The Wankel Rotary Engine

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As some of you all know, I wrote a paper for physics class about the Wankel Rotary Engine (I made a thread about it). Thought it could be helpful to some to learn more about this amazing invention.

Here is my paper (minus intro and conclusion):

(This is a direct copy&paste from my paper... it will blend into about the engine...)

Dr. Wankel was born in Lahr, Germany on August 12, 1902. Being “able to teach himself technical subjects” (Wikipedia) enabled Wankel to think of the rotary engine, the premier invention of his life, by 1924. The period of the Second World War was not an excellent time for Wankel because he first had an argument with Hitler leading to his imprisonment for sometime in Germany, then he made rotary valves for the German military, and then, because of working for the military, he was then imprisoned again at the end of the war by the Allies. As a result of his final imprisonment, his laboratory was closed, his work confiscated (he had already created an engine and received a patent by 1936), and he was forbidden to do more work in the field; however, he continued his work by going to NSU, a German automobile company, and worked to create several rotary-powered vehicles. While at NSU he was able to cause the production of one of the first rotary-powered automobiles: the NSU Ro 80.

The Ro 80 was in production from 1967 until 1977 but sold poorly simply because of reliability problems; many of these problems stemmed from the rotary engine’s complexity. Despite the Ro 80’s troubles, several different automakers, specifically Mazda, have created several different cars that have had long, full production runs. The Mazda RX-7 and RX-8 are most certainly the most popular rotary-powered cars to ever reach production; the RX-8, currently in production, has received great acclaim simply because its power plant’s weight-saving characteristics.

Wankel’s invention, or at least enhancement, of the rotary engine is most certainly why many know of him. The rotary engine is largely identical to regular combustion engines in the ideals of intake, combustion, and exhaust, but is distinctive because instead of having pistons like a traditional combustion engine, it has triangular rotors that turn causing a side of the rotor to create a four step cycle to create power. The Wankel Engine has four major parts of its operation: the first part is intake, the second is compression, the third is power, and the fourth is exhaust (World Book). In order to fully understand how the rotary engine operates, I have added a diagram from The World Book Encyclopedia as Plate #1 on the Plates page. In this diagram, one can see each cycle of the rotary combustion process. The first step shows the fuel and air mix being pulled into the chamber by the movement of the rotary (this pulling action continues throughout the process, simply follow the blue dot on the diagram). Next the mixture is pushed by the rotary into a “Compression Chamber” (a side recess in the body of the engine) in which the mixture is compressed to the side. Then the rotor pushes the compressed mixture next to a spark plug it is ignited causing the rotor to turn and the ignited gases to be sent out of the chamber into the exhaust system just like all other combustion engines.

Despite the major weight-saving aspects of Dr. Wankel’s engine, the main problem as to why the engine is not the usual power plant of automobiles is simple: cost. The engine is expensive because there are few produced and so the problem of even creating the engine, with different mechanical aspects and parts, is financially prohibitive in many automotive industries. Also, the rotary system uses a great deal of oil in its maintenance and average use which can be quite expensive in the long run. And, finally, the rotary system is hard to create correctly, and because so few mechanics know how the engine operates many damage its operation or simply cannot fix it when it is broken. The NSU Ro 80 suffered many problems with the latter point. Some of the Ro 80s were known to have “required a completely rebuilt engine before 30,000 miles,” a process not usually having to be done to piston engines until more mileage has been driven and so later in their lifecycle (Wikipedia).

Despite these major set backs, rotary engines have most certainly received much praise both to civilian and racing communities. In the civilian realm, Mazda, the major producer of Wankel Rotary Engine-powered vehicles, has dominated many sports car classes with its RX-7 (in production starting in 1978 and ending in 1995 with many generations) and RX-8 (in production starting around 2003) sport coupes. They also had much success with their rotary-powered 1991 787B Racecar which went on to win the 24 Hour Le Mans race as well as many other titles.


And thats about it... :thumbs:

Works Cited (cuz we all know what happened to Hobo, always gotta cite!)
"Felix Wankel." Wikipedia, the Free Encyclopedia. 1 Oct. 2005 .
"How a rotary engine works." Chart. The World Book Encyclopedia. Chicago: World Book, Inc., 1996.
"NSU Ro 80." Wikipedia, the Free Encyclopedia. 18 Oct. 2005 .
"Rotary Engine." The World Book Encyclopedia. Chicago: World Book, Inc., 1996.

posted by  StiMan

Thank you very much. A little history lesson is always much appreciated.:thumbs:

posted by  elchango36

Thank you for reading it! :thumbs:

posted by  StiMan

That was a good read:thumbs:...definitely learned some stuff, and raised a question:
Has anyone made a diesel rotary, and if not, can it be done?

posted by  chris_knows

Wow... I dont know... never looked...
*Searches google...*

Heres the first thing that comes up:

So I guess so.... but ask Chris just in case. :thumbs:

Lol... ask ChrisV. :laughing:

posted by  StiMan

So I know it's possible now lol, I wonder if it improves efficiency/performance...I'll ask Chris and see if he knows lol...

posted by  chris_knows

Thanx for posting that, it made very intersting reading. Although I kinda understood it's workings, I've never had to work on one, and the overal history of it was great. So it enlightened me quite a bit!. Thanx again!

posted by  Cliffy

Back in probably the early 70's my cousin gave me a model of this engine.
I was young and didn't have any desire to put it together. It went in my parents attic for quite some time and I guess finally trashed.

I always wished I had put it together---- Oh well

posted by  thefonz

So what grade did you get?

posted by  PontiacFan27

A number of diesel rotaries have been built, but the compression ratios for diesel combustion tends to be hard on them (rotaries hate detonation in normal form, and diesels essentially run on detonation). Instead, people have run diesel fuel with special spark plugs in them.

There wasa company that built marine diesel rotaries, an rather large displacements. But I cna't find anything on them now, which might be a clue as to why we don't see to many pure diesel rotaries.

Something else to remember about rotary engines, before Wankel worked on them, he got his ideas from other people that were trying to do similar things. In fact, one of his designes came from a patent from the US in the late 1800 for a rotary pump. There were a few other rotary engines being designed back then, but as Wankel found, the sealing ability of the enigne was an issue.

Check out some of the designs here:

And if you really woudl like some in depth introduction to modern rotaries, this is the site:

These engines are fun to work with, and fun to take apart and rebuild (I rebuilt a 12A from my RX3 on my kitchen table. Don't try this if you're married, however...)

posted by  ChrisV

Uhh... 94% I think. :thumbs:

posted by  StiMan

Lol! u also forgot to add not to try it if you live with your folks. my mother really didnt like it when i took the turbo apart in the dining table once.... she told my gf and she pinched me really hard.

btw, i had seen the rotary engine site before and its really damn good. ive been waiting around for quite a few months for the owner to update even further. i had also made a thread asking about the diesel rotary engine a few months back.

posted by  Inygknok

that was an intersting read:thumbs: learned a little bit about the way they work cool:thumbs:

posted by  mx3_monster

I would like to issue a thanks to StiMan, he saved my ass and didn't even know it. Me and my friend ahd a short project on rotary engines and he was suppose to draw the 4 parts of it on a poster, as shown in Stiman's post, well he ended up forgetting to do it, so instead I went to his thread through my teachers comp and she projected it on the board and then me and my friend used Stiman's post about the 4 main parts. And I did give credit to where these resources came from lol, Just wanted to thank StiMan though because without his little picture I'd have been screwed.

posted by  Pythias

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