Viva la Revolutions!
The date, as I prepare to push this month's collection of pages and pictures out onto the web, is May the first. Fidel is getting ready to deliver his annual harangue, and various groups are preparing to march and pontificate with varying degrees of justification. So as not to be left out, Model Engine News has decided to headline the May 2006 issue with a very justified shout of Viva la Revolutions!—revolutions per minute that is, and hopefully you'll understand why by the time you've read one particular item for this month.
The effort of keeping 11 racks of IT gear running is still consuming most of my model making time, partially due to hardware failures and partially due to Ron induced failures (don't ask). Presumably I'm enjoying it. I have managed to get a few things done in the past month though, including some anodizing jobs that have been piling up. My Little Dragon has not been touched, but the first MEN Members' plans-built one has run. And as we are now into the second third of 2006, it's time to gather up all the new pages in a download for MEN Members. And how do you become a member and get access to all the cool and useless downloads? Just buy the MEN CD Collection by dropping an email to [email protected]. Ok, enough of all the sinful, decadent, capitalistic marketing already; onto the monthly news...
An Important Update from Classic Model Engine Kits
The name Roger Schroeder will be familiar to most model engine builders. Roger provides a range of very inexpensive casting sets for a wide variety of basic engine types under the Classic Model Engine banner. He was also an "early adopter" of electronic mail—a feature that I know hundreds of engine builders appreciate—even if a certain magazine editor once declared it a
waste of time.
For reasons various, Roger has changed his email address. This can be as painful as changing banks, with a maze of follow-on effects. The Classic Model Engine web site has been updated to show the new address, which is [email protected].
Roger also asked that MEN make publicaly available his drawings for an alternate fuel system suitable for the Schroeder Twin. This was prompted by Schroeder Twin builder, Sol Kornblau, asking what to do when a Cox TD 049 needle valve assembly could not be found—Cox spares no longer being as ubiquitous as the once were. In answer, Roger has made an alternative fuel intake and metering system for the Schroeder twin. The design is borrowed from the Simple Single with changes to make it work with the Twin.
Click here to view the drawings, then use your browser to print or save the image. Alternately, send Roger a stamped, self-addressed envelope and he will provide a hard copy of the drawings. Roger's postal address is on his web site.
Isn't that hexy?
Joe Webster, designer and plan set provider for the Son of EZE, alerted me to Yet Another Cox-based twin that he spotted on the web. Called the "James" engine, it claims to utilize a "...new and unique way of controlling fluid flow to the underside of a piston...". This I take to be what we would usually call transfer. The web site has no details of this system and suggests that the design is subject of a pending patent, although plans and machining instructions are apparently being sold on eBay! Interesting to say the least. The use of a length of hex stock for the crankcase is novel, though I don't immediately see how it could be sensibly mounted. The orientation of the NVA towards the prop would also cause the operator some anxious moments. "New and Unique" ways of improving the humble two-stroke appear with not-so-monotonous regularity, but to date, none has actually delivered. Maybe this one is It? Click on the thumbnail to visit the James engine site.
A Tiny V-twin
A more practical, and far more attractive twin was spotted by our roving reporter Ken Croft, during a free-flight outing at Church Fenton (UK) last month. It is the work of Norman Fallows, he of the very tricky compressed air motors with the conrod operated piston snifter valves—which I thought was on this web site someplace, but if so, the Site Search can't locate it under any search terms that I can think of. Anyway, Ken prevailed on Norman to provide some additional details of his engine. You can read all about it on Page Eight of the Model Engine Gallery.
NAMES is the North American Model Engineering Show, held annually during April. As with all big shows of this type, IC engines form but a small part, and any photographic coverage generally reflects the fixation of the photographer. Mike Rehmus, editor of Model Engine Builder attended and ran a booth for the magazine. He reports they sold out real fast. Expect to see some of the IC exhibits in a future issue of MEB. In the meantime, click the heading photo to visit the New England Model Engineering Society (NEMES) web site coverage of NAMES 2006.
Just When You Thought It Was Safe...
The Sugden Special just won't lie down. Last month we saw Les Stone's Sugden. This month, Motor Boy Vincent Chai has finished casting and heat treating some beautiful cases for our little group. In the process, his enquiring mind caused him to question the astonishing amount of sub-piston induction which I'd blindly accepted. Dave Owen looked more closely, ran some numbers, and came up with a hypothesis: the Sugden drawing contains an error—the between centers distance for the conrod should be 1.000", not 1.050". This got me going, so a new rod was machined to test Dave's theory that this change would produce a significant power increase in a plans-built engine. The thoughts behind the theory and the actual results have been added to the Sugden Special Construction pages and you'll have to go there to find out what the test revealed.
An Unexpected Thread
Here's a championship quality trivia answer that surfaced while completing a long delayed restoration job of a Mk II ETA 29 for a friend. The job required making a few missing parts, one of which, inevitably, was the needle valve. A 3-view drawing in Aeromodeller suggested that the body was diamond knurled all over. This seemed unlikely to me, but David Owen was able to conform this from an original engine in his collection. He provided authoritative dimensions, including the thread of the spraybar stub which he asserted was 3BA. The engine under restoration however had that stub present and it was clearly a 40 TPI thread. The diameter was within a few thou of 5/32", making it highly likely that the thread was one of the British "Model Engineer" series (no relation to the magazine). The thread on the other end of the stub where it screws into the venturi is 2BA, making this an odd combination.
