INTRODUCTION
TO ROTARY HISTORY FOR INTERNET
The
first eight segments that follow are the "Rotary History" columns that
appeared in the printed edition of Tracy's bimonthly newsletter "Rotary
Aviation News" from 1997-2000. I
have corrected minor mistakes, typos, etc., that appeared in the originals and
occasionally made minor changes to clarify things.
Additional comments for this Internet version appear after the original
column, as do relevant links. One
very interesting link you should pursue if you haven't already is this:
Please
feel free to e-mail me at ekrampitzjr@hotmail.com
if you have any comments or complaints. Don't
bug Tracy about boo-boos; I'm responsible for the content.
Look for additions to come.
This
column is Copyright 1997-2001
by Edwin Krampitz, Jr., unless indicated otherwise.
Please ask for permission to reproduce.
ROTARY
HISTORY 1:
THE
SMALLEST WANKEL OF THEM ALL
Only
one other manufacturer besides Mazda has stuck with volume production of
basically the same Wankel engine for over 25 years: the Graupner/O.S. 49-PI,
sold in the US as the .30 Wankel, meant for model radio-controlled aircraft.
This is the smallest rotary combustion (RC) engine ever produced.
The
German firm Johannes Graupner made model airplane kits and became interested in
RC engines after a Wankel symposium in Munich in 1960.
The Wankel's lack of vibration, small size and weight for the power, and
central output shaft offered huge advantages for models: vibration, for example,
damaged expensive radio equipment and servos.
Engineering work mass subcontracted out, and by May 1967 Graupner was
flying a prototype. The firm became
the 17th NSU/Wankel licensee on 12 September 1967--the only one for such small
engines. To produce them, it
immediately teamed up with Ogawa Seiki (O.S.) in Japan, then already well known
for model airplane engines.
O.S. required two years to begin making Graupner's engine because the
specialized machinery to grind the rotor housing wasn't yet available.
After working preproduction bugs out, the engine was introduced in 1970
and became available in the US the next year.
At first it was rated at 0.63 hp at 16,000 rpm, but after revisions in
the early '80s it was capable of 1.27 hp at 17,000 rpm.
(Output will depend on the nitromethane fuel blend used.)
Typical idle speed is around 3,000 rpm; maximum speed is around 20,000
rpm. Rotor radius (-prime) x
eccentricity x width (R' x e x B) are 22.0 x 3.0 x 14.5 mm, giving a chamber
volume of 4.97 cc (0.303 ci). With
its huge muffler it weighs only 380 grams (13.4 oz).
It has a glow plug ignition and carburetor typical of model engines.
Unfortunately,
O.S.'s importer would not respond to my repeated requests for information for a
book about RC engines I had once planned, so I bought one of these little
engines in early 1997 and partially disassembled it.
(For example, I had to measure the rotor dimensions myself, as no
reference source provided them.) The
.30 Wankel then had a list price of about $400 but typically could be bought for
half that. Even now, Graupner's
name appears with O.S.'s on the box, as do the words "System NSU Wankel",
and that box is a cube only about 120 mm (4-3/4") each side.
This engine has an iron rotor and apex seals but does not use side seals,
relying instead on a tight fit between the rotor and the nonferrous front and
rear housings when running. The
apex seal springs are simple pieces of spring steel.
The rotor housing is steel, as is the eccentric shaft, which runs on
ball/roller bearings. Eleven bolts,
two with alignment dowels, assemble the housings.
Outside on the rear mounting bracket is scratched "Z200", the
serial number on my unit, with "Z" most likely indicating the year of
manufacture.
Production is known to be only a few thousand per year, but even today this, the
tiniest Wankel, sells well. It's a
quality machine. This is the kind
of specialty application the Wankel truly shines in--just as the Mazda does in
Tracy's RV-4.
POSTSCRIPT
FOR INTERNET: The .30 Wankel is still available but has shot up in price.
By early 2001 the retail (list) was about $550, though you could
typically buy it from sources such as Tower Hobbies for around $350.
Recent users report that the engine runs best on a 10% nitromethane
mixture. It is a little thirstier than two-strokes of comparable size:
a 6-ounce tank will last 8-10 minutes. Note
that although the glow plugs and carburetor are similar to those of other model
engines, they are still unique to the 49-PI.
An
even smaller Wankel may yet run as an experiment in microcombustion.
