How to Gears Worked

Gears are used in toms of Mechanical instruments, most importantly, they provide gear reduction in motorized instruments. This is key because often a small motor spinning very fast can give enough power for a device, but not enough torque, the power that causes an object to rotate on an axis or twist. For instance, an electric screwdriver has a very biggest gear reduction (reduction in the speed of a rotary machine such as an electric motor) because it needs to lot of torque to turn screws. But the motor only gives a small amount of torque at a high speed. With a gear reduced, the output speed can be reduced while the torque is increased.

Gears also changed the direction of rotation. For instance, in the differential between the rear wheels of your car, the power is transferred by a shaft that runs down the center of the car and the difference has to turn that power 90 degrees to apply it to the wheels

There are many intricacies in the different types of gear. In this article, we'll learn exactly how the teeth on the gear work, and we'll talk about the different kinds of gears you find and all sorts of Mechanical gadgets.

Contents,

·         Gear Basics

·         Helical Gears

·         Spur Gears

·         Bevel Gears

·         Worm Gears

·         Rack and pinion Gears

·         Planetary Gear sets and Gear Ratio

·         Detail on involute Gear Profiles

1. Gear Basics

You have in probably heard of gear ratios, mostly when it comes to cars. The gear ratio is the number of rotates the production shaft makes while the input shaft turns one time. If the gear ratio is 2:1, then the smaller gear is rotating two times while the larger gear rotating just once. It also means that the larger gear has twice as many teeth as the smaller gear. The larger gear is just called a "gear" while the smaller gear is also called a pinion.

One of the earliest kinds of gear we could look at would be a wheel with wooden pegs sticking out of it. The problem with this kind of gear is that the distance from the center of each gear to the point of contact makes a difference as the gears rotate. This means that the gear ratio changes as the gear rotate, meaning that the output speed also changes. If you used a gear like this in your car, it would be impossible to continue at a hurry-up speed you would be accelerating and decelerating constantly.

Many modern gears are used a special tooth profile called an involute. This profile has the very important property of maintaining a constant speed ratio between the two gears. Like the peg wheel above, the contact point moves, but the configuration of the involute gear tooth compensates for this movement.

Now let's look at some of the different types of gears

2. Helical Gears   

The teeth on the helical are cut at the angle of the face of the gear, when two teeth gears on a helical gears system engage, the contact starts at one ending of the teeth and gradually grows as the gears rotate until the two teeth are in full engagement.

The gradual appointment of helical gears makes them operate much more smoothly and quietly than spur gears. For this reason, helical gears are used in practically all car transmissions.

Because of the angle of the teeth on helical gears, they generate a thrust load on the gear when they mesh. Devices that used helical gears have bearings that can support these thrust loads.

The bent teeth of helical gears mean they have to be staggered, with the teeth of the next gear goings in the opposite way so the teeth can mesh. Each gear is called "right-hand" or "left-hand" when it meshes with another gear on parallel shafts. If the angles of the gear teeth are correct, helical gears can also be placed on perpendicular shafts adjusting the rotation Angles by 90 degrees.

3. Spur Gears    

Spur gears are the most common types of gears they have straight teeth and are mounted on parallel shafts. Sometimes, many spur gears are used at once to create a very large gear reduction.

Spur gears are used in many devices that you can see all over How Stuff Works, like the electric screwdriver, dancing monster, oscillating sprinkle, windup alarm clock, Washing Machine, and cloth dryer. But you won’t find it in your car.

This is because the spur gear can be really loud. Each time a gear tooth engages a tooth on the other gear, the teeth collide, and this impact makes a noise. It also increases the stress on the gear teeth.

To reduce the noise and stress in the gears, most of the gears in your car are helical which we will explain next.

4. Bevel Gears     

Bevel Gears are useful when the direction of the shaft's rotation needs be to changed.  They are cone-shaped and usually mounted on shafts that are 90 degrees apart, but they can be designed to work at another angle as well.

The teeth on bevel gears can be straight, spiral, or hybrid. Straight bevel gears teeth actually have the same problems as straight spur gears teeth as each tooth engages, it impacts the corresponding tooth Just as with spur gears, the solution to this problem is to curve the gear teeth. These spiral teeth engage just like helical teeth: the contact starts at one end of the gear and all at once.

