Which mechanisms increase speed

Miter : Miter gears are bevel gears which, when paired, have a gear ratio of This gear ratio is a result of pairing two miter gears with the same number of teeth. This type of bevel gear is used in applications which require a change only to the axis of rotation with speed remaining constant.

Crown : Crown gears , also referred to as face gears , are cylindrical rather than conical bevel gears with teeth cut or inserted perpendicular to the gear face. Crown gears can be paired either with other bevel gears or, depending on the tooth design, spur gears.

Hypoid : Originally developed for the automobile industry, hypoid gears , unlike the previously mentioned types, are a type of spiral bevel gear used for non-parallel, non-intersecting configurations. This design allows for components to be placed lower, allowing for more space in the sections above. Employing curved and angled teeth similar to those used in spiral bevel gears, hypoid gears are even more complex and, consequently, more difficult and costly to manufacture.

Worm gear pairs are comprised of a worm wheel—typically a cylindrical gear—paired with a worm —i. These gears are used to transmit motion and power between non-parallel, non-intersecting shafts. They offer large gear ratios and capabilities for substantial speed reduction while maintaining quiet and smooth operation. One distinction of worm gear pairs is that the worm can turn the worm wheel, but, depending on the angle of the worm, the worm wheel may not be able to turn the worm.

This characteristic is employed in equipment requiring self-locking mechanisms. Some of the disadvantages of worm gears are the low transmission efficiency and the amount of friction generated between the worm wheel and worm gear which necessitates continuous lubrication. Rack and pinion gears are a pair of gears comprised of a gear rack and a cylindrical gear referred to as the pinion. The gear rack can be considered as a gear of infinite radius i.

For either of these rack designs, rotational motion can be converted into linear motion or linear motion can be converted into rotational motion. Some of the advantages of a rack and pinion gear pair are the simplicity of the design and the low cost of manufacturing and high load carrying capacities.

Despite the advantages of this design, gears which employ this approach are also limited by it. For example, transmission cannot continue infinitely in one direction as motion is limited by the designated length of the gear rack.

Additionally, rack and pinion gears tend to have a greater amount of backlash i. Some of the common applications of rack and pinion gear pairs include the steering system of automobiles, transfer systems, and weighing scales. Gears are employed in a variety of mechanical devices, and, consequently, several different types and designs are available.

The suitability of each type of gear and its exact design for a motion or power transmission application is dependent on the specifications and requirements of the application.

Some of the principal factors which may be considered when designing and choosing a gear include:. Some of the operational conditions which may affect a gear are the amount of weight applied, noise and vibration produced, and friction and stress placed on the teeth, while some of the environmental conditions which may affect a gear include temperature, humidity, and sanitation and cleanliness.

These conditions influence a variety of gear design factors, including the construction material, surface treatments, and lubricant type and lubrication method. Gears are available in a variety of construction materials—e.

For example:. However, grinding also increases the overall cost of production. There are several heat treatment services available for gears include surface hardening, tempering, normalizing, annealing, and carburizing.

If adequately and properly applied, gear lubricants can help to extend the overall lifespan of a gear by preventing or reducing the amount of stress and fatigue experienced by the gear body and teeth. However, both the optimal type of lubricant and lubrication method are dependent on the requirements and specifications of the application. Given the employment of the proper lubricant, some of the benefits include the reduction of friction between gear teeth, mitigation of heat generated, and lowering of the amount of noise and vibration produced during operation.

Once a suitable lubricant is selected, it must be properly applied. Proper application of a lubricant depends on a variety of factors, including operation speed and load. The most common application methods for gear lubrication include grease lubrication, splash lubrication, and forced oil circulation lubrication.

Beyond the operational and environmental conditions of the application, gears and their designs are also limited by the dimensional specifications—i. For example, gears are typically mated to suit the center distances between machine shafts. However, some applications may require an adjustment of the center distances to better fit within the dimensions of the mechanical gear system or machine, which necessitates a profile shift—i.

