About Propellers Other Products Articles Bookshop Gallery Links Contact Supercool

Propeller Dynamics

Essential reading for model aircraft contest fliers. This is the only book on the market explaining propeller theory in non-mathematical terms. A rattling good read, I know, I wrote it.


Enya Trilogy

By Bob Allan

Part 1

After stating in an earlier episode that I would not be writing anything more on the subject of Enya’s, I now have to make a liar out of myself (not nearly as hard as it sounds) as during the past year of 2007, three new “discoveries” have come to light. My cohort in all things Enya, Pat King in the U.S. has been kept busy documenting all the engineering details of the two “new” Enya engines we uncovered during 2007, whilst yours truly has the job of making it all sound remotely interesting, to those who maybe aren’t as fanatical as Pat and I am ! We both are of the firm belief that if God sponsored a stunt team, He would choose to use Enya engines rather than some other brand that the Angels provided. Even He has trouble wearing them out, it seems !

Now, our first new “discovery” for this year was the hitherto unknown ( to us flyers
anyway) Enya 60 Marine engine – no, not the reasonably common later 60-11 or
111 / 111B Series, but the very first, sand cast, 6 bolt front housing “Typhoon” 60 which was a follow-up to the earlier, and almost identical, Enya 63.

The only printed reference to this rare engine that I can find, is in an advert. placed
in “American Modeller” magazine ( June 1962 for one) by the then U.S. Enya
distributors, International Models of 33 Union Square, New York (who incidentally,
was the only distributor proud enough of their product to stamp each engine with the
initials I.M.I. on the mount lugs). Alongside a small, indistinct photo is the generic description – “Enya 60 with Throttle Valve Control designed to render top performance. The “Cadillac” of the Model Engines, Enya 60 will out-perform all
others in its class…….$35.00”. Nothing too marvellous about that you say, but the rub is – no mention was made that the photo actually showed a marine engine, and it
is only when a closer look is taken that one of the water cooling nipples (sorry, hose
fittings – can’t be guilty of titillation) is visible. The advert. also contained a brief spec.& prices list, but once again no mention is made of ANY Enya’s being available in a marine version, the relevant 60 listed only as being $25.00 for the Regular ( air cooled, std. C/L venturi & NVA ), and $29.50 for the (simple rotating barrel type) throttle equipped T.V.C. model. Thus, only by close observation and simple mathematics could one deduce that the 60 was available in a marine version, for a $5.50 premium over the equivalent air cooled engine. Still you’re saying – Yeah, so what ? Well, what makes this particular Enya so intriguing is the fact that, unlike most air to water cooled conversions where a separate metal water jacket is fitted (and sealed with epoxy as on other Enya marines) or cllamped over the finned section of the cylinder, this engine just presents an as cast, bare expanse of raw metal – no separate cooling jacket to be seen on the upper cylinder area at all. Looks just like an engine that some machinist has forgotten to, er, machine.

Whatever you may think about eBay, I can tell you it’s a wonderful learning tool as I’ve learnt as much from studying model engines on that site in 4 or 5 years, than I learnt in the previous 50 years or so, and it was on eBay that I first spotted this new Enya. It was in a racing boat hull, and a friend of mine (another Enya fan, and a power boat enthusiast to boot) needed little encouragement from me to fire in a winning bid. That engine bore the Serial # 10111, whilst my engineer friend Pat King has dissected and measured another marinised 6 bolt 60, Serial # 11463. As we know that the Serial #’s for these early 60’s run from about 7000 to around 12000 or so, it means that overall production of those big Enya 60’s was a comparatively low figure, with the number of marine versions probably only constituting a mere handful – maybe just a couple of hundred at most (the most produced Enya model engine of all time would have to be the 5224 Series of 29’s and 35’s – no figures available, but given the frequency with which they appear for sale, several hundred thousand must have been built, maybe a lot more). Proof of the old 60’s rarity was shown when I tried to gather information from the members of the biggest model power boat association in the U.S. – nobody knew anything about them, so I guess the only guys who would remember them have all passed on to that great boat pond in the sky. Or maybe there was just so few sold, possibly just a special order from the US agent.