Just as with spur gears, the solution to this problem is to curve the gear teeth. These spiral teeth engage just like helical teeth: the contact starts at one end of the gear and progressively, across the whole tooth. On straight and spiral bevel gears, the shafts must be perpendicular to each other and in the same plane. If you were to extend the two shafts past the gears, they would intersect. The hypnoid, on the other hand, can engage with the axes in different planes.

5. Worm Gears     

This feature is used in many cars different. The ring gear of the different and the inputs pinion gear are both hypoid. This allows the input pinion to be produced lower than the axis of the ring gear. The figure at left shows the input pinion engaging the ring gear of the differential. Since the drive shaft of the car is coupled to the input pinion, this also lowers the drive's haft. This means that the drive shaft does not intrude into the passenger section of the car as much, making more room for cargo.

Worm gears are cylinders with a spiral thread wrapped around the outsides that meshes with another gear to turn it. They are used when larger gears reductions are needed. It is common for worm gears to have reductions of 20; 1 and even up to 300; 1 are greater.

Mostly worm gears have an interesting property that no other gear set has: The worm gears can easily turn the gears, but the gears cannot turn the worm. This is because the angle on the worm is so shallow that when the gears tried to spin it, the friction between the gears and the worm holds the worm in place.

These features are used for machines such as conveyor systems, in which the locking features can act as a brake for the conveyor when the motor is not turning. Worm gears are also used in the torsion difference, which increases torque for some high- performances cars and trucks.

6. Rack and Pinion Gears

Earlier we mentions that went two gears mesh, the smaller is one called the pinion. A rack is a straight bar with gears teeth’s that meshes with the pinion. So you can probably imagine how rack and pinion gear is used to convert rotation into linear motion. Perfect examples of these are the steering system of many cars. The steering wheel rotates a gear, which engaged the rack. As the gears turn, it slides the rack either to the right or left depending on which way you turn the wheel.

Rack and pinion gear are also used in some scales to turn the dial that displays your weight.

7. Planetary Gear sets and Gear Ratios

Any Planetary Gear set has three main components.

·         Sun Gears

·         Planet Gears and the Planet Gears Carrier

·         Ring Gears

Each of these three components can be the input or the output, or they can be held stationary. Choosing which pieces plays which role determined the gear ratio for the gear set. Let’s take a look at the single planetary gear set.

One of the planetary gears set from our transmission has ring gears with 72 teeth and sun gears with 30 teeth. We can get lots of different gear ratios out of the gear set.  

Gear set table

HOWSTUFFWORKS

Locking any two of the three components together will lock up the whole device at a 1:1 gears reduction. Notice that the first gear ratio listed above is a reduction in the output speed is slower than the input speeds. The second is an overdrive the output speed is faster than the input speed. The last is a reduction again, but the output direction is reversed. There are several other ratios that can be got out of this planetary gears set,

But these are the ones that are relevant to our automatic transmission.

This one set of gears can produce all of these different gears ratio without having to engage or disengage any other gear. With two of these gear sets in a row, we can get as many forward gears and one reversed gear as our transmission needs. We will put the two sets of gears together in the next section.

8. Details on involute gear Profiles

On an involute profile gears tooth, the contacted point starts closer to one gear, and as the gears spin, the contacted point moved away from that gear and toward the other. If you were to follow the contact point, it would describe a straight line that starts near one gear and end up near the other. This means that the radius of the contacted point gets larger as the teeth engage.

The pitch diameter is defined as "the imaginary diameter for which the width of the threads and the grooves are equal," according to science Direct. Since the contact diameter is not constant, the pitch diameter is really the average contact distance. As the teeth first start to engage, the top gears tooth contacted the bottom gears tooth inside the pitch diameter. But the parts of the top gears tooth that contacted the bottom gears tooth are very narrow at this point. As the gears turn, the contacted point slides up onto the thicker part of the top gears tooth. This pushes the top gears ahead, so it compensates for the smaller slightly contracted diameter.

As the teeth continue to rotate, the contacted point moves even farther away, going outsides the pitch diameter — but the profiles of the bottom tooth compensate for this movement. The contact point starts to slide onto the narrowed parts of the bottom tooth, subtracting a little bit of velocity from the top gears to compensate for the increased diameter of contact. The end result is that even though the contacted point diameter changes continually, the speed remains the same. So, an involute profile gears tooth produced a constant ratio of rotational speed.