Gear Types, Design Basics, Applications and More - Basics of Gears

hello and welcome to our introduction to gears video let's start with the function of gears the general purpose of gears is to transmit motion and or power from one shaft to another in addition gears have three primary usages in the system first is speed ratio by using different sized gears the input to output rotational speed of shafts can be changed efficiently the second usage is for adjusting the torque ratio of the system lastly gears are useful means for changing the direction of rotation or converting a rotational motion to a translation motion [Music] at some point

we've all probably seen and used mechanical gears but are you curious to learn more about gears we will cover many details about gears in this video so please stay with us until the end of the video and subscribe to our channel if you enjoy [Music] in this section we will go through different types of gear and talk about their main characteristics spur gears are the most commonly used gears they transmit power through shafts that are parallel the teeth of the spur gears are parallel to the shaft axis this causes the gears to produce radial reaction

loads on the shaft but not axial loads spur gears are usually used for low and medium speed applications which are usually up to 3600 revolutions per minute they are not very often used in high speed applications this is due to the loud noise they produce at high speeds the benefits of spur gears are a simple design cheap production and maintenance helical gears are used with parallel shafts similar to spur gears however helical gears have teeth that are oriented at an angle to the shaft unlike spur gears which are parallel this causes more than one tooth

to be in contact during operation and helical gears can carry more load than spur gears due to the better teeth meshing than spur gears this makes them a better choice for high-speed applications also they operate smoother and quieter than spur gears on the other hand helical gears have sliding contacts between the teeth which in turn produce an axial thrust of gear shafts and generate more heat so this makes them less efficient than spurred gears due to tooth slippage bevel gears have a cone-shaped appearance and are most commonly used to transmit power between shafts that intersect

at a 90 degree angle they can be used at various angles but most are tried at 90 degree angles applications where a right angle gear drive is required and two shafts cross each other make bevel gears the right choice worm gears are used to transmit power at 90 degrees on non-intersecting shafts worm gears produce thrust load and are good for high shock load applications a screw shape cut on a shaft is the worm the mating gear is the worm wheel the main disadvantage of worm gears is their low efficiency which can be close to 15

due to the high friction and associated axial stresses next on the list we have hypoid gears they operate on shafts that do not intersect the hypoid gear is offset from the gear center allowing unique configurations on a large diameter shaft the larger shaft diameter means they can have large pinion diameters and make them a good fit in torque demanding applications a rack and pinion is a type of linear actuator that comprises a circular gear the pinion engaging a linear gear the rack which operates to translate rotational motion into linear motion driving the pinion into rotation

causes the rack to be driven linearly [Music] the internal gear or ring gear has teeth inside of a ring rather than on the outside [Music] a magnetic gear is similar to a mechanical gear and function but uses magnets instead of teeth as gear design is a wide area on its own we will only cover three important topics in this section briefly we will start with the gear profile and continue with the gear ratio and gear pressure angle in the next sections one of the fundamentals of gear design is the profile of the gear tooth before

going any further let's define a few of the important nomenclature of gear profile as shown in this graph a pitch circle shown as the middle circular red line is the radius of which is equal to the distance from the center of the gear to the pitch point this is where the gear speed is measured also it is the curve that outlines the mating point between two gears many important measurements are taken on and from the circle next is the circular pitch shown with the yellow arrow this is the angular distance of the teeth along the

circumference of a disc the other important nomenclature in the gear profile is the gear teeth height the height of the gear is the summation of addendum and addendum shown on the very left of the graph the addendum is the height by which a tooth of a gear projects beyond the standard pitch circle or pitch line and the diddendum is the distance between the pitch circle and the root circle the diddendum is larger than the addendum to assure that the tops of the mating gear teeth can pass the root area without interference there are more definitions

in a gear profile but we should continue to the next step for a gear to drive in a given direction and to transmit power or motion smoothly and with a minimum loss of energy the contacting surface on mating gears must have the following properties first the height and the lengthwise shape of the active profiles of the teeth must be such that before one pair of teeth goes out of contact during mesh a second pair will have picked up its share of the load this is called continuity of action thus the height of the gear makes

