I got curious the other day. Does anyone know the actual material used on the sealing surface of rotor housings? My assumption is a high chromium metal possibly stainless steel. also aside from its hardness, why did Mazda go with it? oil retention characteristics? I often wondered why they didn't go with a ductile iron like they use in cylinder engines. Just pondering, hoping this will open some discussion.

 

Chromed surfaces do last longer.

WWII bombers had cylinders that were ground to size (not machined) and chromed. They had to last something like 3,000 hours between rebuilds, most of that at high power settings. (Drive your car at 100mph with periodic boosts to top speed, and extrapolate how many miles you'd go after 3,000 hours of that!)

They also measured oil consumption in gallons per flight, but then they generally had MANY cylinders = lots surface area. You could expect a 4.0l V8 to use twice as much oil as a 2.0l four since it's twice as much everything, now imagine a nine, or twelve, or eighteen cylinder engine...

http://en.wikipedia.org/wiki/Wright_R-3350 Check it out, .40 BSFC in the 40's!

Allegedly, the Chinese military uss Wankels in some vehicles (without paying any licensing fees...) and they use iron rotor housings with no plating. They supposedly get about 25-60k km's before rebuilding is required.

 

Chromium is used because of it's extremely low coefficient of friction. Probably the lowest of all the metals. Then put oil on it.

 

Don't quite understand if the housing insert that the aluminum is poured around is coated in chrome or if the insert is an uncoated high chromium content metal standing alone. my understanding was that they are not chrome plated. is this correct?

 

It's a corrugated sheetmetal insert, which is then chrome plated and slightly de-plated to make it microscopically porous.

If you look closely at the side of the rotor housing, you can see the insert's corrugation.

I pulled apart a 12A once that had been chattering so badly that it wore through not only the chrome but also the sheetmetal. No idea how that one kept running.

Mazda *did* used to chrome directly onto the aluminum, but it's not strong enough for iron seals. j9fd3s says that the MFR housings are without sheetmetal, as well.

 

To whom would they they pay licensing fees?

 

The DMV!

 

Well given the poor emissions standards of the engine probably an IFTA tax would be appropriate also.

 

They'd have to pay licensing fees to either Wankel GmbH or NSU, which is currently one of the rings in the Audi logo

Mazda is the only manufacturer not bound by the licensing, because they produced engines commercially for 25? years. I think it's 25, they magically stopped putting the "under license from NSU" stamping on the engines around the FD timeframe, 25 years after their first production Wankel-engined car...

 

Thank you for pointing this out. I thought that there were direct plated housings; however, I was flamed (in another thread) for suggesting this was the case....go figure.

 

The Wankel corp was disbanded in the early 80s after the original engine patent expired in accordance with international patent laws. There was no more licensing fees to be collected. The root patent everything has grown from is around ~1961, iirc.

The NSU licensing, from research, had some to do with patents like the Wankel corp. But in NSU's case, Mazda also term licensed the rights to NSU's R&D and the capabilities to improve their work as they saw fit.

In all regards, if the patent is beyond 20 years it is public domain.


Not trying to be an *** with my question before. I wasn't sure in your post if you meant they were using some newer designs/manufacturing techniques that are still within 20 years and therefore under international patent law.

 

^^^

I didn't see an edit icon. So just to clarify. I'm not as familiar with Wankel gmbh. The Wankel Corp. I was referring to was basically a trust to collect the licensing fee on behalf of Felix Wankel and that original patent. To the best of my knowledge, this is the organization that disbanded in the early 80s. To that extent, I believe Wankel gmbh is a different entity all together, no?