The instructions which came with the only marine model engine I’ve ever owned,
warned against over revving the engine on the test bench ie. out of the water, and with no load on the shaft. It seems that is a very good way of destroying a perfectly good piece of engineering, as it literally pounds itself to death. Considering that the air cooled Enya 60 wasn’t exactly as smooth as a Rolls-Royce when revved out, my
imagination runs riot when I think of maybe some poor soul back in 1962, who has
just purchased a brand new marine Enya 60. He bolts it to the bench, connects up the
water tubing and fires her up – tweaks the needle to see how fast she’ll run, and a
hundred miles away, an earth disturbance of 4.9 on the Richter scale is registered !
Back in the shed, our new owner has gone pale and is searching for clean underwear.

But to get back to our description of this big, unique water cooled Enya, I haven’t yet explained what method was used to replace the usual cllamp on water jacket. Well, the castings for the air cooled version were made nice and thick, so the fins could be machined into the metal on the exterior, but on the marine engine, the castings were plucked off the line (actually, the casting dies would have had to be modified slightly
to include the mounting bosses for the inlet & outlet pipes) and had a chamber machined INTO the casting from the top (where the head sits). Normally (as in a lot of full size car engines) the cylinder liners are “wet”, meaning the coolant comes into direct contact with the outside of the cylinder liners, but in the Enya the liner is “dry” meaning a thickness of metal in the case is left to encircle the liner itself, and into which the liner is fitted. Most Enya’s have a “drop-in” liner, and the 60 Marine is no exception – its just that it also has a cavity between the liner casing and the outside surface of the case, for the cooling fluid to circulate and do its work. The six 20 mm long cylinder head bolts pass through the cooling cavity and into the metal below, and the head seals the whole thing off, with the help of a fibre gasket underneath. Incidentally of course, most of an IC engines heat is generated in and around the combustion chamber at the top of the cylinder, which is why some marine engines only have a liquid cooled head. This old Enya, whilst only having a head with a few rudimentary air cooling fins on top, has most of the cooling liquid circulating around the crucial “hot spot” at the top of the cylinder. Not being a high performance, high revving engine helps also, so as with the aero version, this engine would be happier turning a larger diameter, bigger pitched propeller at slower speeds.

So there you have it – if you ever come across an old Enya 60 which appears as if it
left the factory as a raw casting, before someone remembered to machine the fins in, well you’ll know what it is.


Click the enlarge

Part 2

Now, before I start on this segment (which involves an Enya 45) a little history lesson is called for. Back in 1962, Enya released their all new 35-11 (as a follow up to the Model 5001) along with their first ever 45, which had a smooth & finless “bald” head. Both of these new Enya’s were designated as Model 6001’s and both found great favour with the C/L stunt flyers of the day, and even now (in 2008) they are still keenly sought after. By 1964, the 35-11 had been replaced by the newer & lighter (but not necessarily better – see * below) Enya 35-111 Model 5224 with the square, black plastic venturi inserts. The 45 plain bearing however, stayed in production although from 1965 onwards it came with a finned cyl. head. In late 1966, Enya (with the rapidly increasing number of R/C flyers in mind) released a newer and more refined 45, the BB (still Model 6001) which as its name suggests, came with twin ball bearings on the shaft, as well as a ringed alloy piston to replace the older lapped, cast iron piston in the plain bearing 45. This latter engine soldiered on for a couple of years before production ceased around 1969. The 45 BB then became Enya’s only 45 until it morphed into the 45-11 Model 6002 sometime in the 1970’s. The 45-11 remained in production for about 10 years, before being replaced by the newer Schnuerle ported models in the mid 80’s. To us Enya historians (read two nut cases) this is all pretty straight forward stuff which we’ve raked over a hundred times. You can imagine our surprise therefore, when we uncovered a new Enya which hardly anyone outside Japan knew about, the 45S (S for Stunt) – Yes Folks, in the world of model aircraft engines, we had actually discovered our very own “Big Foot”! How embarrassing was it therefore, to your humble scribe, when I discovered that I had actually owned one of these 45S’s about 20 years ago, and had not realised the significance of it at the time. I had written to the Enya factory in Japan (this was all years before eBay & computers remember) and asked them to send me one of these 45S models I had seen listed on the instruction sheets which come with all new Enya’s. My feeble excuse for failing to recognise a rare engine when I saw it, is that back then I wasn’t nearly as passionate (loony) as I am now.

