While it has absolutely nothing to do with model engineering and engines, I had a total ball this past January with two get-togethers of old musician buddies, one of whom I haven't seen for close to 40 years (the bass player, right, in the first photo, with yours truly, left, on guitar). The first weekend jam lasted three days as we abused old jazz stand-bys. The second jam, a week later, had a slightly different line-up playing mostly pop and rock. I don't care what it is. To quote Willie, I get such a kick out of playing music with my friends that I'd happily play country and western if that was what was put in front of me. Next jam, combining as many of the old has-beens as possible, is scheduled for March and my 65th birthday.
The piano player—not in the photos 'cause the back of his head is boring—flew into Maroochydore from Dubbo in his A-36 Beech Bonanza, not knowing that on the day he left, the Australian Civil Aviation Safety Authority (CASA), had grounded the entire fleet over a potential frayed elevator cable issue. Ruthie and I heard the announcement on radio as we were getting ready to drive to the jam. Roderick went a bit pale after we told him, and convinced him we would not joke about such a thing. Several phone calls later, his maintenance people assured him his cable was fine, but to comply with the airworthyness directive, he'd have to have it inspected again after he flew home. Seems excessive, but what price safety?
Just for grins, here's an old photo scanned from a 35mm transparency, circa 1973, showing younger versions of the two in the first photo above. The bald bass player above is the hairy sax player below (he still blows a mean sax, too). I'm still playing the same old red Fender Jazzmaster, but no longer own any loud Hawaiian shirts. The bass player (middle) in this photo and I worked together musically for about 10 years. He was always into health, exercise, and good living. He also died of a massive heart attack about five years ago while the rest of us degenerates seem to soldier on quite nicely, thanks very much. Gotta be a moral there, somewhere.
This time last year, my home state was assessing the after effects of massive flooding. Well we're doing it again, but thankfully, this time it's only bad flooding. Long-time readers will know that until last year, the annual complaint had been the seven year drought. Guess that when it comes to weather, there's just no pleasing some folk.
Ok, enough of all this sinful reminiscence. Back on topic and on with the show...
Last month, after careful research and consultation, we awarded the HP 61 the gong as the first commercial, Schnuerle ported model engine. A reader questioned this, drawing our attention to the Cox Special .15 Mk II, as reviewed by Peter Chinn in the March 1966 Aeromodeller. We had in fact considered and rejected this engine while searching for "the first" for a number of reasons, nevertheless, the engine's porting is interesting, hence this item. As you can see from this photo from the Chinn review (nobody I know has an example of the engine), the cylinder has a single exhaust and transfers not unlike Schnuerle+boost porting. The reasons we decided it was not was that even though the side transfer ports will tend to converge the new charge streams, the direction will be primarily upwards, while Schnuerle ports direct the flow against the cylinder wall opposite the exhaust. Second, the boost port and the transfer ports all open at the same time (according to the review) which is not what we expect today. And last, but by no means least, Peter Chinn does not call the porting Schnuerle and there is no doubt he knew about it, having previously mentioned it in regard to the K&B/Wisniewski "Wart". Hence we decided that the porting of the Mk II Cox Special was interesting, innovative, but not Schnuerle.
On a related topic, I had some hopes that Irving's book on two-stroke design might give us a definitive who and when for the person or company that first added a "third port" to the standard Schnuerle setup so that the confusion of last month might be mitigated somewhat. No such luck. Irving makes no mention of Scott, but describes two "boost" port schemes attributed to Zündapp (1933), and Ehrlich (1956). By coincidence, just after reading about these, a search in old issues of the Aeromodeller led to an article on boost ports for model engines by Mr R Kinnersly, which also deals with the Zündapp and Ehrlich types. As you'll see from the article, the Zündapp type (as adopted by Kaaden—see last month's book review), also provides some additional lubrication of the little end, plus cooling of the piston crown. However there is a third approach not mentioned by either reference where the third "boost" port and associated transfer passage simply connect to the crankcase cavity, just like the other ports. It is this type which we commonly see today in sport class "Schnuerle ported" model engines, probably because it is simpler to manufacture. An example would be the OS FSR series, circa 1980. This series featured a cast cylinder and are a type we really should review, some day.
Building the Little Demon V8
Readers should remember the Little Demon V8" auto type engine designed by Steve Huck who also provides plans with a very diligent update service to registered owners. Steve has begun putting together a series of web pages describing construction step by step. These will be of interest to builders of the engine, would be builders, and those who enjoy watching how it's done. Click on the thumbnail to be taken to Part One of the series.
The Engine Designs of Elmer Wall
As has been pointed out to us more than once, a name which does not appear in these pages and really should is Elmer Wall. Elmer was born in Sweden about 1870, emigrating to the USA in 1891. By 1904 he had begun designing and making miniature gas engines for his son. By 1938, this had expanded to a catalog containing nine different types. Elmer died in 1947. His designs and patterns subsequently passed through several hands, but are no longer available outside the occasional eBay posting. Today, Mr Reed Martin (USA) has assembled a large collection of assembled Wall engines which he regularly exhibits at model engineering shows all over the US. To redress the lack of recognition to Elmer Wall and his designs, we've added a special Elmer Wall Tribute page to the Engine Gallery. As with our other Tribute pages in the Gallery, this will grow over time as more photos are received.
