> This is design particularly good for an airplane with a low
height firewall
> like the KIS and Lancair. Also airplanes with cowls that provide
limited
> room between the firewall and the back of the engine. RV6 is one
example.
>
> For another inch or two of cowl clearance the P-cap can be
recessed into
> a well in the top half of the can. Not shown in this 3D yet.
> -----------------------
> Paul,
> That configuration will not fit in the KIS Cruiser, the cowling
only clears
> the redrive plate by 1/2 inch.
>
> Bill Schertz
> KIS Cruiser # 4045
>
> I am not at the hangar. What is the distance from the top of
Tracy's retrive
> to the top of the plate? From my drawings it is 3.7 inches.
Another 1/2
> inch gets you to 4.2 inches. Just about enough. However if it is less
> than that and my drawings are wrong you can go to Zero part
number ZR56A
> which is 3.48 inch in diameter and 3.87 inches long .071 wall (50
psi anyone?)
> 6061-O. You can also dent in the 1100-O 4 inch can about a 1/2
inch to fit over
> Tracy's redrive.
>
> Here is the 3D showing the recessed pressure cap. A trick I
learned by
> looking at the Continental pressure can. They are fighting the
same cowl
> clearance problems.
>
>
> Paul Lamar ...No rotor no motor.
That traps air.
--
Blake C. Lewis
So! And! Spit it out Blake.
That is not going to hurt. You want the P-can half full of air all
the time.
You need a certain amount of air anyway to lower the air spring rate.
If you have too little air the pressure rises too fast as the
coolant expands.
The worst case scenario would be if you only had enough air space in
there to
accommodate the expected coolant expansion with out a way for the
pressure to escape.
The pressure would approach infinity or something else would burst
first.
You need a sight glass on the side of the can
to inspect the pressure level. If it is over full the coolant will
expand,
the pressure cap will release pressure and and maybe even some
coolant the
first time. When the engine subsequently cools off air will be
sucked back in. At that
point the coolant will be at a new lower level. Kind of self regulating.
Like aviation.... a self cleaning oven. Survival of only the fit :)
Paul Lamar ...No rotor no motor.
Should the temp of the tank be considered? If there isn't any flow of
coolant through the tank - it's just for expansion, then the tank will
stay cooler than the loop temperature. That means the air in the tank
will compress relatively easily. Is there benefit to having the tank
temp track the system temp, or do we want to take measures to keep the
tank cool?
Regards,
Matt-
A fine point Matt. I doubt if you will be able to cool the tank
significantly.
Paul Lamar
Matt
If you recall the gas equation I used to find the change in pressure
due to the change in volume of the P tank, we can also use it to
show how a change in air temperature will effect the pressure.
_P_1 V_1 = P_2 V_2 _
T_1 T__2 _
Solving for P_1 where the volume does not change, and using the
absolute value for T (Absolute temp = 460{F} + T {F})
_P_1 __ T__2 _
_P_2 _ = ---------
T_1
To illustrate if let the beginning pressure in the tank = 20 PSI at
220 degrees F and cools to 60 degrees F. Plug these in the equation;
_ 20 psi x (60 F + 460 F)
_P_2 _ = ---------------------------------- =
15.3 psi
220 F + 460 F
So as you can see, a fairly large change in the air temperature in
the pressure vessel makes less than 5 psi change in the pressure.
The change in volume due to the liquid expansion with temperature
rise is much more critical.
_ Joel_
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