The
Dirty End By
Martin Paffett
From the outset I should say that I am no expert but I do have a
life-long interest in engines of all sorts, and as a
control-liner I have picked up a few tips along the way.
I would like to start by saying that
you need to be aware of all the brass components in your
average glo-plug engine. The
combustion bi-products of nitrated fuel in your engine creates
nitric acid and if left unattended this will eat any of the
following: carb
spray bar, ball bearing cages, ABC brass cylinder liners, etc,
etc. The lesson is
simple, if you use glo fuel with nitro-methane you need to take
some simple precautions to ensure a long life (for your
engine!).
1.
Each time you fly, after the last flight of the day,
whilst the engine is still warm, run it up to max RPM then pinch
the fuel tube. This will ensure that there is the minimum amount of
combustion products left in the engine, and the heat will help
evaporation.
2.
Empty the fuel tank completely.
3.
Lubricate the engine with a light mineral oil (“3 in
1” or similar).
Make sure that it is distributed about the engine by a quick blast with
the starter, but flick
first to ensure you don’t have a hydraulic lock.
If you fly every week you may consider this regime a little
excessive, but if there is likely to be a longer period before
you run your engine again, then it is worth the effort.
You may well notice that the brown, slimy heap on the front of your
model seems to be producing less power than it used to.
Model engines (particularly glo's) are quite susceptible
to coking and glazing on the inside and often form large
deposits of burnt castor on the outside.
This creates higher friction and heat build-up and at the
same time reduces heat dissipation.
Your little brown friend will appreciate, and benefit
from, a good clean.
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Do not be tempted to clean it in one piece. If you are not confident with the following procedure, go
no further, a bodged engine is worse than a tired one!
Never place any part of an engine in a vice, including the
crankcase. Dismantle the engine carefully to all it’s component parts,
but don’t extract bearings from crankcase.
Do not be tempted to lean too hard on fasteners; if they
won’t come undone then try thin oil, heat with a heatshrink gun,
and try again. Carefully
mark the orientation of the piston, liner and con-rod so that they
can be put back in the same positions.
If the engine is a four-stroke then now is the time to take
careful note of the valve timing; you will need to be able to put
all those gears back in at some point.
Clean the parts using one of the many chemical chip pan cleaners
on the market but ensure that it is compatible with aluminium
pans. If you are
un-sure, do the silencer first.
Do not allow the cleaner to come into contact with any
plastic parts; it will dissolve them.
Remove paper gaskets (with a scalpel) and put to one side,
they don’t need cleaning and you don’t want to get them wet.
You may have heard people speak of boiling in washing
powder – don’t do it. It
is highly corrosive, will fade any anodising and is not very effective. Never,
ever use any form of abrasive material on any moving part, no
matter how badly you want to remove the deposits.
After standing for several hours in cleaner (the engine, not you!),
rinse off with a stiff bristle brush under cold
running water then wash with soap under a hot running tap, dry
carefully and then place in a warm oven to make sure.
If there are still deposits on the engine parts, start
again with another coating. Stubborn
corners can be helped by stirring the cleaner with the sharp end
of a wooden cocktail stick.
When you re-assemble your
engine, check every component for damage or excessive wear and
replace as required. Rebuild
using a light mineral oil to coat all components.
Be careful not to over-tighten screws.
If anything feels wrong then stop..... you have probably
put it in the wrong way round (I speak from bitter experience!).
If you are sure that everything is OK, and you do not
intend to use the engine yet, don’t run it.
There seems little point in re-starting the corrosion
process if there is no need; seal it in a plastic bag and put it
away safely.
If you have an engine that requires repair, rebuild, clean or
whatever and you don’t want to do it yourself then please feel
free to get in touch. I
can usually get most things to run and have facilities for making
some items that can’t be replaced.
Martin P
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