SERIOUSLY, I have questions. If we hollow out the e-shaft to run oil
through it, wouldn't we be making the e-shaft intrinsically
_weaker_ as
well?
How much
_can_ we hollow out a stock Renesis e-shaft (just for example)
without weakening it? (Yes, I know, the article is talking about a
_new_
e-shaft, hydroformed to spec.
_But_ if we want to apply to concept to
existing oil-cooled rotaries as Paul suggests, I ask so that we would
not be
required to make expensive, brand new e-shafts for perfectly good existing
engines.)
If we hollow out the e-shaft, would we not be also required to make the
diameter of the e-shaft bigger? If so, how much bigger?
How would making the overall diameter of the e-shaft bigger affect the
engine's eccentricity ("stroke")? How much bigger can an e-shaft be made
until it negatively affects the engine's functioning?
What other questions should I be asking, and have not?
And of course, how do we know, and how do we know we know?
Thanks,
Les Nordman :-)
Most of the stress is near the surface of any shaft. Most of the stress in
the e-shaft is in the fillet area between the main bearing and the
eccentric lobe. It does not need to be any bigger. Nobody has every
broken a
properly balanced Mazda rotary engine E-shaft despite generating up to 800
HP so obviously it is over designed and can be hollowed out without
problems. The same thing cannot be said about piston engine crankshafts
that
all crack sooner or later.
Paul Lamar ...No rotor no motor.
How about EDM an E-shaft for an existing design for testing?????
Just a thought.
C. Smith
Can you EDM such a complex hollow shape?
How is that done?
--
Paul Lamar ...No rotor no motor.
From the JPG image I see 3 axis of cylinders. Cut 2 from each end. The
intersecting cylinder in the center would be cut with an offset tool much
like an angled riveting set. I see no reason this can't be done on existing
machining centers. This is a 2 rotor shaft, right? 3 or more rotors I don't
know I can't picture the e-shaft in my head.
C. Smith
The answer here is that yes if we remove material from the center of the
e-shaft we do weaken it. The point though is that the e-shaft is almost
ridiculously overbuilt in stock form. It just is easier to manufacture
that way. Since the e-shaft has no truly offset throws like a piston
engine crank it is inherently very strong. It would need to be formed
from parts since EDM would be so complex and expensive it would never
fly. Friction welding the parts together might be doable. that is how
they attach the rotor heads on many helicopters. It, (friction welding)
is supposed to be as strong as the base material. I also sent an idea
I've had for some time for center-feed oiling on the non power end of
the e-shaft. I suppose that feeding the e-shaft centerline with cool oil
could help cooling, but I doubt it could do much. It would help the
oiling at high RPMs much more.
Bill Jepson
There are some other problems with running fluids through rapidly moving
shafts namely, balance problems.
I will find the paper on attempts to actively cool turbine shafts with
fluids that caused serious imbalances and subsequent failures.
Sodium is another possibility because it is contained and used only to
transmit heat away.
-Ben
I am sure it is a problem that can be over come. Pressurizing it is one
way. The geometry of the internal cavity is a large factor. Some cavities
geometries would be impossible to unbalance regardless of the amount
of fluid in them. I suspect a hollow e-shaft is one of them. Another
very simple example would a spherical cavity.
--
Paul Lamar ...No rotor no motor.
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