Here we are at the first day of spring (tra-la) in the southern hemisphere. In the past month, we've gone from as cold as it gets here abouts, to shorts and t-shirt weather. This means that the shop is habitable again and it's time I got down to some long-delayed building.
I had sort of been hoping that the bout of enthusiasm occasioned by the unexpected second place win in the State F2B control line aerobatics championship would fade away. But alas, it has not, meaning something needs to be done about it. So wood has been cut for a new 60" stunter. I'll be powering it with a PA 51 that has been lying around unused for the past 12 odd years and want it to be light. So the wing is being built using the Millennium technique that appeared in PAMPA's Stunt News circa 2001. The jig seen here was made by tack gluing balsa and ply bits to a self-healing cutting board with cyno. After turning two sheets of 1.5mm balsa into ribs, the jig was broken down. This method saved about four sheets of balsa over the normal technique, hopefully at very little sacrifice in strength. We'll see how it turns out next month. Now back to engines, but first, some sad news...
VALE Saburo Enya
Although it has yet to be officially confirmed by an Enya family member, reliable reports emanating from Japan by a person close to the family, state that Saburo Enya passed away around the middle of August, 2008. Anyone with the remotest interest in model engines would instantly know that Saburo Enya was the main engine designer at the Enya factory for half a century. His achievements in model engine design and engineering ranks him as an equal to such other greats as Dick McCoy, Duke Fox, John Brodbeck, Shigeo Ogawa, Juares Garofali and many others of similar legendary status. Saburo would have been about 85 years of age. It is hoped a more detailed summary of this great man's life will, in due course, be written. He has left the modellers of the world a legacy of superbly designed model engines, of top notch metallurgy and with un-surpassed reliability. May he Rest in Peace.
The Rarest Enya?
Model Engine News wishes to thank Bob Allan for providing this short tribute to Saburo Enya, and his efforts to confirm the news through his personal contacts with the family. Bob is a great Enya engine fan and font of knowledge on them and during our email exchanges regarding the sad news od Saburo's passing, Bob provided some outstanding photographs of a very, very rare Enya 60. Visit the new Enya 60 Marine page for more details. Bob has written extensively on matters Enya on the SuperCool Racing Propellers web site. It's way past time this site got added to the Links Page, so it has!
Why do I suddenly feel like doing an Austin Posers impersonation? Continuing on from the ED Baby construction series begun last month, part two presents machining of the crankcase and backplate. As always, it is important that the bore for the crankshaft and cylinder be at right angles if running friction is to be minimal. Part two of the ED Baby replica construction series describes a jig that will work well for this, provided the underside of the engine mounting lugs can be milled flat in the plane of the crankshaft axis.
Updates, Updates, Updates
More photos arrived from Charlie Tomalesky and Darrel Peugh which you can see in The Gallery. Pictures on Darrel's page commence with Dick Morris' 1.20 cuin engines and the unusual Hellrazor 90 seen here. Perhaps the word "photo" is not quite right for Charlie's work, but it will do. The new entry on this page is the Arden Super Atom. The complex ignition timer on this engine results in a most satisfying snap sound from the points as the close. Don't know if it helps, but it sure feels like it must.
We have also received photos of a disassembled 4-Some diesel from John Towell (some time in the future, the engine will be refurbished and measured by Motor Boy, Eric Offen. Onkel Eric gets to play with the nicest of things ). These photos have allowed, or more accurately, required a revision of Adrian Duncan's page describing the construction of the 4-Some. As well as moving the engine somewhere near to top in the all-time "why did they do that" category, Eric's photos provide almost overwhelming circumstantial evidence that supports our belief that both the 4-Some and Kalper were products of the same designer. Click the link to visit the update location in the Kalper page.
New Books and Magazines This Month
Issue #15 of Model Engine Builder arrived during August. In the previous issue, editor Mike Rehmus had warned that he was about to expand—if you'll excuse the pun—to include steam engine projects. But there would be no decrease in IC content as new pages would be added. This is exactly what has happened and I think the issue is one of the best ever. Included are the first parts for build articles describing a simple, fully fabricated, horizontal "mill" type steam engine, and a very nice bar-stock four-stroke aero engine designed by Canadian, Brian Farey. Brian sure knows a thing or two about high performance FAI team race diesels, and this design shows that his skills are broader than that. It's one of those elegantly simple sort of designs that almost magnetically draws you towards the shop.
