Un d e r t h e C o w l
Tese drive gears, from a Rotax 582, were run for a short time without oil.
Engine Lubrication
A slippery topic
By Tim Kern
Our engines have many moving parts. Lubricants keep
those parts from touching one another and carry their heat
and contaminants away. The principles are simple. Nothing else is.
Design engineers, when they draw up engine systems,
have lubricants already in mind. They know, for instance,
which materials to use, how close to make the clearances,
and how loose to make the tolerances. Knowing the lubricants' properties, they design the most robust system they
can. Improve the lubricants, and the game changes. ExxonMobil Aviation Lubricants Product Advisor Dr. Shlomo
Antika put it simply: "What oil engineers do is create
molecules that get between the moving metal parts."
Once these engines (and gearboxes and water pumps
etc.) get into our hands, we are expected to meet the de-
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signer's expectations, providing the right kinds, quantities,
and temperatures of the proper clean lubricants.
As an example, in a typical engine, oil is introduced under
pressure into one area through holes in the main bearing
saddles. This oil keeps the crankshaft and the main bearing from touching and welding themselves together. The
crankshaft has holes in it, through which the main bearing
oil gets transferred inside the crank to the rod bearings,
where it keeps these bearings from welding themselves
to the crankshaft. The oil then escapes into the crankcase
as splash and mist, where it lubricates the cylinder walls,
some valve train components, and piston pin; and it puts
its protective coat on all the engine's internals. Then it
flows downhill and gets collected in the sump, goes to the
oil filter and pump, possibly to a de-aerator and cooler, and
back out to the bearings again.