Paul, getting off topic here but I saw your picture of the
 transmissionand CV /drive shafts and I've got a question on these.
 Do you have any
 rule of thumb numbers for what these should be run at [max speed] and
 how far a person can deflect/bend them before running into
 their limit's  or getting into vibration issues etc..[generally
 speaking]..
 Curious is all...  :)

 Jarrett

 Not my my pictures. Jean's pictures.

 That is a complicated subject. I just heard from a consulting engineer
 working for Sikorsky wanting my advice on a tail rotor drive system.
 I had no answers :) Props are big flywheels.

 Helicopters are a loose collection of parts flying in formation
 surrounded by and oil leak :)

 One of the big problems is what happens when the gears wear
 and you get back lash. Defies FEA I suspect.

 Allison went through all this back in the eary 1930's for the
 P39. It was not cheap or quick :)

 As I told Jean it is a good idea to avoid that type of design
 if possible and keep it short and simple :)

 Like this 2D sketch.


Thanks, my application actually isn't aviation related..  I'm building a pivotable drive
assembly. My first thought was to use a set of bevel gears to allow the bottom shaft
to pivot out of alignment from the top shaft.. however I later got thinking about
these CV joint type drive shaft's and figured it might work.. but I wasn't sure
how fast I could spin them, or how much I could deflect them before I ran
into issues. It's going to be operating at ~10hp so it's not a huge load..
[relatively] but it's fairly high speed. At best I'd like to be able to bend
each CV joint ~ 45 degrees and spin them up to 12K or so..

Jarrett

If it is a long shaft carbon fiber is the material of choice because
it is light weight and if the shaft CG location is out of the center line it is
less likely to fail from high RPM centrifugal forces.

The RX8 drive shaft is carbon fiber for that reason.
Prior to the RX8 Mazda used a center bearing in the drive shaft.

Paul Lamar