On Mon, 26 Apr 2004 18:09:25 -0300, "Ken Heaton"
wrote:

Question below:

The
double nicopress fittings could support the load imposed in the tests
only
because they were clamping an eye that was passed around a 3" dia. pipe.
Some of the load on the wire was passed to each nicopress fitting but
most
was carried by the friction inherent in the eye passing around the 3"
pipe.
Think of a rope around a bollard tied back to itself.

Hmmm....you feel that the upper wire end was essentially locked to a
pipe by friction.

And so, I presume, you feel that the pipe was prevented from
rotating, because if your explanation is correct, there would be a
turning couple on the pipe.

Actually, the turning couple on the pipe is counter balanced by an equal
turning couple imposed by the dead end continuing down the other side back
to the nicopress fitting.

Either the pipe reacts some of the tension force in the wire or it
doesn't.
If it does, the pipe will rotate unless restrained, but the upper end
needs a smaller restraining force at the nicopress to resist slip
through.
If the pipe does not resist the tension force, the force is passed to
the nicopress, where it is resisted.

But those are engineer's details.
Beneath, you make a much better, clearer argument against
Nicopress and thimbles - they are bulky, and when safety wired
as needed, are unpleasant to work around.

Actually, light aircraft use double Nicopress swages, but a preferred
setup is to leave a slight loop before the second swage, in order to
observe the onset of slipping failure in the first Nicopress.
Others paint a mark at a joint.
///
Brian W

/// Are you suggesting instead of using
swaged or other ends on wire terminations we use a couple of nicropress
sleeves and a large enough thimble to allow the wire to turn back on itself
without weakening it by bending it too severely? (This is how all the
terminations are done on a Laser II for instance but in that case the wires
are rather small.) Note that in the test they felt they needed a 3"
diameter pipe so as to not bend the cable too abruptly.

The 3 inch pipe issue is immaterial. Engineering usage has confirmed
the value of thimbles of regular size as fit for the purpose.

What then goes through the thimble to retain the end terminated thus? A pin
large enough in diameter to prevent the thimble from collapsing under load?
Or are there thimbles available, strong enough to retain their shape under
load with a small pin passing through like the one in a turnbuckle fork?
The turnbuckle fork would have to be wider than usual to accommodate the
thimble. Wouldn't this make for a rather bulky termination? We are talking
about rigging sized wire, not skinny little cables like the type used on a
light aircraft's controls.

I like the idea of swageless terminals. How much do they cost?
I would choose them as stronger but as prettier and more functional
for the purpose

Brian W.