But it is the center-fold piece that really got to me. This is a fascinating and in-depth look at a variation on the Wankel rotary and differential rotary concept used by Mawen and Clifford. The engine, dubbed the "Hale Rotary" after it's designer, Jerry Hale, provides yet another way of doing away with the diabolical poppet valve. Jerry's engine has a rotating block of four open-top cylinders rotating inside a stationary ring. Openings in the ring provide inlet, exhaust and ignition at the appropriate time as the cylinders and attached power take-off rotate. It is not really correct to lump the Hale Rotary with the Mawen and Clifford, as the designer has accomplished the job of providing four-stroke cycle events without any gearing. He also uses a trochoidal cam to move the pistons rather than the common over-hung crankshaft and master/slave rod arrangement. A while back, I had the opportunity to inspect the Clifford differential rotary, some details of which appeared in SIC issue #67. My comment to the prospective investors was that oil control, compression seal life, general wear, and gyroscopic effects might be a development problem. Jerry is quite up-front in saying the same thing about his design. That aside, I especially like the way he has managed to achieve gas seal of the open top heads using what is essentially conventional, circular, flat, piston ring technology (unlike the Mawen and Clifford differential rotaries), without having to resort to spring assisted seals to provide sufficient compression for starting—and we'll come back to a related subject in a minute.
In the same issue, Ron Cairns' RICE Report details the CKE radial disk engine. This replaces the master/slave rod common to most radial engines with an articulated "foot" that rides in track on a disc driven by a normal looking over-hung crankshaft. The engine also uses electronically actuated poppet valves to good advantage. Ron's dissection points out the positives and negatives. Then there's an informative and useful description of a practical dynamometer for model engine testing and the rather sad news that Robert Washburn, once editor and publisher of Strictly Internal Combustion magazine will no longer be supplying a column due to ill health and advancing years. I don't know which retirement Bob is on now, but whatever number it is, he's sure earned it. Another change in this issue is the stapling together of the plan pages to conform to US postal regulations. The staples have been placed in the fold, but near the edge of the pages, so the inconvenience is minimal. Although they do prevent the plan pages falling on the floor while you are reading, I'd say remove them as all magazine staples seem to rust over time and make a mess, probably due to acid in the paper.
Now on to a book that was scheduled for a leisurely read during September, with an October review. It got me in so deeply and quickly that reading took one very engrossed weekend and excited me so much that the review has been stepped up. And I'll reveal that we are talking about a five star review here. It would have got the highly coveted Koala stamp as well were it not for a small omission—and what that is, you'll have to wait a while to discover. The book is The Wankel Rotary Engine: A History, by John B Hege, McFarland & Company USA, 2002, reissued 2006, ISBN 0786411775. The author states in the preface that over the years, his fascination with the engine and position as an auto mechanic placed him in a position to gather together all the fragments of information that chronicle the rise and fall of this unique invention. This he does in 182 pages and 19 chapters, of so-so paper, well if not profusely illustrated by so-so pictures and diagrams. With so many so-sos in the preceding sentence, you have to know this is a work whose worth is standing firmly on the content, not the presentation.
The structure chosen by the author places the basic concepts right up front with later chapters giving the history of the various applications and developments of the engine from niche perspectives. The result is a sequence of histories that build up into a most cohesive overall history of the designer, the engine, the companies that were involved, and how politics and egos blunted what could have been, and still could be, a true alternate to reciprocating engine technology. For those who have been aware of the basic Wankel rotary engine concepts in a broad sense, but have not followed its rise and fall fanatically, the book will fill in the gaps and provide snippets like what did NSU stand for, and how did Toyo Kogyo get into the act? Then there's the brilliant development work done by Curtis-Wright and the executive games played by GMC with a ferocity that makes one wonder if there might not be a special circle in Hell for such people.
The author of a history where the subject is a piece of complicated technology must walk a fine line in providing enough technical information that those able to understand it don't feel they are being short-changed, while those who do not—and don't particularely care—don't loose the narrative and give up on the techno-babble. I think Hege has managed this aspect very well. A talented model engine builder could design an engine from the information in this book with a fair chance of success, while an RX-7 fanatic who simply wants to know how it all happened and where it all went wrong will not be bored. Yes, there could have been more information provided on apex seal metallurgy, and the illustrations could be better and more exciting, but anyone wanting to know more about the engine, its designer (imprisoned at different times by both the Nazis and the Allies), the companies involved, and the technical problems they faced and solved will find this a most satisfying read. I certainly did. Five stars, no question; and available from Amazon for $35.
Oh, the small flaw that lost it the Koala stamp? Nary a mention of the OS-Graupner Wankel. Now, knowing how NSU carefully and diligently applied licence terms and restrictions, I for one would love to know the details of that one, plus how the designers managed to do away with the end-plate seals and dealt with the chatter pitting problem experienced by all the full-size rotary engine manufacturers. While this probably didn't rate a chapter, it should at least have got a mention and been included in the table of licensees, unless Graupner got a special dispensation as a German firm, although from the description of Gerd Steiler von Heydekampf, head of NSU, somehow, I doubt it...