The MicroElectroMechanical Systems (MEMS) Rotary Engine Lab at the
University of California at Berkeley is fabricating a "mini" rotary
roughly the size of a penny from hardened steel and aluminum. You read right--a penny.
Its displacement will be 77.5 cubic millimeters (0.0775 cc).
R x e x B will be 5.5 x 0.75 x 3.63 mm.
The mini will eventually run on hydrogen, methane, or propane.
The MEMS lab intends to make a "micro" rotary from silicon
compounds with overall dimensions around 1 mm each.
This engine will be driven by compressed air for airflow studies.
LINKS:
O.S. Engines home page: www.hobbies.net/os/
Tower
Hobbies:
www.towerhobbies.com
MEMS Engine Lab:
http://euler.me.berkeley.edu/mrcl/
ROTARY
HISTORY 2:
THE
SMALLEST PRODUCTION AVIATION WANKEL
Not
only have many companies and individuals converted Mazda rotaries for aviation
use, but a few companies have offered their own.
One of the first, surprisingly enough, was from Fichtel & Sachs
(F&S) of Schweinfurt, Germany--a company known for small engines for
industry and recreation. Though its
engine was small, it was capable of providing auxiliary power for a sailplane.
In
1960, F&S became the second NSU/Wankel licensee and was selling production
rotaries as early as 1965. It sold
a variety of engines under different designations, and I'll cover them more
fully another time. But F&S
often used the same basic engine "head" in a variety of applications
by simply using different external configurations.
The complete sailplane engine, designated K 8 B, was one example.
The
K 8 B was a F&S KM 48 engine modified with a shroud, a propeller, and a
simple cylindrical pylon for mounting. The
KM 48 was one of the first rotaries F&S offered in 1965, originally designed
for stationary industrial uses. Its
rotor radius (-prime) x eccentricity x width (R' x e x B) were 71.5 x 10.75 x 40
mm, giving a displacement of 160 cc (9.8 ci).
In its original form it produced 8 hp at 4800 rpm and weighed 17 kg
(37-1/2 lb) less fuel tank, but in the K 8 B application it was more powerful:
10 hp at 5000 rpm with a weight complete of 19 kg (42 lb).
It's evident that this design was quite conservative: the engine redline
was only 5000 rpm. The 900 mm
(35-1/2") standard prop was made by Hoffman.
A picture of a prototype K 8 B appeared in a 1968 Society of Automotive
Engineers (SAE) report; it flew on a single-seat Schleicher training sailplane.
By the early 1970s, production units were apparently available, and
during these years it was listed in the engine section of Jane's All the World's
Aircraft. According to F&S's
1972 German specification sheet, it used a 50:1 gas-oil mixture, and its
expected fuel consumption was in the range of 2.5 liters/hour, allowing about 2
hours of flight on one 5-liter tankful. Top
speed in level flight was about 100 km/hr (60 mph).
Despite announcing a new 40 hp aircraft engine prototype in 1974, F&S
generally stopped producing its rotary engines including the KM 48/K 8 B in
1975-1976--obviously because of the bad publicity the Wankel got after the 1973
oil crunch. How many of the K 8 B were sold and whether any made it to
the US is anyone's guess. According
to correspondence I received from F&S in 1996, production figures and other
data are no longer available. As
you might guess, neither are parts. We'll
see in another segment of this column, though, that one of F&S's other
rotaries took on a life of its own.
ROTARY
HISTORY 3:
BIGGEST
OF THEM
ALL
We
looked at the smallest Wankel in Rotary History 1, but who made the largest?
The answer is the US company Ingersoll-Rand, which became a Wankel
licensee in July 1972 for compressor, pump, and generator assemblies.
Early
on, experimenters had been interested in finding the practical size limits of
the basic Wankel configuration. As
early as 1960 pioneer Curtiss-Wright (C-W) had built a 31.5-liter (1920 ci)
single-rotor engine intended to put out 1000 hp, but detonation problems
prevented it from producing much more than 750 hp.
C-W had seemingly discovered the Wankel equivalent of a fairly well-known
problem with large high-speed piston engines.
Generally, in such engines, above a bore size of about 100 mm (about 4
in) combustion cannot take place fast enough at higher engine speeds.
Weight and cooling also become problems.
Absolute limits hit at about 150 mm (6 in).
