Model Engine News: July 2007

   MPJet 040
   More on Fuel
   Watzits
   Retro Redux
   Hodgson 9 Video
   My Elfin's Bigger Than Yours
   My Bad

   Editorial
   New Books and Magazines This Month
   Engine Of The Month: Mills 2.4
   Tech Tip of the Month
   Standard Stuff

Editorial

There are less "scattered" updates this month than last, but there are still quite a lot, so be sure to check out the New and Changed Pages index. And I should mention that this page changes every month, so if you are not reading this passage in July 2007, expect confusion. The picture here is Les Stone's new Anzani "Fan" which was added last month. Les has sent in new photos, so it's worth revisiting the Les Stone Tribute page.

There is a lot of new material as well. This month I have the pleasure of placing on-line the original patent awarded to Arnold Hardinge for the "Mills" transfer system. As you'll read below, this has been given to Model Engine News for safekeeping and is accompanied by a piece that may raise the odd eyebrow, or three. There's a lot of other new material too. As well as following the links to the items given explicit mention on this page, be sure to have a look at the Engine Finder which has new and updated entries not given explicit mention. I've been tied up doing IT research related things all month, so long days and cold nights have kept me out of the shop. That is a condition I hope to remedy in July, starting with an engine mount for the Cirrus Mk I, but we'll see...

MPJet 040

Dave Owen phoned late in June to say his shipment of MPJet .6cc diesels have arrived and are selling quickly. These are made in the Czech Republic to special order for Owen Engines, MPJet having ceased production of all IC engines five years ago to concentrate on electric models. One of these will set you back AUS$110.00, plus postage. An optional radial mount is an extra $9.00. All engines carry a limited six-month warranty and are supplied fully boxed, with instructions. Contact Dave via this email link and put "MPJ Order/Enquiry" in the subject to prevent your mail being assassinated as spam.

More on Fuel

Last month I mentioned having received a thoughtful and well researched question regarding kerosine, kerosene, and paraffin to which I had no answer. This mail was prompted by the FCB Marshall Miniature Engine Fuels page and the confusion over what the Brits mean when they say "paraffin". I still have no answer, so I've decided, just this once, to publish a "letter to the editor". This feels dangerously like I'm lighting the blue touch-paper, so I shall now, as the instructions on the glorious fire-works of old suggest, "retire".

Watzits

Two new Watzits this month. The first is an old sparkie that someone just may be able to identify. It currently lives in Sydney, Australia, and may not be far from home, but it's not a production model nor "kit" engine that any of our experts can identify. The second is a rather nicely made and beautifully photographed Compression Ignition Four-Stroke about which there is now no great mystery, but you definitely get top marks if you can identify it without looking at the answer.

Retro Redux

Emails from Brian Cox, noted expert on European model engines, has led to a flurry of updates and new entries all over the place. Have a look in the "New and Updated" list of the Engine Finder to get the full list. Naturally my favorite is going to be a twin—in this case the Retro Twin made by André Demesse, Luxemburg. Brian has promised to dip into his store of information on European engines to expand and correct the material on this site, including getting all those pesky character decorations correct at last!

Hodgson 9 Video

Ever wondered what a Hodgson 9 cylinder radial looks and sounds like in action? The Ageless Engines web site now has a 15 minute video of John Collier's newly finished engine being described and put through its paces. At 41MB, it's a big download, but if you have broadband, it's worth it. Lee Hodgson mentioned in a recent email to Model Engine News that he has finished devising a practical machining sequence for porting the sleeves of his scale Bristol Hercules. Next step is to build a proof of concept single cylinder engine. Lee has been working on this for a long time. His aim is a set of plans and job sheets that will be the equal of the very complete plans sets that Ageless supplies for the 9, 14, and 18 cylinder poppet valve radials engines and the BR2 rotary.

My Elfin's Bigger Than Yours

Right-o, out with the Elfins and the tape measure. Brian Cox sent in this rather telling photo showing an early Elfin 149 alongside a late production model. The early (circa 1950) model is on the left. Its crankcase is 1/8" shorter than the other model which was made in the late 1950's. The threaded length of the later shaft is longer too and there are subtle differences in the webs and venturi.

My Bad

Seems that I've had Roger Schroeder's email address wrong for an extra special long time. It's fixed now, but if you've tried to email Roger by clicking the links on the Classic Model Engine Construction Kits page, I must humbly beg your forgiveness and ask you try again now. Roger's low priced casting kits have been the introduction to this hobby for lots of model engineers. Just have a look at the Roger Schroeder Tribute Page to see examples of engines made from his Classic kits. You need more of these Under The Bench.

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 arises, but once available, new rings to accommodate new pistons are quickly made. After use, they should be stored with appropriate labeling 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!