Hi Francois,
How is the Mistral powered Piper coming? I am intensely curious
about
the strange oil cooling problem. Did they check the joint between oil
pickup tube and
the oil pump? Also what is Peter (the test pilot) last
name at Embray Riddle? I would like to contact him directly and see
if
he wants to be on the newsletter.
Paul Lamar
François Badoux wrote:
Hi Paul,
We haven't opened up the engine yet as we wanted to do a few short
flights to test the air side of the installation: dP across the heat
exchangers, so we
could fix things in parallel if needed. This is now done and the
results are excellent. The engine will be removed and the oil pump
checked next week while
we fully instrument the airplane (80 channels, 15 Hz) to gather a
full
set of flight data in the coming weeks. I'll keep you informed.
Having said this, I checked how the oil pump was put together on the
engine we are presently mounting on the bench here in Geneva. Sure
enough, it was
incorrectly put together. As there are 32 possibilities to put the
oil
pump together, with only one correct according to Mazda's maintenance
manual, chances
are that the oil pump on the Arrow is mounted incorrectly. However,
can
someone tell me why Mazda puts those dots on the inner and outer
rotors of
the pump
and insists on having them aligned. On first inspection, it does
not
seem to make a difference. I think that the real problem happens if
the
intermediate
plate is mounted upside down, that would really screw up the flows.
There was no oil bypassing the cooler via the thermostat bypass in
our
oil gallery as we thought there might be. The problem lies in the
pump
itself and in
an air leak either in the pickup tube or at the pump itself (we have
to
check the screw which holds the intermediate plate in place, if it's
unsecured or
gone, then we don't have to look much further for our problem). We
also
found out that the oil we were using has a tendency to foam, so we
replaced it.
Finally, our oil cooler is of the double-pass type with both lines
at
the bottom. Its efficiency is therefore greatly diminished if it is
only
partially
filled, another thing to check. Everything else looks in order, so
we
are pretty confident that the problem will be soon fixed.
Thanks for your time,
Francois
In the course of looking up the info on the oil pump I found some
early
flow data.
At 1000 RPM it is 5 liters a minute or 5.3 US quarts a minute.
or about 8 gallons per minute at 6000 RPM. This is a very early (1976)
13B
so
perhaps later pumps pump more. Here is some stuff from the 13B Cosmo
shop
manual
on the pump.
You do need to line up the marks on the rotors with the marks on the
housing.
Also the little screw holding the intermediate plate needs to be
staked.
Here are some jpg's from the Cosmo manual. I'll send a copy of this to
Peter.
Paul Lamar
Francois,
Yes, I remember rebuilding that geo-rotor oil pump is a learning
experience! Those setscrews have fallen out-I also use locktite on my
oil pumps in engines that I rebuilt (those oil [pumps] don?t seem to wear out,
even the chain to drive it is usually good, but I replace those!). I
think I put my first together several ways before getting it
satisfactory. I even took an extra 13B one to give to my old A/P school
teacher as an example of a classic geo-rotor oil pump-there are some of
almost identical design flying in other aircraft engines.
Question, how much oil pressure does the cs drive unit consume for both
lubrication and for supplying the governor/prop, and do you need it to
be cooler before it goes into the redrive? High oil temp in some
redrives (geared Marcotte) has been a problem.
Nice to talk to you at Sun n Fun, wish I could have stayed longer.
[Marc Wiese]
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