With four core components, calculating the gear ratio of planetary gear systems, also known as epicyclic gear systems, may seem daunting. An epicyclic gear train consists of two gears mounted so that the centre of one gear revolves .. The fundamental formula of the planetary gear train with a rotating carrier is obtained by recognizing that this formula remains true if the angular. This tutorial shows the usage of MESYS shaft calculation with shaft systems. A two-stage For a planetary gear stage we need at least two shaft groups. With a.

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Disadvantages include high bearing loads, constant lubrication requirements, inaccessibility, and design complexity. How to Calculate Planetary Gear Ratio. These relationships can be used to gwar any epicyclic system, including those, such as hybrid vehicle transmissions, where two of the components are used as inputs with the third providing output relative to the two inputs.

Calculating ratios using planet gear instantateous velocities Split ring, compound planet, epicyclic gears of a car rear-view mirror positioner. The three basic components of the epicyclic gear are:. Hypocycloidal gearing Antikythera mechanism — ancient mechanical astronomical computer Continuously variable transmission CVT Cycloidal drive Epicycloid Ford Model T — gar a 2 speed planetary transmission.

Extending this case from the one above:.

The planetary gear train also provides stability due to an even distribution of mass and increased rotational stiffness. An epicyclic gear train can be assembled so the planet calculafions rolls on the inside of the pitch circle of a fixed, outer gear ring, or ring gear, sometimes called an annular gear. The ratio of input rotation to output rotation is dependent upon the number of teeth in each gear, and upon which component is held stationary.


Epicyclic Gears

Cogset Derailleur gears Hub gear Shaft-driven bicycle Sprocket. Calculate gear ratio by dividing the number of teeth on the driven gear by the number of teeth on the driving gear. The assembly conditions of compound planetary gears are more restrictive than simple planetary gears, [7] and they must be assembled in the correct initial orientation relative to each other, or their teeth will not simultaneously engage the sun and ring gear at opposite ends of the planet, leading to very rough running and short life.

Blake Flournoy is a writer, reporter, and researcher based out of Baltimore, MD. The follower is the planetary arm L.

Epicyclic gearing

However, in a steady state condition, only one torque must be known, in order to determine the other two torques. In this simplified case, the sun gear is fixed and the planetary gear s roll around the sun gear. Views Read Edit View history. In bicycle hub gearsthe sun is usually stationary, being keyed to the axle or even machined directly onto it. The driver is the sun S.

Planetary gear ratio calculations

The Ring Gear is fixed. During World War IIa special variation of epicyclic gearing was developed for portable radar gear, where a very high reduction ratio in a small package was needed. If the ratio of rotation of the follower member R A has a ratio of R relative to the driving epicyclid R B rotation i.

This had two outer ring gears, each half the thickness of the other gears. The next steps depend on the state of the planetary gears connected to the carrier, although all use the same formula.

Working independently and alongside professors at Goucher College, they have produced calculaions taught a number of educational programs and workshops for high school and college students in the Baltimore area, finding new ways to connect students to biology, psychology, and statistics.


Compound planets have “timing marks” or “relative gear mesh phase” in technical term. This is known as the fixed carrier train ratio. In many epicyclic gearing systems, one of these three basic components is held stationary; one of the two remaining components is an inputproviding power to the system, while the last egar is an outputreceiving power from the system.

The figure below shows the range of possible epicylclic gear arrangements. The sun gear then drives the planetary gears assembled with the external gear ring to operate. Typically, the planet gears are mounted on a movable arm or carrierwhich itself may rotate relative to the sun gear.

This provides the basic structure for an automatic transmission. Traditional gears rely on a small number of contact points between two gears to transfer the driving force. Typical Epicyclic Gear Arrangement.

Epicyclic gears get their name from their earliest application, which was the modelling of the movements of the planets in the heavens. This curve is called an epitrochoid. Use this information at your own risk. Epicyclic gears can be based on spur gears, helical gears, or bevel gears.

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.