The year is nearly gone and I've not accomplished the three things I set myself to definitely do this year—and no, I'm not going to say what they were; I'm far too embarrassed! Besides, there are two months remaining and who knows? The horse may yet learn to whistle (if it does not croak from equine influenza first). The Wide Brown Land has been getting some rain, although not as much as we should be getting under the influence of la Ninia, so the drought continues. We've getting one hell of a lot of largely useless, brief, destructive thunder storms too. Already it's hotter than I remember it being at this time of the year and with all the dryness, I can only hope we are not subjected to a bush fire season like that which has just caused so much suffering in southern California. Another not completely unexpected side effect of the drought is the rise in prices at the supermarket and the disappearance of grapefruit juice from the shelves. There's a Federal election looming here at the end of the month and the pollies are outdoing each other daily with hand-out pledges. I'd vote for the one who promises to Save The Grapefruit, except then I'd know for sure that he/she was lying!
And wonder of wonders, the Australian dollar continues to increase against the US Greenback. Not all that long ago (ok, five years), an ozzie dollar—or South Pacific Paso as we called it then—was worth less than US$0.50, now it's trading at over 91 US cents. If this keeps up, I'll change the default price for the Model Engine News DVD from US dollars to Australian dollars. Unsurprisingly, the current government is saying it's all their doing. I think they are rather like the artificially inseminated cow: something wonderful has happened; they are not exactly sure what, why, or how, but it sure has put a grin on their face. Voting here is compulsory, which is probably a good thing given how few of us there are. Not to be too cynical, but making the Great Unwashed register their will at the ballot box prevents the agenda from being hijacked by Rampant True Believers of either persuasion. But regardless as they say, it will still be a politician who finally gets elected, so what does it matter? Democracy being after all, the worst form of government except for all the rest.
Last month was another record month for the Model Engine News website. The total traffic registered an all-time high at 17 gigabytes and the total unique visitors (as near as web stats can determine) hit over 16,000 which is another record. Each month, I get an email from someone else who has recently retired and decided that mutilating metal will be a great way to spend their time, to which I agree entirely. This past month I got a 'mail from the other end of the spectrum: a young guy in his twenties who has inherited a nice model engineers' workshop and plans to put it to good use making engines for no particular reason other than enjoyment. It's really great to see that people who enjoy making things with their hands are still out there and not entirely confined to the codger end of the band—unlike model airplane building where the RTF now reigns supreme. Even some of my contemporaries whom I'd rate as Master Modelers are going this route, saying they could not buy the materials to build something like a high-tech F1B Wakefield for what they can get a finished model for. But we're all as busy as lizards drinking these days, so it comes down to making the spend so as to maximize the fun in your valuable spare time. Some like to fly. I've just about had to give that up so I can build engines that never see airframes. Oh well, down to business...
CamCalc Mk II
The original CamCalc program was written ages ago as a "command line" utility to generate tangential lift values from a set of parameters describing a harmonic cam. These values are used to generate the cam by milling down to the calculated value at small rotational increments. This worked well for me, but as command line utilities are for computer nerds only, it was eventually wrapped in some HTML and a Java Applet skeleton, then placed on this web site so others could use it. Many have, and have been happy with the result too, but I've always felt that from a web master perspective, it was a bit of a kluge. As they say across the pond, this dog has fleas.
Java had been used because I know and trust it, but earlier this year, a colleague convinced me that the math package in PHP was up to the task, so I did a rewrite as a way of learning PHP. As well as producing the cam milling data, the PHP version graphs the velocity and acceleration for the cam profile, and unlike the Java version, allows you to cut and paste the table data from the page into a spreadsheet. The data produced by the PHP version has been validated against the Java version (they agree!), so I'm now prepared to crawl out on the limb and declare the PHP version ready for prime-time. The Design Center page has been updated so you can still choose the old Java version, or the newer PHP version, but eventually, I'll retire the old version. Like the Engine Timing Diagram generators on the same page, the code has been written so it can be invoked with preset data allowing other pages to include buttons that produce cam data results. For example, the button below will produce the inlet cam data for the ETW Whippet, and that neatly segues into the second news item for the month...
