I like David's constant pressure design the best for an inverted
system. I'm not sure why the design was dropped so quickly on the
list.
I have been trying to find a way around Aubrey's objection to the
constant "high" pressure when the engine is at rest.
The engine is at rest for quite sometime before the liquid cools
down and retracts reducing pressure. Is this enough time to get the
o-ring shift?
How much does a 75F to 30F then back to 75F ambient pressurize
the system? When the temp falls liquid is suck up from the A-can. Then
the temp comes backup and pressurizes the system. Extremes happen like
this in Arizona where 75F day and a 30F night mid winter. Summer time
might have even higher extremes. Can this produce enough pressure to
get the o-ring shift.
But, to relieve pressure at rest.....
If we put a spring in the liquid side of the P-can as in the
attached picture (badly drawn red spring). Then charge the air side
with the upper bleeder open, so we get the air and the spring in
equilibrium. Then when the system is at rest we have a relatively
non-pressurized system.
?Ideally? the spring provides equilibrium in a short throw. So
that when the system starts to expand it will leave the spring behind.
At rest with the spring and air in equlibrimum and a ambient temp
cycle, as above, the pressure of the system should stay more constant
by allowing the system to grow without exceeding trigger point to
overflow.
--
Blake C. Lewis
The way I see it there are two major problems. As far as I can tell
there is
no way to get dissolved air and gas out of the coolant. Second, it is
expensive
to make as you need a large lathe. The whole idea with the Mazda RX8
system
is to get the air out on a continuous basis.
BTW the cooling system in my RX8 appears to be far more robust than
in my RX7. From time to time the RX7 would get hotter than the
thermostat.
The RX8 never seems to do that.
Paul Lamar ...No rotor no motor.
I like the idea that you can detect coolant leakage past the o-rings in
your pre-flight if you relieve some air ( so I guess you need access to
compressed air at pre-flight ) , but I don't like the failure mode in
flight - how will the system react in flight if the o-rings / piston
fail and all that air is injected under spring pressure into the cooling
system ? I don't think I'd like to learn on a night flight...
Suggestion - invert what you have so the liquid is on the bottom with
the coolant line at the bottom of the vessel. Place the spring on the
air side with a shutoff valve at the base of the coolant for pre-filling
the unit with liquid during maintenance. The package would be at the low
point in the system to maintain fluid in the system. At the high point
in the system have a small accumulator / air bleed valve with sight
glass - at preflight you look for trapped air in the sight glass and
crack the valve to let out the small amount of air. This should not be
regular as the constant pressure accumulator will expand and contract
with the 10% change in volume the system will experience every fight.
Ideas ?
-dave
You can use something as simple as a bicycle pump to preflight
the cooling system. If you want to get fancy you can use one of these
12 volt portable air compressors.
Paul Lamar ...No rotor no motor.
What I will use - since I am not into inverted flight ( yet ? LOL ) I
will use the idea of the cylinder rather than the bladder. In the
cylinder - CPVC maybe - I will have the fluid on the bottom and the
coolant line at the base with the air fitting at the top, but no piston
and no spring - rather a solid foam ball floating in the coolant with
only a few mm clearance between it and the walls. It will keep the
liquid from sloshing near the base and keep mostly air above it. Fail
safe in most modes of flight.
-dave
Dave
You are joking right? Plastic unless you are talking Teflon is not the best
substance to hold up in a stressful environment like an aircraft engine
compartment. I have lots of late night experience replacing CPVC of all
grades in pool filtration systems that are subjected to expansion
contraction cycles. The stuff micro fractures and is they are not apparent
until sudden failure. Ie one large crack. Hard foam abrades and ends up
clogging the radiator. Terrible for heat transfer characteristics:)
Go with aluminum if possible. Lots of tested vessels on the market.
Doug in Japan
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