5/16/2023 0 Comments Freedom planet torque unlockIf the designer adds more planet gears, the load capacity and torsional rigidity increase. READ MORE: When Planetary Gears Meet Servomotors This means no radial forces act on the shaft bearings, so there is less chance of the outer casing distorting. Wear and TearĪnother benefit of planetary gears is that with several equally spaced planets (as is usually the case) the input and output shaft bearings avoid radial loads created by tangential gear reaction forces because the planetary gears’ forces cancel each other out. Worm and planetary combinations are rare because worm reducers already change the speed. If the engineer needs a right-angle turn to the rotation, bevel or hypoid gears can be attached to an inline planetary system. It also establishes an offset between the input and output. Designers sometime prefer this setup, dubbed a hybrid, as a simple alternative to adding planetary stages or lowering input speeds that are too high for some planetary units. For example, high-speed power might get sent through an ordinary fixed-axis pinion-and-gearset before the planetary reducer. READ MORE: Comparing Cycloidal and Planetary GearboxesĪnother option is to insert standard gear reducers into planetary trains. Then, the rotational output of the first stage becomes the input to the next, and the total reduction becomes the product of all the stages. There are also simple ways to reduce or increase speeds, such as connecting planetary stages in series. Compound planetary gears are far more elaborate and can provide much greater reductions. Simple planetary gears can provide speed reductions as high as 10:1. Compound gear trains can also mesh with and revolve around fixed and rotating external gears at the same time, eliminating the need for a ring gear. This option expands the mechanical possibilities and allows more reduction per stage.Ĭompound planetary trains can also be easily configured so the planet-carrier shaft drives at high speed, while the suns shaft turns at a lower (reduced) speed. Compounded planets can have different numbers of teeth, as can the gears they mesh with. They rotate and orbit at the same speed but mesh with different gears. The left and right wheel speeds represent two outputs, which must differ when the car takes a turn.Įven a simple planetary gear train has two inputs with the anchored ring gear providing a constant input of zero angular velocity.Ĭompound planetary trains, unlike simple planetary gears, have at least two planet gears attached in line to the same shaft. For example, the differential driving the axle in a car has planetary bevel gearing. ![]() These planetary arrangements can have a single output driven by two inputs or a single input driving two outputs. In differential planetary gears, for example, every member rotates. As the planet carrier turns, it delivers low-speed, high-torque output.Ī fixed component isn't always necessary. All the planets are mounted to a single rotating member, called a cage, arm or carrier. The planets, equally spaced around the central axis of rotation, mesh with the sun as well as the fixed ring gear, so they orbit as they roll. In a simple planetary setup, input power turns the sun gear at high speed. The planet grouping’s concentricity with the sun and ring gears means torque is carried through in a straight line. A fixed ring gear holds the planet gears in orbit about the sun gear and meshes with both the ring and sun gears. Planet gears rotate around axes that revolve around a sun gear which spins in place. Planetary Geometryīasic planetary gearing consists of three sets of gears, each with different degrees of freedom. ![]() Here’s a look at the construction and mechanics of planetary gears and how engineers can take advantage of them. They are also relatively compact compared to standard pinion-and-gear reducers, thanks to their inherent in-line shafting and cylindrical casing. Planetary gears can supply high levels of torque and high-speed reduction. It was originally published March 1, 2000.
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