yaw control. This way we can eliminate sizeable yaw control slides and leads at tail rotor. So tail rotor shaft is only 5 studs long.

Building instructions
Download building instructions (LEGO Digital Designer)


 I made it 
  June 11, 2013
Quoting sinan bitižik good looking..
Thanks. It was just a minimalist study of a main rotor solution regardless aesthetic. Check out my other helicopter models in "Helicopters" folder for better looking stuff.
 I like it 
  June 11, 2013
good looking..
By Gabor Pauler
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Added August 16, 2012

LEGO models my own creation MOCpages toys shop Helicopter Rotor Bell 4 Blade Articulated 51 StudsTechnic

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