> 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

Hi Tom;
First off, Paul did say that the design sketch he posted
was preliminary and outdated, a LOT of changes have been
made since............The Actuatot Screw and Yoke
assembly is an area which received various changes, the
size thread being one of them, is actually 5/16-24 and
not 1/4-28, this great increase in area places it in an
entirely different structural category.

We investigated the possibility of using an Acme thread,
which BTW, is not available in that diametrical size,
but can be designed and made special by a tool house,
however we decided not to go in that direction after
doing an extensive FEA analysis of both assemblies
employing gargauntuan Torques which the prop will only
be exposed to a fraction of, and easily surpassed
structural as well as longevity period, (Life Span).

The LAEV is well OVER DESIGNED especially in this area
purposelly, since we are looking into higher HP
applications.

        "A HAPPY AND A HEALTHY NEW YEAR TO ALL"!

                      Butch and Linda

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