Obviously, engines with larger bores exist in applications such as ships,
but they are limited to very low engine speeds.
For
the rotary, stratifying or layering the fuel-air mixture is one answer.
But Ingersoll-Rand (I-R) licked this issue by designing its
rotary--originally derived from Curtiss-Wright--to burn natural gas, applying
lessons learned from gas turbine operation, and limiting the engine speed to
1200 rpm. The first I-R rotary
began service in June 1975, a year before formal announcement of the program.
By 1978 I-R had logged 100,000 hours of field operating time.
The engine was available in 1- and 2-rotor versions rated at 550 and 1100
hp; it had a continuous 1000-rpm rating. The
basic design including the cooling system was roughly comparable to automotive
Mazda rotaries before 1974, except that the rotor housings were cast iron
instead of aluminum. The rotor
radius (-prime) x eccentricity x width (R' x e x B) were 16.700" x
2.400" x 12.00" (424.18 x 60.96 x 304.8 mm), giving a displacement per
rotor of 2499 ci (41.0 liters). A
person could easily crawl through an empty rotor housing!
I-R's
publicity stressed the rotary's fuel economy (brake
specific fuel consumption) in BTU/hp-hr in the normal compressor package
compared to gas turbines and piston engines: at the time just around 9000 vs.
10%-30+% more for competitors. The
company offered users a comprehensive service and maintenance package including change outs
as needed, though the expected lifetime of the rotary power module
was at least 8,000 hours. I-R was
aiming for a lifetime of 24,000+ hours! Correspondence
in 1982 put the cost of a complete compressor drive at $400 per rated horsepower
and a maintenance contract including change outs of $5-$6 per operating hour.
However, I-R ended rotary production by 1986.
My written correspondence to the company in 1997 asking about the program
went unanswered.
The
market for this type of equipment was slow in the early '80s recession.
At an industrial show in Norfolk in the late '80s, an I-R representative
who knew of the program told me that the market had become saturated by about
1985. I-R's compressor packages, he
pointed out, were used mostly to pump natural gas pipelines, using the gas
itself as fuel. Since fuel supplies
were stable, few new pipelines were in the works by then.
But just suppose that were to change?
POSTSCRIPT
FOR INTERNET: An I-R manager who
was involved with the rotary program told me by e-mail in October 2000 that, to
the best of his recollection, 101
units had been built for gas compression and power generation.
Production of new engines had ended before 1985, but production of
replacement modules for field support continued through then.
(SAE papers on lessons learned from the I-R rotaries appeared in 1986,
implying that production had ended or was about to.)
According to the successor operation to C-W's rotary division, Rotary
Power International (RPI), some of the I-R units ran for over 40,000 hours. That's 4-1/2 years of continuous running, very roughly
equivalent to 1 million miles (1.6 million km) on a car engine. But the manager confirmed that the capability to make these
mighty rotaries no longer exists. The
largest Wankel engine available as a production unit now seems to be RPI's 580
Series.
LINKS:
RPI:
www.rotarypowerinternational.com
http://www.pegasuspower.com
ROTARY
HISTORY 4:
THE
CITROEN CONNECTION
Most
Rotary History readers know that Mazda and Wankel pioneer NSU actually produced
and sold Wankel-engined cars. But
few know that a third Western manufacturer did too: Citroen S.A. of France.
In 1967 it set up Comotor S.A. in Luxembourg as a joint venture with NSU
to produce vehicle engines. Citroen's
cars would use Comotor's engines.
In
1970 Citroen's first Wankel car appeared: the single-rotor M35, a small 2-door
based on the existing Ami-8. The
4-speed, front-drive M35 was sold only in France to high-mileage drivers for the
equivalent of $2,740 as an experiment. Out
of 500 planned, 260 were actually built (one source says 350, but most agree on
the lower number), but those cars accumulated 18.5 million miles (30 million
km). The rotor radius (-prime) x
eccentricity x width (R' x e x B) were 102.0 x 14.0 x 67.0 mm, giving a
displacement of 498 cc (30.3 ci). The
engine put out 55 hp at 5500 rpm and 51 lb-ft of torque at 2745 rpm and had a
7500 rpm redline. In tests by Jan
Norbye for his book The Wankel Engine, the 1,793-lb (813 kg) M35 took 18.0
seconds to get from 0 to 60 mph and had a top speed of 90 mph.
