| IIn the world of
model aeroplane engines, the 29 and 35 size has long been
a favourite, particularly for flyers of control line models.
The Holy Grail of Enyas
There is no argument about which is the most
famous 35 that title, of course, belongs to the venerable
FOX 35, which has been manufactured now for something like
5ý decades with little change
The title, however, of most famous 29 is open
for debate, and in the following few pages, I would like to
present the case for ENYA’s 29 which has also been around
(in not that many forms) for half a century or so.
Click to enlarge
The name of ENYA was first associated with model
aircraft way back in 1930, when the older ENYA brothers (Ichiro
and Jiro) were making rubber powered models, encouraged by
their father Hachiro.
Hachiro Enya owned a small machine shop where
he produced medical instruments, and it was in this small
workshop, just after WW2, that Saburo, Yoshiro and Jiro Enya
first experimented with producing a model engine of their
own design (Saburo having majored in mechanical engineering
at Tokyo University). Ichiro Enya was sadly, not involved
at this stage, having been killed in a car accident just prior
to the war.
When the first ENYA 29 was released in April
1952 (about 2 years after the 19), it was an instant success,
both in Japan and America where modellers found that it possessed
both excellent durability and great performance. It must be
remembered too, that at that period of time (just after the
bitter conflict of WW2) a lot of resentment was still felt
towards the Japanese people. To make matters worse, for the
Enya brothers, Japanese industry did not enjoy the peerless
reputation that it does today, and the words “Made in Japan”
were often viewed with scorn and contempt by the average Western
consumer.
After the initial success of the sand cast,
red head 29, the Enya brothers were sufficiently encouraged
to produce a die-cast model ll which appeared around 1953.
This new 29 was called a Model 5002 and sported a very attractive
exhaust stack, which was shaped just like the section of a
C/L stunter’s wing a marketing ploy perhaps, for the huge
popularity of control line flying at that time, especially
in the United States.
If the ENYA 29 was a success in the U.S., where
it had to compete with the likes of Fox, K & B, etc.,
it must have been an absolute revelation in England where
modellers were forced to accept wheezing diesels of indifferent
quality (I still fondly remember the story told by a famous
Australian aeromodeller who was working in a well known hobby
shop back in the 1950’s seems his main job was sorting through
each shipment of British made diesels to determine which ones
would actually run!).
High import tariffs however, ensured the ENYA
and others like it, were only sold in small numbers in England,
while modellers in Australia and the U.S. grabbed them with
both hands, eager to embrace these powerful new arrivals.
The real turning point for ENYA though, especially
in acceptance by the modelling public, came with the release
in 1956 of the fabulous ENYA 29 lll, an all new design called
the Model 5103. This was a small, lightweight, high power
and speed 29 aimed specifically at the ‘B’ class team racing
market, which probably explained the prominent transfer passage
bulge (in Peter Chinns words “of truly massive proportions”).
The well made 29 lll, earned great praise from all engine
testers of the day, with glowing statements like “one of the
most impressive 29’s we have tested” and “The peak output
realised as a consequence of this high torque 0.69 bhp at
close to 16,000 rpm is, needless to say, phenomenally good.”
In his Oct. 1959 AM engine test, Ron Warring stated simply,
“ The new ENYA 5cc glow motor is a superb power plant in all
respects “.
Here was an engine weighing only about 6.8oz,
putting out the kind of torque (for size) only matched by
the likes of McCoy 60’s and Fox 29R racing engines and unlike
the latter (which was a real bear) the ENYA remained a pleasant,
easy handling engine, which even a novice could operate with
confidence. One of the features which contributed to the 29
III’s very high performance was it’s intake system, or to
be more specific, the shape thereof.
Previously, most engines of that era featured
an oval or round intake hole in the crankshaft, but the 29
III had a large rectangular port matched to a similarly
shaped venturi aperture. This had the same effect as a quick
lift or“ lumpy “ camshaft in a hot rod engine, in that the
intake remains open for alonger effective period of time,
allowing more fuel mixture to be admitted. Bycontrast, the
corresponding stunt orientated 35 had a similar rectangular
portin the crankshaft, but coupled with a circular hole through
the bronze bearingthis set up gave a less abrupt opening and
closing of the shaft valve.
