I appreciate your friendly sentiment Macky, i would also like to keep this on that level, and continue to discuss this until we either reach a consensus or agree to disagree.
Since i did make some measurements yesterday, i'll refer to that.
I did this, only instead of a scale i used physical weights. With a 16 inch orange cable and 25 pounds the cable stretched to 3 times its length.
This gives us two points to consider. The length of stretch and what does the 25 pounds mean?
Regarding the length of stretch, we all originally thought it should only stretch to 2x the length. Then Lifeline came out with the FAQ which stated 3x, and to add confusion, Ray said 2.5x !!!
Now, my experiment says it is 3x, and Kevin said this was worked out in 1970! So over the years some copy writer messed up, some guy in QC (a field that only attracts the best and brightest) messed up. Over the course of 40+ years not hard to believe. Along comes Macky and someone actually has to go back and dig up the original guidelines which is what the FAQ represents. So for that reason, i'm going along with the 3x number.
Moreover, i forwarded the post to Kevin, who confirmed the 2x was a copywriting mistake, and he aims to right that. (He answered me on a Saturday BTW the same day i forwarded him the message.)
So with that, i hope we can agree, 2x is out and 3x is in.
From there the next issue is what does the 25 pounds mean? From a physics point of view its the amount of weight the cable is holding, and that the ceiling its attached to is holding. The cable is holding 25 pounds and the ceiling is holding 25 pounds. This 25 pounds is the tension on the cable.
Now i don't know the definition of Pullweight, i've never seen it since competitive strand pulling has gone the way of the dodo, it could be that its just the measure of how much tension is on the cable. If so then Lifeline's cable rating is not a measure of Pullweight. I don't see that as a problem though, they have the right to rate the strength of the cables how they choose. And this is where i think the disconnect is between what we are saying. Its a matter of definitions. (I would love to know what someone like Fatman has to say about the meaning of Pullweight)
Now lets go back to my attempt to explain why a 50lbs rating makes sense (or not). If we can get together on this, or at least understand each other we are home free.
I think that the hanging cable is easier to think of than the cable around the scale, but hopefully i can show they will give the same result.
If you have the cable hanging with 25 pounds attached to it, measure the amount of stretch and then take the weight off and with one hand stretch the cable to that same length how much is the hand pushing? 25 pounds, not 12.5 pounds. If you reverse the procedure and with the weight on the cable unhook it from the ceiling how much is that hand holding? 25 pounds.
Again this is just Newton's law for every force there is an equal and opposite force. The force is the 25 pound weight being accelerated by gravity. The ceiling resists that force equally.
So if you take off the weight and unhook from the ceiling one hand is providing the force of the weight 25 lbs and the other the force of the ceiling 25 pounds for a total force being applied by two hands of 50 lbs.
Since this is being applied to strength training we want to know how much both hands are doing, the 50 pound rating still makes sense. And is a reasonable way to define ones cable strength ratings. In other words lets measure how much we are doing with each hand.
If this is the official way strandpullers measure is another question, but i have no issue if LL choose to do it this way, because i know i can just cut the rating in half if i'm interested in tension, AS LONG AS THE RATING ITSELF IS ACCURATE.
Its a rating system. Once you know how to convert it to your way of measuring it works fine, just like inches in the usa and cm in Europe. However, i do think this is a good way to think of pulling strands anyway.
OK now to why LL is showing how to measure as they do.
They don't want to have to explain all this, and i don't blame them, hey even they get confused. So by simply measuring by holding the two handles, you wind up measuring the force at the two handles!
So as you stated, the force at each handle is actually 25 lbs. Now if you hook one handle to the ceiling and pull the cable to the same length how much will you measure at the end? 25 pounds! Just like before, they are equivalent ways of measuring!