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Propeller Dynamics

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Short History of the Enya 19 and traditional Enyas

Courtesy of Bob Allan , August 2004

The Enya 19
For some time now, the existence of a previously unknown type of ENYA needle valve assembly has been suspected but never confirmed. Everyone is familiar with the flexible, spring type NVA assembly which has been standard equipment on ENYA engines for over 50 years, but photographic proof has now emerged of a very early rigid type needle valve which was fitted to the 3 bolt front ENYA 19 and the early sand cast 29's. Thanks to the generosity of David Hughes in the US who kindly supplied me with a photocopy of an exceedingly rare and very early ENYA instruction leaflet , we now know for certain what these first ENYA needle valves looked like, and an original example of these is shown fitted to the 3 bolt 19 in the photograph. Engineering drawings of this type of NVA have now been made, and it is hoped that exact replica's will in due course, become available.

Additional information has come to hand, with regard to the very first model ENYA 19 with the front housing attached by 3 bolts. My U.S. friend and co-conspiritor in all things ENYA, Pat King, has done some very detailed examination on several different examples of the 19 3-bolt, and discovered some ( previously unknown ) marked differences within the 3-bolt family. It now seems clear that at least 2 different "models" of that 19 exist, the earlier one having 7 head fins ( later one 8 ) whilst quite significant variations were also found in the crankshaft intake port timing between the 2 engines. Whether or not the latter was intentional or just lathe operators "licence" ( as was the case even with such highly regarded engines as the British Mills Diesels ) remains to be seen. However, the fact that the earlier engine has a round intakeport in the shaft whilst the later one features a rectangular one seems to suggest a continuity of model development and improvement."

The very first model engine produced by Enya was the 63 which Saburo Enya used at a flying meet in 1949. In October 1949, two types, No.1 and 2 were marketed under the name Enya "Typhoon" 63. Type No.1 was a plain bearing and shaft rotary valve engine, while Type No.2 was a twin ball-race and disc rotary valve model. Only Type 1 reached production levels. The 63 was replaced by 60 in 1956.

In February 1950, the quantity production of model engines began with the very first Enya 19 - a sandcast engine with a 3-bolt front housing, produced in small numbers until the introduction of the Enya 19 Model 4002, which featured an oval exhaust and head fins higher at the front. (the corresponding Red Head sandcast 29 appeared in April 1952-with 4 bolt housing). Slotted screws used on these, "Made in Japan" cast into L.H. mounting lug adge - 4 bolt front-housing and head.. This die-cast 4002 started production circa 1953, followed by the Enya 19 Model 4003 in about 1955, which featured a long, "slopey" intake and thin-walled rectangular exhaust, "flat" on top head fins.

The Enya 19 model 4004 appeared circa 1962 (19-IV) and had Philips head screws, thicker exhaust with markings for muffler bolts, "Made in Japan" cast into backplate and lug for pressure tap cast into the underside of the front housing. Up to, and including this model, all Enya 19's featured "square " bore/stroke 16mm X 16mm and available only in plain bearing. All this changed circa 1969 - 70 with the introduction of the Enya 19-V Model 4005, which was available in a twin ball-race model and the bore/stroke, which was now more modern "over-square" at 16.5mm X 15mm. The 19-V was more powerful ( 0.28 BHP at nearly 13,000 RPM with muffler, compared with 0.24 BHP at 11,750 RPM for the 19-IV), more compact and fractionally lighter than its predecessor, the 19 -IV.

The Enya 19-VI Model 4006 appeared circa late 1970's (?) with same bore.stroke of 0.654" X 0.590", but producing slightly more power at slightly higher rev's. Distinguished by muffler strap lug at top of by pass bulge.

"Traditional" Enya's
(ie., the non-schnuerle ported, bolt together models with steel cylinders)

Model 09: First appeared circa 1955-56 (big exhaust) Model 3001, then
Enya09-II circa 1960, 09-III circa 1965-66, 09-IV circa ?, also
available in BB version, with red prop. drive. Only first 09 had bypass
bulge, thereafter bypass passages machined into cylinder liner.

Model 15: First appeared circa 1956, then Model 1B (2mm shorter shaft)
in 1957, Model II circa 1960-61, Model III (3303) September 66-67, IV
Model 3304 with band around front housing and V (?). The first Enya 15's
had bypass bulges - thereafter bypasses machined into liner.
15 Diesels appeared Mk I, 1956 and Mk. II 1960 with chromed cylinder
liner. Some specials (similar to 29 Special listed below) based on the 15-IB
appeared, but did not enter production.

