On a different note, I am learning how to do aluminum castings.
I am looking for the best casting material for center and end
housings, possibly one to the ceramic metal matrix hyper alloys
and  beralcast 363 for rotor material. It appears to be the
only beryllium alloy on the market and can be investment cast to
near net. Do you have any  knowledge on this stuff? I've been
reading about it for about a day, and  looking for a supplier.
Ed Carver

I have heard of aluminum/beryllium alloys .70% the density of
aluminum.
 Makes great rotors. What is the density of beralcast 363?
Paul Lamar

Ed Carver,the 363 sounds like a good rotor material depending on
 it' coefficient of expansion. It might require pressure assist
or vaccum
 casting. For vaccum assist you can fill a 12" diameter 25 ft
tall pipe
 with water, tap off the top header for the vaccum and open a  90
degree
 plate valve at the bottom with the valve submerged in the
capture tank
 water. We  used this system to raise liquid steel for vaccum
degassing
 and bubbled argon in one side to make it circulate. Three passes
of a 424 ton heat  in 7 minutes. The tower was 150 feet high.I
was thinking of 390 aluminum for end housings.
That is what
 the Briggs and Stratton and chevrolet vega blocks are made from.
No wear
    coating is required since the silicon carbide is in the alloy.

I am currently looking int to NASA alloy designated 398 which
has much higher strength than 356 and other commonly used alloys
and also  needs no wear coating. It will work with gravity
assist which is just a standpipe at the pouring sprue. No rocket
science. I haven't run my patterns on the gantry router yet but
the design is finally  frozen and G code files are done.
george grimes


The rotor runs too hot for 363. Be/Al has higher strength at 500
F. Aluminum loses over half it's strength at 500 F.

http://www.suppliersonline.com/propertypages/6063.asp#Spec
Paul Lamar

Yea George!,
I've spent the past 3 days reading up on which casting alloys are best.
I was hoping I would get some feedback on the 390 stuff. I'm
going to  have to find out which alloy Porsche used in their
928/944/968 cyl.  blocks. The rings rode directly on the alum
wall with excellent wear  characteristics. The cyl walls were
either impregnated with a silicone  substance during the final
surface finishing, or, the silicone was  simply used as a lube
during the honing process. I think it was 390 they  used. This
raises the issue of which rotor side compression seal  material
should be used to ride on 390.

I have seen hypereutectic alloy used as brake rotors with
special pad  material clamping onto them. A local los angeles
engineer developed it  for light weight race cars back in the mid
90s. Porsche developed  aluminum rotors about 12 years ago for
their twin turbo 996 and their  super cars. I would have to
really dig to find out which substance they  used to treat the
rotor surfaces.

I'm not an engineer. It's easy to make comparisons using the
tech data  sheets online. It appears to me that the beralcast 363
BeAl alloy is  really superior to all other options for rotor
usage. Perhaps the 390  hyper alloy would work as a rotor under
low power usage. That is the  purpose in it's usage in oem pistons.

What is of greatest interest here is whether we can use a
casting  process to make the rotor. If we can, it will make light
work once on  the machine table.

Paul, are you telling us that 6063 alum should not be used for
rotors,  or is it the beralcast 363 BeAl alloy you are warning
about? All the  aluminums have approximately the same melt point,
the beralcast 363  should hold up better and longer. I believe I
read that beryllium melts  at about 2100f. Not the same as the
363 alloy.

Time to look into the 398 alloy.

Ed Carver

The only aluminum alloy other than be/al that has a chance for rotors
is NASA 390. Not the same problem as cylinders.

http://www.rotaryeng.net/aluminum-alloy-rotors.pdf
http://www.rotaryeng.net/aluminum-alloy-rotors2.pdf
http://www.rotaryeng.net/Be-Al.pdf

Don't get silicon and silconE confused. In the Vega engine the
high silicon content aluminum used for the cylinders were
etched to  raise  the silicon to the surface. As I recall a
special coating was used  on the pistons. The scheme largely failed.

