What Is a Wheel and Axle?

Wheel axle, as its name implies, is a system consisting of "wheel" and "axis". The system can rotate around a common axis, which is equivalent to a lever system with a shaft center as a fulcrum and a radius as a rod. Therefore, the axle can change the torque of the torsion, thereby achieving the change of the torque.

Axle in Axle Physics

Definition of wheel axle

A machine consisting of wheels and shafts that can rotate around a common axis is called a wheel shaft.

The essence of the axle

A lever that can rotate continuously, the fulcrum is on the axis, and the wheel has the same speed as the shaft when the wheel is rotated.

Axle axle balance condition

As shown in the figure, R is the wheel radius, r is the shaft radius, F1 is the force acting on the wheel, and F2 is the force acting on the shaft. According to the balance condition of the lever: F1R = F2r (power × wheel radius = resistance × axis radius).

Axle schematic

The outer ring of the axle is called the wheel, and the inner ring is called the axle.

The outer ring is called the wheel and the inner ring is called the shaft. The two rings of the axle are concentric circles.

From the above formula, it can be known that when power is acting on the wheel, the axle is a labor-saving lever; when power is acting on the axle, the axle is a labor-consuming lever.

Therefore, the larger the difference between the radius of the wheel and the shaft, the more effort is saved, but the more distance it takes.

Wheel axles such as carriages, door handles, steering wheels, and carts are the simplest. Without power transmission, the axles of powered vehicles are much more complicated. Of course the wrench too.

Taking a car as an example, the power is not simply transmitting the wheel axle. If so, the car cannot turn. In the middle of the car axle, there is a "differential", which drives the left and right wheels through the two half-axes. Only the distances of the wheels on both sides can be different. For the rear axle of a human tricycle, in order to turn, one rear wheel and the axle are fixed to transmit power, and the other rear wheel can rotate with the axle for differential cornering.

When the shaft is used to drive the wheel, such as the movement of a pulley, it can not only transmit power but also change the speed.

Definition: A simple machine consisting of a wheel and a shaft that can rotate around a common axis is called a wheel shaft. The larger radius is the wheel, and the smaller radius is the shaft.

Axle Axle Principle

The essence of the axle is that the lever can be rotated continuously. When using wheels and axles, in general, the forces acting on the wheels and the lines of action of the forces on the axles are tangent to the wheels and the axles. Therefore, their force arms are the corresponding wheel and shaft radii.

Since the wheel radius is always larger than the shaft radius, when power is applied to the wheel, the wheel shaft is a labor-saving distance lever (the first picture below). A practical example: bicycle pedals and discs (big gears) are labor-saving wheels. When power is acting on the shaft, the axle is a labor-saving and distance-saving lever (as shown in the second picture below). Practical examples are: the rear wheel of a bicycle and the frisbee (pinion) on the wheel, the blades of the ceiling fan and the shaft Application of laborious axles.

F1R = F2r Axle is a simple and labor-saving mechanism. (Large wheel radius and small shaft radius save effort)

Application of wheel axle

Common hoes, winches, stone mills, steering wheels of automobiles, wrenches, manual winches, and twist handles of water taps are all wheel and axle machinery.

Axle wheel axle application in water conservancy

In agricultural irrigation, in addition to using the hoe as shown in the figure below, people have also invented many water conservancy tools such as water pumps and water trucks. Many of them combine the principle of the axle.

windlass

Archimedes in ancient Greece was the earliest inventor of water pumps in history. Archimedes was born in the ancient city of Syrah, Greece in 287 BC. At that time, the ancient economy of Syracuse was unprecedentedly prosperous, and the scientific research style was very strong. Many people in the city studied philosophy and geometry. They like to debate and take this as an opportunity to learn. Archimedes has lived in this atmosphere since childhood, and has developed a good habit of thinking and learning.

