It emitted a sound reminiscent of an old Deere Johnny Popper crossed with a
Harley 74. Resembling something one would find strapped to a washing machine,
its appearance could draw a chortle from even the most somber.
Owners shared a love-hate relationship with the most cantankerous power plant to sit
beneath the hood of a snowmobile,
the Winkle rotary combustion engine.
Engineered for industrial and military applications, these oddballs found their way into autos,
planes, helicopters, boats and motorcycles,
lawn mowers and just about everything else requiring a motor to operate.
Sizes varied from teeny air-cooled models to gargantuan, liquid-cooled, multi-rotor units.
Development was slow, due largely to design.
Cooley's rotary piston steam engine of 1901 was converted to internal combustion by 1910.
Millard originated the three-sided rotor concept,
which was modified and improved upon concept, which was modified
and improved upon by Felix Winkle in the 1940's.
The rotating combustion engine has no pistons or valves. A triangular rotor moving in an elongated housing forms the combustion chamber.
The geared rotor revolves on an eccentric once for every three revolutions of the main shaft. Each rotor revolution has three power pulses, with one pulse per shaft revolution.
The result is a compact package with sixty percent fewer moving parts and a huge power to weight ratio over conventional counterparts.
In 1957, Felix Winkle built a refined dual rotor prototype in operation with NSU Motorenwerke of West Germany who help license to the design. Curtis Wright Corporation of New Jersey reached an agreementwith NSU-Wankel in 1958 to broaden development.
In the early 1960s NSU introduced the Spider, the first RC powered auto. Soon following were the Citron N35 and the Mazda RX2.
Rolls Royce produced a fuel injected aircraft engine for the British Military.
In 1968, Fichtel and Sachs of West Germany manufactured the Curtiss Wright recreational version of the Wankel, and the RC1-18.5 first appeared in production snowmobiles.
RC stood for "rotating combustion," 1 indicated the numbers of rotors, and 18.5 were the displacement in cubic inches.
Weight was 56 pounds with recoil, air filter and the muffler installed, lighted than reciprocating motors of equal horsepower.
Carbureted by a tiny, impulse-fed HL Tillotson, the 303cc two strokes produced 20 horsepower at 5,000 rpm. Compression was eight to one.
A Bosch flywheel magneto ignition and 12 volt 40 watt lighting system was used. Timing was set to marks and rotation was reversible.
The RC1-18.5 was used as late as the 1971 model year. Its successor, the KM914 B, was very similar except it no longer bore the Curtiss Wright name. Later models had an energy transfer ignition and 75-watt lighting system.
Scorpion offered Wankel options in 1968 and 1969 in their MK11 and MK111 models, as did Polaris in the Colt and Mustang, Skiroule in the 300W and SW300 models, and later in 1973-74 in the RTW 300.
Leisure Design's Diplomat 300 had the option in 1973, as did Alouette in the 1974 Silver Cloud MK11. Arctic Cat used the Wankel from 1969 to 1975 in various models.
Early models ran hot. Extremely hot. Touted as an easy starter, this was clearly not the case when the engine heated up, causing the carburetor to vapor lock. Manufacturers attempted to remedy this by adding extra cooling vents to the hood and shrouds.
Flooding was also a problem and the only way to remove excess fuel was through the spark plug hole with the gas line disconnected and vigorous pulling. Seasoned Wankel riders carried a starter cord since they were notorious for rewind failure.
Plug life was short and they were not noted for fuel economy.
Despite its shortcomings, the KM914 B owns a hallowed place in racing history. Coaxing an incredible 40 horsepower out of the little mill, Dieter Klauke, head of the Fichtel and Sachs Wankel division, entered the first snowmobile race held in Germany. In Hirtenteich on January 17, 1970, Klauke piloted a 303cc Wankel-powered Arctic Cat to an astounding victory in the 340 Mod class!
Though multiple rotor RC's were not uncommon, few were installed in snowmobiles. Six double rotor 606s were sent to Thief River Falls for testing by Arctic Cat. At least one model made it into the enemy camp because Polaris was reported to have tested one also.
With the size and weight of the double rotor being a disadvantage, the KM24 was introduced.
Available for the 1972-73 season and downsized to 294cc, this new version enjoyed a boost ta23"hoTsepower at 6,000 rpm.
The improved rewind held a more efficient mechanical fuel pump. Electric start was available. A larger carburetor made the KM24 surprisingly snappy and reduced problems of the earlier models.
Outboard Marine Corporation created their own rotary design in an effort headed by Olav Aaen. From 1973-75 the Evinrude RC Q, Trailblazer and rotary models all utilized the OMC RC. The Johnson Phantom and rotary-powered models also featured the 528cc engines in 35 and 45 horsepower configurations.
While experimental models achieved 60 horsepower, these detuned luxury machines were built for comfort and reliability. Even though equipped with an OMC float bowl carburetor, overheating was still a concern.
Once regarded as the engine of the future, the Wankel has become a ghost of the past, never reaching its anticipated potential.
Problems rising from seal longevity and wear led to inefficient combustion, high emission levels and overheating.
Advances in more powerful, cleaner-burning diesel and gasoline engines, both on the industrial and recreational stage, effectively closed the curtain on RC engines.
In 1975, OMC and Arctic Cat became the last to offer an RC option in snowmobiles.
Reprinted with permission. More of Steve's work can be found in Iron Dogs Tracks the official newsletter of the Antique Snowmobile Club Of America.