Not, in this case, the winning strategy frequently suggested by my Mouse Racing pit crew person, rather the ETW side-port four-stroke that has been making an irrepressible appearance in this column for the past few months. This month, we kick off a new project to construct a pair of Westbury Whippets from Hemingway Kits. This may seem like greed, but I've proven before that two engines can be built at the same time with a lot less effort than two separately, and there's a valid reason for building two of them. The first installment examines the background of Whippet, explains the purpose for the pair, and makes a start on the crankcase(s). For the moment, I'm going to rate this project as suitable for the intermediate level model engineer. We'll see if that gutsy call needs to be revised as work progresses. Click the thumbnail to go to the page, call up the Projects Page, or see the New and Updated Page List for other ways to find it.
Rings To Order
Need a piston ring for some old and obscure engine? Frank Bowman should be able to help, and at a very reasonable price, too. As well as standard compression rings for engines like the ETA 29, Dooling, Enya, etc, Frank can also supply Dykes rings for engines that use them such as K&B, McCoy, Veco and others, or even for pistons with pins, like some from OS, Super Tigre, Thunder Tiger, etc. Frank says that making a good ring is a skill; making a fine ring is an Art! He will reproduce nearly any model engine ring. If the ring you want is not available from his list, he'll need a good piston and cylinder to measure, or you can send the motor. Prices range from US$9.00 for a plain ring for engines .65 cuin and smaller, up to $15.00 for a Dykes ring for engines .66 cuin up (shipping extra, with quantity discounts available). Email Frank at ringmaster (at) msn.com for his latest price and availability list. His full contact details have been added to the Suppliers Page. And kindly mention Model Engine News when ordering so he knows who to blame.
Last month, mention was made of Yet Another Elfin reproduction being marketed through Hobby Club in the USA. Kiwi reader Chris Murphy was sufficiently moved by this announcement to part with some hard-earned for an example to add to his growing collection of Elfin reproductions. Alas, no kick-back, graft, or bribes flow to Model Engine News for sales like this, but Chris has kindly taken the time to take some shots of the engine and put down his observations on this not inexpensive engine. Click the thumbnail, or this link for Chris' review and an inside look into a well made engine with the world's most unusual theory of crankshaft counterbalancing.
Top of the Pops
Every month, despite the highly erudite and painstakingly researched feature articles, the most viewed pages (after the Editorial) are the Gallery and the Watzits. So to keep everyone happy, this month we have new entries in both. For example, Page Five of the Gallery (the Les Stone Tribute Page) was viewed over 1,200 times during October—and it's safe to assume that this was not Les admiring his own work as he's produced yet another engine for the page this month. In the same period, the "current" Watzit page (where new Watzits get added) got hit on just over 900 times. In comparison, the ED R/C page, which involved weeks of research and hours upon hours of composition and editing attracted a meager 251 viewers, while last month's Engine of the Month fared not much better at 333 views. The October Editorial page was viewed by 9,500 different readers.
New Build Project at the Craftsmanship Museum
Joe Martin and the crew at the Craftsmanship Museum have kicked off a second group engine building project. The engine this time is Jerry Howell's water cooled V-4, a "bar-stock" project. Progress photos are appearing on the new web page (click the thumbnail to go direct to the page). Right now, the completed engine photos on the page show Jerry's prototype which illustrates quite well that a bar-stock engine does not have to look like one!
The Ageless Sleeve Valve
Back in July this year, we reported on the progress that Lee Hodgson of Ageless Engines has been making on his sleeve valve radial design. Well word arrived this month that the single cylinder test rig mentioned in the earlier news item has just run successfully for the first time. The test rig pictured here was built to validate the port timing. As can be seen, it has no oil system and currently uses automobile points and an R/C carby for simplicity. Lee reports that it started easily, first time, heated up well with no sign of seizing and that subsequent tear-down for inspection revealed no damage or adverse wear. The cylinder has a bore of 1.375" and the stroke is 1.625". The steel liner runs in an aluminum cylinder with two rings in the "junk" head and two more rings on the aluminum piston. The cylinder motion is imparted by a small offset crankshaft and ball joint, geared to the main crankshaft, just like the Bristol Hercules it is modeled from.
