At a ratio of less than 3, the sun gear becomes too big against the planet. So, my question is, utilizing the solid works file. The first constraint for a planetary gear to work out is that all teeth have the same pitch, or tooth spacing. Their number of teeth depends on the demultiplication of the gearbox.
Choosing which piece plays which role determines the gear ratio for the gearset. This paper presents planetary gear transmissions, designed according to iso 6336 ref. Working out the gear ratio of a planetary gear train can be tricky. Planetary gears are common in transmission systems, where they provide high gear ratios in compact geometries. The comparison of planetary gear system over helical gears systems is. Consider a simple schematic of a gear box with an input and output shaft. Planetary gears, gear train, is 4460, torque density. Planetary kinematics note that point 1 on the planet gear is stationary zero velocity due to noslip assumption note that point 2 on the planet gear has the same velocity as point 2 on the sun gear also. Planetary kinematics note that point 1 on the planet gear is stationary zero velocity due to noslip assumption note that point 2 on the planet gear has the same velocity as point 2 on the sun gear also due to noslip assumption, which is given by. We can get lots of different gear ratios out of this gearset.
A carrier connected to a drive shaft holds the planet gears. The gearbox is made from hardened steel and has a gear ratio of 35 times in order to convert a high rotational speed into a large torque. Calculation of a planetary gear train this tutorial shows the usage of mesys shaft calculation with shaft systems. To determine the train ratio between the two gears, we use the following. Now, if we drive the sun gear, we can rearrange the formula to solve for turns of the y carrier. Each composite planet gear is a pair of rigidly connected and longitudinally arranged gears of.
Let us compare a planetary gear train with a conventional one, with fixed gear axes, designed for the same gear ratio of angular velocities of the input and output mechanism links. Planetary gear train with stepped planet gear set matlab. How to i design a planetary gear with a gear ratio of 2. Relations between size and gear ratio in spur and planetary gear trains 1835 applying the equation for the inertia equation 12 on the data shown in figure 11. One of the planetary gearsets from our transmission has a ring gear with 72 teeth and a sun gear with 30 teeth. Planetary gear is a widely used industrial product in midlevel precision industry, such as printing lathe, automation assembly, semiconductor equipment and automation system. Planetary gear calculation in mathcad, made by gar. Each composite planet gear is a pair of rigidly connected and longitudinally arranged gears of different radii. Given i have the solid works file,the pressure angle, and the gear ratios, i can easily calculate the distances, teeth numbers, etc. The compound planetary gear block represents a planetary gear train with composite planet gears. Please start with the tutorial for shaft calculation to see how to introduce geometry and supports for single shafts. I also know the initial driving torque of the sun gear.
Internal gears used in mechanisms such as planetary gear drive. A twostage planetary gear stage is defined using the program. For a threespeed hub, a onestage planetary gear system is used, for a fivespeed hub a 2stage. All the components are modelled in catia to check the assembly and the. The software enables calculation of the system gearbox in one step, including a complete documentation into a pdfa document, according to iso 190051. To compare with traditional gearbox, planetary gear has several advantages. Lightweight design for planetary gear transmissions. The planet gear in figure 23 rotates about a fixed bevel gear at the center of which is the driven shaft. A gear train may consist of spur, bevel or spiral gears. This complicated arrangement see below has a number of modes of operation depending on which.
In examinations one of the first questions will probably for you to work out the gear ratio sometimes called velocity ratio. Two inputs are needed to obtain a predictable output. If the carrier is acting as the output in the planetary gear system, being rotated by the sun gear while the ring gear stays still, divide the number of teeth on the planetary gears the driven gear by the number of teeth on the sun gear the driving gear. Reduction ratios not listed in chart 1 require special design.
Internal gear is a gear with its teeth cut in the internal surface of a cylinder and meshes with spur gears. Pdf relations between size and gear ratio in spur and planetary. Therefore the root stress is only calculated for the pinion in the rest of this report. The planetary gear set, also known as the epicyclic gear train, is one of the most important and interesting inventions in engineering. This block models a gear train with sun, planet, and ring gears. 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. The main purpose of this planetary was to see if i could make it with hand cut gears and how smoothly it would operate. The analysis of planetary gearing often is unwieldy because components. Working out the tooth counts for planetary gears is actually not that complicated, so i initially neglected to mention how to do it.
