Ron,
I had warned Rotamax about surface coating and substrate issues.
I wouldn't be surprised in any way if this caused their problems.
Pity it's a great rotary engine also, copied from the NSU/Norton engine.
Aixro is a generation ahead of the Norton engine, due primarily to the
NSU/rotor/combustion shape.
George
Not copied from the NSU or the Norton. It is an almost direct copy
of the OMC engine. Good thing you warned them George. I can now sleep
better :)
Paul Lamar
--
Paul,
You are quite right: The RotaMax engine is sure not a copy of the Norton
engine, which again is completely different to the NSU engine! Actually
the AIXRO engine is very much based on the original Norton design,
further developed by MWE/Diamond Engines. Just look at the swept volumes
of 294cc! AIXRO, Sachs (KC24 and KC 27), Norton, and MWE rotors and
seals are interchangeable when being re-balanced - as long as you don't
account for leading or trailing cut-outs! MWE rotor housings can be
fitted to AIXRO engines just as easily as water cooled Norton housings.
Actually the first lot of AIXRO engines had MWE twin plug housings...
The combustion chamber of the AIXRO rotor for instance is an exact 1:1
copy of the early Norton motorcycle engines, whereas the later Norton
engines and MWE engines had an additional cut-out in the trailing edge
of the rotor flank in order to prevent pinking at high continuous
speeds.
George,
I would be very much interested in the surface coating issues mentioned
as I am currently in the process of trying to establish a salvage scheme
for worn-out rotors, housings, and endplates for Sachs and Norton
motorcycle Rotaries, as Norton Motors Ltd shall be going out of business
before the end of next month!
Having gathered intimate knowledge of the Norton and MWE engines I
unfortunately have not yet seen a RotaMax engine for a direct comparison
myself - in particular as RotaMax have a picture copied from AIXRO on
their homepage nowadays!
Regards,
Martin.
Here are some internal pictures of the RotaMax Martin.
Paul Lamar
Martin,
I stand corrected on all counts, thanks for the clarification.
I replied to the rotary in error as I was send that e-mail to my new contact
Ron Ligeti ( aviation Engineer) who is further developing his fathers
Stratos development - currently microlight.
My limited input has been to suggest engine choices and some composite and
material specs.
To answer your question Martin I'm unsure what other engine developers are
doing, exactly. I can however tell you what some engine developers have done
in the past and are considering. As stated the primary failure mode ( in
development Al. rotor housings) is substrate failure. Mistral for example
has test every known surface finish and they all failed, primarily because
of substrate failure. Some of the very hard coating are fantastic but
brittle, without that appropriate firmness to support the, sometimes very
thin, coatings - fail.
Paul L. has regularly suggested det-gun coatings, I guess for the same sorts
of reasons, while acknowledging it is an expensive process.
Others has suggested the use of silicone particle aluminium used in Piston
Engines successfully. It has been suggested to me that the apex seal tends
to be too harsh on this finish, and they fail.
Mistral has investigated a more dense aluminium to support the coatings, but
I guess that's one of their intellectual property rights. I sure as hell
don't know what their using.
Not being a metallurgist I sometimes ponder over the matrix that
would be a good solution, my latest thought would be a matrix of Al and
ceramic nano particles. The particles themselves would stand up to the wear,
the al would wear slightly below the particles, providing oil retention and
very light particles should mix well with Al providing greatly improved
density.
There are products out there but only research will identify the more recent
ones.
HTH
George (down under)
Paul,
thanks a lot for the pictures of the RotaMax engine.
They did shed some light on what seems to be a completely
unknown engine here in Europe; very interesting design.
It looks a bit like a bigger, cruder, water cooled
version of the old KC27 engine from Fichtel & Sachs,
fitted to the Hercules W2000 motorcycles in the 1970es.
Looking at some of the parts I could clearly see some
scope for improvement though. Let's hope they pick up
the bits again!
Having worked quite closely with most of the luminaries
of recent European Rotary development for more than ten
years I still remember Hans-Jürgen Klusowski's words: "Those,
who have lots of money and even more time to spend, are most
welcome to test new materials for rotor seals and surface
plating. Those however, who want to get a rotary engine up
and running reliably within a reasonable span of time should
stick to the compounds that have proven to work without any
problems, i.e. Nicasil for the rotor housing,
Molybdenum (or Nicasil) for the endplates, and IKA for
the rotor seals."
Looking at the RotaMax endplates they seem to be Molybdenum
plated Aluminium. So if there was a problem with that
coating may I suggest that people get the Silicon content
in the Alloy right and don't exceed 0.2mm plating thickness.
But maybe it is more of a thermal distortion problem due to
the greater diameter compared to the 294cc Sachs and
Norton/MWE engines. The Wankel SuperTec Rotary Diesel
KKM 501 however appears to be greater in diameter still,
without suffering from THAT particular sort of problem, see
http://www.wankelsupertec.de/
Is there a chance to get a RotaMax single rotor engine
for reasonable costs (i.e. scrap parts FOC?) just to
have a closer look at the major components myself?
Regards,
Martin.
Unfortunately Rotamx never shared their problems even though I tried over
and over again to find out. I and others were perfectly willing to help
them for free. One of the big problems was charge cooling itself and they
refused to admit that. Wankel Gmbh wrote a SAE paper on a liquid cooled e-shaft
that was rather simple to implement which would have largely fixed
the Rotamax charge cooling problem.
http://www.rotaryeng.net/Wankel-CC-paper.pdf
If anybody wants to build a smaller rotary they should just scale down
a Mazda. If you want to build a rotary just copy Mazda exactly. That essentially
what Mistral is doing.
Paul Lamar
Paul,
I have seen their W/C eccentric shaft in Lindau, where Wankel R&D used
to reside in the 1990es. Yes, I agree, it would be fairly straight
forward to implement by the looks of the RotaMax pictures you sent. But,
to be really efficient, it has to be extruded and plasma welded on the
eccentric, what used to be quite tricky and rather expensive. That's why
they refrained from that solution for serial production. Just a
cylindrical hole, drilled all the way through, would not really cool the
eccentric sufficiently, which is where the heat is induced into the
shaft.
I gather that these are exactly the same kind of problems we encounter
in the Hercules Endurance Race Works Replica, a mate of mine has been
running in historic races in Germany and Spain for a couple of years
now, see attachment. We are struggling quite hard to reduce the heat
transferred to the rotor bearing, which is the longevity limiting
factor. Power output is mainly limited by the charge cooling of the
rotor and the air cooled housing, not getting rid of the heat.
Regards,
Martin.
That was quite some time ago. Mistral have since given up on heavy fuel and are
now focused on FAA certification. Latest, as of OSH, is the rumored problem
with finding a plain bearing supplier that is willing to certify for aircraft
use. They may be making their own by now as that is what I suggested.
The break trough that makes hollow e-shafts feasible is hydro forming.
A strong female mold is machined and thick wall tubing is inserted in
the mold. Then extremely high oil pressure is used to form the tubing
to the shape of the mold. That is a production process here in the US
for cross members and chassis rails for trucks and cars. A small e-shaft
is a piece of cake after you pay for the tooling :)
Here is the NSU patent on the liquid cooled e-shaft.
This one was drilled. Patent has since expired. I think it would
be an advantage for an oil cooled rotor engine.
Cooling the rotor bearing would probably allow higher RPM
and make cooling the rotor itself easier.
If you are making enough engines it could also cut the cost of the e-shaft.
Paul
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