>
>>> 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
-----------------------
Doug,
I was not going to use CPVC it does not have the right properties.
does not support a high temperatures.
I can use any of the following, it is individual choice.
Steel wall thickness 1.0mm to 1.6 mm
Aluminimum wall thickness 2.0 mm to 4.0 mm
Plastic wall thicknees approx 8.0 mm
There a only couple of types on the market that suit.
The properties required for the right type of plastic are,
high heat support at least (140 deg C)this rules most plastics out on
the spot.
high impact
high pressure (this rules out most others)
able to see into it (tanslucent at a minimum)
They are only a very few that meet these requirements.
So if you want metal thats fine the functions are exactly the same just
the tube material changes.
Regards David Gaze
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