These figures seem slow but were good for European cars of that size at
that time.
Next
was the GS Birotor, a rather larger front-drive 4-door car already in production
as the GS with an air-cooled piston engine.
This car, announced in 1973, had a water-cooled 2-rotor engine with the
same basic dimensions as the M35's, producing 107 hp at 6500 rpm and 103 lb-ft
at 3000 rpm. With a standard
semiautomatic transmission like the comparable NSU Ro80 with its closely related
engine, the Birotor could reach 109 mph (175 kph), quite good for the time. As production was about to begin, though, the first oil
crunch hit--just as word about the Wankel's poor mileage and NSUs' rotary
durability problems was spreading. Only
874 Birotors were built before production ended in early 1975.
(The regular GS, later updated to become the GSA, remained available well
into the '80s.) Very few survive.
Citroen crushed the unsold cars and those it was able to buy back.
The
Comotor engines were based on the trouble-prone NSU designs, but the firm had
made many changes to improve durability and economy.
The GS Birotor would probably have proven more reliable than the Ro80.
This isn't idle speculation: the only survivor with right-hand drive, now
in Australia, was supposedly used as a daily driver for over 20 years but is
only on its second engine. Citroen
was renowned for its engineering and might have restored the Wankel's reputation
in Europe. But it had been losing
money for years and was already pulling out of the US market by 1974. The rotary fiasco didn't help.
Peugeot, known to be anti-Wankel, took over the firm that year and still
has control. There were to be no
more rotary Citroens, but Comotor struggled on until 1980.
Ironically,
a Comotor engine very much like the version in the Birotor was offered in one
other vehicle: the Van Veen OCR 1000 motorcycle sold in small numbers in the
late '70s. This heavy bike--over
700 lb (320 kg)--could hit 125 mph (200 kph) in just 16 seconds and reached 135
mph (215 kph) in tests. The OCR
1000 cost $15,000+ by late 1978, about the time production ended after some 30
units were built. Such a machine is
a fitting end to the Citroen/Comotor saga.
POSTSCRIPT
FOR INTERNET: Of course, neither
the regular GS/GSA or the GS Birotor were ever sold in the US, and no examples
of the GS Birotor are known to exist in the US.
The Birotor drivetrain was completely different from that of the normal
GS, not least because the rotary was water-cooled. In addition, interiors were rather different in the Birotor,
and aside from the "Birotor" logos, the exterior had subtly flared
fenders. If you thought about
buying a normal GS and converting it, forget it.
Citroen crushed the cars in part to avoid having to carry spares, though
a quarter century later this issue is moot.
LINKS:
GS Birotor pictures and restoration efforts:
http:/
/hem1.passagen.se/chapron/birotor.htm
ROTARY
HISTORY 5:
RUSSIAN
ROTARIES
One
of the most mysterious Wankel programs started behind the Iron Curtain during
Cold War days: that of the Soviet/Russian automaker VAZ (now Avtovaz) of
Togliattigrad. VAZ began building
Fiats under license as Zhigulis 30 years ago; they have been sold as Ladas in
the West.
The
Russians expressed interest in the rotary in the '60s and sent technicians to
NSU in Neckarsulm, West Germany, in 1974. VAZ
began development in 1976 and in late 1980 came an announcement of a
limited-edition 2-rotor Lada. The
rotary was tested in races and rallies. Apparently
2- and 3-rotor engines with power ratings from 120 to 280 hp were produced in
the '80s for use in the USSR. The
most common seems to have been a 2-rotor rated up to 160 hp, used in KGB,
militia (police), and military vehicles. Two
of another 2-rotor engine, the 138-hp VAZ-413, were used in the Volga-2
Ekranoplan--one of the new ekranoplanes that has excited aviators.
The
engine design bureau Aviadvigatel adapted the VAZ-4305 for aviation use as the
D-200. As publicized in 1994, the prop version produced 217 hp and
had a dry weight of 145 kg (320 lb) with installed dimensions of 990 mm length x
623 mm width x 690 mm height (39.0" x 24.5" x 27.2").
The D-200 was liquid-cooled with 2 spark plugs per rotor and used 91-95
octane gasoline; displacement and rotor dimensions have not been given.
