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© 2003 Andrew Chang10/23/031 What Happens in a Fall? lFalling climber builds up momentum (force x time) lWhen climber is ‘stopped’ (either by rope/anchor system or by hard deck) the resulting forces needs to be absorbed lClimbing rope (dynamic) acts like a SPRING and ideally absorbs most of this force (the maximum amount NOT absorbed by the rope is the rope’s IMPACT FORCE rating) l“Fall-factor” (larger numbers are worse) indicates SEVERITY of fall and is related to the ability of the rope to act as a good spring and absorb fall force (less rope equals less good spring) lThe remaining force (impact force) is absorbed by the ANCHOR and THE CLIMBER lActually, the anchor needs absorbs 1.7x to 2x of the impact force WITHOUT BREAKING (extra.7x to 1x due to the belayer force counter balancing the climber and stopping the fall)
© 2003 Andrew Chang10/23/032 FALL FACTOR = Height of fall Total Length of rope out (ie. amount rope acting spring) Fall Factor 80’ 80’ Rope Slack in System Fall 5’ 80’ Fall Factor == 0.0625 5 80 KEY: Climber Anchor Rope
© 2003 Andrew Chang10/23/033 approx force on anchor: 3-4KN 5’ 80’ factor 0.0625 rope out: fall : 20’ 40’ factor 0.5 approx force on anchor: 8-10KN rope out: fall : 20’ factor 1 approx force on anchor: 12-15KN rope out: fall : 10’ 20’ factor 2 approx force on anchor: 16-20KN rope out: fall : KEY: Climber Anchor Rope Pro Fall Factor: Examples LEAD FALLS SLINGSHOT TOP ROPE FALLS
© 2003 Andrew Chang10/23/034 Anchor Forces l Anchor (naturals, gear, runners, webbing, ‘biners etc… ) needs to absorb 1.7x to 2x of the impact force l Ideally, anchor should be built to withstand 30KN of force (approx 1.5x worst case lead fall) KEY: Climber Anchor Rope Zero Motion (stopped): Belayer force EQUALS Climber force Anchor subjected to BOTH forces Force from climber Force from belayer Force on anchor is SUM of both
© 2003 Andrew Chang10/23/035 lDoubling fall factor results in approximately 1.4x increase in impact force lRopes are rated for impact force from a 80kG climber and factor-of-1.77 fall lRunners and anchor need to absorb 1.7x-2x impact force of fall lLead falls generate significantly more impact force than slingshot top rope falls More info: www.climbtennessee.com/train/fall.html www.bealropes.com/english.dir/forces.html Anchor Forces: Details
© 2003 Andrew Chang10/23/036 Forces (approx) l1KN = 220lb (ie. 1 person static) approx 1G l10KN = 2200lbs (max from rope) approx 10G’s l12KN = 2640lbs (ie. Injury/Death) approx 12G’s l15KN = 3300lbs l25KN = 5500lbs
© 2003 Andrew Chang10/23/037 l1m = 3 feet = 4m/s = 10mph l3m = 10 feet = 8m/s = 17mph l6m = 20 feet = 11m/s = 24mph l10m = 33 feet = 14m/s = 31mph l20m = 66 feet = 20m/s = 44mph Speeds from falls (approx)
© 2003 Andrew Chang10/23/038 l1m = 980J = 4m/s = 10mph l3m = 2940J = 8m/s = 17mph l6m = 5880J = 11m/s = 24mph l10m = 9800J = 14m/s = 31mph l20m = 19600J = 20m/s = 44mph Energy from falls (approx) mgh & ½ mv 2
© 2003 Andrew Chang10/23/039 l2” Webbing 30kN ($0.55/ft) l1” Webbing 18kN ($0.30/ft) l9/16” Webbing 7-11kN ($0.22/ft) l5mm Spectra 20kN ($1.05/ft) l4mm cord 3kN ($0.20/ft) l5mm cord 5kN ($0.25/ft) l6mm cord 8kN ($0.35/ft) l7mm cord 11kN ($0.40/ft) l8mm cord 11kN ($0.50/ft) lNylon runner 22kN ($2.0/ft – 0.75’, 2’, 4’ ) lSpectra runner 27kN ($3.5/ft – 0.5’, 2’, 3’, 4’ ) lDynamic Rope (impact force) 7kN-10kN ($0.60/ft (approx): 165’, 200’, 230’) Strength of Webbing Gear Strength Cost
© 2003 Andrew Chang10/23/0310 l‘biner 18-25kN / 6-9kN (gate open) l#1 Nut 4.3/ 9.1mm 2kN l#5 Nut 8.4/13.5mm 6kN l#6 Nut 10.2/15.5mm 10kN l#1 Hex 10.7/15.5mm 6kN l#3 Hex 13.9/20.1mm 10kN l0.5 Tricam 16/28mm 10kN l2 Tricam 28.5/41mm 15kN l2.5 Tricam 32/47.5mm 18kN l0.1 BD Cam 9.9-17mm 7kN l0.2 BD Cam 10.2-16.2mm 8kN l0.3 BD Cam 12.5-21.5mm 10kN l0.75 BD Cam 24-39.5mm 16kN Strength of Gear Gear Useful Dimensions Strength
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