Alexander City, at the estuary of the Nile, was the political, economic, and cultural center of the eastern Mediterranean, where many first-class scientists gathered. Archimedes, who was eager to learn, also came to Alexandria, where he studied mathematics, astronomy and mechanics. One Sunday, Archimedes and his classmates sailed slowly on the Nile River in a wooden boat, and the scenery on both sides made him dizzy. Suddenly, when he saw a group of people scooping water in a wooden bucket, he asked, "Why are they scooping water?"

"The riverbed is low and the farmland is high, so the farmers have to irrigate the water," a local classmate told him. "This way, the efficiency of simmering water is too low. I don't know how many barrels to pour in a hilly field." Archimedes had sympathy for the farmers. That classmate said disapprovingly, "For generations, people do this. What good way do you have?"

After returning, Archimedes's eyes always flashed the peasant's strenuous effort while swilling. "Can you let the water flow higher?" Archimedes began to think about this. Gradually, an idea emerged in Archimedes' mind: "Make a large spiral and place it in a cylinder. In this way, after the spiral turns, the water cannot be brought along the spiral groove to a high place Did you go? "

Archimedes immediately drew a sketch based on this idea. He went to the carpenter with this sketch and asked the master to help him make a tool for pumping water. "After Archimedes' guidance, the carpenter made a weird thing. Archimedes moved this thing to the river, put one end into the river, and then gently rocked the handle. "I saw the river water pouring out from the top of the strange thing while shaking the handle. The water really flowed high.

Archimedes Screw Pump

The peasants who came to watch were fascinated by this magical thing. They praised Archimedes for his great work for the farmers. Soon, this kind of spiral water pump spread in the Nile River Basin and even a wider area. This kind of water pump is called Archimedes screw pump. Until now, some modern factories still use this Archimedes screw pump to move fluid and powder.

Soon after the advent of the spiral water pump, China also invented a pumping tool-the keel waterwheel. It is said that it was invented by Bi Lan, the Emperor of the Eastern Han Dynasty. The main device of this kind of waterwheel is a groove made of wooden boards. Tile-sized wooden blocks are placed at a certain distance in the tank, and these wooden blocks are connected by pins. The whole looks like a dragon's skeleton, hence its name. When in use, a person is holding a wooden frame on the top of the waterwheel and stepping on the wooden block with his foot, and then the wooden block below is moved up along the wooden trough, thereby lifting the water ashore; Move down from the back until it bypasses the lower shaft and wipe the water again. Later, some people improved the keel waterwheel and invented the "animal power keel waterwheel" and "water-to-keel waterwheel".

Axle space aerospace spacecraft "Axle"

Axle

"Axle" is the name given by NASA to a new type of alien vehicle similar to "axle". The "axle" looks very simple, consisting only of a cylinder with wheels on both sides. This is also the simplest NASA new alien vehicle, but its function cannot be underestimated. The wheels can roll over half a meter of rock, and because of its very symmetrical structure, the "axle" alien vehicle eliminates the biggest trouble of alien vehicles on steep hillsides: overturning. Axel's robotic arm can rotate 360 degrees around the wheel axis. The purpose of the robotic arm is to collect soil samples and provide propulsion to the wheels when encountering complex terrain. "It doesn't matter if it turns upside down, because it turns upside down, it just flips upside down." Like the "climber", the wheeled alien vehicle is connected by a rope and a larger alien vehicle at the top of the cliff. The rope can be wound, and the "axle" can explore areas that are too steep for untethered robots to reach. It's just that the "axle" alien car is more skinny and can withstand greater tests. "Axle" wheels can be stowed or inflated, and they can cushion a large impact when landing. NASA has performed simulation experiments on the working style of the "axle". "Axle" set off from the top deck of the solid model of the spacecraft "Phoenix" lander, using ropes to "climb" down a rock formation exposed above the ground, encountering rocky terrain on the way. The tail end of the robot arm can swing, and the "axle" smoothly retrieves the soil sample and puts it into a cylinder connecting two wheels. Then just shake the "axle" back through the rope.