As you should know from Adrian Duncan's review, the first diesels made by International Model Aircraft Ltd and released under their "FROG" trademark, are referred to by collectors as the bicycle spoke FROGs, hopefully for obvious reasons. The four engines in this photo were restored by Jon Fletcher (Oz) and are a good example of the types. Jon reports that the hardest part of the restoration (including reboring, conrod making, 10BA plugging and retapping), was making the closed-end, Thackery springs for the compression screws. These are made from flat spring steel, not wire, and I've don't have a clue regarding how I'd tackle that job! Well done, Jon...
Vltavan 15 and 29 Revisited
What to do when new information comes to hand on an engine which we've already reviewed? When the new data is not too extensive, we modify the file and try to point you at the changes (I'm not in favor of change bars on web site documents). But when the changes are extensive, we think it's better to simply replace the original page content entirely. That is what we've had to do with two old friends from 2007: Adrian Duncan's reviews of the Vltavan 15 and the Vltavan 29. Adrian's new pages are more extensive, more informative, and more accurate, so forget what you knew previously...
Next Month's Members' Free Plan
Model Engine News exists from month to month through the proceeds from sales of our MEN ONLY DVD (plus the occasional plan set). Buyers of the DVD become Life Members and get private access to a growing list of downloadable plans in PDF format with new ones added twice per year in December and March (don't ask). One of the existing Free Plans is the PMC Imp. The example seen here, slightly modified, was built by MEN Member, John Ward. John completed it in three weeks of evenings and declares the project a complete success. Because he happened to have a 0.375" cylinder lap on hand, and because the cylinder wall thickness would take it, John decided to make an economical reuse of existing tooling—something I've done myself more than once 'cause making laps is boring, no pun intended . The original bore was 0.314" and because displacement varies as the square of the bore radius, the displacement went up from 0.62cc to 0.89cc (0.054 cuin). John's photo of his PMC is timely because next Month's Members' Free Plan will be the the EmBee, the progenitor to the PMC Imp. If you are curious, have a look at the PMC Imp review to see how the EmBee differs.
New Books and Magazines This Month
As everybody should know, the References section of a book is frequently an invaluable source of information on where to find more information. While digging further still into the history of Schnuerle porting and the operation of the "boost" port in one of my more technical references, The Two-Stroke Cycle Engine, Heywood and Sher, 1999 ( on account of just how technical it is), I was rather surprised at how little space it devoted to this topic. The authors did however reference another book when mentioning the subject. Although out of print, ABE Books came to the rescue, as usual, and a copy was obtained. The book title is Two-Stroke Power Units and I'm almost tempted to give Heywood and Sher an extra half star for providing the reference...
My copy of Two-Stroke Power Units: Their Design and Application, PE Irvine, George Newnes Limited, London, 1967, (no ISBN), is a hard-bound, first edition with 288 pages, well illustrated with black and white photos, drawings, and graphs. There is also an American edition which is slightly smaller in size and may be more plentiful these days. Now there's a couple of names you might recognize in the opening paragraph: George Newnes, and Phillip Edward Irving. The Newnes publishing company we've had need to reference more than once. Phil Irving's name may be familiar from one of his other books, Tuning for Speed, considered by many to be one of the most important books published on the subject for older (pre tuned pipe) bikes.
Two-Stroke Power Units is one of the most practical books I've ever read on the subject. Of the fifteen chapters, the first ten cover individual aspects of the two-stroke, such as "Scavenging, Breathing and Power" (ch 2), "Some Factors in Design" (ch3, excellent!), "Cylinders, Pistons and Rings" (ch4), etc, etc. The next four deal with the different applications of two-stroke engines: road, marine, stationary and industrial, and racing. The last chapter covers tuning for speed using a more modern context than his 1948 book. The book concludes with an appendix of conversion factors, a bibliography, and a very extensive index. Sadly, Irving makes no mention of model engine sized two-strokes in the book—not even to say they are purposely omitted, and I can't believe he would have been unaware of their existence. I'll have a little more to say about this later.
I can't possibly give a précis of the book's overall content in the space nominally allocated for MEN book reviews (got to avoid the glazed-eye phenomena, you know). Taken from the perspective of his class of engines (chain-saw sized upwards), he does an exceptional job of describing all aspects of two-stroke design in a practical way, alerting his reader to all the compromises and trade-offs one should consider with respect to the intended application. His use of formulae is minimal, but certainly not zero, 'though he does restrain himself to their use only when unavoidable, eg, when calculating the Pitch Circle Diameter (PCD) for the rollers on a roller bearing big-end. Another approach I know model engine designers will appreciate is the way he quotes timing figures and their effect when discussing the two-stroke cycle (more technical texts, such as Blair, approach this from a gas flow perspective—more correct, but too theoretical for many). The example page here shows a table comparing the Exhaust, Transfer, and Inlet timings of many different classes and applications of engines. Most are "three-port" designs (ie, piston controlled like the old Deezil). Many of these are typical of what we'd expect in a model engine designed for a similar type of application; perhaps a bit "wider" in some cases.
