The gear ratio of an epicyclic gearing system is somewhat nonintuitive, particularly. Recent articles in gear solutions have discussed epicyclic gearing, but often in the context of experienced engineers. Design of machinery an introduction to the synthesis and. Basic gear terminology and calculation lets learn the basics of basic gear technology. Planetary gear trains are one of the main subdivisions of the simple epicyclic gear train family. Internet searches for how to proved fruitless and dare i say information is being withheld, so this programmer set out to demystify the methods for calculating the widely used equations of. The outermost gear, the ring gear, meshes with each of the planet gears. Using differentialplanetary gear arrangements it is possible to achieve gear ratios of sev eralhundredtoone in onestagedrive with common planet gears, and. The comparison of planetary gear system over helical gears systems is done on the basis of volume, weight and torque density keywords. Planetary gear stages may be used in series with parallel axis gear stages to get the overall desired ratio. Intuitive method how to calculate derive gear ratio formulas equations for planetary epicyclic gear. The real scope of this paper is on design parameter, gear ratio, gear tooth combination, stress, and factor of safety.
Equation and calculators to determine ratios of planetary or epicyclic gear assemblies. Engagement between internal gear and pinion external gear centre distance ca for the internal. The gear ratio is the ratio of the number of teeth on each gear. Typically, due to the higher torque requirement on the rotor side, planetary gear sets are used in. Contact ratio of gears, tooth modifications, and the. Epicyclic gearing planetary gearboxes neugart gmbh. A wind turbine gearbox typically contains one lowspeed planetary stage with two parallel stages or two planetary stages with one highspeed parallel stage. As mentioned above, two or three stages may be required to get the overall ratio. Relations between size and gear ratio in spur and planetary gear trains article pdf available january 2004 with 6,785 reads how we measure reads.
How to i design a planetary gear with a gear ratio of 2. Here is a gear with 8 teeth meshed with a gear with 40 teeth. Working out the tooth counts for planetary gears is actually not that complicated, so i initially neglected to mention how to do it. Epicyclic gearing or planetary gearing is a gear system consisting of one or more outer, or planet, gears or pinions, revolving about a central sun gear or sun wheel. Basic gear axis for planetary gear train mechanism 2kh a types of planetary b types of solar c types of star aa. In general, a planetary stage is designed for gear ratio up to seven and a parallel stage usually up to five. As more and more of these engineers reach retirement age younger engineers must pick up where they left off, and for many epicyclic gearing is an area where they lack experience.
Bear in mind the difference between the standard reduction ratio fo framenumbers under 315 and over 355. An epicyclic gear train consists of two gears mounted so that the center of one gear revolves. Cylindrical spur gears with standard profile cylindrical spur gears with corrected profile without centre distance variation with centre distance variation. Driver planetary gear character istics this is a c o mp li c a t e d m e c h a n ism to solve. Relationship between the involute elements determination of base tooth thickness from a known thickness and viceversa. This text will not deal with the stress analysis aspects of gear design. Gear train with sun, planet, and ring gears matlab. The gear ratio of an epicyclic gearing system is somewhat non intuitive, particularly.
Abstract it has been said that deriving the formulas for the ratios between the various gears of an epicyclic planetary gear system is nonintuitive and taxes the human intellect to say the least. How to derive the formula for the planetary mechanism gear ratio. In the picture above, meshing is the sun gear a the planetary gear b the planetary gear c coupled with the gear b the sun gear d concentric to but not coupled with the gear b and the gear a is fixed, while the arm e rotates. Us6527671b2 planetary gear transmission with variable. Calculate gear ratio by dividing the number of teeth. Ports c, r, and s represent the shafts connected to the planet gear carrier, ring gear, and sun gear. Planetary gear system is use in varies applications such as, clocks, lunar calendar, car mirror, toys, gearhead motor, turbine engine and many more. A question that i often get is how to work out planetary gears using the gear template generator. Planetary gear ratio calculations this article also available in spanish. Oct 04, 2017 so ive found the following formula for calculating the gear ratio of a planetary gear.
