The neglected potential of the Wankel engine

[Ken McKenzie]

It appears that no thought was published about the potential of the wankel engine that takes it's power directly from the rotor.

I was working on the DKM (Wankels first working emgine) and found that it is designed to run foreward and backwards at the same time. The reason Wankels prototype worked was the high starting speed the sparkplug was on the wrong side of the rotor and the engine had a small eccentricity.

I was in the process of modifying the engine by having the eccentric shaft turn twice counterclockwise as the housing turned once clockwise. The rotor did not turn but rotated on the eccentric shaft the same as a foot pad on a bike this engine fires three times every housing revolution. Or one and a half times every e shaft revoution.

I came to the realization that what I was trying to accomplish was to have a direct drive from the rotor to the drive shaft.

Using a vintage 12A Mazda engine I made a geared shaft link from the rotor to the drive shaft. I briefly started the engine and destroyed my gears. I did it again but this time I hard cased the gears and put them on a 1 1/2"shaft with a 1\4" square key and then welded both sides of them.

I started the engine again and it broke the welds and sheared the key on the engine side gear.

There is one hell of a lot of power potential in the Wankel engine that is not being used. I have designed a transition gear that will make a smooth coupling that should be complete in the next few days.

Cheers
Ken

[RotarySMP]

I'd love to see an animated model of this motion Ken.

[Ken McKenzie]

More on this subject

The manufacturers of the Wankel engine have not studied the engine sufficiently to utilize the last third of the power stroke. When the Mazda RX-7 has completed two thirds of the power stroke the exhaust port opens. The maximum displacement is reached one quarter of an E-shaft rotation later that starts when the e-shaft journal is at the nine o'clock position and finishes at the 12'clock position.

Mazda had great difficulty having the exhaust blow into the vacuum intake portion when the seal strattled the exhaust port. This is why the exhaust port is positioned early. The Renesis engine has the exhaust flow through side ports and this makes superior seperation and allows them to advance the exhaust ports and utilize more of the power stroke.

Had they put more thought into what the problem was they should have designed the exhaust port so the flow out would be through about ten thin slits in the housing that extend a couple of inches before exiting into the exhaust manifold. As the apex seal crossed these slits the exhaust would b e directed away rather than around the tip and into the intake vacuum. They then would have more power and use less fuel.

Cheers
Ken

[turmite]

Not a Wankel but a real interesting engine and one very famous person attached to it.

http://www.ox2engine.com/

I have always wondered why the Wankel was never developed for motorcycles? It looks to me like you could almost use it as a gyro!

Mike

[RotarySMP]

Having ten slits would be highly unlikely to flow well. You may well choke them. Also erosion would have to be a concern.

Turmite, Suzuki made the RE5 for a couple of years in the mid seventies, and at least two other rotary powered motor bikes made (limited) production. The German Hercules W2000 with the Fichtel and Sachs KM914, and the Norton police bike for the british cops.

[ChrisJ]

I came across this website along time ago and lost my link. I just found it once again.
He has a good history of a bunch of types of rotary engine designs on his site. Interesting reading and viewing.

Rotary engines

[wolfgang]

so please explain the driveshaft gearing thing in a little more detail. I know that 13b's and 12a's are notorius for not burning all the fuel, resulting normally in high exhaust temps, and really cool backfires, but this I agree is inefficent. I am always looking for more power out of my rx7, and am I starting to build a 4 rotor soon so I am interested.

[jderou]

Originally Posted by turmite Not a Wankel but a real interesting engine and one very famous person attached to it. http://www.ox2engine.com/ I have always wondered why the Wankel was never developed for motorcycles? It looks to me like you could almost use it as a gyro! Mike

Actually, do a search, I'm almost positive their was one. I think it was Suzuki, I ran across one at a junk yard probably 15 years ago. Talk about ugly, engine was massive looking (of course I was only 10-15 yrs old so it may not be as bad as I remember).

[jderou]

Yup, here it is. Sorry Mike, missed your post.

[Ken McKenzie]

Wolfgang
The Mazda rotary engine has a eccentric shaft with a .591” throw. The combustion pressures on the surfaces of the rotor are applied against this small crank to produce torque. The first third of the combustion is applied against the top dead center as the shaft moves with the rotor. The second third produces torque against the crank. The last third is not used as the exhaust port is exposed. Incidentally the last third is the most potent as the crank has just reached the three o’clock position.

The reason they do not use the last third of a stroke is because they have not figured out how to get separation from the intake stroke. When the port is moved ahead the exhaust has the freedom to go around the apex seal when it crosses the port and apply pressure to the intake manifold and fill the cavity.

When I mentioned the reed type exhaust in an earlier post I failed to say that they should also be designed to be a one way valve to function successfully.

Regardless I find that the use of a crankshaft with slightly over a one half inch throw is absurd. The damage to gear systems that I designed prototyped and tested confirm that the potential torque of a direct drive from the rotor is substantial.

I have a ball bearing inserted at the front of the rotor making the connection between the rotor and a machined down e-shaft. The front of the engine is stock. The center of the rotor spins in a true circle cone about seven degrees from a cut off drive shaft 5 ½ “ from the bearing.

I am currently using a five sided connection but I realize that this is not as good as a triangle.

The connection consists of a round plate with a triangle milled (with its sides at right angle) in the center. This plate is welded in the rotor just behind the bearing. The back of the e-shaft is cut leaving only one half inch of the lobe. A triangle is then milled in the center of the shaft.

A shaft 5 ½” long is then machined with triangle ends that taper seven degrees.

The engine is assembled with the shaft making the connection between the rotor and the exit shaft. If everything is tight it will turn smoothly. .




Cheers
Ken

[RotarySMP]

Can you post any photos of this Ken?

Don't forget that one of the huge advantages of the current rotary is it's simplicity. Adding complexity to "optimise" a cycle is a long and differcult road. We look look forwad to the photos of your journey

[wolfgang]

so basicaly you attached the center of the rotor to the ecentric shaft directly as aposed to having the cam concept that mazda currently uses? I know there was prototypes of this early on in rotary development. The guy's name was soule, and here's some picts of his engine..

http://www.dself.dsl.pipex.com/MUSEU...oule/soule.htm