Here's a question

Re: Here\'s a question

Ron, i think your heat dissipation speed theory will hold; but also we must consider speed as a force applied on it's own?? More speed, more friction needed to compensate; more heat etc. Kinda on the edge there; with recognizing distance as a 'force'; and leverage as a trading of forces of power and distance. But, still; by any other name; sum thing to be mathematically reckoned with...

Also, in with flexing on hinge as a final self tightening/ballast force theory; and using friction on overhead support (or sometimes behind) i like Sweating in a RoundTurn (shown at bottom of pic); but only with lite to medium loads; because of the intense heat/frictions giving off wisps of smoke on even slow lowering of heavier loads (hey; this stuffs took a lot of miss-takes to figure out!!). Once again this is for reducing the elastic length accesible by load force; to allow more/more intense self tightening by tipping over on hinge into wide, undutched face for self-pre-tightening of the ballast force of the line before tearoff. Not for supports under load; for in cases of the load moving towards the support, the line slackens, not tightens.
 
Re: Here\'s a question

Right now, I'm bettin' that the PE is all that matters. I.e. PE is converted to heat - speed, jerks, stops, starts just won't matter. We can't have more or less energy than the PE of the log.

For example, if we lower a log slowly, the loss of PE is the very same as if we lower it rapidly. If we varied the speed throughout the lowering process the change in PE would be exactly the same as if we lowered it slowly and smoothly at a constant speed.

Lowering a piece faster will raise the temperature of the friction device, but speed will not increase the heat - that's strickly proportional to the change in PE. Faster speeds converts PE into heat energy at a faster rate. So if the friction device cannot dissipate the heat into the air at the same rate, the temperature of the friction device will increase.

Rope stretch would be a factor, but since energy is expended to stretch the rope, heat will be generated in the rope. But it won't add more heat to the system. Part of the loss of PE will be used to heat the rope via stretching and the rest will heat the friction device.
 
Re: Here\'s a question

I said I'd do this and I finally got to talk to our physic's guru. Essentially what I said in my previous post (just above this one) is accurate.

Glazing really a function of the rate of PE change. E.g. suppose a 200 lb log falls 5 feet and a groundie catches and stops it in 1 sec. 1000 ft-lbs of energy will be converted to heat in 1 second. Since the energy goes in at a very high rate, the temperature rises rapidly on the friction device. However if the groundie catches it softly, i.e. slows it more gradually, the rate of PE conversion to heat is slower and the friction device has more time to dissipate the heat into the air.

What does not matter is whether a crotch of a tree is used or a porty. I.e. each will have to absorb the same amount of heat for a given load and speed. The difference is how fast the heat can be transferred to the air.

So if you've found that you glaze your rope(s) less when you use a porty, it's soley because you either control the rate of fall better or the porty dissipates heat faster than say a crotch, or some of both. Nothing else really matters.
 
Re: Here\'s a question

Awesome.

Now I really get it...seems simple...only took 4 pages to get it straight!

Thank you much to every contributor.
 
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