The epicyclic gear train family in general has a central sun gear which meshes with and is surrounded by planet gears. For a planetary arrangement with three planets, each tooth engagement of the sun gear would have to carry one third of the total load. Types of gear train and velocity ratio calculation gear train mean. Each of these three components can be the input, the output or can be held stationary. How to derive the formula for the planetary mechanism gear ratio duration. Which motion of planets around the sun gear is called planetary motion.
Planetary gears gsa the easytomount highend economy gearbox for high power transmissions. Question about calculation of planetary gear ratios physics. In order to determine both the speed and force of rotating axles, we need to calculate the gear ratio. Consequently, the dimensions of the sun gear would be onethird of the pinion of a parallel shaft geartrain designed to transmit an equivalent torque. The lowbacklash planetary gearheads of the gsa series are designed for high positioning accuracy and highly dynamic cycle operation. Us6527671b2 planetary gear transmission with variable ratio. Calculate gear ratio by dividing the number of teeth on the driven gear by the number of teeth on the driving gear. Design and optimization of planetary gears considering all relevant influences tobias schulze gear design process lightweight construction and consideration of available resources result in gearbox designs with high load capacity and power density. In the past ive had luck using this site to create an illustrator file that i can extrude in rhino. For similar epicyclic planetary stages with compound planet gears, the practical gear ratio range varies from 8. A carrier connected to a drive shaft holds the planet gears.
Design and optimization of planetary gears considering all. Another class of gear train has wide application, the epicyclic or planetary train. In this tutorial, we will show you an original and easyto. Please start with the tutorial for shaft calculation to see how to introduce geometry and supports for single shafts. How to derive and calculate epicyclic gear ratio equations. Gears range in size but the important number is how many teeth a gear has. How to derive and calculate epicyclic gear ratio equations in. The inputdriver gear will rotate 5x when the outputfollower gear rotates 1x.
When the larger gear makes one full revolution, the smaller gear has to spin faster to keep up. Also the case study to determine the reduction ratio of two stage gear box is discussed. The gear wheel transmitted motion between one shaft to another shaft, so the multiple set of gear transmit motion from single main gear to various revolving parts is known as gear train. Planetary gear systems have very smalllarge train ratios and are very compact. Computational methodology the compound planetary gear train taken from the elecon engineering shown in figure 2. Formulas for gear calculation external gears contents. The smallest number of teeth on a spur pinion and gear, onetoone gear ratio, which can exist without interference is np.
Ground, helical toothed precision components inside the gear ensure low running noise and high running smoothness. The comparison of planetary gear system over helical gears systems is done on the basis of. A twostage planetary gear stage is defined using the program. Planetary gear boxes chapter 10 5 technical information because our supplier is continuously improving its. The number of teeth for spur gears is given by where k 1f fll1 for fulld tht th08f tbt th d ldepth teeth, 0. Jul 06, 2019 epicyclic gear calculations pdf with four core components, calculating the gear ratio of planetary gear systems, also known as epicyclic gear systems, may seem daunting. Our planetary gears accomplish reliable performance in their nume. One of the planetary gearsets from our transmission has a ring gear with 72 teeth and a sun gear with 30 teeth. Solid mechanics tutorial gear systems this work covers elements of the syllabus for the edexcel module 21722p hncd mechanical principles outcome 3. The fundamental formula of the planetary gear train with a rotating carrier is obtained by. Provided that the ring gear has a constant size, different ratios can be realized by varying the number of teeth of the sun gear and the number of teeth of the planetary gears. Figures 6a, 6b and 6c contain three typical types of planetary gear mechanisms, depending upon which member is locked. So when you ride your bicycle, the gear in front might have 48. Technically, a meaningful ratio range for a planetary stage is approx.
Planet carrier types of mechanism fixed member input output formula of gear ratio ratio. A gear ratio is the ratio between the driver gear the one being powered and the driven gear the. Choosing which piece plays which role determines the gear ratio for the gearset. Intro planetary gears also refer as epicyclic gearing consisting three elements sun. Question about calculation of planetary gear ratios. For example, if the sun gear has 20 teeth and the ring gear has 60, the planetary gear has 80 teeth.
