4
Taurus 50
How lift is generated by the main rotor:
As with a fixed wing, the rotor blades feature an airfoil section
and are set at a particular angle (pitch angle) relative to the
airflow. The rotor generates lift when it rotates and passes
through the air. As the rotational speed and pitch angle of the
rotor blades rise, there comes a point where the lift, acting in
the vertical direction, is greater than gravity. The helicopter
then leaves the ground and climbs vertically.
If the lift generated by the rotor is the same as the helicopter’s
weight, the machine remains motionless in the air, i.e. it
hovers. If the rotor’s lift is reduced, the machine descends.
Torque compensation:
The power from the engine which is transmitted to the rotor
head takes the form of a turning force, known as torque. The
fuselage reacts to this force by tending to rotate in the
opposite direction to the main rotor.
This yawing motion of the fuselage is unwanted, and must be
eliminated. The compensation task is carried out by a small
rotor mounted at the tail end of the fuselage. Like the main
rotor, the blades of the tail rotor are profiled and set at a
particular pitch angle, and therefore produce a lateral force. If
the lateral force is equal to the torque reaction, it cancels out
the helicopter’s yawing tendency.
Controlling a model helicopter
The most important feature which differentiates a helicopter
from a fixed-wing aircraft is that its power element - the main
rotor - is also the essential control element.
The helicopter is controlled by varying the settings of both the
main rotor and the tail rotor. The main rotor head includes
what is known as an auxiliary rotor (flybar and paddles) which
transfers the control movements to the main rotor itself.
The swashplate is a sub-assembly mounted on the main rotor
shaft, or mast. It is capable of moving in all directions, and its
purpose is to transfer mechanical control movements from the
servos to the main rotor. The swashplate is actuated by the
collective pitch, roll-axis and pitch-axis servos.
How the swashplate works:
Helicopters are capable of flying forward, backward and to
both sides, and these movements are controlled by tilting the
main rotor in the desired direction.
These movements are generated by varying the pitch angle of
the rotor blades according to their momentary position in each
cycle
= cyclic pitch control
To produce vertical movement in either direction the pitch
angle of the rotor blades is varied simultaneously
= collective pitch control
Four primary functions have to be controlled:
-
Climb and descent: „collective pitch, throttle“
The pitch angle of both (all) blades is altered, and at the
same time the throttle setting is changed to deliver the
appropriate level of power to the rotor.
-
Roll: „roll-axis“
(movement around the longitudinal axis)
The main rotor plane is tilted to right or left as required
-
Pitch: „pitch-axis or forward / back cyclic“
(movement around the lateral axis)
The main rotor plane is tilted forward or back as required
-
Yaw: „tail rotor“
(movement around the vertical axis)
The pitch of the tail rotor blades is altered as required
Stage 1: Installing the skid landing gear
-
Screw the skid landing gear to the chassis using the four
socket-head cap screws, eight washers and four self-
locking nuts supplied.
Stage M1: preparing the glowplug motor
The glowplug motor should be prepared and installed after
you have fitted the skid landing gear.
Note:
Apply „Loctite“ thread-lock fluid, No. 5074, to all points
indicated by this symbol.
-
Fit the cooling fan/fan hub assembly on the motor’s
crankshaft.
-
Fix the motor to the motor mount using the screws, spring
washers and plain washers.
-
Fix the linkage ball for the throttle pushrod to the throttle
arm.
-
Screw the centrifugal clutch to the cooling fan hub.
Stage M2: installing the glowplug motor
-
Slide the starter shaft into the clutch bell ballraces from the
underside.
