ROBBE Spirit M-8 Instrucciones De Montaje Y Manejo página 37

How lift is generated by the main rotor:
As with a fixed wing, the rotor blades feature an airfoil sec-
tion and are set at a particular angle (pitch angle) relative to
the airflow. The rotor generates lift when it rotates and pas-
ses 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 oppo-
site 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 inclu-
des what is known as an auxiliary rotor (flybar and paddles)
which transfers the control movements to the main rotor its-
elf.
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. Three servos are mounted
below the swashplate, and they provide cyclic and collective
control of the main rotor with the help of an „HR 3" mixer set
up on the transmitter.
Assembly instructions
Spirit M-8
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
1.1 Assembling the rotor shaft pivot bracket,
freewheel hub and main rotor shaft
- Fix the pre-assembled rotor shaft pivot bracket S5028 to
the chassis S5000 using the screws S0079.
- Attach the pre-assembled freewheel hub S5030 to the 75-
3
tooth gear S5094 using the screws S4354 and washers
S4366.
- Slide the main rotor shaft S5020 into the rotor shaft pivot
bracket from above, and insert the aluminium spacer ring
(6/8 Ø x 2.7) S5031 and the freewheel hub assembly
S5030.
- Fit a washer S0007 on the screw S0030 and screw it into
the underside of the main rotor shaft.
- Fit the grubscrew S0041 in the collet (6/11 Ø) S5036 and
fit it on the rotor shaft. Position the collet so that there is
zero slop, and tighten the grubscrew.
1.2 Assembling the primary gearbox stage
- Fit the flanged ballraces S5044 in the chassis as shown.
- Press the 16-tooth pinion S5032 into the 60-tooth gear
S5084, and place this gearbox stage between the flanged
ballraces.
- Fit the gearbox shaft (3 Ø x 33) S5027 through the flanged
ballraces and the gearbox stage from the top; the machi-
ned flat must be at the bottom.
- Fix the 16-tooth pinion to the gearbox shaft using the
grubscrew S0041. Check that the screw engages on the
machined flat.
1.3 Assembling the tail rotor drive system
- Slide the long tail rotor drive shaft (2 Ø x 419) S5018 into
the end of the tail rotor drive coupling S5114 as far as it
will go, and secure it by tightening the grubscrew S0041
onto the machined flat.
- Press the 3 x 8 x 3 ballraces S4035 into the tail rotor drive
bracket S5056.
- Push the tail drive coupling through the ballrace.
- Slide the 14-tooth gear S5026 onto the tail rotor drive cou-
pling as far as it will go, and secure it by tightening a grub-
screw onto the machined flat in the shaft.
- Place the drive bracket / tail rotor drive assembly in the
chassis, and secure it with the screws S3370 and washers
S4366. Adjust the position of the tail rotor drive bracket in
the slotted holes so that the gears rotate freely, but with-
out slop.
- Grease the whole gearbox.
Order No.
S 2881