All,
What
is everyone using for oil in their 13Bs? It appears that the shop manual
specifies 10W30 or 5W30 (for cold weather). Are people flying regular motor oil
or are you all flying aviation oil (aeroshell, or
equivalent)?
Gordon
C. Alling, Jr., PE
President
acumen
Engineering/Analysis,
Inc.
540-786-2200
www.acumen-ea.com
From:
Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Lehanover@aol.com
Sent: Sunday, February 26, 2012 3:23
PM
To: Rotary motors in
aircraft
Subject:
[FlyRotary] Re: Thermostats.
I
still know all of that stuff, I just cannot remember it.
The
Mazda and many other engines use a closed loop cooling system when cold.
Where
coolant is free to move through only the engine block during warm up. This
keeps hot spots from forming and keeps the block from growing too big on the
hot (exhaust) side. It also gets the engine warm quickly so the total HC is
low enough to sell the cars in the Peoples Republic of
California.
In
a conventional system, most thermostats have a little bubble valve and
that allows some coolant (and bubbles) to move out of the engine and pull
some coolant in from the radiator. This makes the warm up last longer than
is good practice. In the Mazda version the thermostat from the Rube Goldberg
shops has a conventional looking top to block coolant from leaving to the
radiator, and a plug valve that is open when cold to divert coolant around
only inside the block. When the coolant warms the top opens and the plug
valve closes off the bypass port in the pump body forcing coolant out the
norice to the radiator.
You
can modify the pump casting by tapping the internal (plug valve hole) for a
pipe plug. Then use a conventional American thermostat.
I
use a 160 degree thermostat with three 1/8" holes drilled around
the perimeter. In the event that the thermostat should fail, just reducing
power allows the three holes to pass enough coolant to save the engine. On
very cold days, the thermostat never opens and the engine cools only through
the 3 holes and runs about 150 degrees. For those days we taped off much of
the radiator. We have a big radiator.
The
rotary has dozens of nooks and crannies in which it hides air bubbles to use
to stop the water pump with an air lock when you need it the most. It can
run for weeks with the bubbles in place and when you rev it up for say a
race start, or a take off, zoom there go the bubbles swept along to the
suction side of the pump, followed by no more pumping and then no more
engine. All of this is the same as any engine, however the rotary has the
water pump mounted very high on the block where the bubbles can have the
maximum effect on producing cavitation.
All
of the air must be removed from the system. Mazda did all of the engineering
for that in the RX2-3 and 4. The make up tank on the fire wall (plastic crap
that no American relief cap fits very well) has the pressure cap on it. The
cap on the radiator is just a lid to seal the radiator and has no pressure
relief function. Bubbles popping to the top of the radiator are forced up
the hose to the pressure bottle, then pop to the surface inside the bottle.
With any pressure reduction inside the block, resulting in only pure coolant
returning to the block. The pressure bottle need only be filled to 2/3
capacity allowing a compressible air volume on top of the coolant. After 3
heat cycles you will need to top off the bottle as the coolant will be in
the block and the recovered air will be in the bottle. Works great. Works
every time. Designed by Mazda. Works on Mazda, Cosworth, Chevy and even Ford
racing engines and airplanes.
This
was no genius move by Mazda. This is just an
Accumulator.
These
are used in all kinds of liquid systems to provide bubble removal and as a
back up supply of that liquid. And to maintain a specific pressure. As in
3000 pound flight control hydraulic systems in
airplanes.
The
make up tank or bottle need only have a filler neck that will fit an
American style relief cap. (Stant lever cap 17 to 22 pounds) Consult you
radiator manufacturer for maximum pressure. Taller and thinner is better.
Hose to the radiator top out the lowest point in the bottle. Cap accessible
so you can top off the coolant. The actual location of the make up bottle is
not at all important. It need not be the highest item in the coolant system.
The hose needs to be about 1/8" in ID however.
In
the racer the Mazda make up bottle from an RX-2 sits on the passenger floor,
and works just fine since 1980. I put that or similar in every race car I
ever built. Never a cooling problem.
If
you use a thermostat, keep in mind that they seldom fail in the open
position. They fail by the bellows cracking and loosing the alcohol in the
bellows (or whatever they use now) and the damn thing snaps shut. They do
not die slowly in order to give you a warning.
Many
racers use restrictions in the water outlet to limit flow rate to the
radiator. This is so the restrictor is the main restriction to flow and not
the radiator. You do not want any cavitation occurring inside the radiator.
Notice that the bottom radiator outlet and hose is much larger than the top
(high pressure) hose. Notice also that the bottom hose has an internal
support spring installed to prevent collapse. Deduce then that it is
possible to collapse the bottom hose via a dynamic pressure difference
between the water pump outlet and the water pump inlet even though the
pressure cap is in place an fully
functional.
They
(radiators) die quickly. If you run the rotary up to 8,000 rpm while
listening to the bottom radiator hose through a
stethoscope,
you
will probably install a restrictor after changing you Depends.
Notice
that some aircraft installations run fine with 1" ID radiator hose to and
from the radiator. That is a lot of restriction. And still it
works.
All
of my coolant must pass through a 5/8" sharp edged 1/8" thick restrictor.
And still it works.
For
low RPM installations such as airplanes, a restrictor is probably of no
value.
I
have been searching the archives but to scant successes regarding
thermostats use or lack of use for cooling.
I have been having
issue with cooling lately. I use to be able to idle on the ramp for over
an hour in the middle of a Houston summer with adequate cooling. However,
lately temps are rising faster and higher.
Yesterday, while
troubleshooting this issue I noted that after about a ten minute taxi that
the mounting location of my coolant temp probes was reading about 220
degrees measured with a handheld thermo gage, close to what was being
indicated on the panel However, the top of the radiator was cool to
the touch. The handheld thermo gage read 45 degrees. Ok. Seems
to be a flow/thermostat/pump issue. I will be Looking into this ASAP.
This got me to think about thermostat usage. I have one. I know
some do not use them.
It is my understanding that if you remove
the thermostat you have to close some passage off. What passage is this
and why does this need to be done. Also, what is the accepted method.
While researching I also saw discussion on restrictive plates.
While I am not considering a restrictive plate, the thread discussed
drilling holes in the thermostat itself. Lynn mentioned do it caught my
interest.
It seems this is something I use to know but now forget
where I saw it. I just finished reviewing my partial scan of Tracy's
conversion manual to no avail and my archive search is giving me hundreds
of returns.
Thanks,
Chris