AIXRO had a customer CAD step file on their web site so I downloaded
it into Rhino. Here are a few 3D's. Still need a rotor
and a rotor housing.
Paul Lamar
I noticed that that engine uses a caged needle roller bearing for the
rotor bearing. I understand that they have to since it is a charge
cooled engine but if it works for them running up to 10k rpm then maybe
a similar setup could be used for a mazda type engine. There shouldnt be
any "weirdness" in the bearing such as you described earlier posts since
the cage holds it together. For that matter they are used on every 2
stroke connecting rod out there and nave no problems even with high
rpms. It would seem to me that there are benefits to having a
antifriction bearing vs. a journal bearing in terms of assembled
stiffness, oil supply issues and reduced friction. The only downsides I
could see would be cost and surface hardness requirements on the needle
to rotor since it is cast iron.
Rob Woods
That would be a big mistake. Those bearings are the Achilles heel of the
charged cooled rotary engine. The charged cooled rotor and the e-shaft run way
too hot for those bearings. They are right at the life limit at 10,000
engine RPM. Remember, they have to really zing RPM wise. If it were not
for the fact that the rotor was also turning on the e-shaft they would
not work. As it is they are turning only 6000 RPM while the e-shaft is
turning 10,000 RPM. 6000 RPM is the absolute upper limit for that size
roller bearings.
Paul Lamar
Something to remember is that needle bearing small ends in two cycle
engines never see high ROTATIONAL speeds.
In fact they tend to occillate through a portion of a rotation. The
reason they are used is the means of lubrication, (oil suspended in fuel),
rather than the being a better bearing. A [oil pressure fed] thin-film bearing
is better in holding up to high pressures, and very close on rolling friction too.
Bill Jepson
In addition to what Bill is saying I might also point out that the pressure fed
oil flowing through the thin-film (AKA plain) bearings is carrying away a lot of
heat in the process. Also the bottom ends of small 2 cycle engines do rotate but
the diameter is generally lower than the rotor bearings hence the limit RPM is
higher. Roller bearings are not used in large 2 cycle engines like diesels.
Here are some interesting charts for the friction HP of the rotary compared to
the gas piston engine and the diesel. The e-shaft friction is a significant part
of the total friction. The friction HP is converted into heat in the e-shaft
and rotor and thence to the oil. That is why it is important to keep the oil
temperature down or the plain bearings will melt. They are usually coated with
soft silver or aluminum.
Paul Lamar
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