Planetary gear ratio calculations this article also available in spanish. A question that i often get is how to work out planetary gears using the gear template generator. 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. A planetary gearbox design calculations filetype displays safety factors and life expectation as function of. In its manufacturing, because of its shape, the usual hobbing machine used in spur gear production cannot be used. Program help in the help menu an instruction in form of diploma thesis in pdf format is opened. The nature of the train used depends upon the velocity ratio required and the relative position of the axes of shafts. Gears c and b represent a compound gear as they appear fixed together. Two forms of planetary gears of the bevel type are shown in figures 23 and 24. Design of machinery an introduction to the synthesis and.
How to calculate the gear ratio in a planetary gear set where one member is stationary. Gear stages gear ratios gear types bearings materials lubrication interfaces etc. Each of these three components can be the input, the output or can be held stationary. Another class of gear train has wide application, the epicyclic or planetary train. Nov 08, 2012 the overall demultiplication of multi stage planetary gear units is calculated by multiplying the ratios of the single stages.
N is usually in revmin but the ratio is the same whatever units of speed are used. Ronald walters multilayer planetary drive ronald walters sent me some pictures and a description of a very complicated planetary gear drive that he built. Planetary gear design a planetary gear system, also referred to as epicyclic gearing, consists of three elements a sun gear, one or more planet gears, and a ring gear. An epicylic gear is a planetary gear arrangement consisting of one or more planet epicyclic gears p meshed and rotating round a central sun gear s. Ports c, r, and s represent the shafts connected to the planet gear carrier, ring gear, and sun gear. Planetary gearing could increase torque and reduce load inertia while slowdown the speed. Understanding, selecting and applying planetary gearheads. When drawn with a compass they have the same centre. The results can only be used for information purposes. Figure 3 gear box ratio the ratio of the gear box is defined as 2 1 n n output speed input speed g. At least one warning has occurred during the calculation. This does not generate planetary gears, and im also unclear as to how design a planetary gear with a 2.
In the past ive had luck using this site to create an illustrator file that i can extrude in rhino. How to derive the formula for the planetary mechanism. The planets are merely seen as a bridge between the sun gear and annulus gear. In mathematical terms, the smallest reduction ratio is 3.
Pdf relations between size and gear ratio in spur and. One additional constraint is needed to allow 5 the planets to be positioned symmetrically around the sun gear. The number of teeth of the planets has no effect on the ratio. But the small gap between gear teeth leads to lost motion. 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. The number of rotations of the second gear has then to be worked out. The gear ratio formula for two meshing gears is simple and intuitive, while the gear ratio formula for the planetary mechanism is not.
Two gears fixed together in this way rotate together and at the same rpm. A question that i often get is how to work out planetary gears using the gear template generator working out the tooth counts for. If the carrier is acting as the output in the planetary gear system, being rotated by the sun gear while the ring gear stays still, divide the number of teeth on the planetary gears the driven gear by the number. You can click on any of the images for a larger view. The comparison of planetary gear system over helical gears systems is done on the basis of volume, weight and torque density keywords. Jan 19, 2012 planetary designs also cannot have ratios less than 3. Sample of planetary gears setup with proper mates and relations. Calculate the number if teeth required in the ring gear for the ratio 5. This is a c o mp li c a t e d m e c h a n ism to solve. Planetary epicyclic gear ratios equations and calculators. It allows us to find a gear ratio without actually having to build a gear train and turn the gears. Planetary designs also cannot have ratios less than 3.
As a guide always assume that the larger gear revolves one revolution. An epicylic gear is a planetary gear arrangement consisting of one or more planet epicyclic gears p meshed and rotating. Also the case study to determine the reduction ratio of two stage gear box is discussed. For convenience, lets denote r, s, and p as the number of teeth on the gears. Design and optimization of planetary gears considering all. This relationship between the tooth ratio and the gear ratio is very important. Also, locking any two of the three components together will lock up the whole device at a 1. Feb 20, 2015 how to calculate the gear ratio in a planetary gear set where one member is stationary. This complicated arrangement see below has a number of modes of operation depending on which members are locked.
Calculating load on planetary gear from driving torque. So the planetary gear ratio is and the speed of each planet gear is 4 where l is the central angle between two adjacent planet center lines and a is the addendum of the planet gears. Gear train with sun, planet, and ring gears matlab. Gear optimization macrogeometry the following shows the gear optimization in some case studies. Each planet gear system has a reduction state, a direct coupling and an acceleration mode. We can find the ratio of any two gears if we know the number of teeth on each of the gears. Using differentialplanetary gear arrangements it is possible to achieve gear ratios of sev eralhundredtoone in onestagedrive with common planet gears, and. Intro planetary gears also refer as epicyclic gearing consisting three elements sun. The number of teeth has most influence on the root bending. 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.
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