Posted for "Mark Steitle" <msteitle@gmail.com>:

Ron,

Welcome to the club, we're glad to have you aboard.

Concerning #1, please see my response to Robert. The RWS re-drive design
has thousands of hours on it, tens of thousands are still a ways away. They
are proving to be very reliable re-drives. I'm using the RD-2C, which has
six pinions, providing 6" of tooth contact area. That should be more than
enough for 300hp.

No, the power pulses of the rotary are not harsher than a 4-stroke piston
engine. In fact, they are actually milder. Unlike a recip, the rotary
engine's pulses never go negative. I have a chart comparing the two, but
not handy at the minute. The 3-rotor fires every 120* of crankshaft
rotation, same as a 6-cylinder recip. Couple that to a 2.85:1 gearbox and
the prop sees more than 8 pulses per rev, compared to three on a direct
drive 6-cylinder, or 2 on a 4-cylinder. Clearly, the geared rotary is
smoother.

#2 - Yes, yes, yes. Rotaries can be obnoxiously loud, but they can also be
muffled. Tracy Crook, and others have settled on the stainless steel
Hushpower muffler. It quiets the beast and can take a licking and keep on
ticking. Other mufflers they have tried have lasted only a few hours before
being destroyed by the severe exhaust pulses of the rotary. On my 3-rotor,
I'm using a baffle, or insert into the 3" downpipe. It is similar to
the Spiral Flow mufflers used on the big block Corvette's with side pipes.
Not exactly quiet, but acceptable. Besides, the 3-rotor has three firing
events per revolution (versus 2/rev on the 2-rotor) and therefore has a more
pleasant sounding exhaust tone. Believe it or not, I've actually had some
people at the airport say to me that they like the sound of my 3-rotor and
enjoy hearing it run. Imanine that!!!

Concerning #3 & #4, I could try to add something else to Marv's response,
but I think that he did an excellent job answering them already. So, I'll
skip those.

Mark S.
(heading for the airport)


On 6/8/07, marv@lancair.net <marv@lancair.net> wrote:
>
> Posted for "Ron Laughlin" <ronlaughlin@gmail.com>:
>
> Hi Mark,
> I was also intrigued by the concept of a Mazda 3-rotor aircraft engine
> conversion. I liked the power to wt. ratio and the typically
> non-catastrophic failure modes. I researched the 20B rotary a little
> bit as a possible engine option for my Legacy. There were some issues
> however that concerned me enough that I abandoned the idea and haven't
> tried to keep up with newer developments. I was wondering what your
> opinions and/or solutions might be for my concerns:
>
> 1) The propeller reduction drive (RD). These have historically been an
> Achilles' heal for automotive conversions. As I understand it (or
> perhaps mis-understand it) rotary engines produce some really
> impressive power pulses which regularly destroyed early RD designs. Do
> you know of an RD, that is available now, that has several thousand
> flight hours of reliable performance mated to a 3-rotor, 300 hp
> engine?
>
> 2) Un-muffled rotary engines produce a LOT of noise. Actually, it is
> more like a painful hellish howl (to my ears). Do you intend to run a
> muffler of some sort? If so, where do you plan to mount it and how
> heavy do you think it might be? A turbo would be helpful here but that
> adds another layer of complexity.
>
> 3) Their exhaust manifolds get significantly hotter than a
> "traditional" aircraft engine. IIRC, Mazda had trouble with the heat
> from the exhaust system on the Lemans racer igniting the the car's
> plastic body panels. Are you planning to use shields to protect the
> cowling and engine accessories from the additional heat?
>
> 4) Like 2-cycle engines, they require oil in the fuel for lubrication.
> Will you be using a separate oil tank and automatically injecting the
> oil into the fuel system or pouring it into the fuel tank? It seems to
> me that either method could introduce more possible failure modes.
>
> Thanks,
> --
> Ron Laughlin
> Legacy N44L (res)