Outer Limits 4x4 Board

macca81 wrote:
it locks onto the cable....



vibrations are mearly an example. u said vibrations are different to kinetic energy, when infact they are not. if a solid object is in direct contact with something before it is vibrating, and then you make it vibrate, then said solid object will vibrate with it.
put a soft object in direct contact with something before it is vibrating, then make it vibrate, the soft object will absorb those vibrations and minamise the total movement.

a snapping cable is just one big vibration. your just looking at it to narrowly

is just one big vibrating cable? and you think im looking at it narowly?

Vibrations have absolutely, positively, nothing to do with the elastic potential energy released when the cable snaps. Sure there are vibrations involved, but they are totally insignificant to the danger involved. It is not vibrations that is going to kill someone, its the cable, a mass, moving at high speed.


When you stretch a cable, elastic potential energy is stored within the cable itself. When the cable snaps the elastic potential energy is converted to kinetic energy acceletrating the cable rapidly to some velocity(a combination of velocities infact), to stop something moving, you need to act with an equal but opposite force, we cant do that in this case, so we dampen the acceleration and finally the velocity by making the cable accelerate a larger mass which decreases the final velocity of the cable and also damper to a hopefully safe speed.

Trying to say it is just a vibrating cable shows a complete lack of understanding of the forces involved. The fact that it recoils in a wave like motion has nothing to do with vibrations, it is because the velocity of the cable is not constant over its length, the velocity increases toward the broken end. So you have the tip going faster than the middle, and so the cable bunches up and makes a wave shape as it does so.

The only valid point you have raised is that the winch saver block is fixed at the middle of the cable, which will dampen the acceleration of the first half of the cable, and have a reduced effect on the last half, toward the broken end.

That is to say it is fixed, I very much doubt that the push on lock is going to stop the incredibly high acceleration of the cable once it snaps, it will just slide within this cable lock as it tries to accelerate the block. Sure, the block will start to move, but no-where near as fast as the cable is moving within it.

also, it says the cable lock is for steep angles etc, what does a normal cable damper do on steep winching angles?

a damper is a device designed to smooth out or damp a sudden shock impulse and dissipate kinetic energy. in the form of a cable dampener it does this by spreading the energy over its own area rather than let it stay in the cable.

tie a 15m rope to a fence post, then stick a sheet of canvas or a blanket over it in the mid point. shake it like crazy. it will move, but not to much.

do the same but replace the canvas or blanket with a lump of metal of similar weight. shake it again. it will again move, but moreso than with the blanket, and more eraticaly.

if it was weight that did the job, why dont we strap rocks to the cable?(cable damage aside)


the dampener must take the energy away from the cable, thats how they work.