/ NEW ARTICLE: Fall Factors

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UKC Articles - on 20 Nov 2007
The term fall factor is often bandied about by climbers but what exactly does it mean?

Read the article here - http://www.ukclimbing.com/articles/page.php?id=647

The article is taken from the book Trad CLIMBING+ published by Rockfax - http://www.rockfax.com/publications/books/item.php?id=140
This is the second thread about this article, that is because we had an earlier one in which I had made a huge and very significant mistake, and kept trying to reinforce my mistake. The mistake was all my own addition both in the article, and then more dramatically on the thread itself. It was only by going back to Adrian's (now-printed) text that I was able to see my mistake.

We got quite a few replies to that thread and many of them made good points. An especially useful mathematical point was made by jkarran:

If you have a runner at R meters,
climb X meters past it,
and there's an additional Y meters of slack:

Based on the "distance fallen/available rope" equation

FF = (2X + Y)/(R + X + Y)

plug some numbers in and it becomes apparent that you need to be falling past your belayer before increasing Y reduces FF, up to that point increasing Y marginally increasess FF. Not a common scenario in my limited experience.



Since this article is tied to an FAQ, it is important that it contains good information, therefore I had to remove the thread with all my nonsense in it.

Apologies for all who took the trouble to reply (and especially those I made condescending replies to) and rest assurred, the information in the book is correct, is it only this numpty who doesn't know what he is talking about.

Alan
Kane - on 20 Nov 2007
In reply to Alan James - UKC: The article still implies a longer fall is better than a shorter fall which is wrong.

When talking about the length of a fall I think of the free fall before the rope tightens. In most cases this should be kept as small as possible, as given by the above equation. I get the impression that the article talks more about the distance fallen whilst the rope and belay are stopping the fall, which should be long to keep the forces on the runner low, however this is a small portion of the overall fall and to say,

"if the only thing you are going to hit when you fall off is fresh air, then you will almost always load your gear less if you take a longer fall and hence you should be safer."

is still mis-leading.

Kane
In reply to Kane:

I think you are looking at the old version since that line has been removed. Try refreshing your browser to see the later version.

Current article views number at the bottom is 417. If you see a number less than this then you may well be looking at an older version.

Cheers

Alan
Kane - on 20 Nov 2007
In reply to Alan James - UKC:
> (In reply to Kane)
>
> I think you are looking at the old version since that line has been removed. Try refreshing your browser to see the later version.
>
> Current article views number at the bottom is 417. If you see a number less than this then you may well be looking at an older version.
>
> Cheers
>
> Alan

yeah the view count is only 200. tried refreshing the browser but it stays the same.
In reply to Kane:
> yeah the view count is only 200. tried refreshing the browser but it stays the same.

Try holding down shift at the same time. Seems to be a problem with Firefox in particular where by you really have to insist that it gets a new page.

Alan
Offwidth - on 20 Nov 2007
In reply to Alan James - UKC:

Funny thing is that fall factors are rarely crucial but really important when they are. People seem to get away with terrible treatment of their ropes in the lower fall factor region (eg repeated biggish indoor falls around 0.5 with no rope rests in between) where if you logged it cummulatively (as manufacturers say), ropes could be retired in a single session! Also in this area of rope lifetimes, many people worry too much about ropes snapping and too little about losing elasticity.
Kane - on 20 Nov 2007
In reply to Alan James - UKC: yeah that worked. many thanks.

kane
Chris the Tall - on 20 Nov 2007
In reply to Alan James - UKC:
There is also a problem refreshing it using Internet Explorer (I'm using version 7)

Yes I could delete my entire cache, but I don't want to do that - it means I have to log on to sites like this
In reply to Chris the Tall:

Generally just repeatedly refreshing tends to do the trick eventually. Holding shift works for some browsers and holding 'control' I think works for others.

Emptying your cache shouldn't touch your log in cookies, just stored pages and images. It might clear them on old browsers but most now have a 'Clear Private Data...' function where you can specify exactly what it is you want to clear. Having said that, you shouldn't need to do it in this case since the key-hold refresh trick should work.

Alan
Adam Long - on 21 Nov 2007
In reply to Alan James - UKC:

Alan, I think there's still too much emphasis on the 'long falls can be safer' schtick. On the second diagram you say:

'a longer fall of 3m, the fall factor would be only 0.15 - significantly less - and safer' (than a 2m, factor 0.2 fall)

The difference in fall factors here is not at all 'significant', its slight. In reality other factors would become more important as to which is safer. I think you should drop the second diagram and just explain fall factors before trying to introduce the concept that sometimes a longer fall can be safer.

I have to teach this to industrial users most weeks so I have some experience of confusing folk!
jkarran - on 21 Nov 2007
In reply to UKC Articles:

Finally got it refreshed (Ctrl+refresh IE6 or 7?).

Now much clearer than it was.
jk
Paz - on 21 Nov 2007
In reply to jkarran:

Did you work out that effect of slack yourself, or pick it up from my ramblings, (in particular my post on planetfear over two years ago)?
Paz - on 21 Nov 2007
In reply to Adam L:

Yeah, a .15 is only about 9% less than a .2 (on my Beals).

The reason is that peak force only goes up like the square root of one plus the fall factor, even though the coefficient of it (within the root) is very large, being twice the reciprocal of the fractional extension under body weight (so 1/0.07 for mine - a 7 % stretch), you're only talking between 2 and 8.5 times body weight. According to the linear spring `bounce forever' `independent of length' model which I don't believe anyway.
ads.ukclimbing.com
Chris the Tall - on 21 Nov 2007
In reply to Alan James - UKC:
<Ctrl + F5> does the trick

I really ought to have thought of that !

To busy working out questions for the quiz tonight (plug, plug)

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