When I got the thing, I was a little disappointed frankly ( I am, first and foremost, a
collector) as it looked just like any other Model 6001 Enya 45 with the plain bearing, although I did note that the castings were not nearly as neat as is normally the case with Enya’s. There seemed to be an abnormal amount of flashings on the cast pieces, and the metal itself was not the usual dull Enya grey, but much lighter in colour, so I presumed it to be a remake. I had my shiny new Enya 45S for only a short time before trading it for some other engine which I’ve forgotten already – that’s a collector for you ! I forgot about this Enya, although every so often I’d see it listed on the Enya spec. sheets, and I saw a brief mention of the 45S once in Aero Modeller magazine, when they published a reduced size plan of a stunt model called “Super Hurricane” which was flown by Mr. Takashi Hara at, I think, one of the World F2B Champs. Anyway, just before Christmas 2007, with the help of the Enya factory, Kaz Minato and Mr. Ken Maruyama, we finally nailed our “Yeti”. It seems a bunch of top Japanese stunt flyers (guys like Shoji Sasaki, Atae Yamazaki and Tasaro Fujita) got upset when Enya pulled the plug on the plain bearing 45, and approached the factory with a request for a remake of the old 45 Model 6001. This they did, but a few stunt improvements were incorporated into the newer 45S which makes it a “stand alone” engine in the Enya lineup. The “new” 45 appeared around 1972, as (thanks to my good friend in Japan, Ken Maruyama) a test report was written by Akira Fujimuro in a Japanese modelling magazine in 1973. Visually, from the outside, the 45S looks pretty much identical to the finned head, plain bearing 45 which all stunt pilots aspire to own – even has the trademark, cast pressure tap lug beneath the rear of the main bearing housing. Inside the 45S however, a few modifications have been made, the main one being that the crankweb design has been changed slightly, presumably in an attempt to further dampen vibration (iron piston remember). Both old & new crankwebs are cut away either side of the crankpin, however the older design had a thinner section at the crankpin with a thicker section on the crescent shaped counterweight opposite. The new web is of a constant thickness heavier construction, and cut away more on the crankpin side (see photo – 45S shaft on the left, Model 5224 35 shaft on the right). The engine has almost the same bore / stroke as the old engine – bore remains the same at 22.2mm, whilst stroke is increased slightly by 0.2mm to 19.2mm. The weight increase of around 5 grams could probably be put down to the heavier crankweb and slightly larger diam. bolts holding the front housing in place. As mentioned above, the castings (the cyl. head in particular) were not quite finished off to the usual Enya impeccable standard and as a senior Company executive explained – “45-1 and 45S are the same as a basic specification. However, all parts were newly produced as for 45S. Therefore, parts of both differ in detail though can use together.” We also suspect that the internal shape of the head may have been altered, but until we can find a specimen to examine, that will remain conjecture. Compression was dropped slightly (quoted power output is down slightly to 0.7 HP from 0.9 HP) and all in all, the 45S looks every bit the stunt flyers engine it was intended (and requested) to be. It was made only in the control line version, so if you can find one – buy it. Sorry, but I’ve already asked, and at this stage anyway, the Enya factory have no plans to remanufacture it. They do, however, still stock (as at late Jan. 2008 ) some genuine spare parts for the 45S, and your humble scribe has obtained enough to build up a 45S from scratch. This engine will be duly poked at, examined, and the results recorded !

* Re. the 35-11 and the 35-111 - the 35-11 Model 6001 was a robust, “heavy duty”
35 designed from the outset to be the basis for the larger 45, whereas the Model
5224 Enya 29-IV and 35-111 were basically the same engine, to a newer design
and built on lighter castings than those used for the 35-11.

Part the last

During the past year of 2007, something quite extraordinary happened in the aero modelling industry – an engine manufacturer actually started production on a brand
new engine which was aimed specifically at the Control Line flyers, the Enya 40 XZS
Pro (since joined by a 61 XZS Pro, as well as a dedicated Stunt 4 Stroke) Sure, there are other small “boutique” C/L engine makers who turn out top grade products in small quantities, but Enya has been around for almost 60 years now (the Company “Enya Metal Products” being established in Nov. 1953) and must be regarded as a mass producer of model engines. Not only that, but they also have introduced more C/L versions of their established engines plus did a small run of remakes of the ever popular 29-IV and 35-III Model 5224 ! The factory website now lists 18 dedicated control line engines, from the 09 through to a 61, which I’m sure would have to make them producers of the largest range of Diesel and glow plug C/L engines in the world today ( P.A.W. list around 23 engines, but they are all Diesels ). Check out too, the very cool purpose built stunt NVA’s on the 40 & 61 Pro, also available separately.