Two of these 2-rotor engines are used in the Mil Mi-34V 2- to 4-seat
light multipurpose helicopter, replacing the Mi-34's standard radial engine and
allowing a greater takeoff weight (max. 1,960 kg or 4,320 lb) and range (up to
980 km or 609 mi). The Mi-34 was
developed for training and acrobatics, but the -34V, first shown in 1992, was
planned for emergency and rescue missions.
Why a rotary? Mil's general
designer said, "We could not find a gas turbine small enough."
[!] [Tracy's exclamation
point.--EK]
Aviadvigatel
had planned to replace many of the original VAZ components with
"aircraft-type materials" and certify the D-200 by 1996 under US and
European aviation regulations, but it isn't clear what has been happening since
1994. Avtovaz has had severe financial problems, and I suspect that
Aviadvigatel has run into legal snags.
The
D-200 may not be legally marketable in the West.
I have found no evidence that VAZ or any other Soviet entity got a
license from NSU/Wankel in the '70s. Despite
mentions of rotary Ladas, no specs for any Soviet vehicle with a Wankel ever
appeared in any of the standard reference sources such as World Cars.
Believe me, I've looked. I
have searched Russian books on vehicles and engines, including Russian-language
Zhiguli repair manuals, at the huge Victor Kamkin bookstore in Maryland but have
found absolutely no reference to VAZ's rotary efforts--though aside from
licensing issues, the KGB and military uses may also have mandated keeping them
secret. In fact, in such books
published there in Russian or English, discussion of the Wankel engine and its
principles is conspicuous by its total absence! To top it off, my correspondence to Avtovaz and Aviadvigatel
in 1996 went unanswered, despite my getting a Russian trade representative
involved.
Few
technical details are therefore available about VAZ's rotaries.
I suspect one reason is that they are probably direct copies of NSU's or
Comotor's--as the rotor dimensions would likely reveal.
Since most of the Wankel patents didn't expire until the '80s, Avtovaz
would probably be liable for back license fees and penalties if it or
Aviadvigatel tried to sell these rotaries in the West.
It would be interesting to find out if licenser Wankel Rotary GmbH in
Germany has pursued this issue with the Russians and kept the D-200 off the
market. Can any of you provide any
info?
POSTSCRIPT
FOR INTERNET: Avtovaz has a
Russian-language website describing its rotaries, though it is hard to find even
through its normal website. Rotary
versions of the front-drive Lada Samara have supposedly been available to the
Russian public since 1997. The
displacement per rotor is given as 654 cc, which is--surprise!--the same as that
of the Mazda 13B. Indeed, a related
website devoted to car sales gives the rotor dimensions.
They are the same as the 13B. My
Russian is lousy, but what I can make out of an interview transcript on the
website seems to imply that VAZ got some sort of sublicense from Mazda.
This wouldn't solve the licensing issues with Wankel Rotary itself,
however. Can someone expert in
Russian translate the interview? Variations
are offered for aircraft. However,
Jane's has recently dropped the Mil-34V from its list of production helicopters.
General Motors has recently become involved with Avtovaz, though what
will happen with the Russian automaker in the wake of the upheavals there is
still open to question.
The
USSR expressed an interest in the engine soon after production versions first
became available, it appears. As
early as 1968 came a book in Russian, "Rotoporshnevye dvigateli"
("Rotary-piston engines"). A
technical congress dedicated to the Wankel was held in Tbilisi, Georgia, then
part of the USSR, in 1981. Several
Soviet-bloc technical articles on the Wankel appeared in various journals from
the late 1960s through the 1970s, particularly in Poland.
Military interest in the engine can be gauged by a two-volume translation
of a Russian manual that the US Department of Defense translated and released in
1975. The manual's title is
translated "Army vehicle engines" and it contains much about the
Wankel. Copies can be ordered from
either http://www.ntis.gov or http://www.sti.nasa.gov (Part I: order no.
75N75300 or AD-A003129; Part II: order no. 76N78318 or AD-A016229).
These volumes are horribly expensive, though.
Aside
from the overall level of technology in Soviet piston engines, the main reason
the Russians were interested in the rotary was its ability to produce high power
ratings from low-octane fuel. Soviet
research on piston engines to combat knock because of their poor gas is
discussed extensively in a recent SAE paper: no. 980117, "On the future of
combustion in piston engines". When
they learned of the capability of the Wankel to run happily on fuel that would
blow a high-performance piston engine, they naturally became interested.
