Falling climber builds up momentum force x time

1

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 ropes
  IMPACT 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)

2

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
3
Fall Factor Examples
SLINGSHOT TOP ROPE FALLS
LEAD FALLS
4

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
5
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
• More info
• www.climbtennessee.com/train/fall
  .html
• www.bealropes.com/english.dir/forces
  .html

6
Forces (approx)

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

7
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

8
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

9
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)

10
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