16
Fuel
Use a good quality commercial fuel or one of the blends
shown in the table. Fuel "A" is suitable for running-in and
ordinary use. Fuel "B" is for use when more power is required
and for improved flexibility. Note that even a small quantity
of nitromethane (3-5%) will improve flexibility, making the
needle-valve adjustment less critical and improving throttle
response. Use only materials of the highest purity. Synthetic
oils are permissible but are less tolerant of a "lean run" than
castor-oil. If, therefore, a synthetic lubricant is used in the
fuel, readjust the needle-valve to a slightly richer setting, as
a safety measure, in case the fuel/air mixture becomes too
lean through maneuvers in flight. If a higher nitro fuel is used,
the engine should be checked out to make sure that it is
sufficiently run-in to operate on that particular fuel without
overheating. Do not use fuels containing less than 18%
lubricant.
ADVICE ON SELECTION OF FUEL, GLOWPLUG & PROPELLER
A
B
75%
20%
5%
65%
20%
15%
Methanol
Castor Oil
Nitromethane
Model engine fuel is poisonous. Do not allow it to
come into contact with the eyes or mouth. Always
store it in a clearly marked container and out of
the reach of children.
Model engine fuel is also highly flammable. Keep
it away from naked flame, excessive heat, sources
of sparks, or anything else which might ignite it.
Do not smoke, or allow anyone else to smoke,
near to it.
Reminder!
7x4
8x4
9x5
10LA
15LA
25LA
7x3-5, 8x4
7x5-6, 8x4-5
9x5-6
PROPELLER
Suggested propeller sizes are given in the table. As the
ideal propeller diameter, pitch and blade area vary
according to the size, weight and type of model, final
propeller selection can be made after practical experiment.
Trainer & Sport
LA Series
Never touch, or allow any object to come into
contact with, the rotating propeller and do not
crouch over the engine when it is running.
Running-in
Reminder!
17
GLOWPLUG
The role of the glowplug
Glowplug life
Particularly in the case of very high performance
engines, glowplugs must be regarded as expendable
items. However, plug life can be extended and engine
performance maintained by careful use, i.e.:
Install a plug suitable for the engine.
Use fuel containing a moderate percentage of
nitromethane unless more is essential for racing events.
Do not run the engine too lean and do not leave the
battery connected while adjusting the needle.
With a glowplug engine, ignition is initiated by the
application of a 1.5-volt power source. When the
battery is disconnected, the heat retained within the
combustion chamber remains sufficient to keep the
plug filament glowing, thereby continuing to keep the
engine running. Ignition timing is 'automatic' : under
reduced load, allowing higher rpm, the plug becomes
hotter and, appropriately, fires the fuel/air charge
earlier; conversely, at reduced rpm, the plug become
cooler and ignition is retarded.
Apart from when actually burned out, a plug may
need to be replaced because it no longer delivers its
best performance, such as when:
When to replace the glowplug
Filament surface has roughened and turned white.
Filament coil has become distorted.
Foreign matter has adhered to filament or plug
body has corroded.
Engine tends to cut out when idling.
Starting qualities deteriorate.
Since the glowplug and fuel combination
used may have a marked effect on
performance and reliability, it would be
worthwhile to experiment with different plug
types.Recommended O.S. plugs are No.6
(Former A3) ,No.7 and No.8.
Carefully install plug finger-tight, before
final tightening with the correct size plug
wrench.
