> Paul;
     > Here are the rest of the pictures of the Actuator
     > assembly........Enjoy!
     > FYI, the last 2 pictures I sent (Parts count) are Assy-1
     > and Assy-2. Hold on to them for reference in case we
     > need to refer to whatever.
     >                                       Butch

Concerns/Questions:
   Is the gearbox a compound planetary?

Yes.

   Are the pitch forces from the blades present at the pitch change yoke?

Yes.

   Is it possible for the motor to backdrive due to the pitch forces

creating unrequested pitch change?

No. Its a screw jack just like the one in your car. Try pushing on a nut
sometimes and see if you can get the bolt to rotate :-)>

Chris
microcosman.com

This is an early version sketch.

Paul Lamar

OK, now I'm curious.  I'm sure this was all covered eons ago when the
mechanism was being designed, but I wasn't on the list back then ;-)

Looks to me like we're hanging our hats on a 1/4-28 pitch control lead
screw.  Not much material there.  Especially when it is to be driven in both
directions with an axial load.  In one direction it will be easier to turn
than the other, with torsional stresses varying accordingly.  No doubt the
DC motor can handle both with all that gearing down.

But what about the wear 'n tear on the screw and pitch control yoke (female
threads)?  It these are standard 60 degree machine screw threads in typical
materials, I would expect them to wear very rapidly under these conditions
unless the pitch forces are very low.  What kind of lubrication and
inspection interval provisions are planned?  This almost sounds like a
miniature version of the elevator ball-screw that took down that Air Alaska
flight a while back.

An ACME square thread would be much better suited here, although I doubt
that they can be made in such small diameters and pitches.

An inquiring mind wants to know!

Tom

I agree to a certain extent. An ACME screw would be better. On the other
hand we have a lot of company on this. Several European electric adjustable
props use the same type screw. The saving grace is you don't change the
pitch that often and we have a lot of threads engaged. The pitch forces
are also minimized by blade sweep back.

Paul Lamar
 
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