LINKS:
Avtovaz http://www.vaz.ru/skbrpd
The
interview appears at
http://www.vaz.ru/skbrpd/inter.htm
See
also
http://7verst.carsale.ru/rpd
("RPD"
is the Russian acronym for "rotary-piston engine")
SAE
paper available from http://www.sae.org
ROTARY
HISTORY 6:
THE
ORPHAN MAZDAS
Most
of you are familiar with the Mazda family of rotaries that includes the 2-rotor
12A and 13B, the 3-rotor 20B and 13G, and the 4-rotor R26B.
The numerical part refers to the engine size in deciliters, excepting the
13G. All have a rotor radius (R, or
actually R-prime) of 105 mm and an eccentricity (e) of 15 mm. The 12A has a rotor width (B) of 70 mm; B for these other
engines is 80 mm. The 12A, 13B, and
20B have all seen extensive production for street vehicles and other
applications, and the 13G and R26B were variants for racing.
Of course, the R26B powered Mazda's 1991 Le Mans winner.
But Mazda went into production with other, forgotten rotaries.
One
was the L10A and 10A, the first variants of the 12A/13B family.
R-prime and e were the same; B was 60 mm, giving a displacement of 491 cc
per rotor or 982 cc (59.9 ci) for the 2-rotor engine.
The L10A was used in Mazda's first production rotary car, the rare
L10A/L10B Cosmo Sports of 1967-1972. A
very few were exported as the 110S, after the original power rating of 110 hp at
7000 rpm. Only 343 of the original
L10A Cosmo were built before the extensively revised L10B came out in 1968.
With different port timing and carburetion, the 10A engine (the
"L" was dropped) now put out 128 hp at 7000 rpm.
When production ended, 1,176 L10B Cosmos had been built.
In contrast to later Mazda practice, these 10A engines had aluminum side
and intermediate housings and triple oil seals.
These housings' rubbing surfaces were hot-sprayed with layers of carbon
steel.
The
10A was detuned and revised for the other cars it was used in: the Familia/R-100
and Japanese and European versions of the Savanna/RX-3.
The R-100 was sold here in 1970-1972 with the 10A, but the US RX-3 always
had the 12A. This 10A typically put
out 105 hp at 7000 rpm. It remained
available elsewhere until about the beginning of 1974: using the 2x factor for
equivalent displacement as European authorities did for taxes kept it in the
under 2-liter class. The 10A
established the normal Mazda practice of cast-iron side and intermediate
housings and double oil seals. Unfortunately,
the parts unique to the 10A have been unavailable for years, and most in
surviving Mazdas have been replaced with 12As.
Supplies started drying up as soon as the early '80s.
But several years ago Mazda cast a replacement 10A rotor housing at a
huge loss for an Australian restoring a Cosmo Sports. I doubt Ford would let Mazda do this now!
The 2-rotor 13A was rare even when new. It
had completely different rotor dimensions: R' x e x B = 120 x 17.5 x 60 mm, for
an engine displacement of 1309 cc (79.9 ci).
It produced 126 hp at 6000 rpm and 127 lb-ft of torque and had a 9.1:1
compression ratio and a 6500-rpm redline. The
13A was used in one car: the 1970-1972 R130 Luce rotary coupe, never exported
here. It was styled by Bertone and
related to the rear-drive piston-powered Mazda 1500/1800 sedans. This was the only production front-drive rotary Mazda, though
only 976 were made, and the 13A was designed just for this application to give
relatively more low-speed torque. The
R130 was capable of 118 mph. The
13A was never developed further or offered in any other vehicle, but the Aussie
Cosmo restorer--who also restored an R130--found that some parts were still
available from Japan!
Mazda
made many experimental and developmental rotaries, and the 20B's status is
questionable. Also note that early
12As are almost completely different from late 12As.
But the (L)10A and 13A qualify as true orphans.
POSTSCRIPT
FOR INTERNET: If you're aware of
how Japan taxes cars, you may wonder how Mazda has been able to sell any cars
there with the 12A, 13A, or 13B. Taxes
shoot up dramatically when displacement exceeds 2 liters. Japanese authorities use a 1.5x factor to tax rotary engine
displacement instead of the 2.0 used in Europe and elsewhere.
This means that even the 13B still is taxed as an under 2-liter car.
