Yes and the needle bearing has another problem. The centrifugal
loads on the needles tend to vary causing the needles to slip on the shaft.
This is aggravated by any wear. See the diagram below.

The engine still uses an air cooled rotor which requires a 
air pump that subtracts HP from the output causing a higher
BSFC. This is not a problem in a motor glider or a sport
airplane not used for long distance transportation.

Paul Lamar


Mark Wrathall wrote:

Mark wrote:
When Paul and I visited Diamond and had a tour from Martin, it was clear to
us that Sachs, Norton, Mid west, Diamond started with a flawed design and
have stuck to it until it was forced to work through force of engineering.
The problem is the needle rotor bearing (a design requirement due to the
decision made nearly 50 years ago to pursue air cooled rotors rather than
the oil cooling Mazda choose). This bearing runs fast, hot and with very
little lube (being a total loss system, you optimise the oil injection
system to min consumption).

The solution is an e-shaft, rotor, bearing which have to be hand selected to
a matched set with some ridiculously tight tolerance if the engine is to
return decent reliablity. This is expensive on a 1/month production rate. It
is out of the question if the engine was ever to be produced in any numbers.

Dispite this need to select a match set, the rotor bearing is still the
limiting component on RPM and reliablity.

Martin was very proud of his engine, and cited enough examples to indicate
that the reliablity is very good. At the end of the day you have a light
powerful engine, with good reliablity which is simply not competitive on
price.

The motorgliders are a nich market. The machine is optimised for incredible
performance and costs a small fortune. In this market, the diamond rotary
offers the best performance, and the price is only a few percent of the
complete aircraft price.

Regards,
Mark Wrathall
www.wankel.org

Dirck Hecking wrote:

Amusing Comment from Chris Gries....

OK Paul, so that teaches me that they have a money arrangement with the
recip guys that is so favorable to Diamond, that that money arrangement
killed the better engine. With 400 plus motor glider rotary powerplants
shipped they decided to keep on installing rotary there... This teaches

me

that the recip guys, even with their preferred dealing privledge money
arrangement, could not compete in an arena where good science defeats
greed. Sorry, to be SOBlunt here, but the notion that science defeats

the

rotary just wont fly!

Dirck Hecking

I had a brief conversation with Chris Gries at OSH owner of Diamond

Aircraft.

Diamond is neck and neck with Sirus on being the second largest
light airplane manufacturer in the world. They are also the distant

second largest

wankel engine builder with over 400 single rotor engines shipped
for motor glider use. Chris said they have no plans to market the
certified two rotor as it is too expensive to produce. You can send

him

email and say you will pay $12,000 US and he might change his mind.
He does plan to sell an enlarged 75 HP single rotor version.

Paul Lamar

 
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