Hey Paul, ok so I took apart my second and third Sachs 293. One was totally seized, the second was not but again inside was damaged as if some type of debris found its way inside while the engine was running.

Now both of these have a super thin steel lining in the main block.
The end plates do not, all the end plates are just aluminum.

The seized engine the rotor was locked into place, basically I had to beat the engine apart damaging a lot of parts. However there was so much corrosion in the main housing the thin steel lining has come off in places. The ballpark thickness is around .020, the thinnest was .014 and the thickest was .032 .


So now we know lots of heads and complete engine blocks for piston engines are aluminum, usually 356 alloy because of the high silicone content that allows lapping it down to make a hard silica surface for the rings and such to ride on. Some use high flame coatings that are super hard. Some use Nikasil coating. In fact it was used by other auto makers when developing their rotary engines instead of the steel liner used by Mazda. It is a really hard coating but it can be expensive.

I do believe I will bit the bullet and have my new housing Nikasil coated. Well, unless we can come up with something cheaper, that can take the wear and the heat.

We could use a hard anodized finish for the side/end plates is we are able to use the Teflon/carbon fiber side seals.

Now need to think of a material to use on the rotor apex seals that :

1- will  [not] dig into the aluminum housing

2- that will not gall the aluminum or weld the aluminum to the apex seal itself.

3- that can withstand the combustion and exhaust port temperatures.

Now I do not remember where but I had seen a statement that the apex seals perform really well at low speeds but are not a absolute necessity at high speeds. If this is true then the seals could be a type of high temp plastic that can withstand the pressure of combustion. One critical thing that has to be thought about is the peak temp as the seal passes the exhaust port and the flame passes a small portion of that apex seal at 900 to 1200 degrees F. The exhaust port could span more of the chamber but then you could get greater seal wear going over a long oval port vs a rounder port.

If we have to make them from a high temp metal then we have to be very careful of the seal shape to lessen the chance of galling or gouging the aluminum housing. To me this would mean a wider seal face or less seal pressure, or a combination of both.


David Mikesell

Fantastic information David thanks.

What are the dimensions of the Sach's Apex seals?

You might be able to use cut down 12A Mazda ceramic or cast iron seals.

That is REAL interesting about the thin steel liners.
That would be relatively easy to duplicate. They could be chrome plated
with out much cost. They are trapped in  there.  They could be hard
enough to act like a spring. Squeeze them in at the waist to install them.

Sort of snap in place. Small buttons, or tiny hills  would or could be used to lock
them in place. This has some thermal heat loss advantages. The way Mazda does it
is actually not as good thermally. Too much heat is transfered to the aluminum.

Also long small diameter screws could be screwed in from the out side into small metal bars
welded to the thin steel sheet around the hump area to hold them in place.

Kind of funny I did not know about that. Thin hard stainless steel might work as well.
Even less heat transfer. Same for the side plates. Thin SS side plates could be water
jet cut and be the cheese in the sandwich :-). Much much cheaper to repair.

Doing away with the charge cooling will improves the volumetric efficiency up to 20 to
30% which translates to 20 to 30% more HP and a lower BSFC. We might
just come up with a world record low BSFC for all Wankel engines.

BSFC is pounds  of fuel burned for each HP generated.

Currently it is .47 for the leaned Mazda while a Lycoming is .45. The Cont. engine
in my C182 is as bad as .52. If we can get it down to .46 that is a HUGE reduction in
the history of rotary BSFC's.

Currently the BSFC for an air cooled Austro Engines one rotor is .52 to .55.
Higher for all charged cooled engines. Over .6x for the OMC's.

All turbo props are over .65 and as bad as 1.0 !!!!

Seems the thermal heat loss thing was the last thing on Kenichi Yamamoto  mind
when he designed the Mazda. He just wanted it to work.

Paul Lamar

Could you use a plasma deposition stainless application for the rotor housing. Would be sort of like detonation gun application.
Dale Davies


 The Rotary Engine free News Letter. Powered by Linux. If you want off
the list PLEASE let me know and I will remove  you.  ACRE NL web
site. http://www.rotaryeng.net You Tube http://tinyurl.com/beqqxas
Copyright 1998-2016 All world wide rights reserved.