LINKS: Mazda in Japan http://www.mazda.co.jp
ROTARY
HISTORY 7:
THE
ONE THAT WON IN '91
Edwin
Krampitz,On 23 June 1991 Mazda won the 24-hour Le Mans endurance race with a
Category 2 (C2) 787B racer, #55, powered by a 4-rotor R26B--the first and likely
last rotary win because of C2 rule changes prohibiting rotaries in 1992.
Just to finish Le Mans is an accomplishment--let alone win. The 787B covered 4923.2 km (3059.1 mi) at an average speed of
205.3 kph (127.6 mph), exceeding 320 kph (200 mph) on the main straight.
Yet it still had 30.0 liters (7.9 gallons) of fuel left of the maximum
2550 liters (673.6 gal) allotted, giving an impressive 4.6 mpg.
Here's a look at this historic engine, emphasizing the DIFFERENCES
between the R26B and the 13B whose geometry it's based on.
The
R26B develops 700 net bhp (Japanese) at 9000 rpm, its redline, and 449 net lb-ft
of torque at 6500 rpm. It's only
39" long and weighs just 396 lb. The
R26B has a 3-piece eccentric shaft; the long main shaft has journals for rotors
#2 and #3 and tapered extensions for 2 hollow shafts with journals for rotors #1
and #4. Counterweights are used at
both ends. To stiffen the engine,
aluminum honeycomb is used where needed, including the aluminum oil pan, which
is mounted on top. The R26B uses a
dry-sump oil system. Tension bolts
are anchored throughout the intermediate housings, further increasing stiffness.
Engine coolant and oil enter through the center housing.
Rotor and side housings are coated with hot-sprayed chrome-carbide cermet
(ceramic in a metallic array) for high-temperature wear resistance.
The intake as well as exhaust ports are peripheral. Each rotor housing has 3 spark plugs: a third
"far-trailing" plug was added for better fuel economy and power.
Rotors were precision cast to a 10.0:1 compression ratio using the
lost-wax method to reduce rotating mass. Two-piece
silicon nitride ceramic apex seals have, in the words of one summary, "a
'sprinkle' of an ingredient that raises heat conductivity", and they use 2
springs. The R26B has a
sophisticated electronic port fuel injection system and telescopically variable
intake pipes whose length vary with engine speed to improve airflow.
After
winning, this historic engine was taken apart in front of the press.
Little performance deterioration had been noted during the grueling race,
and the R26B looked nearly new after dismantling.
Even Mazda's head office engineer said, "In the case of the rotary
engine, damage to the apex seal is the best reference.
And as you can see, it's nearly untouched."
After measurement, wear on apex seals, rubbing surfaces, and bearings
were found to be only 1/3 to 1/2 the upper limits--in Mazda's words,
"indicating remarkable durability and reliability".
As racer Paul Frere was to say of the win, "A pity Felix Wankel has
not lived to see it."
It
would be a shame for this racing development to be a technological dead end for
the rotary. Am I the only one who
sees potential for adapting the R26B and this technology for aviation use?
What say you, Mazda?
POSTSCRIPT
FOR INTERNET: Because of the
collapse in the 1990s of the sanctioning organization that issued the rule
changes, Mazda could run a rotary racer similar to the 787B again at Le Mans if
it wished. Despite rumors to the
contrary, so far it hasn't. You
can buy a 90-minute video of the 1991 race showing Mazda's victory.
A special synthetic oil was developed by Idemitsu Kosan Co. just for the
Le Mans race. It has a
polyalphaolefin base with a detergent inhibitor package and a molybdenum
friction reducer. A street version
of this oil called "Rotary 1", meeting API specifications, became
available in 1996 in 1-liter and 4-liter tins painted like the Le Mans winner.
Be warned that it's incredibly expensive: $38 per LITER (1999) or $133
for 4 liters.
LINKS:
1991
Le Mans video
Order
VIDS315 from EWA & Miniature Cars USA: http://www.ewacars.com
About
the oil: http://www.tamahito.com/poweraxel/mazdaspeed/news/ms07.html
To
buy the oil: http://www.mazdaspeed.net
ROTARY
HISTORY 8:
CHINESE
EXPERIMENTS
This
column has discussed rotary development in Russia.