Engine Of The Month: OS Max 15D
Oh yeah, you say, so someone has done a dieselization of an OS Max 15 glow, what's the big deal? Well first, the someone in question was OS themselves, and what looks like a stock, plain bearing Max 15 is most definitely not as the careful examiner will instantly see all the tell-tales of a twin ball race engine. This is a rare bird and a recent eBay offering went over $300 even before the final bid-robot clash (the auction was pulled, so we can't really say what they are trading for at this time). But as might be expected, Adrian Duncan has one under the bed and this month he tracks the history of the engine and delves into what makes it rather unique: a diesel with a cross-flow, baffle piston! Click here for the OS Max 15D review.
Tech Tip of the Month
If you have a mill and a rotary table, you are going to spend a lot of time centering the table under the quill. The most accurate way is through the use of a co-axial DTI, but somehow, despite having a rather nice one, I find that I can hardly ever use the thing because the amount of vertical space it requires and the sad fact that I can't change the head height of my round column mill/drill without loosing X-Y positional registration. Fortunately there's a way that provides quite acceptable accuracy using a GHT-type edge finder.
To explain: this sort of edge finder has a ball socketed probe with a lapped cylindrical tip. The ball is under spring pressure, so tends to stay where it is nudged to. When mounted to the spindle, spun, and brought up to a flat, or round surface, contact tends to knock the probe towards the axis of rotation. Coming closer reduces the "cone angle" of the probe until it is perfectly aligned with the spindle axis at half the probe diameter from the work. Moving past this point by even a few tenths of a thousandth throws the probe violently off to one side thus giving excellent indication of the edge distance in relation to the spindle.
- You need to know the precise diameter of your rotary table, or the work clamped axially to it. You also need to know the diameter of the spud end of the edge finder. Add these two numbers together and divide by two. We'll call this value "L" (the spud is usually lapped to a very accurate 0.2000" diameter making it east to add 0.1 to the work radius, or 0.099 if you need to allow for kick out as we shall see later).
- Grip the edge finder in a drill chuck (or collet) and eye-ball center it on the rotary table. Zero the X and Y dials with the backlash taken up in a known direction (or zero the Digital Read-Out and forget about backlash—DRO's are worth their price for this alone!)
- Wind the Y axis in the opposite direction to the taken-up backlash (if no DRO) until the edge finder is clear of the table or work piece. This will be distance "L", plus a margin.
- Set set the mill to low speed and lower the quill until the edge finder spud will contact the circular surface. Start the mill and wind back very slowly until the edge finder "kicks out" indicating you have just gone past a known distance (one half the spud diameter) from some point on the curved edge of the work, or table. Stop the mill and reset the Y axis dial or DRO so it reads distance "L".
- Crank the X axis a similar distance "L" plus a bit, then wind in the Y axis to precisely indicate zero, observing backlash directions. Repeat the kick-out maneuver in the X direction. I find it helpful to place a finger on the work near the edge finder so it does not kick-out wildly and try beating the table and itself to death and destruction. Reset the X dial to distance "L".
Ok, what's happened here? We set the zero-zero point to a guess, then indicated two orthogonal points on a circular surface, resetting the dials by the known distance of work (or table) center to edge finder spud center each time. This effectively moved the zero-zero position a bit closer to the real center alignment. If we repeat steps 3 through 5, the dial or DRO indicated center will be moved closer to the actual axis alignment center a little more each time. When you find that the edge finder is kicking out at distance "L" indicated on the dials, you must be accurately centered. In practice, this generally takes no more than three X-Y centerings and is accomplished in a lot shorter time than it has taken to read this procedure and understand it.
I always perform the operations in the +Y and +X directions for no readily apparent reason. If you are dubious, after arriving at the center position, crank out in the opposite X and Y directions and repeat. If the game is fair and you've correctly taken up backlash in the absence of a DRO, the kick out points should again be at a distance "L" on the dial readings, proving the table and work if any, are centered under the quill. If there is an error, it will be small (0.001" or less) and is probably due to how much the edge finder had to go past center to kick out. This will be exacerbated by winding too fast as you approach the kick out point, so go real slow so any error is minimal. You can always "split the difference" on the dial setting, or take off an allowance for kick-out from distance "L" in step 1. In practice, I've come to trust this method completely when centering round stock under the mill.
To close with an acknowledgement, the technique is not mine—I'm not that smart. I read it in Guy Lautard's Third Machinists' Bedside Reader and think the book was worth it for that tip alone.