Saturday, July 20, 2019
Physics of Rock Climbing :: physics sport sports rock climbing
Anchor systems are vital for a climber and whether or not an anchor is secure can mean the difference between life or death for the climber. Good anchors are not difficult to set up and all they require is a little experience in setting up and some common sense. We will anaylze the forces generated in two different types of anchor systems. Another factor in the forces generated in an anchor system that can be applied to both systems is that of the angles involved in the system. The greater the angle at the bottom of the anchor system, where the rope attaches to the anchor, the greater the force that is exerted on each anchor point. The table below reflects this. The American Tringle is an anchor made in the shape of a triangle. The force on either anchor point is equal to where F is the force exerted on the lowest carabiner in the system. With an angle of 60 degrees this force is equal to the force exerted on the system. Any smaller angle will mean a greater force on the anchor points. This anchor will effectively double the forces present in the anchor system compaired to the Equalized V anchor, making it quite a bit more dangerous. The Equalized V is an anchor in the shape of a V. The force it exerts on each anchor point is , where F is the force exerted on the system. At 60 degrees it exerts a force of F/2 on each anchor, so it is much better than the American Triangle. This is a fall. If you climb it will happen to you. Sometimes in hurts. The rest of the time it really hurts. This is especially applicable in lead climbing where you place protection or clip into bolts as you climb. In lead climbing you can easily take falls of more than 10 meters. 'Static' climbing ropes are not really static, but actually just low elongation. Suppose, climbing with static rope, a 60 kg climber was to fall from thirty meters, with his last piece of protection 5 meters below you. He would then fall 10 meters. Assuming that his rope stopped him in 1/10 of a second, the stopping force he would feel would be equal to 8.4 kN, and the force on the anchor would be twice that, 16.8 kN. While most carabiners are rated up to 20+ kN, most ropes can withstand significantly less, usually about 9 kN.