Centrifugal force of a rotating object is MVVR.   Where V is the
velocity, and R the radius and M is mass.

This means  that unless C.G. is matched exactly, it is impossible to
ballance the  engine at different speed.

Fortunately, I think the C.G. Of the rotor  travels in a circle.
Therefore it is van be balanced by a weight at the  C.G. path of the
rotor. The same goes for the imbalance of the  eshaft.

Since counter weight is located only at the end of the engine,  I
think you will get from limited twisting on the shaft.

That's  IMHO. No guarantee on accuracy.

Henry Nee

Hi,

Can you  please explain the problem and solution of balancing when
using  a cut  down e-shaft  with single rotor 1/2 Mazda 13b engine.

Regards  Zahid


Balance is controlled by these equations. The Wankel is not  just
statically balanced but dynamically balanced as well.

In a  single rotor engine the counterbalance weights must provide a
STATIC  balance for the e-shaft eccentric and its rotor and must also
account for  the DYNAMIC wobble caused because the static counter
weights are not  located at the mechanical centres of the rotor and
the eccentric. It is  impossible to do this.

They must be mathematically sized relative to  their lateral position
from the rotor and eccentric centre  line.

Paul Lamar


the Tracy ISO is physically attached to the  flywheel. Does that need
to be brought in to balance equation  as  extra mass to mF (front
counter weight) or mR (mass Rear  Counterweight)?

Regards Zahid

The rear counter weight is hiding  behind the ISO.

Paul Lamar

Here is how I solved some of the  balancing issues. There are a whole
lot of issues interacting when building  a new engine configuration.
Weight control influences almost everything. A  single rotor engine
certainly requires a considerable flywheel, if one  wants the idle
speed somewhere below 3000 RPM. I integrated the rear  balance weight
in the flywheel (picture). The front balance weight I  modified with
tungsten inserts before dynamic balancing. I ended up with a  clean
rotating setup. My engine is based on 12A rotor and housing, so I do
not have any direct comparison to 13B size parts.  FWIW.


Richard Sohn  N2071U

http://www.fairpoint.net/~res12/home.html


Hi Richard,  I have read some postings where some have machined a
single rotor eccentric  shaft from a 2 rotor unit. Paul mentions the
shaft needs to be hardened  after machining. Could you give a
overview of the process you used to build  your shaft ?

Thanks, Steve Carlisle

Here is what I  did.

On the first e-shaft I concerted, I left the oil pump side of  the
shaft with the front lobe unchanged. After machining the rear end of
the shaft to my mods, I only had one bearing surface to create.  I
picked an inner ring of a INA needle bearing with an outer  diameter
the same as the original MAZDA bearing, and pressed it on the shaft.
As it turned out, it was a solution, which never failed during  all
the ground testing of the first engine I build, with a run time  of
around 50hrs. I did not consider this a solution for a final,
flyable  configuration. The solution I have in the engine now is a
case hardened  bearing section. The biggest problem was finding
someone for the case  hardening and grinding who was willing to do it
for and affordable cost.  FWIW


Richard Sohn  N2071U

http://www.fairpoint.net/~res12/home.html


I  misunderstood the last email by Richard Sohn. He was referring to
case  hardening process for e shaft . I thought he was referring to
case  hardening for bearing. So please do not publish my last email.

Zahid  Rahman



I am thinking, since the rotor rotates at one third the  speed of the
esfaft. One needs a 3:1 reduction gear on the counter weight  to
matched the rotor's rotation speed.

Corrections  welcome!

Henry Nee


I'm not sure at all, but you have to  compensate for the weight that
is centered in the shaft eccentric, and this  rotates at shaft speed.
Or not? Thanks. Best regards. Salut † Jose  Gros-Aymerich Madrid,
Spain


Yes, I believe you need two counter  weights. One rotates at reduced
speed to balance the rotor, and a second  one in same speed with the
eshaft.

That's why two rotors is much  better balanced.

Henry  Nee


Twin rotor engines comes  balanced from the mazda factory with counter
weight on one end and flywheel  on the other. However when using single
rotor the counter weight from the  factory is out of balance especially with
the shorter e-shaft.  So for  these two reasons (single rotor, shorter
e-shaft)  you will have to  make modifications to counter weight and or
flywheel.  Most likely  lighter flywheel.

Zahid Rahman


The two rotors weigh about 9.7 plus pounds and provide considerable
flywheel effect on their own. In a single rotor
there needs to be a flywheel with enough mass to at least partially replace
the flywheel effect of the missing rotor. The distance from the center of
the  rotor to the center of the counter balance determines the amount of
mass  required to get a perfect balance. In an ideal engine both counter
weights would  be the same distance from the center of the rotor and of the same
weight.  In no way is perfect required as pure rotary motion is involved. The
offset or different distances from the rotor center of the counter balance
mass  induces the "wiggle" actually called a "rocking couple" ., So, Mr,
Sohn's  solution is elegant more than sufficient. All of the weight of the
eccentric  bearing offset and the rotor weight, plus a tiny amount for a rotor
full of  foamed oil needs to be accounted for by the counterweights.

Both counter weights are firmly affixed to the shaft. The problem is
complex in theory and rather simple in execution.
Lynn E. Hanover



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