What Happens in a Fall?

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# What Happens in a Fall? - PowerPoint PPT Presentation

What Happens in a Fall?. Falling climber builds up momentum (force x time) When climber is ‘stopped’ (either by rope/anchor system or by hard deck) the resulting forces needs to be absorbed

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Presentation Transcript

What Happens in a Fall?

• Falling climber builds up momentum (force x time)
• When climber is ‘stopped’ (either by rope/anchor system or by hard deck) the resulting forces needs to be absorbed
• Climbing rope (dynamic) acts like a SPRING and ideally absorbs most of this force (the maximum amount NOT absorbed by the rope is the rope’sIMPACT FORCE rating)
• “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)

• The remaining force (impact force) is absorbed by the ANCHOR and THE CLIMBER
• Actually, 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)

KEY:

Climber

Anchor

Rope

Fall Factor

FALL FACTOR = Height of fall

Total Length of rope out(ie. amount rope acting spring)

80’

5

Fall Factor =

= 0.0625

80

80’

80’

5’

Fall

Slack in System

80’ Rope

factor 2

factor 1

factor 0.5

factor 0.0625

fall:

fall:

fall:

fall:

rope out:

5’

20’

20’

20’

20’

rope out:

80’

rope out:

rope out:

10’

40’

approx force on anchor:

8-10KN

approx force on anchor:

3-4KN

approx force on anchor:

16-20KN

approx force on anchor:

12-15KN

KEY:

Climber

Anchor

Rope

Pro

Fall Factor:

Examples

SLINGSHOT TOP ROPE FALLS

Force on anchor is SUM of both

Force from climber

KEY:

Climber

Force from belayer

Anchor

Rope

Anchor Forces

• Anchor (naturals, gear, runners, webbing, ‘biners etc… ) needs to

absorb 1.7x to 2x of the impact force

• Ideally, anchor should be built to withstand 30KN of force

(approx 1.5x worst case lead fall)

Zero Motion (stopped): Belayer force EQUALS Climber force

Anchor subjected to BOTH forces

Anchor Forces:

Details

• Doubling fall factor results in approximately 1.4x increase in impact force
• Ropes are rated for impact force from a 80kG climber and

factor-of-1.77 fall

• Runners and anchor need to absorb 1.7x-2x impact force of fall
• Lead falls generate significantly more impact force than

slingshot top rope falls

www.climbtennessee.com/train/fall.html

www.bealropes.com/english.dir/forces.html

Forces (approx)

• 1KN = 220lb (ie. 1 person static) approx 1G
• 10KN = 2200lbs (max from rope) approx 10G’s
• 12KN = 2640lbs (ie. Injury/Death) approx 12G’s
• 15KN = 3300lbs
• 25KN = 5500lbs

Speeds from falls (approx)

• 1m = 3 feet = 4m/s = 10mph
• 3m = 10 feet = 8m/s = 17mph
• 6m = 20 feet = 11m/s = 24mph
• 10m = 33 feet = 14m/s = 31mph
• 20m = 66 feet = 20m/s = 44mph

Energy from falls (approx)mgh & ½ mv2

• 1m = 980J = 4m/s = 10mph
• 3m = 2940J = 8m/s = 17mph
• 6m = 5880J = 11m/s = 24mph
• 10m = 9800J = 14m/s = 31mph
• 20m = 19600J = 20m/s = 44mph

Strength of Webbing

Gear Strength Cost

• 2” Webbing 30kN (\$0.55/ft)
• 1” Webbing 18kN (\$0.30/ft)
• 9/16” Webbing 7-11kN (\$0.22/ft)
• 5mm Spectra 20kN (\$1.05/ft)
• 4mm cord 3kN (\$0.20/ft)
• 5mm cord 5kN (\$0.25/ft)
• 6mm cord 8kN (\$0.35/ft)
• 7mm cord 11kN (\$0.40/ft)
• 8mm cord 11kN (\$0.50/ft)
• Nylon runner 22kN (\$2.0/ft – 0.75’, 2’, 4’ )
• Spectra runner 27kN (\$3.5/ft – 0.5’, 2’, 3’, 4’ )
• Dynamic Rope (impact force) 7kN-10kN (\$0.60/ft (approx): 165’, 200’, 230’)

Strength of Gear

Gear Useful Dimensions Strength

• ‘biner 18-25kN / 6-9kN

(gate open)

• #1 Nut 4.3/ 9.1mm 2kN
• #5 Nut 8.4/13.5mm 6kN
• #6 Nut 10.2/15.5mm 10kN
• #1 Hex 10.7/15.5mm 6kN
• #3 Hex 13.9/20.1mm 10kN
• 0.5 Tricam 16/28mm 10kN
• 2 Tricam 28.5/41mm 15kN
• 2.5 Tricam 32/47.5mm 18kN
• 0.1 BD Cam 9.9-17mm 7kN
• 0.2 BD Cam 10.2-16.2mm 8kN
• 0.3 BD Cam 12.5-21.5mm 10kN
• 0.75 BD Cam 24-39.5mm 16kN