design manual for enclosed epicyclic gear drives.pdf

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Both floating and non-floating (fixed centers) systems were treated.

The ELSM is a physics-based tool that is derived from a physical explanation of the load-sharing phenomenon.

Therefore, in an n planet planetary system, each sun-pinion-ring path is designed to carry 1n of the input torque.

In the presence of positional type manufacturing errors, equal load sharing is not realized, and the degree of inequality in load sharing has major implications for gear system sizing, tolerancing schemes, and torque ratings.

It is a plot of the Load ratio (or of input torque) versus a non-dimensional parameter Xe.

The non-dimensional parameter is a function of combined system stiffness, tolerance level, and operating torque.

The ELSM maps out the operating space of any epicyclic gear set, and a given gear set at a given operating condition maps to a point on the ELSM.

Once a gear set is located on the ELSM, its behavior under any load and error condition can be quickly predicted.

Also, the advantages of adding extra planets can be accurately estimated.

The general case when there are errors on the position of every carrier pinhole will be considered.

Statistical simulations will be performed for a given manufacturing error distribution for three to seven planet systems.

In the absence of manufacturing variations, perfect load sharing between the different parallel paths is possible.

The power density of such epicyclic gearsets can be improved by simply adding additional planets (up to the maximum number that can fit).

Some of the planets will transmit higher than nominal loads, while others transmit lower than nominal loads.

Previous experimental 1-6 and computational 6-13 studies of varying complexities have demonstrated the significant load sharing inequalities that result from these errors.

This load sharing inequality needs to be accurately estimated in order to properly size epicyclic gearsets and reliably estimate their torque capacity 14.

These deviations from ideal location are due to manufacturing variations, and will be referred to as positional error or simply error in this paper.

Bodas and Kahraman 11 classify the manufacturing errors into time invariant, assembly independent errors (pinhole position error, pinhole diameter error), time invariant, assembly dependent errors (planet tooth thickness, planet pin and bore eccentricities), and time variant, assembly dependent errors (run-outs of the gears).

In this work, error will refer to this cumulative positional error that includes the contributions from all sources.

Some of these factors are the transmitted torque, error level, directionality of error, system flexibility, number of planets, and amount of float in the system.

The sensitivity of load sharing inequality to many of these variables has been studied 1-5, 10-14.

In recent papers 16-18, the author has proposed a physical mechanism that explains all known load sharing behavior.

Design Manual For Enclosed Epicyclic Gear Drives.Pdf