Paul, et al -

   Here are a few shots of the rear motor mount before welding.  I am doing
   the final fitting tomorrow to precisely position where the rod end
   will be.

   Mark

   Did he machine those inserts out of solid bar stock?
   Looks heavy. The inserts inside are a bit too long but that will
   only add weight and other wise not hurt.

   What is the wall on those tubes? Looks thin.
   It also looks like electric welded tubing which is a no no.
   Electric welded tubing is mild steel with lousy fatigue
   characteristics.

   It needs to be 1.25 OD seamless 4130 .065 wall.

   Make it like the drawing. Welders are like that some times.
   My Numerical Control machine tool programming teacher at Ventura
   College, Scott Rabe, used to tell jokes about welders.

   That guy might be a bit too independent for you Mark :)



The material was represented (by the metal dealer) to be 4130.  It is
1.25 OD.  It is .080 wall -- so *thicker* than you specified.  It does
have a seam -- but you did not specify seamless earlier.

Given that the load on this member is less than 50lb static, I have
trouble believing it won't do the job.  Perhaps there are vibration
effects I am not thinking of.  I am curious as to the concern which the
seam introduces -- presumably, it is a failure point under some specific
condition.  Would the addition of a gusset on the longer tube section
eliminate the concern?

We don't have easy access to supplies here in Colorado - if the material
is not what is was represented to be, we won't be able to use the local
provider & instead we'll need to order all supplies in from CA.  If
there is some straightforward way to test the tube, I will do it to
confirm what it is.

Mark

To my knowledge 4130 does not come seamed. I think the metal
dealer lied. You will have to mail order it from Aircraft
Spruce. Too risky even at .080 wall. Any cracks that develop
would be hard to see. It would mean taking the unit out and
magnafluxing it on a regular basis.

Vibration would be the problem. No way to test for that
short of a large and VERY expensive shake table.

Paul Lamar ...No rotor no motor.

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