It shouldn't be surprising, then, that such work has also taken place in
the People's Republic of China, particularly at the South China Institute of
Technology at Guangzhou. But this
rotary program is even more mysterious than the Russians', and my primary source
for it is a US Society of Automotive Engineers (SAE) paper, no. 880628 of 1988,
by Chen Teluan of the institute. The
paper cites a few other sources, all Chinese.
My letters to Mr. Chen for an update and technical information have so
far gone unanswered.
Wankel research began in China back in early 1960 (!); the paper reports a claim
that over 150 "factories and research institutes" were involved with
the engine in the '60s. Testing was
rather extensive, including engines of 1 to 3 rotors, "water and air
cooled, compression- and spark-ignition, with a displacement per rotor ranging
from 150 to 1500 c.c." In the
early '70s "common technical key difficulties" led most researchers to
end their work. Chen's institute
and a few others concentrated on solving these and had done so by the early
'80s. The emphasis was mostly on
vehicle use.
Two water-cooled 2-rotor gasoline engines believed suitable for production by
the time of the SAE paper were the GZ2-900 with 900 cc per rotor, a 9.5:1
compression ratio, 120 hp at 3600 rpm and a weight of 454 lb; and the JZ211B
with 1094 cc per rotor, 8.5:1 compression ratio, 158 hp at 4000 rpm, and weight
573 lb. The rotor dimensions were
not given, though curiously the overall engine dimensions were: the GZ2-900,
23.9 in long; the JZ211B, 36.2 in.
These engines are clearly on the large side.
Their state of technology can be gauged by the use of alloy cast iron
with (apparently) NO coating for the rotor housings and, at first, steel apex
seals! Newer apex seals are
ceramic, and the paper implies but does not explicitly say that the housing
material is now different.
Manufacturing economy has obviously been emphasized as much as improving fuel
efficiency. Longetivity compared to, say, a Mazda rotary has been
secondary. Tests in trucks and
buses in the mid-'80s showed that the JZ211B could typically go for 60,000 km
(37,000 mi) before overhaul, though one made over double that.
According to cost analyses based on fleet use in rugged Chinese
conditions compared with piston engines, the rotary was more economical because
of its much lower overhaul cost. Its
fuel cost was quite comparable and in certain applications even lower.
By 1988 endurance tests of 1,000 hours were about to begin.
Tests of compound-induction and multi-fuel stratified-charge versions were also
occurring and showed much promise. Multifuel
capability would include safer, cheaper diesel fuel, and this rotary would have
"the advantage over a reciprocating diesel engine in specific weight and
specific volume, and over [a] small gas turbine [!] in fuel consumption rate,
air consumption and production costs".
Aside from the trucks, buses, "high-speed boats", small
hovercraft, and generator sets the conventional versions have been tested in,
multifuel versions "will play an important role" in
"special-purpose vehicle[s] as well as military applications".
Note that comment.
All this research is meant to benefit the Chinese military in the long run.
It probably explains the relative lack of specific engineering details in
this paper. If the US ever faces
war with China, their troops just might be using rotary-powered vehicles!
POSTSCRIPT
FOR INTERNET: Since writing this, I
have found that a number of books and papers were published in China about the
engine in the '70s-early '80s. Most
were of course in Chinese; a few
were in English. After that, except
for this 1988 SAE paper, nothing surfaces.
A Chinese paper published in 1987 does discuss multifuel rotary engines,
giving an idea of development trends.
In 2000 SAE published a comprehensive guide to engine manufacturers in China.
None were listed as making rotaries.
I have since contacted the editor asking about the status of rotary
engine manufacturing there. He knew
of none being made but intended to have his colleague in China look into it.
For now, it appears that rotary research there has either largely ended
or been driven underground. I doubt
it has ended. And if it has indeed
gone underground, that has obvious implications.
The fly in the ointment is that though China has impressive research and
manufacturing capabilities, the technological level and execution are less than
ideal (though this is changing). Compare
Japanese tractors to Chinese tractors as an example.
Both by various manufacturers have been sold in numbers in the US. From numerous accounts, the Chinese tractors produce less
power and are heavier, more trouble prone, and less durable and reliable.
Much the same issues plagued Russian equipment.
If China is to produce rotary engines in any number, perhaps it will have
to do as VAZ in Russia did (see Rotary History 5): build copies of Mazda
engines. But what has happened
since 1988? Please e-mail at ekrampitzjr@hotmail.com
me if you have any information.
Real World Solutions, Inc
