On Wed, 10 Sep 2008 19:01:03 -0700, Larry Jaques
wrote:

On Wed, 10 Sep 2008 17:03:46 -0500, with neither quill nor qualm,
Ignoramus24166 quickly quoth:

On 2008-09-10, Larry Jaques novalidaddress@di wrote:
On Tue, 09 Sep 2008 22:29:46 -0500, with neither quill nor qualm,
Ignoramus15131 quickly quoth:

On 2008-09-10, Larry Jaques novalidaddress@di wrote:
On Tue, 09 Sep 2008 17:48:49 GMT, with neither quill nor qualm, "Ivan
Vegvary" quickly quoth:


"Larry Jaques" wrote in message
news:5p0dc49m9715uqhj8n9ogtdcbnedofds0h@4ax. com...
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?

No.

Try an experiment, you will need two pulleys.

"Try an experiment, you will need a block and tackle."

NOT the same as he was talking about, Ig.


Fix two pulleys and hang a rope on them like this:

,___________x_________.
|O O|
| |
X X

Again, that's not what he was describing, Ig.

x-------------y-----------x Pull on Y, no pulleys.


Q: Who here on RCM has 3 spring scales with which they can perform
this experiment?

Yikes! I hadn't been following this thread. Something will give. Dad
used this technique in 1949 or so to unstick some early tracked
combines cutting rice. He'd tie on with 100 ft. of 1" cable, take the
steel wheeled poppin' johnny out and spin it down at the end, then get
in the middle with another tractor and pull sideways. He later
realized that he could have been killed had something let go.

It's just trig. At 0 deg deflection, the load on the ends is
infinite. At 1 deg,you've moved sideways 1.7%, and decreased the
length by 0.015%, so mechanical advantage is already down to 114:1. At
0.1 deg, the mechanical advantage was 1145, and at 0.01 deg, 11,459
and so on. I used sin/(1-cos).