an important role here second the shape of the contacting surfaces of the teeth must be such that the angular velocity of the driving member of the pair is smoothly imparted to the driven member in the proper ratio lastly the spacing between the successive teeth must be such that the second pair of tooth contacting surfaces is in the proper position to receive the load before the first leaves the circular pitch will be a critical factor to study here to explain the gear ratio we need to build a gear train a gear train consists of two or

more gears in series also it is necessary to define two terminologies as we will be using them frequently first when two gears are meshed together the smaller gear is called opinion second the gear transmitting force is referred to as the driver gear and the receiving gear is called the driven gear a gear ratio is the ratio of the sizes of two gears it is calculated by dividing the number of teeth of the driven gear by the number of teeth of the driver gear in this example when the pinion drives the output gear for every three

turns of the pinion the output gear will complete one revolution this drive mode of gears is called gear reduction now if both the driver and driven gear have the same size this mode of gear is called direct drive this means the ratio between the number of teeth if the driven and driver gear is one thus for every revolution of the driver or input shaft the driven or output shaft will revel at the same number also in the direct drive mode the torque transferred between two gears are same the last gear mode is called overdrive as

the name suggests in this mode the driven gear rotates faster than the driver gear when a larger gear drives a smaller one for one rotation of the larger gear the small gear must complete more revolutions so the output will be faster than the input for our example dividing the 10 teeth of the driven gear by the 30 teeth of the driver gear gets us one third this means that the gear must turn only one third of a revolution to get the pinion to make one complete turn also in this mode the output torque will be

less than the input torque so if we want to put all the three gear modes in one picture we can make the following conclusion since the rated output power of a motor is a fixed value speed and torque are inversely related in the gear reduction mode shown to the left of the graph a larger output gear is used thus the output speed decreases and the available output torque increases proportionately on the other hand in the overdrive mode shown to the right of the graph a smaller output gear is used and this causes the output torque

to decrease and the output speed to increase proportionately so in conclusion one of the primary purposes of the gear ratio is to increase the torque by reducing the speed and vice versa this characteristic of gears provides engineers with the option to select different gear sizes in the design process of a device depending on the speed and torque requirement of the application the other important aspect of gear design is the pressure angle pressure angle is the angle between the tooth face and the gear will tangent and it gives the direction normal to the tooth profile this

angle is formed by the common tangent to the pitch circle shown with the horizontal black line in the graph and the line tangent to the base circles of the mating gears also called the pressure line the pressure line is normal to the tooth profile and can be shown in the graph by drawing a red line passing through points a and b it is important to note that if the gear is positioned at the center of the graph the angle between the horizontal black line and the red line is the pressure angle a common value of

14.5 degrees was historically used in diametral pitch gearing the basis for this selection was that this pressure angle allows for reduced noise in the gear mesh and exhibits a lower rate of wear however it was recognized by american gear manufacturers association that a 20 degree pressure angle was more suited for most applications the benefits of selecting a 20 degree pressure angle include additional power transmission capacity better lubrication in the gear mesh and reduce numbers of teeth for the pinion without undercutting the 20 degree pressure angle gear tooth has a wider base that allows for additional

load capacity but it incurs additional wear on the tooth flank during the interchange of teeth in and out of meshing for some special applications where noise is not an issue but strength is a larger pressure angle of 25 and 30 degrees can be used now let's put each of the explained gear types earlier in this video in a real life application to demonstrate its function in the system we will create a separate video for each of these applications later so please make sure to subscribe to our channel to be notified when they are available one

of the common applications for spur gear can be found in hydraulic pumps in this example we are showing you an external gear pump an external gear pump utilizes two identical spur gears meshed side by side the top gear is driven by a motor and it drives the bottom gear each gear is supported by a shaft with ball bearings on both sides of the shaft fluid trapped between the gear teeth is displaced from the inlet shown with blue arrows in the animation to the outlet port shown with red arrows the gear mesh at the center will

