New Books and Magazines This Month
Malcolm Stride's eagerly awaited book on the design and construction of model internal combustion engines arrived during June. This one has been on the boil for a while. At one time, we looked at the possibility of including CamCalc with the book, but that was too hard and a reference must suffice. Model Engine News pre-announced this book in the April Page and that may have generated some activity as Malcolm reports sales topping 400 so far. This is terrific and indicates the growing interest in home built engines that I've been sensing for a few years now. I must also come clean and say up front that I've been exchanging emails with Malcolm ever since he took up the IC baton at Model Engineer some years back. Does this impact my impartiality? Maybe, but I'll try hard to be objective.
First, the physical details: Miniature Internal Combustion Engines, by Malcolm Stride, is published by Crowood Press, England; ISBN 978-1-86126-921-8. It measures 8"x10", is hardbound with a wrap-around dust-jacket, and contains 178 glossy pages with extensive color photographs and illustrations. While the cover features Malcolm's NE15S four-stroke that ran as a construction series in the Model Engineer, the book is not a detailed construction manual for that engine; the intent being to explain the techniques involved in producing all the components required for a generic IC engine. That said, many of the photographs of actual set-ups used to illustrate the techniques are of the NE15S. The author's aim is to show that building a running, miniature, internal combustion engine is not an arcane art requiring extraordinary skills. To quote the Preface:
This book aims to show that, in fact, building an I/C engine requires no more skill than building other similar working models of engineering subjects. This book is also aimed at those whose interest lies in internal combustion engines, who sometimes have the misconception that these require greater skill in construction than a steam engine, or who believe that model engineering is all about steam.
The book is organized into three parts. The first (chapters 1-3) covers the operating principles of two and four-stroke model engines and concludes with a discussion of the workshop equipment needed for their construction. There have been a lot of books that cover the theory and constructional details of model engines. Dave Gierke's two-stroke book is an outstanding example, as is Peter Chinn's four-stroke book. Where Malcolm's book differs from these is his inclusion of material intended for the would-be engine designer, not just the user. While the discussion is rather high-level, it still involves a bit of math, but no more than necessary.
Chapters 4-18, the second part, comprises the bulk of the book. These chapters contain detailed discussions of the techniques, materials and processes involved in making the engine components. Each chapter is devoted to a type of component, or system. For example, balancing is discussed separately from crankshafts and bearings. For the most part, the text focuses on single cylinder engines, but where applicable, unique issues associated with multi-cylinder engines are presented. Now remember, the author is from a metric country, but as no plans are presented, the issue of metric verses Imperial measurement does not intrude. However, the alloy types mentioned (HE15, EN30B etc) are not going to mean a lot in the USA and many other countries. Some more "internationalization" here, or in an appendix, would not have been amiss.
I think it is correct to say that the prime focus of the book in on four-stroke engines. Two-strokes and other types are not ignored, but do not feature strongly in section two. There are two ways to approach the subject: describe each separately, or describe one, then cover the differences to the other. The book takes this latter path. The prime focus is the four-stroke with the last part (chapters 19-21), providing additional information on two-strokes, radials, rotaries, and unconventional types such as the Wankel and rotary cylinder valve (RCV) engine. The concluding chapter describes operation and is followed by a Trouble Shooting Appendix and a Glossary of Terms. This is a valid approach, but those intent on building a two-stroke and wanting to see examples of the various ways to "port" a cylinder will feel short-changed. Luckily, there's always the Model Engine News construction projects to fill the gaps.
I wanted to like this book, but as a reviewer, I also have an obligation to people who might expend their hard-earned on the strength of my words. So, should you? Yes. This is possibly the best book on the subject of home-built model engines since Westbury's Model Petrol Engines which was published half a century ago. It is not perfect. My review copy came with a slip-sheet listing corrections to be applied to four different pages. Make that five as the URL for Model Engine News on page 101 is wrong too (it's the thought that counts 
). Then there are things beyond the author's control. The art department at Crowood have taken layout liberties that grate on the sensibilities. For example, they changed the aspect ratio of the NE15S "exploded view" photograph on page 6 so that circular parts are distressingly oval. Digital publishing raises its ugly head too. A number of photos look like thumbnails blown up to epic proportion, thus inducing annoying pixilation. This is hard to understand as Malcolm was required to submit 8 maga-pixel images, and did. These effects also are also evident in some of the CAD illustrations. But I've heard my text book writing research colleagues rant and rave over what publishers do with and to their work. Taken on balance, the damage to Miniature Internal Combustion Engines is far from terminal and I have no fear in recommending this book over Westbury's—completeists, naturally, must get both.
You can order it from Amazon
at a substantial discount off list price. The link now has a picture of the cover and their Search Inside™ feature has been activated.
Engine Of The Month: Mills 2.4
Our subject this month is the third and last model engine made by Mills Brothers (Model Engineers) Ltd, the rear-rotary induction, long stroke 2.4cc diesel. As can be seen in this photo, the family resemblance to it's two older, smaller, brothers is striking, but as you'll read, the engine was not well received. I'm also pleased to provide as part of the overall Mills story, an on-line copy of Mills Patent and the story surrounding the patent holder, Arnold Louis Hardinge. The patent copy and the story were generously provided by Mike Harding, son of AL Hardinge. In some ways, Mike's account differs from what has become accepted is the semi-official account of the genesis on Mills engines. This makes the second time I've lit the blue touch-paper this month, so retiring is probably no longer sufficient and I must, like the brave knights in Monty Python's Holy Grail, run away, run away!
Tech Tip of the Month
This gadget seemed so obvious to me that it came as a surprise when others expressed delight on seeing it. It is a holder for piston finishing. As should be obvious, the central section is drawn into the shank by the screw in the end. A dummy wrist pin inserted through the piston and draw-bar pulls the piston down onto the gadget's seat. The shank is gripped in the lathe chuck and the hand held hone/lap applied to the job which will be running close enough to true for finishing.
What may not be so obvious is the way pistons are seated on the tool and the way the jig is made "universal" (within limits). As the skirt walls of a piston are thin, we don't want to subject them to any compression. We also want the shank of the tool to be smaller than the piston so the lap/hone can be easily stroked over the full length. In this photo, the ring is made a close sliding fit inside the piston skirt and longer than the depth of the lower recess in the piston. This means the piston seats on the inner ridge and the thin skirt is under no pressure whatever. A significant side-benefit is that by replacing the ring, the same basic jig can be used with a multitude of pistons simply by turning up new rings.
The cross-drilled hole in the draw-bar needs to be accurately drilled. If it is not at right angles to the axis, it will be impossible to insert the dummy pin, assuming the wrist-pin hole in the piston is correctly aligned. And if it is not central in the draw-bar shank, it will force the piston off center with relating to the ring, making it impossible to slide it over the ring mandrel. Making the draw-bar a loose fit in the jig shank can provide a small degree of latitude, but there is no substitute for accurate work.
A range of jigs like this can be made as the need arrises, but once available, new rings to accommodate new pistons are quickly made. After use, they should be stored with appropriate labelling to say which piston they are for, and perhaps even which jig if you have more than one. Just throwing them in the box is a recipe for chaos— ask me how I found that out!
Editorial
