Bradley Darville wrote:

Dear Mr. Lamar.
I have read about the tortional vibrations produced by rotaries. I was

wondering what your thoughts are on the use of a morse Hy Vo chain  type
p.s.r.u. ? I understand that this type of chain is very good at dampening
vibrations, and I know they are extremely reliable in other applications. I
am also fascinated by 60 degree V6's for various reasons.. anyway, I
stumbled across one that I found very interesting. This one is used on a
yamaha outboard motor. It is very compact, 4 valve, injected, with the
exhaust ports on the inside of the "V". They claim 225 H.P. from this gem of
a four stroke, 60 degree V6. If yamaha builds an Inboard version of this
engine, It may make a beautiful conversion. I have experience with some of
yamahas recent motorcycle engines and I find the design and execution of
these machines to be awe inspiring , and would not be surprised to find the
same to be true of their marine products. Im telling all this to you because
my wife no longer lets me talk !

about engines around the house...thanks for your time. Sincerely, Brad.

____________________________________________________________________________
_______

Actually the torsional vibrations of a rotary are less severe than a four

cylinder

piston engine.

The lightest psru's and the ones that fits airplanes the best are made
from planetary gear sets.

A rotary is totally unlike any piston engine. There are not a zillion

little

parts rubbing together and jerking back and fourth to wear out. It is also
far more robust structurally speaking and never fails in the hand grenade
mode like a piston engine.

There is absolutely no comparison.

Paul Lamar

I agree with Pauls accessment of engines & redrives but I understand your
attraction to the Yamaha.  The potential of some of the marine outboards is
awesome, mainly for their power to weight ratios.  Reliability wise, the
rotary is tops.

I once flew an OMC V4 (2 stroke) on an aircraft which showed some of its
potential.  It was an aerodynamically dirty thing and the engine was direct
drive with a short prop; the worst possible combination, but it still flew
rings around similar planes.

If I get serious about competing in time to climb competition I may retrofit
my RV-4 with a 250 - 300 HP outboard engine fitted with a redrive (Planetary
type).  The engine would probably be one of the two strokes for weight
reasons. This will of course have to wait until my 20B RV-8 is finished.

The Hy-Vo chain drive is a viable configuration but like any of the others,
it must be properly engineered for the application.  Pound for pound it's
hard to beat the planetary though.  The offset of the chain type could be an
advantage with some engines, especially V engines with those odd valve
devices  :-)

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

Heresy. You of all people? An outboard motor? Two stroke? Why don't you just
use a turbo rotary and nitrous oxide and get 800 HP? A 300 HP outboard is
10 or 15 thousand dollars. What have you found out about rotaries that
you are keeping secret from us Tracy? :-)>

Paul Lamar

Paul,

Pistons shure sound as heresy but there is one point in the favor of an outboard.
These are usually used at WOT for much of its life (at least my 200 hp V-6 OMC)
and I have never had one that died while running. Sometimes, hard to start but
once they are on the go, there is no comparison with their earthbound 2-stroke
counterparts and the low weight is something to very seriously consider as well,
even taking into account the cooling system.

I will continue pursuing the rotary as the safest alternative, but besides this,
if there was an apple in Eden, that was the outboard above any other
reciprocating engine.

Corrections and flaming are welcome.

Alfonso Lebron-Berges

The AirCraft Rotary Engine NewsLetter.              Powered by Linux.
ACRE NL web site.
http://home.earthlink.net/~rotaryeng/            http://www.linux.org