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
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