David Carter wrote:
Brian Wilkinson,
I perceive there are two rather different uses of a pre-oiler: 1) For
routine use in normal operations (I infer that from your response Wed,
Mar 3rd), and 2) for wetting the insides of an engine that has not been
run for a long time, before starting it - so don't trash cam lobes,
lifters, etc (piston engines, not rotary).
I'm only interested in #2 above, "preventing or reducing damage" when
starting an engine that hasn't run for a long time.
Speaking of a long time, I downloaded an excellent article off of
AVWEB's site, where they post previous articles, kind of an archives.
This one was titled "10 myths about aircraft engine operatons". It
included cogent discussion of oil, turbos, and other items, but a lot on
oil. The author, an experienced pilot/operator and maintainer, felt
that any engine that hadn't been run for a week was probably going to
suffer a bit, as most of the oil, even 50 wt, will have run off of cam
lobes, etc, in that time. For that reason, he recommended that those
who fly their aircraft infrequently use straight wt 50 wt oil, not
multigrade, as the thinner multigrade will simple fall off the parts
faster than straight wt.
Now, back to details: I measured the dip stick tube on my VW and my
Mercedes Benze 450 SE V-8 today - both were 1/4 inch ID. Went out today
and bought a 10" length of 1/4" OD copper tubing (toilet "refill tube"
for water refill valve) - fits nicely into tube and reaches bottom of
crankcase so can withdraw oil. Got some 1/4" OD straight stainless
tubing in a longer length for the MB.
My main premise is that I'll be pumping oil under pressure into engine's
oil galley (through the oil pressure sender's hole in engine) and don't
want to overfill the engine, so need a way to extract oil. Could simply
loosen the drain plug; or, would prefer to withdraw oil from the
crankcase through the dip stick tube if not too complex to do so.
As far as injecting oil under 50 psi plus or minus 10, I think I'll
purge and clean an old propane tank, drill and tap or braize a steel
"oil outlet fitting" to the side, near bottom (being careful not to blow
my self up and end my airplane building and flying days), install a
valve, oil strainer/filter, and oil line (which will go from that lower
fitting to the oil pressure hole in engine), then modify the top valve
area of propane tank/pre-oiler to have an air shut-off valve and a
standard shop air system quick disconnect, and a means of pouring in oil
through an oil filler valve.
For operational use, I'll remove engine's oil pressure sender, install a
brass T fitting's male end into engine, install oil pressure sender into
one of T openings, and connect oil outlet line from pre-oiler to other
opening of T fitting. Remove 2 qts of oil from engine (loosen drain
plug or suck out of dip stick tube). Then assure oil outlet valve is
closed, put 2 qts of oil into pre-oiler/tank, close the oil fill valve
at top, close the air fill valve at top, turn on the air compressor, set
air compressor output pressure to 50 psi, connect shop air hose to
tank's quick-disconnect, then slowly open the air "fill" valve on tank
and pressurize the oil, turn on car's key to activate oil pressure gage,
open oil outlet valve and monitor engine oil pressure - should see a
pressure drop when viscous oil is depleted from pre-oiler and air starts
flowing through engine. Have helper turn off oil outlet valve
immediately upon noting air coming in so don't purge all oil out of oil
galleys.
Disconnect pre-oiler hose from engine, plug/cap that opening on T
fitting - or remove T fitting and replace oil pressure sender, and start
engine.
David Carter
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