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ESDU - Geneva mechanisms. Part 2: computer program

Organization: ESDU
Publication Date: 1 July 2010
Page Count: 28
scope:

INTRODUCTION

ESDUpac A9611 provides a computer program for calculating the key dimensions, motion characteristics, forces, torques and power requirement for the operation of either external or internal Geneva mechanisms. Both constant and varying crank angular velocity definitions are permissible. Power is transmitted between the crank and wheel by either roller bearings or pins. Crowned or cylindrical profiles of these components are included. Two design strategies are provided. The designer may specify the Geneva wheel dimensions and the distance between crank and wheel shaft centres will then be calculated. Alternatively, the centre distance is specified and then the wheel diameter is evaluated.

The program determines the dependent dimensions, wheel motion, contact and bearing forces plus the crank torque and power required to drive the crank and produce the specified motion. Contact stresses and the dimensions of the contact area on the slot face and roller (or pin) are determined and compared with the specified limits. When a bearing is selected, its strength and life are calculated and compared with the published performance criteria. Similarly, the characteristics of a lubricant film are evaluated when oil lubrication is specified. If any of the applicable performance limits are exceeded, the program will issue an appropriate warning. If the crank angular velocity has been specified as constant, the limiting speed will be determined and a warning issued if this speed is exceeded.

In addition to a descriptive output file reproducing the input specifications and listing the results of the analysis, the program generates a series of data files in ASCII format. Separate files are provided which define the wheel motion, mechanism forces, contact stresses and deformations and lubrication data (when applicable). A DXF output file provides a graphical representation of the outline of the Geneva wheel, for the external Geneva only.

The analytical techniques implemented in the program are those described in ESDU 96002, entitled "Geneva mechanism. Part 1: Design" (Reference 2) and ESDU ME3, entitled "Analysis of Geneva mechanisms: derivation of kinematic and kinetostatic equations" (Reference 1). The applicable assumptions are stated in these documents and the program output must be considered in respect of the theoretical limitations and practical considerations of the design process.

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