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On the balancing of a steel rod

June 11th, 1960

Project report for Part II of the Engineering Tripos, Cambridge University, 1960.

S F Bush


This is a report on the analysis, design and building of a servo-mechanism to control the movement of a uniform steel rod. The servo-mechanism is required to maintain the rod in a vertical position by moving it at the bottom. The bottom of the rod is fixed to a radial arm by a ball-bearing and is allowed only to move perpendicularly to the arm.

The report has been written with the intention of recording, more or less in order, the things which were done in all three stages of the project. With this in mind, those parts of the analysis which were central to the problems presented are included in the main text, while the subsidiary parts, and an account of abortive attempts to solve problems, are contained in appendices.

This report is written to illustrate the methods of dealing with the problems as they arose in the course of proceeding from the first analysis to the final building of a rather unusual system; it is not intended to be a concise account of the final design. An alternative design, using a relay, and basically simpler than the one actually used is, however, given towards the end. The report ends with a short conclusion which surveys the whole project in retrospect and in particular considers the role of the theoretical analysis.