7
If the fitting of the "klunk" type fuel pick-up weight in the
fuel tank is incorrect, the weight may stick to the tank wall,
resulting in an irregular fuel flow to the carburettor, or,
alternatively, in the fuel flow being cut off during the course
of sharp aerobatic manoeuvres. Therefore, it is advisable
to make slots in the end of the weight, with a file or
hacksaw blade. Thoroughly wash out the weight to remove
any minute particles of metal before reinstalling it in the
tank.
FUEL TANK
Alternatively, a 'NON-BUBBLE WEIGHT' FUEL PICK-
UP(Code No.71531000) may be used. This is an improved
type of fuel pick-up weight which prevents air bubbles,
generated by engine vibration, from reaching the
carburettor and causing the engine to malfunction or stop.
It is available from O.S. stockists as an optional extra
part. A silicone-rubber O-ring surrounds the 'Bubbless'
pick-up weight to prevent internal damage to the fuel tank.
Use thick silicone tubing
10mm
For piping, use heavy duty silicone tubing of approximately
2.5mm bore and 5mm outer diameter. It is advisable to
secure connections with commercially available tube clips.
Tube lengths should be kept as short as possible. Take
care not to cause any kinks in the "plumbing".
PIPING
Connect to fuel tank
IN
OUT
PD-06
8
Below is an example of a typical installation. A muffler
pressurized fuel feed is not required.
It may be convenient to lead the pipes outside the fuselage
and connect with approx. 35mm(1-1/2") length of silicone
tubing, as shown.
When filling the tank from any position other than that
shown in the sketch, be sure to pinch the silicone tube with
a clip on the pump side to prevent fuel entering the pump.
Overflow
L-shaped nipple or
aluminum tubing
Silicone tubing
Disconnect here when filing the tank
Connect to "IN" nipple
of the pump
GLOWPLUGS
Since the compatibility of glowplug and fuel may have a
marked effect on performance and reliability, it would be
worthwhile to try different heat range glowplugs.
Recommended O.S. plugs are A5, No8 and TYPE F.
Carefully install the plug finger-tight, before final tightening
with the correct size plug wrench.
The role of the glowplug
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.
Glowplug life
Particularly in the case of very high performance engines,
glowplugs must be regarded as expendable items.
Fit 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.
However, plug life can be extended and engine
performance maintained by careful use, i.e.:
9
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.
FUEL
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 open 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.
Select, by practical tests, the most suitable fuel from
among the best quality fuels available in your country for
model use. For the best performance, a fuel containing 5%
to 20% nitromethane is preferable. Lubricants may be eith-
er castor-oil or a suitable synthetic oil ( or a blend of both )
provided that they are always of top quality.
For consistent performance and long engine life, it is es-
sential to use fuel containing AT LEAST 18% lubricant by
volume. Some fuels containing coloring additives tend to
deteriorate and may adversely affect running qualities.
Once a satisfactory fuel has been selected and used for a
while, it may be unwise to needlessly change the brand or
type. In any engine, a change of fuel may cause carbon de-
posits in the combustion chamber or on the piston head to
become detached and lodged elsewhere, with the risk of
this causing unreliable operation for a while. If, however,
the adoption of a different fuel is unavoidable, check the
engine for the first few flights on the new fuel, by temporar-
ily reverting to the running-in procedure.