As much as I like Enya’s (haven’t you noticed yet ? ) I must admit that over the last 50 years, they haven’t spent a lot of money on Customer Relations, and apart from a 2 page article in a 1968 magazine, they have remained almost an enigma – probably
the only Westerner who knew the Enya Brothers to any degree was the late Peter Chinn. As proof, it was Peter who provided us with our only insight into the personal world of the Brothers Enya, the fact that a couple of them were keen on motorbikes !

(Actually, this is a good place to relate another interesting snippet of information we uncovered when researching this article. I had contacted Jerry Asner who, trading under the name Eureka, was the first official distributor of Enya engines in the US. Jerry told me that he had been a GI stationed in Tokyo around 1950, and had got to know Mr.Hachiro Enya, who apparently, rode to work on a bicycle powered by a large Enya engine, no doubt providing R&D feedback on its performance to Saburo! Jerry also mentioned the fact that he had supplied (?) the ni-chrome wire needed, to produce the early Enya glow plugs,and then later, at his request, the engines supplied to him back in the States had non-Metric threads). This has now all changed, with a senior executive willing to personally answer any queries that a customer may have. There may be new Enya family members in charge of the Company now, but the older (and more famous ! ) Enya men are still with us – Saburo is now 85 years of age, Yoshiro is 81 and Goro is youngest at 75 years of age. The founding President of the Company Hachiro Enya sadly passed away in December 1963. I for one, would like to applaud this fresh and open new approach by the Company Management, and I trust the World’s modellers (particularly Control Line flyers) will support the Company which is supporting them by continuing to supply World Class products of peerless quality.
Bob Allan 2008

Post Script

I sent this article to Ken Maruyama in Japan for his approval, and he added this information which is printed below. I have taken the liberty of “Westernising” Ken’s
English where needed.

1) Although it is true that Atae Yamazaki used the Enya 45 PB & 45S for stunt, he is also known to be the first to use the 45BB seriously for stunt. I remember he once wrote in a magazine – “A light weight plane with the 45S is good, but a heavier plane with the 45BB (higher revving and more power) also has advantages.”
Yamazaki still competes in F1C.

Footnote - In late Dec. 2007, Enya re-introduced the 45BB Model 6001
2) Akihiko Yamada is an ex Japanese stunt champion (also competed at the World Champs) who successfully proved that the Schnuerle ported Enya 49X was very suitable for stunt. It is a pity that almost no one outside Japan realised this engine’s
potential – the exception was the US flyer Bill Simons, who used the 49X in his
plane named “Rogue”.

Apparently, Yamada had a big influence in the development of the new Enya stunt
engines, like the 40XZS and 61CXS Pro, 20S etc. The special NVA’s on the bigger stunt engines are a result of Yamada wanting to produce a better needle valve than the
Nelson, and he also designed the nylon venturi inserts seen on stunt Enya’s.
Akihiko Yamada has a website (in Japanese only) at - http://tencaichi.zero-yen.com/

3) Jinichi Furusaki is a highly skilled machinist, used to fly C/L Speed and is a Diesel
specialist, developing his own 4 stroke Diesel around 2000. Enya and Furusaki have a good relationship with exchange of information, so its possible that Furusaki provided
some input in the design of Enya’s own 4 stroke Diesel released in 2004. Every few months in Japan, Mr. Furusaki sponsors a meeting for Diesel airplanes, both R/C and C/L, and Mr. Enya frequently attends these meets. Mr. Furusaki is also involved in a
personal project called “Mokoken” (Model Aviation Institute) set up around 2002.
This involves repairing, as well as developing new, engines both for modelling & industry (meteorological research), and also teaching kids the basics in control line & rubber powered model planes. His website at - http://mokoken.driven.jp/index.html

My thanks to Ken Maruyama for this added information.

By now, most people will be aware that the Enya Factory DID (in early 2008) produce a couple of small runs of the 45S which sold out rapidly to stunt freaks
worldwide. Initial inspections reveal an engine almost identical to the older 45S
but with a lighter front housing from the 5224/5 series. As the compression is in
the “stonking” class, it may need lowering by head shims for serious stunt work.
Finally, it is my belief that (in engineering terms) Saburo Enya and the engine
which bears his name will go down in history alongside Henry Ford the car maker
and his Model T. Both designs were simple and basic yet almost perfect in conception and execution. They were both, the “right” design at the “right” time.

 Back to Top