Hi, in flange type rotary joints the torque is transferred through
the matting surfaces through friction.  The bolts are loaded in
tension to supply sufficient contact force and thereby the friction
to carny the torque.  If the bolts are loose and loaded in shear
they will usual fail. If they are sufficient to carry the load in
shear on paper they should be able to provide enough clamping force
if tightened enough.  Sufficient contact area is also needed.  If
you are familiar with the aircooled VW flywheel mounting you will
see the problems with pin type shear couplings on engines....

Murry I Rozansky

Far too many years ago when I worked with paper-mill technology,
  the  Defibrators (the machines the ground up wood chips into
cotton-like wool) had a a huge motor (~ 600 to 800 HP if I remember
correctly) driving about a 5" diam shaft turning a 3' diameter
grinding disk. The entire shear-load was handled in a tapered-
friction-fit hub  that  was maybe a bit wider than yours (maybe 3 or
4 inches wide).  But  there were no pins, no splines, no keyways, no
RTV or Loctite used. Nothing but skin-friction transferred all that
torque, and I never knew one of them to slip.  Admittedly, there was
a huge nut that  was  well-tightened on the end of the shaft that
held everything together.

R

BTW Robin do a longer signature file than just "R" :)
We have lots of R's on here and you are not allowed to copyright
  the  capital letter "R" :)

Paul Lamar

I notice "Lamar" is copyrighted on many bill boards, I guess names
are allowable;)

I cut the female splined extension off of the planet set. Now wish
  I  would have left it in place for the reason Robin mentioned
above.  We  could have put a pipe thread on it or something to
thread into  the  end of the shaft.

Ed Carver

Correct :)

"Tapered" is the key word Ed. I don't think a steel taper will work
in an aluminum shaft.

Paul Lamar

  Engine power is transfered from the crankshaft to the flywheel by
  friction between the crank mounting face and the flywheel.  The bolts
  are not to transfer the torque, they supply the clamping force to
  enable the friction required.  This should work fine on the planet
  carrier to the Al shaft.  It is the trick to ensure the bolts do
NOT  work loose from the expansion and contraction as the parts heat
and  cool.  Inserts in the Al or studs with a long thread in the Al
to  prevent pulling the threads in the Al.

  Dale Davies

  I have an aluminum fitting on the RV4 PSRU adapter plate with a
4130  3/8 course thread eye bolt holding the entire empty weight of the
  RV4. That is over 1000 pounds. The length of the threaded portion
in  the aluminum is about inch and a half.

  Paul Lamar

One and a half inch is good for that weight. It would hold much more.
The problem is the heat cycles and vibration with the bolts torqued
up.  The clamp load needs to be maintained under working loads and
after many heat cycles.  The bolts alone will not be sufficient if
the clamp load of the bolts goes away because the heat cycles
compressed the Al or pulled the threads out over time.

Dale Davies

If you are bolting one piece of thick aluminum to another the
temperature cycling is likely to cause a problem with threads as the
steel bolts do not expand along with the thick aluminum. My Honda V6
Odyssey had that problem with the head bolts. The heads were 4
inches thick and the head gasket actually failed in the area of the
overhead cam shaft oil gallery causing a bad oil leak. Subaru's will
have the same problem. It took 8 years and 130,000 US miles.

In this case that it is not an issue as we are bolting a steel
planet carrier to an aluminum shaft. The steel bolt and the steel
planet carrier expand at the same rate.

In any event there is always thread inserts.

Paul Lamar

Yes the gaskets fail with time. The cycles is the issue. A vehicle
driven short trips with a lot of heat and cool cycles will fail much
sooner than a vehicle driven longer each time.  I agree the chunk of
Al will expand more causing more chance of thread failure.  Lots of
thread engagement or inserts is the answer.

Dale Davies

Btw the Jabiru LSA engine seems to be suffering from the same thing.

Paul Lamar