This article is printed with permission of its author, Mr. Neil Tidey,
the designer and manufacturer of those magnificent world famous LASER engines.
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The engine in your motorcar has a 4-stroke engine. A pump
circulates the oil through an oil filter. The oil has many additives to combat
the effects of products of combustion and improve other properties.
Motor oils are manufactured to high standards and the type of
oil to be use in your car will be specified. The engine is unlikely to suffer
from rust if standard maintenance is carried out. The engine is fitted into a
carefully designed environment and engine management systems look after things
like fuel mixtures and detonation. There will be some people that always have
more problems than others, this is simply because we all drive differently.
Lubrication of our model 4-stroke engines is through oil
passing the piston ring and the oil you put into the engine after or before
running the engine.
Some by-products of combustion are included in the oil that
passes the rings. These include acids and water and some neat fuel. The most
potent acid is nitric acid which is produced from nitromethane. If you run on
fuel without nitromethane you eliminate this cause of corrosion.
Methanol can contain water through absorbsion and water is
also a product of combustion. It produces a mild acid when burnt. The crankcase
heat will reduce the possibility of condensation of water and the possibility of
rust; an engine running at tickover will create more condensation than one run
flat out. The thicker sections of the Laser crankcase encourage a higher
transfer of heat to the crankcase and this further reduces the problems.
Rust is not in the crankcase initially, it is caused by the
products of combustion and the lack of preventative maintenance.
Using 2-stroke motor oil as an after run dilutes the acids in
the crankcase and reduces the harmful effects. The reason for using 2-stroke oil
is that it is a motor oil and has high pressure characteristics. It is also
designed to pass through a combustion chamber. The oil used in the fuel would
also be good but most are too thick and would not distribute very well in the
crankcase.
Products such as WD 40 consist mainly of a solvent, this
dilutes the oil and unless drained out of the crankcase or allowed to evaporate
could cause seizure. Imagine filling you car sump up with WD 40.
Small 2-stroke engines are lubricated with oil in the fuel.
The bearings in the engine are generally roller or ball bearings as the oil is
very diluted and the quantity is small. Petrol contributes to the lubrication
which is why a higher percentage of oil is used for methanol burning engines.
Larger high performance 2-strokes use a separate high pressure lubrication
system; the oil is not mixed with the fuel. Don't be fooled, methanol and
nitromethane also cause corrosion in 2-stroke engines.
Castor oil is an excellent high pressure lubricant and will
stand very
Synthetic oils do not create carbon or lacquer, are excellent
lubricants, but do not tolerate abuse as well as castor. By abuse I mean
allowing the engine to overheat or insufficient lubrication. Causes of
overheating are another subject.
Oils may have additives to combat corrosion; these will be
better in some fuels than others. Morgan Coolpower fuels now seem particularly
good. 1 to 2% castor may have a beneficial effect added to synthetic fuels.
For my own engines I use ML70 oil (not available in every
country). I do not use nitromethane except for test purposes and have never
experienced any significant corrosion problem. I do lubricate each engine with
2-stroke oil before flying after a lay up longer than a few weeks. It is also
worthwhile to lubricate before lay up.
By lubricate, I mean fill the engine up through the breather
nipple on a 4-stroke or through the carburetor on a 2-stroke. Turn the engine
over and point it in different
directions to circulate the oil. Before flying, let it drain back through the
nipple or carb. With most engines, you will get an increase in rpm. If you have
not done it before - try.
Enough for now!
Neil Tidey
http://www.laserengines.com
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Lyman’s comments: I don’t know if the “ML70” oil Neil refers to
is available here in the Colonies. However, as stated in my “Care and Feeding
of Four-Strokes” article suggests, the use of Marvel Air Tool Oil (MATO) is
strongly suggested for use as an after-run oil. For “Lay Up” use a 50/50 mix
of MATO and automobile transmission fluid (ATF).