Brief background: the oil temp was getting too high on extended climb -
coolant temp was OK, but I knew the wing-root radiator was not doing
much due to low air flow.
Mods: I installed an oil/water cooler in the return line from the
in-cowl radiator, I re-did the scoop and the shape of the diffuser to
the wing-root rad, and installed an in-line 170F thermostat in the feed
to that rad. A number of other small fixes; and converted from the OMP
injecting pan oil to using pre-mix. I put Mobile 1 15-50 in the pan.
First test, a ground run to check everything out find leaks, purge air
etc. After that some power running on the ground. The oil temp was no
longer the limiting factor, and stayed closer to coolant temp as
expected. What wasn't expected is that overall cooling on the ground
was significantly better. The only explanation could be that the new
scoop and diffuser are so much better, just sitting face into the 10-12
kt breeze helped the cooling.
First test flight: OAT 68. Climbed to 3000' and orbit the field. Temps
stayed well below limits in climb, and at cruise conditions the oil was
165 and the coolant 140. Too cool? Not even up the 170 temp of the #2
rad. I had drilled some small holes in the thermostat to give at least
some flow, apparently even that was too much.
Second flight: Went east over the hills to the dessert where the temp a
Borrego Springs was 85. I did a touch and go; then climbed at 1500-2000
fpm from 800' up to 6000'. Oil stayed below 210; coolant about 195.
Cruising back the coolant temp again dropped to about 145.
Is it not a good idea to run the coolant that low? I can change
out the
thermostat and not drill holes in it.
The oil cooler I installed is a MoCal Laminova. These had also been sold
by Aeroquip, but not any more. Not very high capacity, but very compact
and fits where I wanted to put it (on the firewall, below the filters,
where my HP3001 filters no longer fitJ). (photos 1 & 2) I had wanted
to use the Setrab TOC300, but they are not currently making those.
On the re-do of the scoop and diffuser, I made a mold and formed a unit
the would fit inside of the previous cutout in the wing. It is a curved
adaptation of the K&W coordinates, and includes provision for bleeding a
¼" boundary layer to the top edge of the core. (photos 3 & 4). My
previous flow measurements had indicated the BL was about ¼". Whatever;
it seems to be working very well. Perhaps had I done that same
treatment to the oil cooler scoop and diffuser I could have skipped the
complex task of installing the oil/water cooler. Nah, don't even go
there!
Al
Hi Al,
Glad to see everything is working well.
The Hornet guys at Ramona want me to go for a ride in the
Rotamax powered LSA Hornet. I said I would drive down to Ramona
if I could coordinate a ride with you on the same day.
Can that be arranged?
Matt at Hornet's phone number is
619 417 8895
web site is www.sporthornet.com <http://www.sporthornet.com/>
Folks, here is a wonderful video of Al's beautiful 3 rotor powered
airplane.
http://www.rotaryeng.net/Velocity_Vignette.wmv
-
Paul Lamar ...No rotor no motor.
Al,
Thanks for giving us an update on your oil cooling problem. So glad to
hear that it is now cooling. I only wish you had made one change at a
time so we would know which "fix" actually provided the most benefit.
Mark S.
Paul and Al,
Very nice video. Was there discussion about your muffler design? Very
quiet.
As a student pilot, I can confirm that beacons draw the eye to your
plane for increased safety. Should this have been in the LSA rules?
Coolant temps may be on the low side now, especially for oil temps. It
is best to get above the boiling point of water (220?) to reduce acid
production in the oil. I also believe using synthetic oils is better.
Dan F
Let's stop this OWT about oil temp minimums. Yes, water evaporation
rates are somewhat proportional to temperature - the higher the temp,
the faster a liquid evaporates. So, it is unnecessary for engine oil
to reach 212F (or 220F) in order for the oil to be "dried". Yes, the
drying process happens more quickly the higher the temperature, but
water concentration in the oil will be minimized even at 180F - a very
normal oil temp for internal combustion engines. Basically any temp
above ambient will dry the oil to some extent.
Boiling temps are reduced as ambient air pressure is reduced.
Somewhat rarely are airplanes operated at sea level (where the boiling
point is 212F). At standard pressure, the boiling point of water is
down to 196F at 8000ft.
Also, the hotter the oil is kept, the faster its constituents will be
oxidized "wearing it out." For synthetic oils this probably isn't a
concern at "normal temps," but for conventional oils it might be.
The oil needs to be hot enough to flow properly and lubricate
completely, but no hotter.
That said, it sounds like Al's airplane might be running cool enough
to be sacrificing something in terms of BSFC, but I don't know.
Questions for Al: How does indicated speed (IAS) vs. manifold pressure
(MP) compare to what you were seeing before? Any sense that drag was
markedly increased to achieve this cooling success.
Also, did you keep track of how much all of these mods weigh?
Regardless, bordering on too-cool is the right kind of problem to
have. Great work!
Matt-
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