The ultimate design will be a 14 cylinder, dual bank radial with full lubrication system, electronic ignition, and a total displacement of 34 cuin (554cc). Lee is working hard to ensure that not only is his design a success, but that others will be able to replicate it using the tooling and techniques he is developing—only then will the plans be prepared and released. More information on the engine and the other Ageless designs can be seen on the company website. Reaching this point is a milestone and while there is a way to go yet, Lee is certainly to be congratulated on this achievement.
I don't watch a lot of TV. This allows me insulate myself from most insults to average intelligence by being very selective. While scanning the local cable guide this past month, my eye was caught by a History Channel documentary on Sir Frank Whittle titled Whittle: The Jet Pioneer. Having just read and reviewed Whittle's biography here the previous month, the serendipity of the scheduling seemed too much for coincidence, so after setting my time-shifter to grab the program, I went looking for the "third" event, as they say things like this happen in threes. It was a stretch, but I found it, more of which in a moment.
If you have the chance to watch the Whittle doco, do not let it slip by! It is well produced, informative, and includes lengthy sections of an interview with Sir Frank himself, recorded before his death in 1996. For balance, it also includes recorded interviews with Dr Papst von Ohain (both pictured together above) who designed the turbo jet engine which was the first to fly in the Heinkel He 178 in August, 1939. Many sources, including the History Channel documentary, assert the German work was derived initially from ideas appearing in the Whittle patent of 1930. This patent effectively placed the concept in the public domain following the refusal of the British Government to act on Whittle's offer of his concept. Britain's first jet, the Whittle powered Gloster Type E29/38 did not take to the air until May, 1941. British officials chose not record the event, but fortunately, an amateur cameraman did and the footage of both first flights appears in the documentary. Also included is an all too brief segment of a pair of RAF Avro 504N's performing a "crazy flying" sequence, presumably with Flying Officer Whittle at the controls during the Hendon Aero Pageant of 1930.
The 50 minute program covers the same territory as does the book, made more "real" by Frank Whittle's narration. Several still shots are recognizably taken from the photos appearing in the book reviewed here last month, including the cover painting showing Whittle standing before his first experimental engine, no photos of which survive. Some events are illustrated by short extracts from an earlier RAF documentary featuring a younger Frank Whittle reconstructing the first self-sustaining run, and run-away of the WU (Whittle Unit) engine. The "acting" is so amateur it is positively charming. In the recorded interviews, Whittle comes across as earnest and humble. At times he displays an understandable degree of frustration and regret but surprisingly little bitterness over the way he and his invention were treated and the delays this incurred—he was a most remarkable man. I've set the "keep" flag on my hard-disk based recording of this one—altogether, quite a treat for people who love engines, aircraft, and the history of both.
New Books and Magazines This Month
It's Internal Combustion, Jim, but not as we know it. Readers could be excused for assuming that my thinking is well and truly rooted in the 1950's. I'll concede that description—'though maybe rusted-on would be more apt. I know that diesels are so yesterday and turbines are like now, but I just don't get as excited by the smell, plus the sound of tiny, hot things spinning at 150,000 RPM just scares me witless. But I have harbored thoughts of making one someday and to this end, I've had Kurt Schreckling's book sitting quietly on my shelf for the past 12 years. This is the second reprint of 1995 and the subject of this month's review, thus completing the turbine trifecta.
My first plan was to review Gas Turbines for Model Aircraft, by Kurt Schreckling, ISBN 0-9510589-1-6, 2nd edition, Traplet Publications, 1995. But as I re-read it, I began to realize just how far model gas turbines have progressed in the past ten years, so I ordered a copy of the latest Schreckling book, Home Built Model Turbines, ISBN 1-900371-37-5, Traplet Publications, 2005, to see how home-build turbines have evolved. The different title should have been a give-away: this is not an update or revision of the earlier book, it's almost 100% new. Although there is some unavoidable overlap between the two, they reflect a market change from highly technical experimenter to an almost everyday user. The first provides excellent coverage of the design process including performance and material stress calculations. The new book omits this entirely. Both include a very detailed construction section, including full size plans (two in the case of the new book). The engines however, are totally different animals. Of necessity, the FD3/64 detailed in the first required the builder to fabricate compressor and turbine stages. The later KJ-66 and TK-50 are able to use off-the-shelf components. From a technical standpoint, I prefer the first. But if I was going to actually build the thing, then the choice would overwhelmingly be the second (unless, that is, I were to suddenly find myself in the grips of an irresistible and bizarre death-wish ).