Other methods of managing dimensional restrictions include employing gear types and designs that are better suited for limited- or restricted-space applications. For example, internal-external gear pairs allow for the gears and their shaft or base components to be positioned closer together than external-only gear pairs, and hypoid gears allow for components to be placed lower within the machine or system, allowing for more space above.

Gears are used to transfer motion and torque between machine components in mechanical devices. The specification and requirements of the applications—i. In regard to gears, change of direction can refer either to a change in the direction of rotation or a change in the axis of motion. For example, parallel axes configurations which employ external-only gear pairs allow for a change in the output rotation, but not a change in the axis of rotation.

On the other hand, intersecting and non-parallel, non-intersecting axes configurations allow for a change in both the output rotation and the axis of motion. The directional change requirements also influence the optimal type of gear as each type is characterized by a particular configuration e. When mated gears are of different sizes, the resultant output torque and rotational speed are affected as the gear ratio is not equal to i.

Depending on which of the driving and driven gear is the larger and which is the smaller, and consequently which has more teeth and which has less, the resultant gear ratio can produce output speed and torque which are increased or reduced with respect to the input speed and torque. Additionally, as there is an inverse relationship between the two values, either speed can be increased, or torque can be increased, but not both.

For torque, the gear ratio represents the ratio of the output torque to the input torque. Therefore, the output torque can be calculated using the following equation where t represents torque:. Based on the above equation, if the pinion gear is attached to the driven shaft i. On the other hand, if the pinion gear is attached to the driving shaft i.

Because torque and speed have an inverse relationship, output speed can be calculated using the following equation where input speed is multiplied by the reciprocal of the gear ratio used in the above torque equation:. If the pinion gear is attached to the driven shaft i. This result is referred to as gearing up. This result is referred to as gearing down. There are a wide variety of specifications for gears. But unfortunately, no universal industrial standards exist which define how a gear should be designed and manufactured.

Typically, gears are produced either to the standards set by the individual manufacturer or to suit the design and specifications of a particular machine or system rather than those machines and systems being designed around a standard gear component. The former case makes it more difficult to find the proper gear type and design for an application among the standard components available from gear manufacturers, while the latter case increases the difficulty and cost of finding replacements for the customized part.

While there are no universal gear standards, some countries have implemented their own industrial gear standards, especially in regards to precision gears. When producing a custom gear , the cost of manufacturing is influenced by several factors, including the gear design, construction material, surface treatments and finishes, precision standards, and lubricant and lubrication method.

Cage and peg gears are mostly used to transmit rotation between perpendicular axes. A peg gear is basically a disc with short pegs sticking out from it around its circumference to form a spur gear , or on its face parallel to the axis of rotation to form a bevel gear.

The pegs in these gears act as the teeth, and contact one another to spin each of the gears. A cage consists of two discs with pegs running between them parallel to the axis of rotation. A cage gear can be used like a worm gear, as each of the dowels on the gear contact the pegs on a normal peg gear. However, this system can be driven from either end. A mutilated gear is a gear whose tooth profile does not extend all the way around its pitch circle.

Mutilated gears can be useful for many different purposes. In some cases, you may not need the entire tooth profile of a gear because the gear may never need to rotate degrees, and you could have a linkage, beam, or other mechanism as part of the mutilated side of the gear. In other cases, you may want the mutilated gear to rotate degrees, but you may not want it to be turning another gear all the time. If you rotate a mutilated gear with half its teeth missing, whose teeth mesh with a full spur gear at one rotation every 30 seconds, the spur gear will turn for 15 seconds, and then stay put for 15 seconds.

In this way you can turn continuous rotational motion into discrete rotational motion, meaning that the input shaft turns continuously and the output shaft turns a little, and then stops, then turns again, then stops again, repeatedly. Although rare in industry, non-circular gears are pretty interesting mechanisms.

