More pictures of Everett's work.
Super simple.
Paul Lamar
Paul, The picture you have there may be even more rare than you
think.
I talked with Alan Tolle several times about some of the things Everett
had
done. Alan said He was never satisfied with the aluminum end housings he
had done. Alan said that he designed end housings made from steel with
the
internal pockets machined and then the housings (two parts) were furnace
brazed togeather making a steel housing that has hollow. The picture you
posted looks like exactly that. I may be mistaken but it looks like
there
is braze material on the sides of the end housings. Plasma sprayed parts
are more uniform in appearance. Modern det gun coatings would probably
make
the aluminum housings OK, but there is another possibility.
Bill Jepson
PS I would be ready to buy housings at $500 now more than that would
require thought.
Bill
I went up to Everett's farm several times before he died.
Paul Lamar
Alan Tolle wrote:
Paul, this is another message to which I should add some input regarding
the subject of aluminum end and center housings.
The picture that was shown here was of the 180 SL (super light) engine
which I flew in the RV-3 for a little over 100 hours. The all up engine
weight was 180 pounds including accessories and the hp out put was 180
at
6000 rpm. Besides being peripheral port it was also dry sump, hence no
oil pan. It was a plugs up engine with water induced into the block
around
the plugs (the hot side) and the engine rotated the opposite direction.
Yes, the opposite direction.
Everett Hatch built the end and center housings of A356 aluminum and the
internal passages were simply mirror images of the normal 13B engine.
While they achieved the goal of making the engine light, they proved to
be
unsatisfactory for two reasons.
First the wear coatings tried were not satisfactory. I don't recall
exactly what he used, but it would have been what ever was available in
the
early 1990's. As you have noted on occasion better wear surfaces are
available today, though perhaps at considerable cost.
Second, the main reason for abandoning the aluminum end and center
housings
was what Everett referred to as "creep distortion." Each time we
disassembled the engine it was clear from the wear pattern on the side
surfaces of those housings that the sandwich of five aluminum parts was
going back together differently each time. The required clamping
forces of
the through bolts were compressing and distorting the end and center
housings. We were using the original four steel alignment pins and it
was
unlikely that adding more would have made any difference. I doubt that
aluminum end and center housings made anyone else is going to perform in
any different manner.
A solution was obvious --- build up the end and center housings from
4130
steel plates, posts, and dividers, furnace braze everything together,
and
nitride the wear surface. Somewhere around in Everett's shop there was
the
beginning of that project.
However, the 180 SL was abandoned for two reasons. First was poor
durability of the planetary gears. The cut of the planetary gear
(spiral
or straight) and the number of planetary gears (three, four, or six)
made
no difference Even with second and fourth order dynamic counter
weights
on the shaft the planetary gears went away. Why? Due to the lack of
pressure lubrication of the needle bearings on which the planetary gears
ride. In the end it was decided that the lack of such pressure
lubrication was not a solvable problem. The second was cost of
production
--- cost to the customer would have been in the range of 30 to 35
thousand
dollars, sort of what Mistrel is trying to pedal today.
I was the one who encouraged Everett to take the 13B engine out of the
box
and do as little as possible to make it flyable, namely create a usable
gear box. (He already had the ignition and fuel solved.) The cost of
fabrication the ring gear and pinion turned out to be less than
anticipated, and the one problem encountered was the large bearing
supporting the ring gear in the prop shaft housing. I blew three
different iterations of that bearing in the testing process. When
Everett
died in the plane crash in October of '97 that problem had been solved
and
three firm engine sales had been made for 15 thousand each.
I know many on this list now prefer planetary gear boxes, perhaps
because
that is what is available at a reasonable cost. Same with electronic
fuel
injection and electronic ignition. I don't intend to knock anyone's
efforts, but time will tell. When we talk about hours flown to date we
must always ask "at what power output?" The only way to know power
(other
than on a dyno) is rpm AND manifold pressure. By the way, does anyone
know
how to get a manifold pressure reading on a peripheral port engine?
Concerning apex seal life and the peripheral port, we were certain that
the
seals would last at least 4000 hours. Just our opinion for what it is
worth.
Alan Tolle
Thanks for the report Allan. It is very rare information indeed. So much
of what you
and Everett did went undocumented.
I have always known the aluminum iron sandwich
with long steel bolts was problematic. What frequently happened when the
engine
was over heated the aluminum rotor housings would shrink. It was caused by
the difference in the thermal coefficient of expansion between the steel
bolts and aluminum.
Porsche had the same problem with their all aluminum cylinders and they
solved
it by coming up with a strong steel based alloy stud that had a more
comparable rate
of thermal expansion to that of aluminum.
My first thought was to neck down the tension
bolts to reduce their stiffness. Mazda originally made the bolts like
that but they
apparently failed to solve the problem. The bolts were costly to make so
Mazda did away with them. I think they mitigated the problem by using a
high silicon eutectic
aluminum alloy that has a much lower coefficient of expansion for the
rotor housings.
The same stuff is used for pistons now a days. I need to do a bit more
research on that.
Also high strength aluminum bolts could be used. There is enough meat in
a stock
rotor housing to use 1/2 inch bolts. Drilled out 5/8th bolts could be
used.
Currently the bolts are about 10 mm or .4134. 5/8th bolts would be twice
the area
and less than half the stress for the same clamping force which is in the
range
of possibility for 7075T6 aluminum bolts. Match drilling and reaming all
the holes
to fit the anodized aluminum bolts would be like adding 17 dowel pins.
Another possibility is to do away with all the long bolts and bolt all the
sections together with flanges and short bolts. CW built some rotary
engines using that technique. A lot like a jet engine is built.
Paul Lamar
Alan Tolle wrote:
Paul;
Don't miss my point. The problem with the aluminum end and center housings
was not in the strength of the through bolts, it was in the weakness of the
housings themselves. They crush with successive exposure to clamping
torque. Aluminum housings made by anyone, including Mazda, will exhibit
the same weakness. Only the external flanging you mentioned would get
around that, and now we are talking in theoretical terms about a whole new
program.
Our point was that "creep distortion" would be acceptable in a race car
engine destined for one race or maybe one season. But for a 4000 hour
aircraft engine --- no way. Hence the entire notion of an all aluminum
engine was abandoned.
Alan Tolle
Sorry Allan I don't buy it. Lots of high power all aluminum heavy duty piston
engines out there with stud bolted heads and cylinders. I have no idea what
alloy Everett made the end housings out of or the heat treat or the wall thickness.
Racing Beat has well over 300 dyno hours on a 1200 HP three rotor
with aluminum center and rear end housings. That is over 400 HP per rotor
and would be 800 HP in the case of a two rotor of course.
I still say there is a differential thermal expansion problem that Everett did
not address. Racing Beat has not addressed it either but they are very careful
about warm up and not overheating the engine. The aluminum rotor housings
that "creep" are from engines that have been overheated. A common problem
in the old days. If you run the engine hard before the steel bolts are
as warm as they are going to get the problem is worse.
Paul Lamar
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