Kurt's first book details the way in which the author set about designing a practical gas turbine suitable for amateur home construction at a time when no such commercial product existed. His book covers the preliminary experiments used to prove the concept was practical with commonly available materials, followed by the development of the first prototype and a very in-depth coverage of the design process including the calculations to show that properly constructed, it will not be a danger to men, women, and small children. Next he covers how performance can be tested against the calculated figures (a much more precise and repeatable process than that for reciprocating engines), followed by the required accessories and the actual step by step construction with full size engineering drawings and extensive photographs. It concludes with operating procedures and sources of supply.
The book was first published in German (1992). The second edition (1995) was the first English translation and is quite a good job. The text reads well. I spotted a couple of typographical errors in spelling and figure to text symbol usage, plus the not entirely consistent use of Continental conventions such as the use of a comma as the decimal separator. But anyone who can follow the math will have no trouble with the differences and those who can't won't notice! The book serves as a milestone to show just how far we have come in this technology in the past ten years. Kurt's FD3/67LS engine used a compressor stage fabricated from plywood bound circumferentially with resin impregnated carbon fibre. The turbine stage was fabricated from a disk of nickel-chrome steel that was slit radially to produce 17 blades. These were twisted then filed to shape and a hub TIG welded to the center of the disk. Kurt points out that drilling through for a hub would have reduced the strength by half! The part of the book I found most fascinating was the way Kurt worked backwards from the turbine in his design calculations. Using the maximum safety-factored strength of the turbine material, he arrives at a diameter, turbine speed, and operating temperature. From there he moves forward showing along the way what the requirements of the later stage impose on the previous, and that all components will withstand the temperatures and stresses imposed on them, while being within the capabilities of an amateur constructor (who is able to perform TIG welding, hard soldering, moderate machining, and some very precise balancing operations).
The author presents the fully worked example for those desiring to design their own, but says this section can be skipped by builders provided they follow his detailed instructions to the letter. It was reported in SIC that the late Lew Blackmore whose scale Bentley BR2 rotary is a masterpiece from a totally different era, built a FD3/64 from Kurt's book, but was so concerned for the wellbeing of others that he never tried to spool it up. This I can understand, but the kits on offer today to gas turbine home-builders such as the Wren are a total different kettle of fish—as should be expected for £1,400 for the kit, or £1,600 ready to run!
The second book provides some history, general principles and fully describes details of two gas turbine engines suitable for home construction. But this time the focus on design has gone, reflecting the market maturation from experimenter to user-land. The engines are treated as pure construction projects using commercially available compressors and turbines. They are more sophisticated, powerful, and user-friendly too. First, to show how easy it can be, Kurt describes a kit-built engine, the Beohtec J-66. This can be assembled using only simple hand tools, care, attention, and a bit of hard soldering. The other two require a lathe, milling machine, TIG/MIG, and spot-welding. Both books contain chapters dedicated to operations including starting, safety, and testing procedures. All the engines require an external device to spool up the engine for starting. A major advance is evident in the use of computer control of the fuel supply in the modern engines. Current kits like the Wren mentioned earlier carry this even further by including an integrated electric starter for "press and go" operation. A very informative feature in the second book is a table that compares parameters like exhaust temperature, maximum RPM, pressure ratio, RPM, etc of the two engines described with the primitive FD3/64 from the earlier book, and a commercial product. The advances are startling.
Even if you've no intention of building such an engine, seeing how others have done it may be inspiring. I'm ranking the first book slightly higher at four and a half stars , verses four for the second. Someone who likes math less than me might easily reverse those scores. Both books are available from Amazon, though Traplet Publications is probably a better source, even if they don't send me graft, or review copies...
Engine Of The Month: ED Mk III
Honestly, it's not like I'm obsessing over the English company Electronics Developments Ltd and all its works, even though it may seem that way of late. This month's old diesel is a review I've been planning for ages, even tracking down an example for my collection to assist. While waiting for inspiration to hit and words to emerge, information and pictures arrived from Adrian Duncan. These prompted a three-way discussion with supremo ED collector, Kevin Richards. The final result is the most in-depth history and review of this short-lived product ever presented, anywhere! So what I'd thought was going to be a simple page lay-out job mutated into a complex editing and revision task as more and more information, corrections, and revelations arrived. This includes the fact, unknown to me, but easily verified after I knew to look for it, that the highly popular ED Racer was initially designated the "ED Mk III, Series 2". Read all about it in the long and comprehensive ED Mk III page.
