The 6 Simple Machines in Action: Real-World Examples

Modern machinery has gotten remarkably complex. As complicated as these systems can be, though, they often operate on surprisingly basic underlying principles. At its core, much equipment relies on the same six simple machines that have driven advancements throughout human history.

What Are the 6 Simple Machines?

The six simple machines are the most basic mechanisms to make work easier. These are:

• The wheel and axle
• The lever
• The wedge
• The inclined plane
• The screw
• The pulley

It’s worth noting that some of these systems build on each other. Pulleys, for example, are technically a combination of levers and wheels, though they affect force differently. A screw, likewise, is a form of wedge that you apply force to.

The concept of simple machines, much like the mechanisms themselves, dates back millennia. Archimedes described them roughly 2,000 years ago, and they’ve since become a foundational concept in physics education.

As rudimentary as these systems are, they’re still critical to modern engineering. Many of today’s most disruptive technologies center around varying versions and combinations of these six simple machines. Here’s a closer look at how they work in the real world today.

1. The Wheel and Axle

It’s difficult to think of an invention with more long-term impact than the wheel. Some applications of this machine have not changed much in thousands of years — cars still rely on them the same way chariots did. But wheels and axles have other, more surprising uses, too.

Robotic arms are among the most exciting examples. Diagnostic robots would be unable to achieve their six degrees of freedom and high precision without rotating joints. These pivot points are crucial to their operation but are little more than a wheel and axle at their core.

In cases like this, the rotation of the wheel itself is less impactful than that of the attached structure. The way these machines pivot around their axle facilitates easier motion in the same way they would enable forward movement on the ground. Door hinges, gears and the driveshaft of a combustion engine all exemplify this concept.

2. The Lever

Levers affect force in two ways simultaneously. First, they transfer it from one side of the fulcrum to the other. Next, they amplify it via the mechanical advantage of a longer arm on one side, resulting in more movement on the other.

Wheelbarrows and crowbars are straightforward examples of levers in everyday life, but the applications do not end there. Winches like those in industrial cranes or ratchet straps for securing vehicle loads are a type of lever. The longer the crank or handle is on these systems, the easier it is to tighten the strap or lift a payload, ensuring quicker, lighter work.

Compound levers, which magnify force by using a series of simple levers, can produce even more impactful results. Railway brakes capitalize on this concept, letting conductors bring massive vehicles to a halt simply by pulling a stick. The handle acts as one in a series of levers resulting in considerable pressure on the wheel, creating enough friction to stop the train.

3. The Wedge

The wedge is among the simplest of the six simple machines. This system is just an object that tapers from a wide end to a narrow one. As uncomplicated as that is, it can still have a considerable effect when applied properly.

Wedges play a crucial role in aerodynamics, as a tapered shape reduces the amount of force needed to push through air molecules at high speeds. A single spike on a nose cone can decrease pressure by up to 33% on an aircraft’s body. Such a significant drop in air pressure translates into a substantial drag reduction, enabling greater air speeds and preventing damage to the plane.

Axes and needles exhibit the same principle. It’s easier to pierce or cut through a surface when the object’s shape focuses pressure to a finer point. The concept works in reverse, too, which is how doorstops and wheel chocks can prevent unwanted movement.

4. The Inclined Plane

Inclined planes are similar to wedges but center around a different mechanical principle. It takes less force to move an object up a slope than it does to lift it vertically, so pushing items along a wedge shape offers a mechanical advantage. Machines can also reverse this concept by letting things slide down a slope gently instead of dropping and risking damage.

Ramps on the back of a truck use these systems to facilitate easier loading. Similar structures provide a more manageable alternative to stairs for wheelchair users.

Gutters are another familiar example of this simple machine. While they appear level, these structures follow a slight angle, causing water to run in a consistent direction to direct it away from a house. Considering water damage restoration costs between $1,300 and $5,600, the return on investment for such a simple solution is considerable.

5. The Screw

Scews apply inclined planes and wedges to facilitate easier penetration into and a tighter grip on a surface. The wedge at the tip magnifies the force of whatever’s driving it, and the inclined plane circling the shaft provides an easy path for debris to follow and secure the screw in place via friction.

The most obvious example of screws in the real world is the fastening hardware of the same name. However, complex machines can apply these mechanisms differently.

Rotary air compressors use rotating screws to increase air pressure. Air moves along the channels the same way wood would move along a fastener, but these mechanisms force it into a smaller area to create compression. As a result, they can produce continuous air pressure with a relatively low amount of force.

6. The Pulley

The final simple machine is the pulley. This is essentially a wheel and axle that magnifies the force of a cable moving downward at one end. The rotation of this mechanism means less power is needed to lift a heavier load.

Tower cranes use this principle to raise payloads hundreds of feet off the ground safely and efficiently. Many combine pulley systems to further reduce the amount of force needed, the same way train brakes multiply levers to amplify power.

Elevators operate on the same concept. Some frameless 3D printers use pulleys, too. In these cases, ropes and wheels lower and raise the printing nozzle to deposit material where needed with minimal surrounding infrastructure, enabling larger prints.

Simple Machines Form the Basis for Complex Systems

Even the most complicated of equipment relies — at least in part — on one or more of the six simple machines. Consequently, understanding these mechanisms is crucial to designing more cutting-edge and impactful equipment. Much like how simple devices themselves amplify force, combining and applying them leads to exponential mechanical improvements.