This new ENYA also established the qualities
that, even today, are synonymous with the brand that of
build quality (especially the piston/cylinder fit) and sheer
longevity. The stories of ENYA’s just refusing to wear out
are legendary, with some flyers complaining about the length
of time required to run one in.
The Company in the U.S. that used to market
ENYA’s (MRC) called them “The Hand Lapped Engine” and used
this as a slogan on their clear plastic engine boxes. Whilst
it is true that ENYA did indeed, hand lap all their iron piston
motors, a first hand witness report and consideration of the
millions produced over the years, suggest that this process
was more of a cursory one, and less of the time consuming,
laborious one so frequently imagined. I suspect that care
and attention to fine tolerances in the initial machining
of the metal parts had more to do with it, than the (necessarily
brief) lapping procedure, but regardless of whether it took
5 seconds or 5 minutes, the fact remains that no other mass
produced engine in history can better ENYA’s consistently
good piston fit (and this last bit is for the Cox enthusiast)
over such a wide range of sizes from 09 to 60. I exclude the
V series 29’s & 35’s from this claim, because as mentioned
elsewhere, they were much looser.
How ever you look at it, the ENYA 29 lll established
new standards for a quantity produced engine with performance
akin to a hand built “Special”, and in 1959 ENYA released
the almost identical 29 lll B. This motor still came with
the popular and convenient option of 3 different size venturi
inserts, but also included for the first time, a spare higher
compression cylinder head enabling the owner to give his nice
new ENYA an easy couple of hours running to bed things in
before fitting the H/C head and going racing. Price in Australia
in 1960 was 137 shillings, and fierce rivalry developed between
the ENYA and its nemesis, the OS Max lll 29. Indicative of
just how good both these engines were, is the fact that even
now (45 years later) they are still highly prized and sought
by T/R enthusiasts. If any stunt fliers still remain un-convinced
that the ENYA 29 wasn’t intended for them, just read Peter
Chinns July 1964 MAN test report of the 29 - IV where one
of the headings reads “ Big First in Racing Engines “, referring
to the large number of combinations possible with 2 cylinder
heads, 3 venturi inserts and pressure or suction feed. If
my mathematics are correct , a theoretical maximum of 16 different
set upswould be available for use on the later 29, but some
of those would be entirely impractical eg. no venturi insert
with no pressure ( incidentally, with the ENYA pressure tap
being underneath the shaft housing, the available pressure
is much higher than that derived from a backplate tap
).
The company always intended the 29 to be the
racer, whilst the 35 was aimed at the stunt flyer, and for
the next 30 years, the 29 was rated at the same power as the
35, indicating a higher state of tune in the smaller engine.
This however, didn’t stop modellers from fitting the 29 into
their new Nobler, and the result was that ENYA got a bad reputation
as a stunt engine, probably even to this day (give a dog a
bad name….). One credible report I’ve heard even had one hopeful
trying to stunt with the ball race 29 Racing Special ! As
an aside, probably the best ENYA 35 for stunt flying was the
Model 6001 of 1961, which is hardly surprising as it was produced
concurrently with the great ENYA 45 6001 plain bearing, one
of the best stunt motors ever. These two engines represent
the zenith of ENYA stunt technology, conceived as they were
in a time when model engines were primarily designed for the
C/L flyer, and the R/C throttle was added later as an afterthought.
That process would be reversed in years to come, but back
then the ENYA 35 was pure stunt.
Designated the 35 ll, it replaced the earlier
5001, but suffered from a very short production run of only
some 3 years (making it one of the hardest to find of all
ENYA’s) before the company embarked on a marathon 2 decades
or so of producing the familiar 5224 series. Those wishing
to confirm the 35 II’s cred as a dedicated C/L stunt engine
should contact a certain West Australian propeller maker.
The ENYA 35 ll had very steady and torquey running characteristics
and was both heavier (only by about 0.75 oz. though) and physically
bulkier than the 35 lll which replaced it in 1964. Some
idea of the grunt that the 35 II was capable of, is apparent
when it is compared with a FOX 35 Stunt from the same era.