In the Porsche cylinder a process called Nikasil by Mahle  was used.
http://www.ebsracing.com/content.wws?fname=Porsche-
Cylinders.html  I think this was done by exploding a nichrome
wire down the  down the center of the cylinder with high current.
This was tried  on certain Wankel engines with bad results.
Quality control was  less than satisfactory.

Porsche also used:
"Depending on their silicon content, aluminum alloys are
referred to as either hypoeutectic or hypereutectic. Alusil
has a hypereutectic aluminum content of 16% to 18% so that
primarily silicon is precipitated. The Cayenne engine
manufactured to precipitated during solidification. A
special three step honing process is applied. The silicon
grains in the cylinder bores in form of microscopically
small, very hard particles, giving the necessary
wear-resistance of the cylinder surfaces for the pistons
and piston rings, are laid bare in the final step."

Probably etched like the Vega.

Mazda successfully used a expensive process called detonation
gun  coatings for  alloy end housings for the LeMans winning
engine. To my knowledge  that is the  only process proved over
long hours at high power. We await the 16x  to find out  what
will be used on that. If I were Mazda I would stick to the  steel
inserts.

http://www.rotaryeng.net/Mazda_R26B_US.pdf
http://www.rotaryeng.net/material-tech.pdf

http://tinyurl.com/26yhecj

The rotor housings have a die cast in hard steel chrome plated
insert of course. Highly successful.

Paul Lamar

Ok, the nasa 398 alloy is designed to hold up to about 750f, and that's
much better than the other common hyper alloys for piston use listed
on the nasa 398 tech page on your main site. There is no specific
data on the same issue with any of the other castable alloys I can
find. The 398 may also be best for the center and end plates. I
doubt anyone will create new iron side rotor seals to ride on the
etched 398 aluminum like the Porsche rings on the 390. This leaves
us with flame spray coating, or ferris plate inserts.

The albemet162 is not their castable alloy, but specs out about the same
as the beralcast 363, which is castable. The albemet IC910 is
castable at a much lower Be content, and has much lower specs. There
are other castable Be/Al products, but beralcast 363 appears to me
to be better.

There is a rather odd spec about melting points of these Be alloys.
Can't figure out why, but they put two melting points on some of the
pages that are wildly different. The albemet162 specs show a 2000f melt
point and a 1200f melt point on the same column! Whats with that? I have
read similar on other spec pages.

If it has some 30% alum in it; it will melt at 1200f, no matter what.
Yea? Pure Be melts at ~2000f~.

For the moment, it appears we use the nasa 398 as rotor material, or
beralcast363.

For center and end plates, several materials will work, but why not
stick with what Mazda uses for the rotor housings. Isn't that a356?

Should I consider it conclusive that we now have 2 potentially good
castable materials to try light weight rotors? Or do I keep looking?

Ed Carver

I think we are talking about three different things here.
Mazda used the high silicon content Al alloy to reduce heat expansion
and contraction in the rotor housings. The old Al alloy would over heat
to 250 F and then permanently compress under the restraining force
of the steel tension bolts. The rotor housing was then junk.

Then there is the question of the Al wear surface.
Unfortunately the term flame spray is used on a lot of coatings.
One must be more specific as there is a world of differences
in coating procedures with vastly different characteristics.

The major problem with coatings in general is no way to check
adhesion non destructively in the manufacture process.
You have to build thousands and then see what percentage fail.

That is why I am a fan of two piece end  housings one of which is
a replaceable steel wear surface.

Then there is the question of what to make the rotor out of.

This should be three different threads. Lets separate them.

Paul Lamar

Would it not be just as cost effective to use the Racing Beat Al housings for
the one and two rotor engines. To build three and four rotor engines, the RX7
Specialties wide housing, (two piece Al with Cermet coating) can be used with
the RB housings. All the R&D is done. Takes the fun out of it but also the risk.

Then the only challenge is to find the right alloy for the rotors.

Dale Davies

BTW Dale your book went out today. Thanks.

Paul Lamar