House-Building Basics: How Do Pulleys Work?

The idea of building your own homes is an exciting one for many landowners. We get to design it to our specifications, ensure it meets all our needs, and add features that accommodate our personal lifestyles.

But if you’re going to set out to build your own home from scratch, you should know what goes into the actual construction process. Pulleys, as the dominant tools used to lift heavy objects, are vital to not only getting large construction materials into place but also helping to conserve your energy as they do.

This is how pulleys work and what makes them so important when building homes.

A Brief History of the Simple Machine

The pulley, though redesigned some for modern use, is an invention that dates back to at least the early Mesopotamian years. Dominantly used to hoist large buckets of water out of wells, these devices allowed villagers to lift items much heavier than their strength alone would allow.

While they only consisted of a stone wheel and rope at the time, their appearance would evolve with the times. Eventually, their usefulness began to extend to other tasks, and they became the primary tool for any project that required lifting heavy loads—especially in construction.

The ancient pulley soon inspired the creation of many industrial tools that we use to this day. Cranes, forklifts, and even the basic crank jack are all relatives of fundamental pulley technology. So, just as our ancestors would use them to construct their homes, we, in one form or another, continue to do so today.

How Pulleys Lift Heavy Loads

When it comes to understanding how pulleys work, it’s important to have a grasp on what forces are in play when we lift objects. The fundamental lifting process consists of gravity pulling down on an object, relative to its weight, and the force you exert on the container with your own strength.

Gravity is pulling downward, while you’re trying to exert a higher amount of force upward. If your strength exceeds the force of the box’s weight, then you will succeed in lifting the object. However, if it doesn’t, the parcel will remain in its place. This is where pulleys come in handy.

By introducing a pulley into this equation, we can enhance the amount of strength we exert on the object by changing the directions at which the necessary forces work. With a single pulley system, the process is a simple exchange of upward and downward force—your strength and weight pulling the load down, while the object moves up.

In this case, you still need to exert the same amount of force to move the object—you just have better leverage to do so. But when you start to use double or more complex pulley systems, it’s interesting to note that the amount of force you need to exert to move the item decreases.

The more pulleys of different types you use in a lifting system, the more force exists in the rope between them. This additional force between the pulleys is constantly seeking to push them closer together when you pull on your end of the rope.

When this occurs, that already present tension provides enough energy to make up for a person’s lack of strength. With two pulleys in a system, the force required on your part to lift an object can be as much as halved, and with even more pulleys, it can decrease even more.

image credit: twenty20.com