Building My Rack. For a beginner.

Fat Dad wrote:Is this a troll? SMC pins? Stubai malleagle pins? Those have to be, what, 50 yrs. old? Really?

Nope, not a troll. These SMC do actually look about 50 years old. Most likely will never use them. They were just thrown in with some newer gear i bought. Also came with a few nuts that will never be used as well. The heads look fine, but the wire is old. Definitely dont want to take a fall on those.

TheCrux wrote:.... Pay little attention to fall factors as they relate poorly to fall forces.

Um... No. Fall factor is a critical factor when determining the force exerted on your top piece. Maybe you are refering to something else such as vectors and direction of pull.

Greg D wrote: Um... No. Fall factor is critical factor when determining the force exerted on your top piece. Maybe you are refering to something else such as vectors and direction of pull.

No....actually fall factor is a completely useless calculation. It is non-linear to actual fall forces. Fall factor is calculated by dividing the distance of actual fall to the point of rope tension by the total amount of rope out from belay. It doesn't factor in rope stretch, friction, velocity or climber weight.

TheCrux wrote: Fall factor is calculated by dividing the distance of actual fall to the point of rope tension by the total amount of rope out from belay. It doesn't factor in rope stretch, friction, velocity or climber weight.

This is true. You can't calculate the impact force on your top piece of gear or other forces generated in a climbing fall simply by calculating fall factor. Many other factors must be considered such as mass of the leader, mass of the belayer, friction through protection pieces, friction of rope against the rock, and dynamics of the rope to accurately calculate these forces. But, fall factor is a quick and simple way to estimate the severity of a fall before or after it happens. Few climbers carry a spreadsheet with them to input the necessary data to make accurate complex calculations.

True, fall factor alone won't determine the forces generated in a fall. But, for any given climber their body weight could be considered a constant during the course of a climb save minor changes due to food, water and gear. Whereas the fall factor changes constantly during the course of a climb usually descending with distance from the belayer provided solid protection is being placed at regular intervals. This is why fall factor is so important for the leader to consider. Forces are generally greatest when closest to the belay, but not always.

For what it's worth, there is a drop test chart comparing a range of fall factors using a dynamic rope and three mass amounts; the numbers came out to be about 1kN less to the force calc, & were linear.

I think for every .3 increase in FF in this test, the resulting kN increased by 1 (But hold on, read further as this not an answer all test).

The FF works well within a range of normal climbing whippers, but I have reservations that it inflates as compared to actuals when moving to hitting the anchor at the FF 2.0; as well doesn't offer how much a belayer will get hit in duration from a huge fall so as to be able to control a load successfully -- the rope properties & belay device in question may be a setup for loss of rope control; something the FF itself won't be able to accurately give us -- i.e. the force above the belayer's braking strength could be a milli-second or several seconds. How does the FF tell us anything here?

A good belayer can only hold so much, but this can be a great thing taking energy away from the pro, so long as rope control can maintain and a counterbalance can help you out. Something worth knowing is how much you can actually hold with your device & rope and how long you can maintain control when force exceeds your braking strength.

Some more thoughts -- the mass is important, amount & composition. Force is a wave that has duration, so these data points may just be peak-force at one point in time; on this again, the steel drop mass will behave more to the force calc and less like an actual person. The FF is really meant to give an approximate ballpark; why it has been applied to the rigging standards that it has been, just says to me the folks writing the standards are not accurately testing systems if they don't take into account system components, system resiliency, mass composition, & fall distance/mass acceleration.

But this concept makes for better periodicals and easier to write a standard to just take the FF because everyone can understand rope out and where the pro gets hit. It can be an over-applied though I think.

There is some intuition here -- do you really want to hammer your system with an 80+ footer? Uh, No. (but that 79 footer...)

Did I mention tri-cams are the shiz-nizzle for building a rack? Okay, tri-cams are the shiz-nizzle. And I luv hexies, they make good grappling hooks and tell the bears that my partner can't run as fast, cause they have the rope.

Great. On the way back from Harpers Ferry WV, my 2003 Trailblazer transmission died.. there goes spare money for a month or 2. At least I was able to get some more time on the Appalachian Trail.

Of course the girl in 2 inch hills isn't really setup to hike.