The FOX produced 0.45 bhp and 46 oz. in. of torque at 7,000
rpm, as opposed to the ENYA’s 0.52 bhp and 54 oz. in. oftorque
at 7,000 rpm nothing remarkable until you consider that
the ENYA ‘s
figures were obtained (both Peter Chinn) from the choked
down R/C model.
The racing Special mentioned above appeared
in 1960, and was based on the standard 29 IIIB but modifications
were minimal and the engine was nota great success. Employing
a new and heavier front housing for the single rear 11.5 x
24 mm chrome moly ball race, the main visual cue was the FOX
29R style “ashtray” intake designed of course, for pressure
feed although the engine did come with 2 venturi inserts.
Timing remained the same as the standard 29 but the shaft
had both a larger gas passage and intake opening than normal.
Like the 15D II, this 29 Special had a hard chromed bore,
but the speed flyers for which it was designed had trouble
with the piston, which ( like Topsy ) just kept growing, requiring
constant lapping.
By this point in time (at the end of 1963),
some staff changes had occurred at the ENYA factory. President
of the company, Hachiro Enya passed away and was succeeded
by the eldest son Jiro (then 46 years of age). A younger brother
Goro Enya, had joined the firm in 1956 (after graduating from
St Paul University in Tokyo) and by 1968, he was in charge
of final inspection and sales. Of the two other brothers (who
all apparently enjoyed tinkering with BMW and Moto Guzzi motorcycles
in their spare time) Saburo was managing director in charge
of engine design, whilst Yoshiro handled flight testing and
the design of the smaller ENYA engines, eg. 049 & 06.
Mention of the 5224 series leads me into the
next chapter of this ENYA fanatics ramblings, the ENYA 29
lV which appeared in early 1964, and for me at least, the
lV is the definitive ENYA 29 and a real classic. Yes, weight
had crept up to around 7.7oz due to all new and heavier castings,
also a bigger shaft, but the factory claimed an increase in
power to 0.80hp. Now sporting a 6 bolt head and provision
under the front housing for a pressure tap, the 29 had also
lost its distinctive appearance from the 35, both 5224’s being
visually identical apart from the 29 or 35 cast into the bypass
bulge. On the plus side, these twins had an advantage over
the previous, far from shoddily built models with superior
fits and finishes, and this beautiful standard of workmanship
would continue right through the 60’s and 70’s until a slight
drop in quality (mostly in the piston / cyl. fit although
some would claim this resulted from the manufacturers desire
to reduce running-in time) became evident in the ‘V’ 5225
series, indicating the age of the basic design, compounded
by the declining interest in C/L flying. Radio control flyers
were now calling the shots and archaic, loop scavenged, iron
piston technology was outdated and redundant, Schnuerle porting
being all the rage.
To ENYA’s eternal credit though, the factory
continued to produce standard venturi engines for the C/L
flyer ( by that time an endangered species ) long after their
accountants probably told them to, and the 5224 series of
29 and 35 size engines must rate as one of the best ever made
on a quality / reliability / performance / price basis. The
modelling equivalent of a stone axe.
About 10 years after production of the square
venturi Model 5224 commenced, both the 29 & 35 engines
morphed into the 29 lV B & 35 lll B Models, now with
a round, turned alloy venturi insert in place of the previous
square, black plastic inserts. This made it easier for stunt
flyers in particular, to tailor make a venturi size to their
own requirements (square lathes not having been invented at
that stage) and by adding a head shim to lower the compression,
and resisting the temptation to use the largest available
insert, a decent stunt run could be obtained. While an ENYA
( particularly the 29 ) could never hope to match a Fox for
the perfect aerobatic characteristics, the 35 however did
a better job at stunt than the Fox 35 did as a team race motor.
Horses for courses, and anyway Duke Fox himself
would probably admit that the 35 was just an engineering fluke
how else do you explain a piece of machinery which was basically
perfect for its intended use, right from the start. That’s
akin to the Wright brothers building a 747 to fly at Kitty
Hawk.
