nuckolls.bob(at)aeroelect
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 Posted: Fri May 15, 2009 5:55 am Post subject: Of pop rivets and locknuts . . . |
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I replaced two ground wires using pop rivets with solid driven rivets. Much
tighter connection and it makes me feel better anyway.
Given that the new joints are 'tighter' is an
obvious good thing. But be aware that a rivet
is a fastener designed for shear loads. I.e.,
the shank swells in the hole thus capturing the
two sheets radially. But the axial clamping
forces are spread over a much smaller area
than the nut, screw and washer process described
earlier. Thus we have lower retention forces
in torque. Further, aluminum rivets are softer
than steel fasteners and more likely to loosen
under temperature cycles and vibration over
time. The gas-tightness of this joint over time
is doubtful. We would never use a rivet (of
any kind) for making up a life-of-the-airplane
electrical connection to airframe in a TC aircraft.
I'll refer the readers to Section 15 of AC43-13
http://www.aeroelectric.com/Reference_Docs/FAA/AC43.13-1B_Change1.pdf
where one can become deeply immersed in the art
of attaching electrical conductors to airframes.
I hesitate to offer this reference because it
tends to take something simple and make it
complicated. But there is value in understanding
the design goals along with some processes and
materials to achieve them.
In addition to the noise reduction benefits for
the single-point ground system proposed in Z-15,
the processes by which wires get attached to
ground are already taken care of by using the
fast-on terminals. But once you venture out of
the forest-of-tabs ground block, then a rudimentary
understanding of the design goals is useful.
Bob . . .
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( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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