Wren 44 Gold Helicopter Owners Manual
Page 10
How do I lock the output shaft to fit my clutch and fan components?
To enable the output shaft to be locked for attaching output
components, clutch etc, unscrew the lower part of the gearbox
using the simple plastic tool supplied.
DO NOT
attempt to jam
the gearbox shaft by sticking a screwdriver or metal rod in
between the 2
nd
stage turbine blades – you may cause severe
damage to the blades and this
will not
be covered under the
warranty.
After removal of the access cap use a
clean 12mm A/F socket or ring
spanner to the large nut at the inner
end of the shaft (which is high-strength loctited to the shaft) to lock
the shaft and enable the supplied washer to be fitted to output
shaft first, followed by clutch, fans etc, followed by securing nut.
Be extra careful to keep everything clean here and do not leave
the gearbox interior exposed as dirt particles getting in will
eventually be washed into the turbine bearings as soon as the engine is started up and this
may cause permanent damage to the bearings. As we cannot control access to the gearbox
interior we cannot warranty 2
nd
stage turbine bearings, however such access has not proved
to be a concern in the development testing.
It is most important the black washer supplied is fitted
before
the clutch unit so the
clutch cannot foul the top bearing on the gearbox.
What is the effect of forward airspeed on the engine?
Once the helicopter is in the air and traveling forwards the rotor rpm
will increase as its load reduces with forward speed. An rpm increase
of 10-15% can be expected in the air so choose a pitch setting that
keeps the output speed below the rotor safe maximum.
It is this increase in rotor rpm in the air which gives the turbo-shaft
powered aircraft a high airspeed capability and shows a definite
edge over it's I/C engine counterpart. I/C engines have a more
limited unloaded speed capability, as it can result in the engine
mixture strength "leaning out" which can cause engine damage. By
contrast the turbo-shaft engine will enjoy running cooler as the rotor speed unloads leading
to longer life and reduced loading on critical components.
How is the unit it mounted in the airframe?
The unit is housed on the standard i/c
engine bearers provided in the heli
airframe, by the four M4 mounting holes
provided on the gearbox.
The output shaft will then be presented in
the correct position for the clutch and fan
components as per the normal i/c engine
install.
Support is required for the main body of
the engine forward of the gearbox and
simple aluminium or stainless steel strap
around the engine will suffice.
