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

If the shaft is turning 10,000 RPM then the rotor would be turning 3,333 rpm
in the same direction. Wouldn't that make the bearing actually only running
6,600 rpm?

Bob Mears

Yes you are correct. Well put. I got it right way back the first time and
screwed up the second time.

Should be 2/3rd and not 1/3rd. Thanks Bob for catching that. Rob was wrong
as well in his last post. E-shaft doing 10,000 rotor bearing doing 6333.

How's the 20B Spitfire coming Bob?

Paul Lamar