Vance Jaqua wrote:

Paul - You need not share this but I have some second
thoughts on the existing prop design.
I am considering converting my prototype from a slot
driven pin to a link system - I think that there is
room, and it has the potential for less backlash and
reduced friction, and much reduced wear effects (line
contact with the slot).
The screwed on blades give rise to the thoughts of
unscrewed blades.
The existing torque path (balls to needles thru the
center tube) seems close to the center of rotation.
I guess I do not understand the "conduit coupling" and
how it is to be used - I must have deleted a picture
without putting it in either my, or my computer's
memory.

You can mark much of this up to the fact that I am a
COWARDLY  engineer - Vance

I agree on the links. I tried to simplify however.
Also however one would have to account for torque on the the links
from friction from the adjusting screw. Links work great with
hydraulic designs as there is no such torque.

The conduit coupling is very low stress as it is bonded into
the carbon fiber blade hub. Since epoxy bonded to steel at best is
only 3,000 psi the mild steel coupling is way more than that.
 
Being 2.25 inches ID and two inches long
the stress on the threads is also very very low. I intend using a safety
wired jam nut to prevent the blade from coming unscrewed. Perhaps
a roll pin after we find the best position of the blades on the test stand.

Hey if it makes you feel better make it out of 4130 :-)
The bond is not quite as good.

The test stand I have in mind is going to be a real torture test.
One hour on this stand is going to be the equivalent of 50 to 100 hours
in the air. The stand will constantly tilt up and down at the rate of
60 degrees per second. If the prop (and PSRU) goes through this it will 
go through anything.

Paul Lamar
 
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