Fancy wire rope ends?

Try

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I bought one, couldn't find 5/32" wire rope in the junk pile so tried it on 3/16", and messed up the weak spring that holds the clamp jaws. Now the jaws don't stay in place so I haven't been able to test it for strength.

I would tend to shy away from those in favor of properly swaged couplings. They don't seem to have a very high load rating. I have seen (somewhere, don't remember off the top of my head) a company that sold protective/decorative "boots" for swaged couplings that concealed and protected them.

On Mon, 08 Sep 2008 23:48:48 -0700, with neither quill nor qualm, JR North quickly quoth:

-- Music washes away from the soul the dust of everyday life. ---- --Unknown

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.

Ivan Vegvary

So it sounds like they're about par for the course with most Harbor Freight items. I am mostly looking at them for some purely cosmetic applications, nothing where any sort of significant load would be applied. If safety were a factor I would absolutely look elsewhere, but at the moment I'm just tryin to find something that's "pretty" and not terribly expensive with perhaps some better quality than what Harbor Freight is normally known for. I really like the Sta-Lok ones, but the price is just way too high (although the quality is most likely there).

On Tue, 09 Sep 2008 17:48:49 GMT, with neither quill nor qualm, "Ivan Vegvary" quickly quoth:

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.

For S&G, I asked the question to the guys at Feeney, the Cable Rail people. I'll post their answer if/when I get one.

No.

Try an experiment, you will need two pulleys.

Ivan is right, and the easiest way to grok that is to make a vector diagram of the forces involved.

Suppose you have a stretched, fairly straight rope and then hang a weight at the middle of it. The rope stretches a bit, so you get an angle. The downward force on the weight is counteracted by an upward force, or you wouldn't have equilibrium.

That upward force is the resultant force of two force vectors, one along each side of the rope.

Draw the diagram and you will see for yourself how huge the force along the robe gets with even a little force downwards.

S.

The pull he's talking about is at right angles, like plucking a guitar string.

On Tue, 09 Sep 2008 22:29:46 -0500, with neither quill nor qualm, Ignoramus15131 quickly quoth:

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

NOT the same as he was talking about, Ig.

No, this is not a simple straight line mechanics problem of pulleys acting as levers, it's a vector addition problem. When you pull the rope out of line at the center, the component of tension perpendicular at each end of the main rope has to be very high to match the small component needed to offset the sideways pull, and this approaches infinity the tighter the main rope gets.

As soon as you begin to pull the main rope out of a striaght line, all the angles change and your advantage goes way down. This is not something you can do for a sustained pull, it's a game of inches. Pull, retension to shrink the angles again, repeat, ad nauseum.

--Glenn Lyford

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

Tighten your environmentally responsible solar powered clothes dryer (clothesline) as tight as you can, then drop a towel over it. It will sag.

No, you need caulk and jars and GPS units.

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

,___________x_________. |O O| | | X X

Attach heavy weights to points X. zThe rope on top will be almost straight, the lighter the rope, the straighter. Then hang a much lighter weight on point x. You will see the rope sag in the middle.

No, this is not a simple straight line mechanics problem of pulleys acting as levers, it's a vector addition problem. When you pull the rope out of line at the center, the component of tension perpendicular at each end of the main rope has to be very high to match the small component needed to offset the sideways pull, and this approaches infinity the tighter the main rope gets.

As soon as you begin to pull the main rope out of a striaght line, all the angles change and your advantage goes way down. This is not something you can do for a sustained pull, it's a game of inches. Pull, retension to shrink the angles again, repeat, ad nauseum.

--Glenn Lyford

I have successfully used this technique to grunt a car up a incline into a garage when a pusher vehicle/come-a-long were not available.

Anchor end of rope to immovable object. tie to a chain with a hook. Fasten other end of chain to bumper tightly. Have a helper with a chock ready behind wheels. Grab the middle of the rope and lean back Car moves, and helper moves chock. Release, take another bite on the chain and repeat

Works a treat.

mark

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

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?