How does a tube-style belay device create friction?

Rope bending around the device edges creates friction proportional to the contact angle and normal force. The capstan equation models this: T_hold = T_load x e^(mu x theta), where mu is friction coefficient and theta is contact angle.

How does an assisted-braking device differ?

Devices like the Grigri use a camming mechanism activated by load. When the load (climber) pulls the rope, the cam pinches the rope against the device, greatly increasing friction without brake hand force.

Belay Device Friction Coefficient and Holding Force Calculator

Calculate rope-on-belay-device friction and required holding force. Assisted-braking devices require less than 2.5 kN brake hand force to hold 80 kg climber fall with ATC-style factor of 0.5-0.8.

Use the full interactive calculator below, or

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Belay Device Friction Coefficient and Holding Force Calculator

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Frequently Asked Questions

How does a tube-style belay device create friction?

How does an assisted-braking device differ?