Comparison of the engine serial numbers placed Dave's engine as earlier than the restoration subject, so here's what we believe happened. The needle thread was initially 3BA. This has a pitch of 34.8 TPI (BA is a metric thread, but even in metric, the thread pitches are not whole numbers). Sometime during the Mk II production run, this was changed to the ME 40 TPI thread to make adjustment less sensitive. With the release of the Mk III and later marks, the spray bar and needle was changed to use a gland nut design, almost certainly to prevent inconsistent running problems due to air-bleed through the friction slit in the earlier version. Can we prove this? Not really. The serial number on the restored engine is 29484. So we would expect engines with serial numbers higher than this to also have 5/32-40 threads. But spares remained interchangeable via the 2BA venturi thread so engines with "wrong" threads are possible—and after my replica 3BA replacement oxidizes a bit, the waters will be even more murky. We'd be interested to hear from ETA 29 Mk II owners giving their serial number and needle thread.
Big Whatzit Airscrew
This rather attractive and large prop has come into the hands of a collector who would very much like to know who made it, who sold it, and when. We know what it is not and those wooden blades ring a vague bell with me of a relatively modern item that appeared in an R/C magazine ad. Visit the Watzit pages for more pictures of this nice, but scary item.
First Members' Little Dragon Running
Honors and accolades for achievement and persistence go to Gail Graham (USA) for the first Little Dragon built from the MEN Xmas free plan. Gail made buckets of pistons, rotary valves and spent hours reworking the piston/liner fit, testing different compression ratios, glow-plugs, fuel, fitting a bronze crankshaft bearing (due to galling of the 6061 aluminum front housing), etc, etc. The Little Dragon is now at a state where it will start readily enough and run acceptably, if not brilliantly. In comparison, builders of the ML Midge have experienced success with less of a learning experience. It seems to support my feelings that the original design is far from optimum as an introduction to the gentle art of model engine building—which makes Gail's accomplishment all the more worthy.
New Books and Magazines This Month
Issue number five of Model Engine Builder arrived in my Australian mail box early in April. By the end of April, it had also arrives in such out of the way places as Arizona, Oregon and California . Timely delivery is still causing Mike grief, but as usual, the wait was worth it. This issue contains an article by Brian Perkins explaining how he goes about machining components from the solid for engines like his Bristol Hydra that end up looking like lost wax castings. The issue runs to 36 pages in full color, plus nine double-sided, separate 16x11-1/2" pages of CAD drawings. The drawings include samples of the sleeve valve layouts for Brian Perkin's Bristol Aqulia, the Feeney Hit'n Miss Farm Engine, and a highly innovative concept engine that offers a Variable Compression Ratio (see the MCE5 web site).
Engine Of The Month: NE15S 15cc Four-stroke
A forthcoming construction series for a 15cc OHV four-stroke was announced in the Model Engineer, Vol 195, No 4261, of 25 Nov-8 Dec, 2005. The designer, who writes under the name "Nemett" (thus following a long standing tradition in UK published model magazines), stated that the engine had been designed to answer most of the construction queries sent in by readers of the ME. At that time, the engine had been designed, but not built. However late last month, an email arrived providing advance photos of the completed, operational engine, together with some words for readers of Model Engine News.
The NE15S has been designed to be machined from bar-stock, so no expensive castings are required. The full size drawings (15 A3 sheets), dimensioned using the metric system, will show an ETW type cam finishing jig—although you may like to use CamCalc to produce a lift table from the cam radii, and machine it that way. North American readers can order the Model Engineer from Wise Owl Publications. So click on the GA thumbnail for a more detailed overview of the engine.
Tech Tip of the Month
If you are into home anodizing and live in the USA, run down to your local Radio Shack and get a roll of Aluminum Ground Wire (part number 15-035). If you live someplace else, then spell it with an 'ium', then find someone who is visiting and get them to pick you up a roll (thanks, Van). The material used for this product is a very soft grade of aluminum, malleable and ductile. This allows it to be easily squeezed in a vice to make it larger, or smaller. After this, it can be forced or threaded into a convenient hole in the part you are anodizing. Being so soft, a compression screw thread cut in an aluminum cylinder head (for instance) will easily cut a thread in the flattened wire without damaging the head thread. This provides the electrical contact for the anodizing process. The photo here shows the 40 foot coil and a few hangers made from it after holding parts for color anodizing. For terminal misers, the hangers can be de-anodized in caustic soda and reused.
BE4 We Go...
Sorry, just could not resist it. The engine here is a Czech BE4, circa 1942 or 3 according to Jiri Kalina's "modelarske motory" book. The engine pictured is in Bert Streigler's collection and the photo is typical of Bert's fine ability to capture the essence of his subjects with subtle lighting. And don't you just love the little brass thimble on the end of the needle valve? Bert believes that this engine was never produced commercially (there was a little war on at the time), although other commercial repro BE's exist, produced, we think, by Miroslava Bedricha in the early 1950's. One of these, a twin , has come into Eric Offen's hands, and we'll look more closely at it next month.