I am currently e-mailing foundrys trying to find someone
    casting 398 alloy. Currently waiting for a responce from Leitelt
    Brothers INC  (info@LBfoundry.com <mailto:info@LBfoundry.com
   <mailto:info@LBfoundry.com>) located
    in Chicago.  My gantry router is running and I pick up some 1" MDF
    tomorrow to cut patterns for the side housings. Apparently 1.3%
   oversize
    patterns are required for aluminum alloys or if your are using a
    pattern makers scale it is 7/32" per foot oversize. If you happen on a
    foundry using either 390 or 398 let me know on the yahoo e-mail
   since it
    seems a little off topic for the rotary engine newsletter.

    george grimes


    Ok george I did send a revised dwg to jeff to see if he can
   machined the parts
    you said you can make the pattern if let know

    Jean



   Spotted this checklist for prototype casting. Lots of good details,
   so worth reading.

   http://www.alumacast.com/casting_tips/

   Just curious as to why you picked 390 or 398 as your alloy?

   Tom Walter



Tom,  390 is the alloy in lawnmower cylinder blocks that don;t need a
liner. The  16% silicon  and 4.5% copper provide the wear surface.  398
is a similar alloy with significantly better mechanical properties and
also needs no wear surface. For the aluminum side housings of a rotary a
wear surface that also retains oil is necessary and long term use of
detonation gun coatings, nikasil, and plasma spray have not been
reliable. The coatings seem best suited for cylindrical bores and have
problems with flat surfaces. My housings are a  two piece sandwitch and
may have a magnesium casting for the non wear surface parts. The
threaded holes for the exhaust flanges are a problem with magnesium and
may require these parts to be cast in 356.  I would use 398 for
everything but the outer housings have "O" ring grooves which need CNC
machining and suitable end mills don't seem to be produced.
    For Jean's PSRU housing something like 356 or 388 seem appropriate
for castings or 6061 extruded billet stock for CNC parts. Jean needs a
fine accurate finish to mount bearing shells and that would be difficult
with 390. Nearly all the side housing machining is done in a lathe. Just
port flanges in the mill.


george grimes