Along the way, both ENYA’s were available (from
the early 70’s) with a twin ball race crankshaft and although
a lovely engine in its own right, most modellers stayed away
because of the extra cost (most being notorious pennypinchers!)
and added weight. These BB models incidentally, had smaller
threaded portions on the shaft than did the plain bearing
models, so prop nuts are not interchangeable. The early BB’s
had a radiused front on the prop driver; later ones were stepped,
and while they were rated at 0.05 more hp than their bronze
bushed brethren, they also weighed an ounce heavier and had
around 6mm more overhang. Still supplied with dual heads,
the spare one in the BB box gave half a point extra compression
over the plain bearings 9:1 ratio.
In the 1980’s the last of the line appeared
and this was the 29 V Model 5225 (35 same designation) which
looked very similar to the earlier 5224, apart from bumps
at the rear of the crankcase, deeper head fins and one less
cyl. fin (6 instead of 7). The 5225 BB had a noticeably smaller
front race than the previous model, but weighed the same,
due to extra metal mentioned above plus an exhaust bridge.
Other distinguishing features of the last ball
race 29 & 35 were the round venturi and the parallel sided
prop driver; less visible was the fact that these final models
were not supplied with a spare H/C head, but instead used
a (cheaper) metal head gasket for the first time, removal
of which provided the higher compression. Factory specs for
the 5224 and 5225 29’s and 35’s are identical, apart from
higher peak revs in the earlier models, both plain and ball
raced.
So in the final analysis, the ENYA 29 distinguished
itself by its record breaking production run for a 5cc motor,
and the fact that it was never emasculated like, for example,
the OS Max which (like the ENYA) started off in a builders
labourers T-Shirt, but ended up in a lilac coloured suit,
with a limp wristpin.
Sadly, these fine engines are all now out of
production, but as vast numbers were produced over a long
period of time, new in box examples are still fairly easy
to obtain at reasonable prices. My advice? Buy one, and enjoy
a genuine classic while you and they are both still around.
Post Script
To demonstrate to yourself how good an ENYA’s
lapped piston/cyl. fit can be, try this experiment
1 Select a new unrun ENYA (09-35 size) which
is free turning & well oiled remove glow plug and prop.
2 Turn engine slowly and gently by gripping the shaft threads.
3 On the downstroke, take particular note of how close the
piston top is to the exhaust port before the seal is broken
( this actually is the release of pressure as the piston uncovers
the transfer port on the opposite side of the cylinder, but
out of view ), also how the piston will pop back up again
when released.
4 Now install a glow plug, and on the upstroke, the compression
should not leak away, even when the turning force is continuous.
This is known as the “ Excellent , Not Your Average “ compression
test or E.N.Y.A. for short.
Some Important Updates !!
1) Further to the "first hand witness report " mentioned
above, I recently came into possession of an MRC-ENYA catalogue
dated 1965, in which it states that - " The machinists
in the ENYA factory turn out more than 50,000 engines a month
to satisfy a world wide demand." Now, in the 1968 Model
Airplane News article done on ENYA, it showed just one person
doing the Hand Lapping, and I decided to dig out my calculator
to try and figure how many piston & liner sets that one
poor overworked machinist would need to produce to supply
50,000 engines a month. I don' t know the Industrial Rules
& Conditions ( if any ) which applied in Japan at that
point in time, but I worked on a benchmark set at 9 hours
a day, a 6 day week, over a 30 day month period. This would
mean that, if only one person was involved in the Hand Lapping
process, he would need to turn out around 3 sets a minute
or about 1 lapped piston & cylinder every 20 seconds (
and that's not including meal breaks or smoko's ! ). I figured
there HAD to be more than one person doing the lapping, so
I contacted the "first hand witness" and here is
his reply ( with non relevant parts edited ) - "I probably
visited the factory in 1961, I know I went to see one of the
Enya Brothers in their office in Tokyo. There were four Enya
Brothers and I met three of them, Saburo was the eldest and
did the designing and worked in the factory. The second Brother
spoke very good English and ran the office in Tokyo. The third
Brother worked in the factory, and it was this one who was
doing the Hand Lapping. I remember watching him do this -
he rubbed on some lapping paste and sent it up and down the
cylinder about TWICE ! I did make a comment at the time about
how little lapping was actually done, and they just laughed
and said it covered their advertising ! Sorry I cannot give
you any more specific information, but you are correct when
you suggest that they were lapping about 3 cylinders a minute.
" ( end of quote )
2) The 29 & 35 size BB Specials first became available
in 1965.
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