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


   Paul,

   A email to the engineering division of Timkien would be the answer to
   how approprate they would be for that purpose. The bearing load diagram
   you sent indicated that the bearings would have to support 5000 psi at
   10K which is waaaaayyyyyy under what the bearing will support. Timken
   has proven through testing that a roller bearing has far less
   drag/friction than a pressurized oil journal bearing. They pretty much
   ended the theory vs. practice discussion on that. I'll look for the
   video and report I read. You have no furthur to look than modern cnc
   machines for journal vs. anit-friction bearing setups. All cncs use
   stacked up taper roller bearings with pressurized lubrication in order
   to get the rigidity and strength necessary for their function. Journal
   bearings wouldnt surive at the spindle speeds they run today. You will
   transfer less heat into the oil if you are using it to lubricate metal
   on metal contact versus shear forces from hydrodynamics.

   Rob Woods

   It is way under what the bearing will support if the RPM is less than
   6500 RPM
   for one minute :) That number is not the final answer. You must go
   through the life calculation spelled out in the catalog. See pages C64
   though C68.
   That is the gist of the problem with any kind of so called anti-friction
   ball or roller bearing. The minute deflections cause the rollers or
   balls to fatigue over time not to mention the e-shaft or rotor
   deflections if they are running directly in the rotor. You have a very
   high pressure line contact between roller
   and running surface.

   Plain oil pressure fed bearings on the other hand have indefinite life if
   one can avoid metal to metal contact. Many Mazda engines have proven
   that with well over 300,000 miles in car use.

   Norton/Midwest/Diamond have plenty of history with needle or roller
   rotor bearings. I was told at the Diamond factory this is the big
   problem with charged cooled rotary engines. I have also visited the
   Wankel Gmbh factory in Korf Germany and they say the same thing. In fact
   they advocate water cooling the e-centric shaft to mitigate the problem.

   As far as stiffness is concerned the hotter rotor will expand more than
   the cooler e-shaft. You will get slop like it or not :) The only way around
   that is oven heat the rotor before installing the rotor roller bearings
   and let everything deflect when cool. Plain bearings tolerate the differences.

   Paul Lamar

   First I love Timken ROLLER bearings, so understand that I am not trying
   to discourage their use when I say that there are several problems
   putting them into use. I worked at Kawasaki durring the Z-1 900 and KZ
   1000 days. These engines used an all ROLLER bearing bottom end and were
   very tough. The trouble is NEEDLE bearings are more difficult in most
   applications and need to be caged to handle any kind of high rotational
   velocity. Buy a small end needle for a Yamaha road racing 2 cycle. They
   were super expensive. They often used a silver plated cage. The larger
   roller bearing on the big end could cost $125-$175 each and that was 25
   years ago! The roller bearing also has a limited oil pressure range.
   They will tollerate lots of flow but the pressure needs to stay below
   about 40 PSI. After that the bearings start to skate on the outer race
   which kills them in a hurry. Perhaps the latest Timken bearings have
   gotten around this trouble. The fact is that the plain bearing works, is
   MUCH MUCH MUCH cheaper, and will handle the higher oil pressure the
   rotary needs to feed oil inward to the plain bearing and cool the
   rotor.  If we wanted to convert to rollers then a execentric shaft
   centerline feed for oil would be advisable. That adds to the
   complication and isn't needed if you run the engine at 7k RPM and below
   with the standard setup.
   Bill Jepson



   When I speak of stiffer I am referring to the fact that clearances on
   the bearings vary from stock to twice than stock for heavy duty race
   applications based on the fact the journal bearings dont take moments
   well at all. Scoot uses roller bearings in their stationary gears, Guru
   uses them on center bearings and Aixro uses them on their engines more
   out of necessity. You are dead right about the sizing. My mistake. I was
   just throwing an idea out and not a fully looked through thing We might
   be able to fit them in there without all that mess I talked about. Hard
   to say since I dont have a rotor in front of me. I am sweating my ass
   off in Phoenix right now calibrating converter temps. Sorry about not
   swinging an attachment. Time factor. Can you explain your rpm numbers
   for the rotor bearings? Not sure were your 6000rpm number is coming from
   if you e-shaft is higher. Just to note the max rpm for e-shaft sized
   bearings is 9500-10000 depending on type. I know that these speed
   ratings are based on R10 life and not actual max speeds.

   Rob

   Well the rotor rotates in the same direction as the e-shaft but slower.
   Take a look at the first two pictures in this graphic.
   As the e-shaft moves through 180 degrees the rotor moves 60 degrees about
   it's own center  or 1/3rd of e-shaft revolutions. What is a bit weird is
   the acceleration vectors on the rollers.

   Paul Lamar

Ok that is what I thought. So if the e-shaft max rpm is 10k then 3.333k
is the max rpm of the bearing then. You quoted 10k and 6k in your
previous post. That is why I asked the question.

Rob Woods