Hey  Paul,

What do you think of designing the coolant and oil heat exchanger  systems to
be somewhat self contained and modular?  I realize that  cooling issues are
getting pretty well licked on the rotary, but I can't  help but think things
could be even better..

What I envision is  building the inlet scoop and diffuser to attach to one
side of the  exchanger, and the outlet plenum and restictor flap attached to
the other  side of the exchanger.  Attach this whole assembly directly to  the
motor mount.  Where exposed to heat from the exhaust, the  construction would
be of metal, but otherwise composite.  The rest of  the cowl would be
designed to attach to the firewall, and ot the exchanger  plenums.  Louvers
would be used to provide direct ventilation for the  remaining engine
components, and to reduce problems related to heat soaking  after shutdown.

A couple of the benefits are:

-  Direct/idealized control of airflow to/through/from the heat  exchangers,
allowing smaller, lighter, and more efficient  installations

- Elimination of the "pressure cowl."  A  pressure cowl mandates relatively
heavy, stiff sections in order to  maintain effective sealing around the heat
exchangers.  The pressure  cowl must contain (withstand) the dynamic pressure
associated with ram  inlet air at flight speed times the total containing
area - significant  forces involved.  Additionally, since the pressurized
section involves  many penetrations for controls, structure, and
instrumentation, the sealing  becomes piecemeal and complex.  If the critical
pressurized sections  are contained around the heat exchangers, the rest of
the cowl becomes  essentially a lightweight fairing around the engine.

Another idea I had  was to design the exhaust system so that much of it is
external to the  cowl..  Some people would think this is ugly, but I maintain
that  proper design would make it adequately aerodynamic, lower the heat load
in  the cowl, make inspections much easier, and thus represent an  improvement
in efficiency and safety.  I have seen quite a number of  artfully designed
and constructed motorcycle exhausts that i don't think  would be the least
ugly were they mounted on an  airplane..


Matt-

Good idea Matt. Good write up  too.

Paul Lamar

Great Idea, but not new. In the home built world, some are using plenum
cooling, on air cooled engines. In these, air is contained above the cylinders  in
a plenum which is continuous with the baffles. The top of the cowl has no
specific air pressure. With these, the lower chamber is, of course vented out
the bottom, or top. Even with these, it is a good idea to have some airflow
around the engine, to help eliminate radiated heat.

Now, there is a welding company who manufacturers a liquid oil cooler which
is plumbed into the radiator. Thus there is no need for an air cooled oil
cooler. This unit may be mounted anywhere under the cowl, or, I suppose anywhere
else. The radiator will probably have to be enlarged.

With a liquid cooled affair, the heat exchanger does not have to be mounted
on the engine mount (with it's increased stress due to arm and weight,) but
can  be mounted on the firewall (easier in a pusher) since the coolant tubes are
flexible and all you need to do is duct the cooling air to the high pressure
side and exit it blow or above in a lower pressure area.

The Baffling does not have to be made of metal. It can be made of  fiberglass
and epoxy (better curvature and less eddies in the airflow.) If you  are
anal, you can even use high temp resin.

Rich