SO… CAN YOU HOLD THEM?
Properly used belay devices paired with appropriate ropes will hold falls in almost all cases. When might this not be the case? Let’s run through a few scenarios: Transmitted force is too high. High fall factors combined with heavier climbers will transmit a lot of force through the system. It would take a huge transmitted force to overcome the combined efforts of the hand/grip force and AF, but it is technically possible. AF is too low. Possible if using an inappropriate device for the rope, or perhaps using a well-used and worn-out device. Hand force is too low. Can be caused by a weak grip, inattentive belaying, by wearing gloves, using a new/slick rope, a thin rope, or a rope that is difficult to grip.
H × AF > F H × AF < F
GRIP FACTOR
Because a device amplifies the belayers hand force or grip, this force is extremely important when determining whether a fall can be held or a climber lowered safely. Hand force varies quite a lot between individuals – the largest hand forces measured are around three times greater than the lowest. Other factors can reduce or increase the hand force, such as whether the rope is pulling upwards or downwards, the rope diameter and condition, and whether gloves are worn or not.
Top tip 4:
Wearing belay gloves can be useful to stop you burning your hands and letting go of the rope, but they also may make it more likely that you cannot hold the rope in the first place.
Top tip 5:
With many devices, you can increase amplification by using two belay karabiners instead of one. Check that the instructions allow you to do this first.
In some situations, a manual device may no longer be suitable and devices with assisted braking come into their own. We’ll look at these devices in a future article.
Words: Dan Middleton, BMC technical officer.
FURTHER INFO DOWNLOAD:
our free Belaying and Abseiling leaflet here:
www.thebmc.co.uk/belay-leaflet
SUMMIT#90 | SUMMER 2018 | 67
PHOTO: SHUTTERSTOCK.
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