Dan FPersonally I am inclined to use the 398 aluminum if it is
available to purchase. It is a patented alloy which may make it
unavailable in a quantity of a few hundred pounds. It is desirable due
to the mechanical properties as the first choice. The 390-17 aluminum is
easy to get at a scrap yard from old lawn mower engines and after 26
years in common use likely available as ingots which a foundry would
have access to. I am thinking about running the patterns in MDF on my
gantry router and using them with plaster moulds to make permanent
foundary patterns out of scrap aluminum, The actual parts would be green
sand cast at a foundary.

The concern with after cast coatings is that the cost is more
than the part it is coating. Also there is no guarantee that it will
remain viable and if it fails the rotor housings would be at risk. Bruce
Terentine had a quantity of ceramic coated rotors on his assembly bench
when I visited him a while back and he was comfortable with useing them.
I have not heard of a failed engine that he has built and would conclude
it works on the rotors. Where I think coatings are usefull is when the
end housings are CNC machined out of billet aluminum which limits the
choice of alloys to those rolled into plates that the billets were cut
from. Without the silicon carbide in the aluminum I would choose the
.187 thick stainless wear plate. If a billet could be obtained in 398 it
would likely me slow to CNC machine.

george grimes

I have seen ceramic coated rotors that had the coating come off.
It utterly destroyed the $800 rotor housings. It is not worth
the risk IMHO.

Paul Lamar


George,

ref to your mentioning CI part on my single rotor engine. On the final
design as going in the airplane, and already been on the ground extensively,
the side housing main part is AL 356 T6 with CI insert, as shown in my
recently posted attachment. This is for both side housings. These side
housings have very little in common with the MAZDA side housing. Power take
off from the e-shaft is through a 30mm 10:1 taper, the flywheel is
independently attached to the e-shaft. Stationary gear is on the oil pump
side of the engine, which is pretty much all, as far as MAZDA commonality is
concerned.

This configuration has been tested for many simulated flights without any
indication of problems. Off course, all durability options where not tested
mainly due to the lack of  resources, called MONEY.

Richard Sohn
N2071U