Fatal crash Arizona
At 17:28 13 September 2016, BobW wrote:
On 9/13/2016 9:26 AM, Dave Nadler wrote:
On Tuesday, September 13, 2016 at 10:34:20 AM UTC-4, BobW
wrote:
As for the report's claimed missing pawl spring...I must be
getting
dense
in my old age, since I'm still puzzled by the intended function
and line
of force of that implicated piece of (missing?) hardware. Back
to the
hook design - what am I missing? Thanks!
Bob W.
If I understand correctly, the missing spring pushes the pawl in
the
direction opposite of pulling the release knob. Otherwise, the
pawl is
not
secured in the "latched" position, except by a bit of friction with
the
hook plate (from the spring that is present and any rope
tension).
Do I understand correctly??
Quite possibly. I suppose such a spring fairly might be considered
the
"suspenders" to the hook-retract-spring's "belt." It's not obvious
from the
photos (Figure 1 shows it best), but installed-geometry, plus
gravity, in
the
pawl's as-installed position/angle work "against" the pawl
remaining
detent-seated...i.e. the pawl pivoting by itself (no other physical
contacts)
would tend to flop its "business end" *away* from the detent due
to the
longer
cable-attach arm's length compared to the detent-engagement
arm's length
(unequal length teeter-totter).
Nonetheless, whether the absence of a compression spring
between the pawl
and
receptacle/pawl-spring-housing was a crucial element in this
accident is
debatable; it would take very little force on the rope to rotate the
cable
hook from the barely-engaged position (Figures 9) to the fully
engaged
position (Figure 8). Once there, further testing definitely required
to
determine whether the design would be more or less prone to
back-releasing
in
the absence of the pawl spring, in the presence of a rope bow...
That said - and since a number of these hooks have been installed
into the
noses of German-built ships originally entering the USA with only
a CG hook
-
owners of ships with these hooks SHOULD (and easily can) VERIFY
the
presence/absence of such a compression spring by checking to
see if the
pawl
is positively forced against the rotating piece of the cable hook
throughout
its rotation range. Positive engagement = spring-present. (Note
that the
spring itself is hidden in the hook's assembled state...and might
easily
escape unnoticed in the event of the hook being disassembled for
any
reason.)
Bob W.
I am now confused by the "installed in German" part. Is the release
you are talking about a TOST release?
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