Balancing Small Engines

Notes on basic principles and practical methods of procedure

by ET Westbury, 1951


EVERY new development in engineering brings with it new problems, or causes old problems to become accentuated, and it is often found that the methods of dealing with them have to be revised to cope with advanced design and more exacting performance. While engineers of today are very fortunate in having available a vast amount of accumulated data, obtained laboriously by the research workers of the past, it is often found that this is inadequate to cover the conditions which arise when producing something entirely new, such as, for instance, a racing engine. In some respects, one may be hampered rather than assisted by faith in ready-made data, and it is often better to tackle the problems from first principles, or even by the much-despised "rule of thumb", which although crude, is often effective.

A problem which is brought to my notice with ever-increasing frequency these days is that of balancing engines or other mechanism. Many readers who attempt to construct engines which will go just a little faster than ever before, find themselves in trouble with excessive vibration or overloading of working parts, as a result of unbalanced forces, and ask my advice in finding a practical solution. Some of them are rather disappointed to learn that I cannot furnish them with a few figures and symbols which will clear the whole matter up tidily and accurately; the childlike faith which some of my querists have in formulae is most impressive!

It is perhaps necessary for me here to make one of my frequent disclaimers regarding my attitude to theoretical solution of problems. I am not, nor have I ever been, antagonistic to, or contemptuous of, theory, wherever it can properly be applied; but the factors involved in what may, at first sight, appear to be quite a simple practical problem, are often so profound and complex that their solution by theory alone is almost impossible to a person of normal intelligence. By all means use theory in its place, and where you can be quite certain that the premises on which it is based are correct; but always remember that it must be a supplement to, and not a substitute for, practical knowledge. In many problems, practical experiment will find the solution more quickly and no less accurately than theoretical calculation.

So far as the particular subject of balancing is concerned, I may mention that many years ago, in the attempt to solve problems personally encountered, I studied text-books by three of the best-known authorities on the subject namely, Sharpe, Dalby, and Schlick; but I must confess that, so far from being enlightened, I was scared stiff with the immensity of what I had regarded as a mere elementary problem of design.

First Principles of Balancing
  Single Cylinder Balance
  Balancing Multi-cylinder engines


The Model Engineer, Percival Marshall & Co. Ltd. Volume 106, Numbers 2651, 2653, 2655.



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