Original Year
# of pieces
Aircraft:  Helicopters
without rotor
Rotating main and tail rotor, ratcheting winch
on deployable boom, retractable landing gear,
working two axis cyclic
Other Views

8856 Whirlwind Rescue

iso revolve
Click the image to download the LDraw file of this model.
Model by Eric Albrecht

Set 8856, released in 1991, is the best helicopter ever released in the Technic line in my opinion.  It's big and it's functional.  This set is similar to a Sikorsky HH-60 or other Search and Rescue helicopter.   It is literally packed with features.  The main and tail rotor rotate, and there's even a cyclic which tilts the main rotor using the new flex system parts.  The tricycle landing gear is retractable.  A rescue winch on the port side can be stowed or deployed.  Once deployed, the winch can be lowered with a ratchet system.   The model is built almost entirely from beams pinned together at various angles.  The flex system is even used as diagonal bracing on the tail boom.

This is both the largest and most functional helicopter released in the Technic line.  (OK, the helicopter which is part of the 8277 Universal Set is technically bigger, but I decided it doesn't count.)  It is one of only two four bladed helicopters.  It is the first with a cyclic system, an honor which it shares with only two others.  It is also quite detailed aesthetically, with a pair of red 20x30 Technic wheels used as turbine engines.  This is the only Technic set ever to include them in red.


The rotors' rotation is driven by an input crank on the left side.  This crank drives a set of 14 tooth bevel gears giving the main rotor a ratio of 1:1.  The crank axle also drives a set or gears made up of a 24 tooth crown mating with two stacked 14 tooth bevel gears (one of the rare places this pairing is made) which passes torque along the length of the boom to the tail through 3 universal joints.  Here another set of 14 tooth bevel gears drives the 4 blade tail rotor.

A pair of simulated turbine engines are nestled beneath the main rotor head.
main    tail
Ldraw file courtesy of Benjamin Wendl.
Click for an animation of the rotors in motion.
Cyclic Pitch
A number of new parts made a simulated cyclic system possible.  Real helicopter cyclic works by changing the pitch of individual blades as they rotate using a swashplate.  For example, the leading and trailing blades may be at 10 degrees of pitch, while the port and starboard blades are at 5 and 15 degrees respectively.  This model pivots the entire rotor head instead.  If a real helicopter did this it would risk striking the rotor against the frame.

The rotor axle drives a spherical ball gear.  A  part with 4 ball joints which is similar to a swashplate connects to a pair of flex cables to allow the head to pivot on two axes.  The ball joints also keep the swashplate from rotating.  Inside the swashplate is a four blade rotor part.  The rotor has tabs on the inside which mate with the ball  gear to transmit torque.  Because of the shape of the gear, the rotor can pivot on two axes while still rotating.

The control of the cyclic is from a stick at the pilot's position.  There is one flex cable and sleeve for each axis.  Fore-aft motion of the stick pushes and pulls the cable using a ball joint.  The flex cable runs up to a link which lifts the swashplate using a suspension control arm!  Lateral motion of the stick rotates an axle which runs aft.  At the end of the axle is a ball joint which connects to another flex cable.  This flex cable attaches to a ball joint on the side of the swashplate.
cyclic    cyclic 2

cyclic    rotor
Ldraw file courtesy of Benjamin Wendl.
Click for an animation of the cyclic in motion.
Landing Gear
The 3 point landing gear retracts using another crank on the port side.  The crank turns a worm gear which mates with a 24 tooth spur gear.  The spur gear drives an axle which runs both forward and aft.  The nose gear retracts forward via a set of 14 tooth bevel gears.  The main gear pivots forward via a 24 tooth crown and spur gear.  The final gear ratio is 24:1.

Each gear pivots a little over 90 degrees.  In both the extended and retracted positions the gear rests against a hard stop.
gear   gear
Ldraw file courtesy of Benjamin Wendl.
Click for an animation of the landing gear in motion.
Rescue Winch
A pair of cranks on the starboard side operate the rescue winch on the port side.

The first crank turns a worm gear which drives a 16 tooth spur gear.  The next axle pivots a lift arm which deploys the winch boom.

The second crank attaches to a 16 tooth spur gear used as a ratchet plate.  A set of 14 tooth bevel gears drive the second axle which works as a cable drum.  The cable runs out to the winch and attaches to a metal hook.
winch   ratchet

Ldraw file courtesy of Benjamin Wendl.
Click for an animation of the winch boom deploying.
Click for an animation of the cable in motion.

Other Views

Side View
side view
Top View
top view
Front View
front view
Back View
back view
Computer Render

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