Tech Tip of the Month
Reference books on turning will say that turning between centers is still unrivalled where accuracy is essential. For a lot of the sort of work we do making model engines, turning between centers will provide no benefit, but there are times when simply nothing else will do, such as when making a shaft with steps in it, all of which must be concentric, especially if the work must be swapped end for end during the process. There was a time when all basic equipment for a lathe included a pair of centers and a "catch-plate". Many still do; others don't. And even when they do, the size of the catch-plate driving pin may be a poor match to model engine sized work. This month's tip shows a way of doing accurate between centers work with just a dead center and some home made accessories.
The center that goes in the tailstock is termed a dead center as it does not rotate, while that at the headstock is a live center, because it does. Dead centers are hardened as they are subject to friction from the work. Live centers are soft, allowing them to be trued up as required. Now you won't be producing precise work unless the tailstock is accurately aligned on the lathe axis and as the average tailstock leads a hard life, occasional testing and adjustment is called for. But we'll assume that the tailstock is correctly set and the dead center has been carefully stored, clean, and free from bumps and blemishes that preclude it aligning correctly in the tailstock.
The headstock end is much easier to get right, and we can solve the problem of the catchplate at the same time. Because the live center is used only to position the job and does not have to act as a bearing like the dead center, it can be "soft". So all we need to do is chuck a piece of rod, set the compound slide over 30°, and turn a point on the rod. No need for a needle point on the end, just enough to accurately register in the drilled center will do. Now as long as the live center is not disturbed, it must be perfectly aligned with the lathe axis. Naturally, if moved, you need to skim it again, but that is only a few seconds work.
This illustration from the Model Engineer of February 24, 1949 shows how the jaws of the chuck can now act as the drive. All that is required is a drive-dog that can be fabricated from scrap, to dimensions that suit the small sizes model engine makers frequently work at. The work center at the tailstock end will require a good dob of grease. The tailstock should be adjusted so that the dead center is just tight enough to hold the work so it does not rotate under the weight of the drive-dog. Friction, and more significantly, heat generated by the cutting tool, will cause this to tighten up, further increasing friction and potentially causing the shaft to bend. So be prepared to relieve the tailstock pressure until the work temperature stabilizes.
Provided the component is to be machined all over, the centers drilled in the work do not need to be perfectly centered in the ends. There are limits, but three-jaw chuck centering which can be variable by up to 0.003", or maybe worse, will pose no difficulty—after the first pass the outside diameter will be aligned with the axis between the centers. As mentioned earlier, one of the greatest advantages of working between centers is the ability to remove the component, test it for fit, and replace it in exactly the same place with perfect repeatability for further work. It can even be swapped end for end (moving the drive-dog) again maintaining perfect concentricity. And as we've seen, all that is needed is a tailstock dead center. Tailstock live centers do not generally have sufficient precision for final cuts, although they can be used while roughing down. But again, beware of the workpiece bending due to expansion as it heats up. A last word on drilled centers: nothing looks worse on a finished part than a giant size center drilled in the end. Choose a center drill proportionate to the finished shaft size and don't drill in further than one half the length of the tapered section.
Free Plan Next Month
Model Engine News survives on proceeds from sales of the MEN Only DVD. To acknowledge the contribution made by all the generous folk who have bought the disk, twice a year I prepare a special set of fully detailed CAD plans for some type of model engine, complete to the last dimension, and suitable for constructing running engines. The drawings, in PDF format, go on the DVD and into the Members' Area for download. For various reasons, the end of the calendar year is celebrated all over the world, so December is a good time to release a new plan set. In the past, we've had the simple diesel, a simple glow, a somewhat less simple spark ignition engine, and a rather complicated orbital valve, high-speed, three cylinder radial compressed air engine. What's left? See if you can guess—engine recognition devotees should have no difficulty from the silhouette. The answer, and the plans (Members only ) next month...