I had no idea Curtis Wright investigated aluminum
   rotors. I was going over some old 1963 booklets and
   tech papers Don Sherman sent me awhile back (his complete
   collection. Thanks again Don.) and ran across this illustration.
   The booklet was written by Max Bentele and was called "Curtis-Wright's
   Experimental Rotating Combustion Engines". Here is an excerpt.

   "A rotor made from an aluminum forging offers the benefits of
   lightweight and
   high thermal conductivity, but requires adequate cooling.
   One of the most successful aluminum rotor designs is cooled by forced
   circulation of oil from the engine lubrication system. The cooling
   circuit is
   schematically illustrated in Figure 18. Oil is supplied from the
   hollow shaft,
   through radial feed holes in the eccentric, and then to the rotor
   bearing
   central annulus. The oil then divides, one part to lubricate the
   bearing and the
   other to cool the rotor.

   Integral fins in each rotor lobe provide adequate cooling surface
   and a small
   hydraulic diameter. A recess at each end of these finned passes acts
   as a
   manifold for distribution of the oil. The oil from the rotor exit,
   after
   passing the bearing end annulus, is discharged from timed shaft
   eccentric
   passages directly into the housing drain annulus.

   The oil entering temperature, temperature rise, and period of
   contact with the
   metal are controlled to avoid coking or other lubricant
   deterioration. To date,
   we have had no evidence of adverse effects in this regard. While the
   oil flow of
   this design is continuous, the velocity varies as a function of the
   system
   dynamics: shaft and rotor inertia pumping superpose a roughly
   sinusoidal
   pressure increment onto the oil supply pressure. The cooling oil is
   metered at
   the exit; in this way, the rotor cavities are maintained full. Cast
   iron rotors
   can be made very much simpler than aluminum rotors but at present,
   not quite as
   light. Their cooling system is, however, different; it is adjusted
   to the lower
   thermal conductivity of cast iron and the thinner rotor walls. It is
   expected
   that by further design and casting improvements, the weight of iron
   rotors will
   approach that of aluminum rotors."

   Curtis Wright failed to take advantage of this weight reduction not
   realizing
   that someday the RPM of the rotary would be limited to 11,000 RPM by
   the weight
   of the rotor. Modern material, like Beryllium aluminum alloy, would
   make
   aluminum rotors even better. Be/Al alloy is three quarters the
   weight of just
   aluminum. My guess is the RPM of a two Be/Al rotor rotary (weighing
   180 pounds)
   would double to around 22,000 RPM and the HP would also double to
   about 1600 HP
   for an all out p-port turbo charged racing version. That would be a
   power to
   weight ratio much better than a pure turbine with about 1/3rd the
   fuel burn and
   1/10th the cost in a turbo compound rotary configuration.

   http://www.berylliumproducts.com/Attributes.aspx?id=AlBeMet162

   When this happens it is going to be an earth shaking event.
   A 300 HP car engine could shrink to below the size of a soccer
   (foot) ball.
   The empty weight of the car would also decrease as it is largely a
   function of
   the engine weight. The light aircraft industry would never be the
   same if these
   super power to weight ratio rotary engines were used in VTOL designs.

   Paul Lamar

   Paul, isn't there a major toxicity issue with machining beryllium?
   This was to be the super metal of the late 40's and 50's and it
   didn't happen.

   best,

   George W

So? You want hi tech you deal with it. So is nuclear energy.  Machining magnesium is dangerous as well.

Paul Lamar