Jerry Hey wrote:

I finished the swirl pot yesterday.   All that remains for the

cooling

system is the overflow tank which I think I will make out of
welded
aluminum.  Is there any problem with having it fill and empty from

the

bottom?    Jerry

I use the original Mazda system from the RX-2 on the race car. The

overflow tank has the pressure regulating cap. My swirl pot has a
filler cap
to seal it but no guts in the cap to regulate pressure. The overflow
bottle
acts as an accumulator. The outlet of the overflow bottle could exit
th cowl
in front of the pilots side windscreen. This would allert you to a
problem.

Lynn E. Hanover

Cliff Manzke wrote:

Jerry, hate to tell you now, but the on-axis, bottom outlet of your
swirl
pot is bad news.  Here's why:  When you first fill the system with
water you
will also fill it with some air.  When you start the engine, the swirl
pot
starts to do its thing by acting as a centrifuge, forcing the water
outward
and at the same time forcing the air inward, forming a column of air
in the
center of the swirl pot.  At the same time, a strong whirlpool will be
formed inside the swirl pot by the outlet.  So, when enough time has
passed
(several seconds) and enough air gets separated out, the column of air
will
reach the bottom of the tank, at which point the whirlpool will
instantly
suck it down and back into the system, starting the process all over
again.
It may sound crazy, but these are words of experience that Jeff
Spitzer can
confirm.  We (at General Atomics) pulled our hair for a few days over
this
one.

The solution is either a much taller swirl pot (heavy) or one with a
tangential outlet as shown in the attached picture. With this design,
the
tank can be quite small and still function.  Something like 6 inches
tall
and 3 inched in diameter ought to do.

Also, the swirl pot does not need to be at the highest point in the
system
to do its job, although filling the system with water is impossible if
it
isn't.  A separate filler plug at the highest point will solve this.
In any
case, small bleed lines from all the high points back to the swirl pot
are a
must.  Your swirl pot may look like a porcupine when you are done.  If
you
don't get ALL the air out of the cooling system your just shooting
yourself
in the foot!

It is also my opinion that the "radiator" cap (and swirl pot) should
be on
the inlet side of the water pump so that the cap controls the pressure
on
the inlet of the pump.  Pump cavitation is a big no-no.  Having a known
positive pressure (cap pressure, something like 15 psi)) at the pump
inlet
will help prevent (or at least reduce) cavitation.  Another name for a
swirl
pot is "header tank" which implies "keeps a constant head (pressure)
on the
pump inlet."  Entertain yourself and install a pressure gauge (or for
some,
a vacuum gauge) on the inlet side of the water pump and see what it
reads at
full engine speed.  You may be surprised!

Another good idea is to install a clear sight tube (permanent or
temporary)
in the water system.  When you have air entrained in the flowing water
it
will be obvious.  When you get ALL the air out, the sight tube will be
clear
and you'll swear your pump stopped working.

Happy flying!
Cliff Manzke

Cliff,  I copied my swirl pot design  and location from the Star Mazda
Series where these cars are running (according to them) without cooling
problems.
However, that does not mean that your points are not valid.    Nice
rendered drawing.  It would not be too difficult to change the swirl pot
outlet to tangential per your drawing if it proves necessary.   Jerry

 
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