The diameter of the gears where they are contacting each other change as the gears rotate, so the output speed of the system oscillates as the gears rotate. Non-circular gears can take almost any shape. If the two axes constraining the gears are fixed, then the sum of the radii of the gears at the point where they mesh should always be equal to the distance between the two axes. A ratchet is a fairly simple mechanism that only allows a gear to turn in one direction.

A ratchet system consists of a gear sometimes the teeth are different than the standard profile with a small lever or latch that rotates about a pivot point and catches in the teeth of the gear. The latch is designed and oriented such that if the gear were to turn in one direction, the gear could spin freely and the latch would be pushed up by the teeth, but if the gear were to spin in the other direction, the latch would catch in the teeth of the gear and prevent it from moving.

Ratchets are useful in a variety of applications, because they allow force to be applied in one direction but not the other. These systems are common on bikes how you can pedal forward to turn the wheels, but if you pedal backward the wheel will spin freely , some wrenches, and large winches that reel in loads. Clutches are mechanisms found primarily in cars and other road vehicles, and they are used to change the speed of the output shaft, as well as disengage or engage the turning of the output shaft.

A clutch mechanism involves at least two shafts, the input shaft, driven by a power source, and the output shaft, which drives the final mechanism. As an example, I'll explain a simple 2 gear clutch mechanism, referencing the image above.

The input shaft would have two gears on it of different sizes the two blue gears on the top shaft , and the output shaft contains two gears that mesh with the gears on the input shaft the red and green gears , but can rotate freely around the output shaft, so they do not drive it. A clutch disc the blue grooved piece in the middle sits between the two gears, rotates with the output shaft, and can slide along it.

If the clutch disc is pressed against the red gear, the output shaft would engage and turn at the speed defined by the gear ratio of that set of gears If the clutch disc presses against the green gear, the output shaft drives at a different gear ratio, defined by that gear set If the clutch disc sits between the two gears, then the output shaft is in neutral and is not being driven. The clutch disc can engage with the gears in a few different ways.

Some clutch discs engage via friction, and have friction pads mounted to their sides as well as the sides of the gears. Other clutch discs, like the one in the image above, are toothed, and they mesh with specific teeth on the faces of the gears.

A gear differential is a pretty interesting mechanism involving a ring bevel gear and four smaller bevel gears two sun gears and two planet gears that orbit around them , acting sort of like a planetary gearbox. It is used mostly on cars and other vehicles, because it has one input shaft that drives two output shafts which would connect to the wheels , and allows for the two output shafts to spin at different velocity if they need to.

It ends up that the average of the rotational velocities of each output shaft always has to equal the rotational velocity of the ring gear. I'll explain how a differential works using the images above. The input shaft spins the yellow bevel gear, which spins the green bevel ring gear.

A carriage is fixed to the ring gear that spins with it. Both the carriage and the ring gear rotate around but do not directly turn the axis of the red output shafts. The two blue bevel gears turn in big circles around the central axis, the axis the output shafts go through. Lets imagine this differential sits with the output shafts connected to the back two wheels of a car. If the car is going straight, the two blue bevel gears will spin around the output shafts, because of the rotation of the carriage, without rotating about their own axis.

Their teeth will push the two red gears at the same speed, each connected to their respective output shafts. Thus, the wheels spin at the same speed and the car goes straight. You'll notice the blue gears have the ability to spin about their axis though, which is important to the mechanism.

Keep reading! Should the car turn, then the two wheels will want to spin at different speeds. The inner wheel will want spin at a velocity slower than the outer one because it is closer to the center point of the car's turn. If the two wheels were connected on the same shaft, then the car would have a difficult time turning: one wheel would want to spin slower than the other, so it would drag. With the differential gear mechanism, the two shafts not only allow the wheels to spin at their own speeds, but also are still powered by the input shaft.