Now, if we drive the sun gear, we can rearrange the formula to solve for turns of the y. Pdf relations between size and gear ratio in spur and planetary. D rotation of driver per revolution of follower or the driven gear or pulley. Gear stages gear ratios gear types bearings materials lubrication interfaces etc. One of the planetary gearsets from our transmission has a ring.
Pdf in this report equations for the minimum gear sizes necessary to drive a. How to derive the formula for the planetary mechanism. A simple planetary with a single carrier, sun gear, and ring gear can be connected. Calculating gear ratios within a planetary gear set youtube. This factor takes into account the application load conditions. Feb 20, 2015 how to calculate the gear ratio in a planetary gear set where one member is stationary. For simple, epicyclic planetary stages when the ring gear is stationary, the practical gear ratio range varies from 3. Reduction ratio i 833 808i 1,500 examplesof selection select the nearest reduction ratio from among the ratios of the standard reduction ratio chart see chart 1. Working out the tooth counts for planetary gears is actually not that. Understanding, selecting and applying planetary gearheads. Types of gear train and velocity ratio calculation.
The next steps depend on the state of the planetary gears connected to the carrier, although all use the same formula. A planetary gear transmission with a steplessly adjustable transmission ratio where the gear transmission comprises a first and second sun gear 11, 12 arranged on a first and second operating shaft 7. The gsf090 planetary gear, with a gear ratio of i10, is used as a machine axis. Reduction ratios not listed in chart 1 require special design. Calculate the number if teeth required in the ring gear for the ratio 5. Divide the number of teeth on the driving member by the sum of the sun gear and ring gear teeth on the planetary gear for a system set in overdrive with the carrier as the input. You can obtain large speed ratio using small machine. The resulting number is the gear ratio for that transmission setting. Epicyclic gear calculations pdf with four core components, calculating the gear ratio of planetary gear systems, also known as epicyclic gear systems, may seem daunting. Jan 09, 2018 the gear ratio formula for two meshing gears is simple and intuitive, while the gear ratio formula for the planetary mechanism is not.
In general, a planetary stage is designed for gear ratio up. This paper presents analysis and design of planetary gear arrangements that provide extremely high gear ratios. It is also called as planetary gear or sun and planet gear trains, because of the gear b goes around and around the gear a just for planet gear move around the sun gear. Calculat ion of a plane tary gear train this tutorial shows the usage of mesys shaft calculation with shaft systems. On completion of this short tutorial you should be able to do the following. Relations between size and gear ratio in spur and planetary gear trains. This does not generate planetary gears, and im also unclear as to how design a planetary gear with a 2. Multistage gears are required to obtain the desired ratio. A gear ratio is the relationship between the number of teeth on two or more gears that are meshed. Pdf relations between size and gear ratio in spur and. Elec tric mo to r gt1 gt2 scre w driv er sh af t sw itc h mo t o r sha f t t. Planetary epicyclic gear ratios equations and calculators. The gear ratio formula for two meshing gears is simple and intuitive, while the gear ratio formula for the planetary mechanism is not. A question that i often get is how to work out planetary gears using the gear template generator working out the tooth counts for planetary gears is actually not that complicated, so i initially neglected to mention how to do it.
A complete gear train design will necessarily involve considerations of strength of materials and the complicated stress states to which gear teeth are subjected. How to calculate the gear ratio in a planetary gear set where one member is stationary. Gear size, pressure angle, number of teethwe introduce the basic terminology, measurement, and relational expressions necessary to understand basic gear technology. Planetary gears, gear train, is 4460, torque density.
43 994 62 1605 185 989 1296 328 1515 1070 14 872 705 1199 453 709 202 539 939 624 548 215 407 1568 835 614 1212 1332 310 525 1169 1471 743 422 327 1236 1070 868 1321 1216 453 1014 1093 84