Model 19: see previous article

Model 29: First appeared April 1952, then "airfoil" exhaust Model 5002
circa 1955, the III 5103 1957, IIIB 1959, IV-5224 1964 (square venturi),
IV-B-5224, round venturi, 29-V-5225. Twin ball-race versions of the
29-IV and 35-III appeared 1965-66.
In about 1960, a special racing version of the 29-III was produced, with
single rear ball-race and "ashtray" intake (similar Fox 29R) This 29
"Special" was listed in MAN Sept. 61 at $19.95 (regular III "Speedy"
$15.00) and had chromed cylinder bore. Still designated Model 5103, this
special compared poorly with the standard 29-III (rated at 0.69 BHP
@ 16,000 RPM) being rated only at 0.75 BHP. The later 29-IV Model
5224 was rated at 0.80 BHP, and this with the plain bronze bearing and
suction feed. The 29-3B had 2 interchangeable cylinder heads with deeper
cooling fins than the earlier 29-III, which came either with a 10:1 or 9:1
head installed. The 29 IV-B appeared in 1973/74

Model 35: The 5001 replaced the 36 circa 1957, similar style to first 15
& 19 4003, then 35-II circa 1961 (model 6001), then 35-III 5224, 1964,
(square venturi), III-B 5224 (round venturi), 35-V 5225. The first
model 45 was based on the same castings as 35-II. The V -series 29's and
35's were the only ones to be fitted with head gaskets (removeable for
higher C/R). The BB versions had round venturi and smaller front race.
While most Enya's had grey, matt-finished crankcases, some (like the
09-II and 15-II) came in shiny polished alloy, also 60-II. No Enya 35-IV
produced - the numbering system went from IIIB to V, and Model 5224
to 5225. The 35 III-B appeared in 1973/74.
The Enya 35-V Model 5225 BB has smaller front race than 35 III BB
"Special", but same weight. Could be better suited to stunt . Mine has
noticeably lower compression than "Special", due to the cost-cutting
measure of fitting a removeable aluminium head gasket instead of optional
head. Also has very small venturi I.D. and much "free-er" in the
piston/cylinder fit (hand lapping axed?)

Model 40: Only Enya with Dykes ring, Model 6002 appeared circa 1973
- no variations.

Click to enlarge

Model 45: First appeared with plain head (no fins) circa 1962, then finned
head 6001, 45 BB 6001 circa 1968, 45-II 6002 (R/C timing) circa late
'70s. A dedicated C/L stunt 45 was also produced, designated 45 'S',
based on the plain bearing 6001 45. Specs on this motor were bore/stroke
0.877" X 0.748" (22.2 X 19 mm), displacement 0.449 cu.in. (7.35 cc),
weight 8.4 oz, max BHP 0.70.

Model 60: First appeared 1956, then 60-II (2-ring 7032) circa 1965,
60-III (2 ring 7033) circa 1970, 60 III-B circa 1973 (single ring-bigger
G8 carb.)

General notes: Standard venturi 1968 Enya prices were: 09 III $8.95,
15 III $10.50, 19 IV $13.50, 29 IV $15.95, 35 III
$17.50, 45 BB $32.50, 60 II $43.50
Early 29 and 35 had radiused prop driver, later ones
stepped, both with square venturi.
No production figures are known, although in his 1966
MAN test of the 09 III, P.G.F. Chinn mentioned that
"some 95000 units of the 09 II" had been produced
and sold between 1960 and 1965.

Enya 45 6002, Enya 40 6002 and ST46 timings by Supercool

The following transfer and exhaust durations were measured by Supercool on his Enya 45 6002 and Enya 40 6002. The Enya 40 is by far the most powerful of the 3 motors.

  Transfer Exhaust
  Open Closed Open Closed
Enya 45 6002 126 234 141 219
Enya 40 6002 108 252 126 234
ST 46 118 242 134 226

Below I have included my correspondence with Bob on these articles:

As this ENYA business is very much an ongoing process, I will send you any new "discoveries" as they come to hand, so here's some now -
On my sheet ( refering to Models 6001 & 6002 in the 40/45 size ) I mentioned about the timing being " C/L stunt " or " R/C " - ENYA never designated these as such, its  just that the earlier, more conservatively timed 6001's suited the C/L stunt flyer better than the later 6002's ( in the quest for higher power output ). Now, my latest finding is that there are variations even within the 6001 group and as an example, the 1968 ENYA 45 BB has different timing to the earlier 45 plain bearing - both 6001's.
Port Timing ENYA 45 BB ENYA 45 pb Shaft Timing ( 45 BB )
Exhaust 122 degrees 132 degrees Open 38 degrees ABDC
Bypass 102 degrees 118 degrees Close 52 degrees ATDC Total induction period 194 degrees
Capacity 7.499 cc 7.354 cc
With regard to the sand cast, 6 bolt front 63 & 60, the mistake was made in the 1959-60 Aeromodeller Plans Handbook, where it claimed both shared the same bore and stroke. An engineer friend of mine in the States has examples of both the 63 and 60, and he kindly ripped them apart and measured them -
ENYA 63 ( serial # 6928 ) ENYA 60 ( serial # 7751 )
Bore 24.5 mm 24 mm
Stroke 22 mm 22mm
Displacement 0.6335 cu. in. 0.6073 cu. in.
That will do for now, my missus wants the computer !