If one wheel is spinning faster than the other, the blue planetary bevel gears just rotate about their axes instead of staying fixed. Now, the planetary gears are both rotating about their axes and about the output shafts because of the carriage , thus powering both wheels, but allowing one to spin faster than the other. This is a pretty tricky mechanism to explain. If you're still confused, I encourage you to check out this video , also shown above, which shows the process visually very well.

While you can purchase gears of specific sizes from vendors, there are also situations in which you may want to design your own gears for a specific purpose or so that you can modify them to create non-standard gear parts. Here's some software to help you get started. If you know of any more, let me know and I'll add them!

Autodesk Inventor Free for Students : Has a gear design feature for spur and helical gears, worm gears, and bevel gears. RushGears: Contains a customizeable online gear template that allows you to download 3D CAD files of your designed gears.

Gearotic: Online gear mechanism design software. DelGear: Gear design software package. WoodGears: Gear design software for designing laser cut and wood gear profiles. Now its your turn to make something cool with gears! I made this simple GearBot to go along with this Instructable, but there are many other directions to go in from here. Use what you've learned and don't forget to share it! If you have some more gear advice or ideas to share, or have any questions about mechanisms, please do so in the comments.

Question 7 weeks ago on Step I want to try and make a waistcoat with a sort of steam punk panel of moving cogs and gears. I was just wondering what it is that you attatch the gears onto rotor or axle or something? Also, if possible, where I might be able to get some small spur cogs for it. Thank you! Question 7 months ago.

Question 8 months ago on Step 4. Question 9 months ago on Step 1. Question 9 months ago on Introduction. This is very informative and nicely illustrated but I did not see how the bearings interface with the gears and shafts. Let's say you are using only one compound gear on each shaft.

Does it require one bearing on each side of the shafts resulting in 2 bearings per gear? Or would one bearing in the center of each gear on a stationary shaft work also so only half the number of bearings are needed? Question 1 year ago. This is a nice write-up but I am looking for something similar. Maybe you guys have some ideas. What I am looking to do is drive a parallel set of shafts in the same direction at the same speed The bevel gear is commonly used in vehicle differentials to rotate the motion provided by the engine 90 degrees in order to drive the wheels along their proper axis.

Spur Gear The most common type of gear is a spur gear. Spur gears have teeth that protrude outward from the perimeter of the gear. They are mounted on parallel axes and can be used to create a wide range of gear ratios. One drawback of this mechanism is that the collisions between each tooth cause a potentially objectionable noise since the entirety of each tooth meshes at once. Helical Gears: In an effort to reduce the noise from spur gears, helical gears can be utilized. The teeth of helical gears are cut at an angle to the face of the gear so that the tooth engagement begins at one end and gradually transfers to the rest of the tooth as the gear rotates.

This design leads to noise reduction and an overall smoother system. The helical pattern of the gears creates a thrust load as the gear teeth come into contact with each other at an angle that is not perpendicular to the shaft axis. Bearings are often incorporated into mechanisms with helical gears in order to support that thrust load. Bevel Gears: Bevel gears can be used in mechanisms to change the axis of rotation.

Although they can be designed to work at other angles, they are most often used to change the axis of rotation by 90 degrees. Similar to spur gears, bevel gears may also feature straight or helical teeth. Worm Gears: In mechanisms where large gear reductions are needed, worm gears can be used to achieve gear ratios of greater than if necessary. Worm gears also possess a natural locking feature in that the worm can easily turn the gear, but the gear cannot turn the worm due to the shallow angle of the worm causing high friction between the gears.

These mechanisms also change the axis of rotation by 90 degrees, but in a different manner than bevel gears. The circular gear, or pinion, meshes with the rack and the rotation of the pinion causes the rack to translate. The steering mechanism in automobiles utilizes a rack and pinion system.

As the pinion rotates, it forces the rack to move linearly. Since the length of the rack is not infinite, these mechanisms are not used in applications that have continuous rotation. Planetary Gears: Planetary gear sets may be the most interesting mechanism in the gear world. These mechanisms have three main components: the sun gear, the planet gears and carrier, and the ring gear.