Pole climbing, standard and novel
Jearl Walker www.flyingcircusofphysics.com
July 2014 Repairs to transmission lines supported by poles (tall tree trucks) are normally made by a repair person climbing a pole. The standard way is to climb by using boots with spikes along the inner edge of the soles and by using a harness wrapped around the pole.
The climber rams the spikes into the sides of the pole, moves the harness up the pole, and then steps up by releasing the spikes on one boot, moving that boot up the pole, and then ramming the spikes back into the pole. The climber then leans forward somewhat toward the pole to loosen the harness, moves the harness up the pole, and then leans back to increases the friction between the pole and the harness.
The interplay of forces on the climber and harness forms a basic problem in physics textbooks. Here is drawing showing the force vectors when the climber is stationary.
The downward weight vector is balanced by the upward force at the spikes and the upward frictional force on the harness. The horizontal forces (at the harness and spikes) balance each other. The torques due to these several forces (calculated around any given rotation axis) also balance, and the climber is said to be in equilibrium.
Here is a novel (no, actually, clever) alternate way of climbing a pole when you cannot use spikes, such as when a palm tree must be climbed:
The physics is the same.
The weight is balanced by two upward forces, the horizontal forces balance each other, and the torques also balance. However the climber does not lean back to set up the forces. Rather the forces are set up by the downward tilt of the main support rod once his weight is placed on the outer end.