>
     > Paul-
     >
     > Just FYI, we found a local machinist to perform the mods.   He has
     > finished re milling the S-Beam & I will be picking it up  tonight to
     > perform a test-fit.  If it works, I will return it to him to  get the
     > key stock welded on.
     >
     > He's having some sort of problem re milling the aluminum  mounting
     > plate -
     > he thinks the starter dimensions on your CAD differs from the
     > dimensions
     > for the existing starter hole.  I'll try to get it  straightened out
     > tonight when I get the S-beam, otherwise he wants to wait  until I
     > have a
     > starter in-hand to compare against.
     >
     > Mark & Mark
     >
     > Good idea. There seems to be a lot of slightly different  starters
     > floating around. Best to have the actual one you are going  to use.
     >
     > Paul Lamar

    Mark,  weld the key stock from the center outward.  With every  stitch
    weld the key stock will shrink slightly lengthwise.  If  the  ends are
    welded first, the ends of the beam will be pulled upward by the
    contracting key stock. This would not present a problem on new  engine
    mount construction, but changing beam end locations on a completed
    mount might make it difficult to reassemble,   On my next one,  I will
    keep the stitches shorter, around .375 inches and at least one  inch
    apart.  But the main thing is to start in middle and work  toward the
    ends.     Jerry



Thanks for the tip, Jerry - I will pass it along to the machinist.

Fortunately, he insisted I test-fit the part after milling before he
welded on the keystock.  I have discovered that my S-Beam still  suffers
interference after milling.  I tried bolts both per-Tracy, and  reversed
& they still hit one side or the other.

The CAD drawing was ambiguous on which side was which.  I had him mill
the angled sides on the redrive side of the S-Beam, since the  purpose of
the angles was to clear the wide washers on the damper plate.

In any case, it will have to be milled further.  My question is  whether
the bolts are supposed to be reversed or not.  If so, then the milling
must be done on the already narrow side -- I am concerned that milling
this side further will result in the keystock being wider than the
remaining width of S-beam top.  On the other hand, if the bolts are to
be reversed, then the milling is done on the (wider) engine side.  It
appears that this would result in a symmetric amount of material being
removed (both sides would have the same resulting top width).  If this
is the case, then I will have him mill out the same angled shape as on
the redrive side -- I do not see any reason the shapes of the milled
sides cannot be the same.

No question now that I am not moving forward on cutting the mounting
plate for a new starter hole until I have a starter in-hand.  We're  not
quite at the point of interchangeable parts with all this.

mrs

Got any pictures Mark? Should not matter which way the bolts go.
You could also shorten them and use shear nuts. Or better yet.
low shear castle nuts with cotter pins. AN320-7 in the 2004-2005  Aircraft
Spruce cat. Page 86. The over all height of this nut is .219  instead of about
.5 for the Nylocs. Furthermore one or two threads must protrude
from the top of the Nylocs to be safe. Not necessary with a castle nut
and cotter pin.

Cut down the bolts you have about a 1/4 inch
and drill them for the cotter pins. That will save about 1/4 inch in
length. The bolts tracy supplied for my PSRU appear to be AN7-14 with
an overall length under the head of about 1.6 inches. .6 inches
of that is threaded portion. .25 off that should give you plenty
of room for a castle nut and cotter pin. Namely about .35 inches.

The 1/2 inch high Nylocs supplied by Tracy are marginal from a heat
point of view anyway.

The shorter bolts and lighter weight nuts will reduce the cantilever
loads on the metal spacers due to centrifugal forces.

Bill Dube, if you don't mind could you do a FEA of this config?
There has always been a question in the back of my mind about
just how viable this torque damper scheme really is. It seems
to be working for hundreads of hours so far on several airplanes.

Volme of the parts in cubic inches is:
Large washer ---- .24227
nut-------------- .13924
shank of the bolt .25368
head of the bolt  .07956
little washer --- .01821

Parts are on a 4 3/8 inch radius whirling at 8000 RPM.
The flat sheet metal is the flex plate assumed to be 3/16 inch thick
steel for now. There is a simultanous side load applied to the  center of the
spacers of about 160 ft pounds of torqe divided by four
spacers and rubber bushings.

Paul Lamar

Both sides should be milled 7/16 inch. If you are looking at a
drawing that says otherwise, it is not the latest drawing. I think
this is the case as  you mentioned doing the back and front
differently.    It looks like one size shorter bolt will still engage
the nylock  nut but I have not yet done this myself.    The key stock
should be flush with the outside of the beam so there  is plenty of
room to open the notch a tiny bit more.      Jerry

Good call Jerry. Here are both in chronological order.
First was 08-23-2005  second was uploaded 08-31-2005

Paul Lamar


This is what it looks like if you cut a 1/4 inch off the length
of the bolt and use a shear castle nut and cotter pin.

Paul