SKILLS TECH STOPPING POWER:
Learning how to use a belay device safely is one of the most fundamental skills in climbing, and your partner will thank you for it. But do you know the difference between each type and how they work? Here we’ll explain how to choose which device to use, and what factors affect how well it does its job.
HOW DO BELAY DEVICES WORK?
THE TWO TYPES OF DEVICES
Belay or abseil … or both? While all can be used to securely control the rope when a climber falls – and lower them safely – many modern devices can also be used to abseil. Devices which do both are called braking devices. These have two categories: manual braking devices and assisted braking devices. In this article we’ll take a look at manual devices – the most popular of the two with the widest range of uses.
USE THE FORCE
You don’t need to be strong to belay. Manual braking devices amplify the force which the belayer applies to the dead end of the rope with their hand. The amplification factor (AF) of a braking device is a measure of how many times the device multiplies the force the belayer applies. The higher the AF, the more effective the device will be at allowing a belayer to hold a fall or lower a climber in a controlled manner.
FICTION? IT’S NOT JUST FRICTION
Research has found that two things contribute to provide this amplification effect. As expected, one of these is the friction between the rope and the surface of the device. More surprisingly, the greatest contributor to the AF is from distortion or flattening of the rope as it is pulled through the device under tension.
What determines the AF for a device? The largest influence comes from its design – how much it distorts the rope and the amount of friction from contact between the rope and device. Devices with V-grooves often provide a high amplification factor, as they distort the rope by forcing it into the groove in addition to having more surface area of the device in contact with the rope.
Top tip 1: 66 | CLIMB. WALK. JOIN.
Take extra care and read the manufacturer’s instructions before using a new or unfamiliar device.
LEARNING THE ROPES
The rope also has a significant AF effect. Thinner ropes give less AF for most devices, but it also depends on the condition of the rope: the age and/ or presence of surface treatments such as a dry coating. Most importantly, newer ropes give a lower AF than older worn ones.
Top tip 2:
Be careful when using a new rope or one that is thinner than you are used to.
The angle that the dead rope is held in relative to the device is also vitally important, with a narrower angle providing higher amplification.
Top tip 3:
Always be attentive when belaying and hold the rope at a narrow angle, often called the ‘locked-off’ position, unless you are paying out or taking rope in.
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