"Larry Jaques" wrote in message
...
On Tue, 09 Sep 2008 17:48:49 GMT, with neither quill nor qualm, "Ivan
Vegvary" quickly quoth:


"Larry Jaques" wrote in message
. ..
On Mon, 08 Sep 2008 23:48:48 -0700, with neither quill nor qualm, JR
North quickly quoth:

I don't kniow what the tensile rating is of the chuck joint, but I bet
it's nowhere near that of a properly swaged coupling.

2,680 pounds weight capacity. I wonder if you're supposed to divide
that by the 4mm opening, which would cut it to 422 lbs. Still, that'd
hold a couple large guys standing on one strand of the railing wire.

Actually, no. When applying force perpendicular to a tight wire, the
force
multiplies by a large factor. In a pinch, you can winch a vehicle out of
a
tight spot by tightly tying a rope between the vehicle and a tree and
applying force perpendicular to the middle of the rope. Needless to say
you
have to take up the slack between each push on the rope.

I don't grok that, Ivan. A pull on the middle of the rope would be
equal on all 3 ends, wouldn't it? Even if it were a nice round pulley,
it would not give you any force increase. The individual snatch
blocks (pulley with a hook) we used on the tow trucks (at Flynn's
Frame and Collision eons ago) would only give us the -same- pull the
winch had, but it would be at a different angle, better for that
particular extraction. Multiple pulleys (forming a block and tackle)
would multiply the force.

If you still disagree, please cite the formula/law for us.

Larry, picture this.
You have a horizontal cable, say 100 feet long between two fixed points. In
the middle you hang a 50 pound weight. Going to one end, you try to tighten
the cable as much as possible in order to raise the weight and take all the
sag out of the cable. Impossible. It would take infinite amount of force
to make that cable truly horizontal since it has no vertical component
(needs to lift 50 pounds) of force. Accordingly if you were able to
tighten an unloaded cable (impossible, since it due to its weight it will
hang in a catenary shape) to a horizontal plane, a force in the middle will
induce an untold amount of tension in the cable. Of course, as soon as the
cable begins the develop sag the tensile force diminishes.

The whole point is that in cabled barriers, if the cable is extremely tight,
my stepping on the middle with my 280# of force, will induce tremendous
stress in the cable and connections.

Ivan Vegvary