Its not generally known that an ENYA engine with the bolt - on front housing can very easily be made to run in reverse, simply by rotating the front housing 90 degrees to the right ( when viewed from the rear of the engine ). Why would you want to do this ? Well, I' ve been wanting to fly a C/L model with 3 line throttle control ever since I was a kid, and the information I' ve gathered suggests that an engine turning in the opposite direction to normal is highly desirable, as sudden throttling up will usually cause the model to bank in on the lines, due to torque reaction in an anti - clockwise ( viewed from the front ) turning motor. So, I contacted my ENYA friend in the States who is an engineer, Pat King, and asked him to check the shaft timing on an ENYA 35 - lll B, firstly with the intake upright as delivered from the factory, then with the shaft housing rotated 90 degrees to the right hand side of the engine - here are his findings
ENYA 35 - lll B shaft timing, normal configuration - With housing on the side ( reverse rotation )
Port opens at 48 deg. ABDC Port opens at 46 deg. ABDC
Port closes at 48 deg. ATDC Port closes at 50 deg. ATDC
Pat says that " The timing is so close that a dynometer is probably the only thing that could detect the horsepower difference ". Obviously, the shaft timing duration remains the same, so 5 minutes with a screwdriver and you can convert your ENYA to run in reverse ! Don' t forget to bolt on a pusher prop.

If you want to use that ENYA stuff, thats fine but with the proviso that everyone is aware that it is NOT the definitive history of ENYA engines, merely a gathering of any information that was printed by Peter Chinn and Ron Moulton over the years. There is almost certainly some omissions and errors, and the further I delve into the history of the ENYA company, the more I am aware of how little I know ! Engine companies these days are run by bean counters,who know little ( if anything ) of the brands early history. As an example, that 1958 OS Max 35 Combatnik I have does not appear on the OS wall chart, and when I emailed the OS factory in Japan for information they admitted they had trouble identifying it, eventually deciding it was a Max 1 ! Shows how much they know. The only printed article on ENYA ( that I am aware of ) appeared in Model Airplane News, way back in March 1968, so any information I have just results from cross referencing early mentions of ENYA's in Aeromodeller, MAN and Model Aircraft, and as my collection of these magazines is far from complete, there' s probably still a heap of info out there that I haven' t even seen yet !

More from Bob Allan:   The Enya 45 6001 versions
Stuart, some fresh information has come to light on the very early Typhoon 63 mentioned elsewhere.

This comes courtesy of Alan Strutt in the UK, who is a very lucky ENYA collector indeed - not only does he own the Typhoon bearing Serial # V 2191 , but also another example with the Serial # 2069 - this latter one being the one pictured on page 65 of Mike Clanfords engine book. Although at first glance these 2 engines look very similar, on closer examination some startling differences become evident, maybe indicating that at that early stage of development, each individual engine was basically a handmade "Special" with standardisation still aways off, and in Alan's own words - "On V2191, the crankshaft is shorter and more heavily overhung. The front housing is a different casting with the rear bearing housing visible. Interestingly, the front bearing is a twin row ball race...something I personally have never seen on any other engine. The rear cover is different in that the moulding for the inlet open area is smaller : the induction tract is shorter and horizontal as opposed to up-angled. They have different pistons, with the height between wrist pin and piston top being shorter on V2191. V2191 is assembled with 3mm screws, whereas the other one ( Serial # 2069) uses the much more unusual 3.3mm. The photos show a 1950 Type 2 ENYA 63 "Typhoon" glow engine with a twin ringed piston. Although the plug appears to be a sparking type, it is actually a Champion VG-2 glow
plug which was one of the first glow plugs available, and even today, highly sought after ( a new one can fetch up to $70 ! ). It seems that these big ENYA's came from the factory
with 3 hole mounting lugs.


With regard to the fabled ENYA 36 mentioned elsewhere, I have found some technical data on this engine, and have included it in a comparison with
the following Model 5001 ENYA 35 -
  Bore   Stroke  Capacity  Factory claimed max. HP Comp. Ratio
ENYA 36   0.794 in.   0.735 in 0.36 cu. in. or 5.99 cc 0.60 7 : 1
ENYA 35    0.794 in.    0.715 in 0.354 cu.in. or 5.8 cc  0.70 7 : 1
Also, the first ENYA 19 Model 4002's ( produced concurrently with the Red Head 29 ) had a red head & prop. driver, with the head being flat topped as on the 29. Later 4002's had the distinctive rounded shape head fins, higher at the front.


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