act as a seal between the ports helical gears are used with parallel shafts similar to spur gears however helical gears have teeth that are oriented at an angle to the shaft the gear teeth orientation is called the helix angle and is measured from the center axis of the gear as shown in this illustration the helix angle for single helical gears is between 12 to 20 degrees the helix angle causes more than one tooth to be in contact during operation and helical gears can carry more load than spur gears due to the better teeth meshing than

spurred gears this makes them a better choice for high-speed applications like inside vehicle transmission a vehicle transmission is made up of a series of helical gears the transmission takes power from the engine and delivers it to the wheels to help power the vehicle in the next example we will show the application of bevel gears inside a differential of a vehicle simply a differential is a system that transmits engine torque to the wheels it takes the power from the engine and splits it allowing the wheels to spin at different speeds the engine to wool connection configuration

requires the differential to transmit the toke with a 90 degree angle as shown in the animation for this reason bevel gears are a perfect fit to be used in a differential [Music] next we have the hypoid gear which is generally used in the rear drive axle of trucks the rear drive axle is located between the differential and the driving wheels and transmits power between them as explained earlier the hypoid gear has an offset from the spiral gear so what is the benefit of the offset the reason for the offset is to lower the center of

gravity and avoid a bigger propeller shaft tunnel the hypoid offset causes a relative length sliding between the meshing flank surfaces and enlarges the diameter and spiral angle of the pinion this leads to an additional dampening in the tooth mesh increased contact ratio and improvement in pinion strength in addition a larger diameter shaft can be used in high point gears which enables the engineers to use larger pinion diameters this makes hypoid gears a good choice for higher torque demanding vehicles such as trucks have you ever wondered how your luggage is delivered to you at the airport

within minutes or how thousands of items are transported in a factory with minimal effort thanks to conveyor belts for making this possible the belt on the conveyor is the platform for transportation but what components enable it to deliver linear motion for its transportation to understand this we should take a look inside the gearbox of a conveyor belt inside the gearbox you can see a worm gear set the worm gear is the primary component and it uses a screw shape to turn the worm wheel which translates the rotational motion to a linear motion also the other

purpose of using worm gearboxes is to reduce speed to slow down conveyor belts and in the meantime transmit higher torque from the electromotor next up let's take a look at an example most people interact with on daily basis the steering wheel of a car the steering wheel assembly primarily controls the direction of a vehicle but what type of gear enables this motion the rack and pinion is a type of steering mechanism with a pair of gears that convert the rotary motion into linear motion this system consists of a circular gear called pinion that engages with

the teeth on the linear gear shaft called the rack if we look inside the steering mechanism it consists of a pinion at the end of the steering column that meshes with a rack the pinion is fixed to the steering column at its end it meshes with the rack which moves either to the right or the left side depending upon the movement of the pinion one of the common places that internal or ring gears are used as planetary gears planetary gears are often used when space and weight are an issue but a large amount of speed

reduction and torque are needed this requirement applies to a variety of industries including tractors and construction equipment where a large amount of torque is needed to drive the wheels other places you will find planetary gear sets include transmissions of helicopters turbine engines automatic transmissions and even electric screwdrivers planetary gear systems are able to produce a lot of torque because the load is shared among multiple planet gears this arrangement also creates more contact surfaces and a larger contact area between the gears than a traditional parallel axis gear system because of this the load is more evenly

distributed and therefore the gears are more resistant to damage [Music] a magnetic gear is similar to a mechanical gear and function but uses magnets instead of teeth here you can see the main components of a magnetic gear the gears don't touch at all they only interact magnetically which makes them unique the gear ratio is determined by the number of magnets used in each rotor magnetic gears are relatively new in the industry in recent years the magnetic geared motor has emerged as an interest in electric vehicles and electric bikes we briefly covered the applications of gears

in real engineering applications however there are more details that need to be covered to understand their functions so we will be creating videos for each of these examples individually and we'll cover more details about them we hope you enjoyed this video please stay tuned for more videos by subscribing to our channel goodbye