Irving devotes quite a bit of space to Schnuerle porting (even if he does spell it "Schnürrle") and the various types of "boost" ports which have been added over the years. Reading about these is bound to give an engine designer thoughts about things to try. I rather like the boost port system patented by Dr J Ehrlich, further developed by Bristol Siddley Engines Ltd. This uses ports in the piston to "charge" chambers connected to the boost ports which are then isolated so that when they open (shortly after the Schnuerle ports), they will be at a higher pressure than the crankcase. At model sizes, the volume would be so small, I doubt it would be effective, but it is interesting to think about. One concept described in the book which was new to me is the Kadenacy Effect and how this applies to quickly opened exhaust ports and scavenging (Google it).
I could go on and on. Zimmerman (rotary) inlet valves get good coverage, as do tuned pipe exhaust systems, reed valves, engine balancing, desaxé, etc, etc. In almost every case, I found aspects and ideas presented which of which I'd been previously unaware, or which were discussed in a way that increased my understanding. Two-Stroke Power Units is probably not for everyone, but if you like to tinker with engine design, even just on paper, this book should be on your shelf. I have doubts about how some of the concepts which are beneficial in engines over 100cc would work at sub-10cc size, but finding out would be part of the fun. An unreserved Five Stars for this one. Out of print, but I notice that a few copies of the American edition are available from Amazon Booksellers.
Engine Of The Month: Fuji 099's
Adrian Duncan is back this month with the third part of his epic story on Fuji's Model Engines. I'm frequently amazed when I receive Adrian's raw text for formatting into the "house style" at the depth and quality of his research. Let me go on record as saying that "amazed" is an inadequate description for Chapter 3 of the Fuji Story and I felt the need to resort to "astounded", or even "whelmed" (I'll keep "overwhelmed" in reserve for later ). The new installment deals with Fuji's .099 cuin displacement engines and I very much doubt that a more in-depth examination of these engines has ever appeared anywhere before, in any media or language. Adrian and his co-researchers really outdid themselves this time!
Tech Tip of the Month
We often receive emails asking for help regarding aspects of model engine design. Some of these, generally from engineering students in India, seem to want their thesis provided for them by return email; they get pointed at the relevant text books. Others request an answer which would consume a text book, though perhaps they don't know this. Where we can we point them to information on this site, or the web in general which may help.
As far as I'm concerned, ignorance is fine—if you don't ask, you never know. This was the case last month with a reader who wanted to know "how to exactly balance a single cylinder engine". The word exactly was bold, underlined, which is a bit of a red flag because that is physically impossible and so suggests that our correspondent may have a bit to learn before getting concerned with fine-tuning a design. The best that can be done is to approach balance at TDC and BDC. In between, that balance weight acts against you.
The accepted rule of thumb for model engines is to provide a crankshaft counterweight equal to one half the reciprocating mass. This means, the weight of the piston, wristpin, and the weight found by resting the conrod little end on a balance while supporting the big end. You should also add the weight of the crankpin, if feeling particularly pedantic, but remember that whatever you do, it is just an approximation. Our Book of the Month says the figure used for balancing single cylinder competition motorcycle engines varies between 30 and 70%! And we know that makers of many small sport model engines don't bother at all, with quite acceptable results.
I knew we'd touched on this subject before, but nothing appeared in the How-To Index. A search using the Site Search for "crankshaft" + "balance" on the same page gave 64 results, but knowing it would be an Editorial page, we found it easily, and a link to it, via this entry, has now been added to the How-To index. Visit the March 2004 issue for the original and rather extensive Tech Tip.
Lost Pages Restored
Last month in the HP .61 piece, I lamented that an external site referenced from our Bill Wisniewski obituary entry had gone away and was probably lost forever. The Internet Archive tries to archive the entire world wide web at regular intervals, but sadly, this did not work for us—in fact, the first ever web page posted in 1991 by Tim Berners-Lee, has also been lost forever. But I'm pleased to say that thanks to the foresight of our old mate, David Burke of Adelaide Aeromotive, we've rebuilt the missing pages, fixed all the broken hard-coded links, and now host the data on this web site. This means they'll never go missing again—cross fingers. Thanks DB!
This section is intended to alert you to little things that are hard to expand to a full news item, or cunningly wind into the Editorial, but are worthy of note never the less.
- We often receive emails offering engines which the writer wants valued, or to sell. Please, Please, PLEASE tell us where in the world you are located. Sometimes the email domain name gives the general location away, but just as often, it does not. This plea is so important, it is now part of the Standard Stuff waffle—not that we expect folks read that more than once, even if that... *sigh*
- A redirect page for Elmer Wall has been added to the People section so that his name appears as a Pioneer.
- The Dick McCoy Tribute Page has some new images.
- The Poppet has been added to the list of Vic Smeed free flight designs.
- A photo attribution has been added to the Morton M42 page.