Original Year	1986
# of pieces	519
Categories	Other: Arctic Action
Dimensions	42(L)x24(W)x25(H)
Features	Front ramp, helicopter rear pneumatic lift
Other Views

8680 Arctic Rescue Base

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

Set 8680 was released in 1986 as the largest of 4 sets in the new Arctic Action theme. This set features a helicopter with rotating rotors, an opening front ramp, a pneumatic rear helicopter lift, and two of the new Technic figures with a helmet, skis, and poles (three figures pictured).

The model is not recognizable as any real vehicle that I can identify, but appears to function as an Arctic mobile hospital. Although Technic models would not become highly stylized until much later and typically only represented a skeleton of whatever their subject was, this remains one of the least stylized Technic sets ever. It is basically just a box and uses a large number of big (4x12 and bigger) plates to make up the floor, roof, ramp, and lift. However, if you like white beams and don't have the money for 8480, this is the place to get them. This set has 10 12L white beams and 12 16L white beams!

Except for the first year (1984), this is the only other set which ever included the original style single acting pneumatics, and is one of only two sets to ever include the long stroke pneumatic cylinders. This set also includes the brand new 2 blade rotor element and the new worm gear.

Features
Pneumatics This model contains a single acting pneumatic system. The components of this system are connected with rubber tubing routed through the holes in the beams. A single pump provides air pressure. Depression of the piston produces positive pressure, and raising the piston produces negative pressure (suction), limited by atmospheric pressure. This particular pump uses the longer piston from the 64mm actuator which gives it a longer stroke. The pressure is fed to a distribution block under the floor with an input (pump) and two outputs (switches). One output has a check valve which flows out and the other a check valve which flows in. Each of these is routed to a different inlet of a selector valve (switch) with one output. Selection of the switch in one direction therefore allows pressure output, while selection in the other direction allows suction. Finally, there are two pneumatic actuators connected via a T-connector which have a port at the head end to accept input from the switch. Positive pressure extends the piston, while suction retracts it. This model has the long stroke (64mm) pneumatic actuators which are only found in two models.
Lift The rear helicopter lift is driven pneumatically by a pair of tandem 64mm actuators. A 4 bar linkage keeps the lift parallel to the ground. It is even with the floor when lowered, and even with the roof when raised. A small step on the aft end of the platform keeps the helicopter from rolling off while the lift is in motion. Because the actuators are connected to a common air source, their output force remains equal. This keeps the platform from skewing side to side during motion.	Click for an animation of the lift in motion.
Ramp A front ramp/gate can be opened via a crank on the right side of the vehicle. The crank drives a worm screw through a set of 24 tooth gears. The screw then drives a 16 tooth spur gear. This stage results in 16:1 gear reduction and cannot be backdriven (because the axial friction is higher than the backdriving torque due to the screw pitch angle) which allows the ramp to be supported so that it does not fall under its own weight. A second 16 tooth gear on the same axle drives a long gear rack. The rack is attached to a link which pulls the ramp up via a beam acting as a lever arm. The lever arm always remains perpendicular to the ramp, but the angle of the link changes during motion.	Click for an animation of the ramp in motion.
Helicopter A small one-man helicopter is stowed inside the base during motion, but can be raised onto the roof for takeoff via a pneumatic lift. The main and tail rotors of the helicopter can be rotated via a crank. The crank turns an axle through a set of 16 and 24 tooth gears. The 24 tooth gear also drives the main rotor through another 16 tooth gear, resulting in a gear ratio of 1:1. The tail rotor is driven through a set of 14 tooth bevel gears. The helicopter has fixed tricycle landing gear. Since the pilot has no flight control input devices, it is assumed that this helicopter is controlled via some sort of advanced neural interface, though it is possible that it is remotely controlled from the command base and the pilot is only ornamental.	Click for an animation of the rotors in motion.
Skis This "vehicle" slides on the snow on skis, though the method of propulsion is not known. There are four small wheels and tires hidden within the skis.

Other Views
Side View	Top View
Front View	Back View
Computer Render

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8680 Arctic Rescue Base

Features

Other Views