Re: Lycoming engine fails! Pilot survives!

Rick Pellicciotti wrote:
> 
> "Corky Scott" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
> > On Wed, 03 Dec 2003 02:05:35 GMT, Roger Halstead
> > <[EMAIL PROTECTED]> wrote:
> >
> >
> > >The life of a PSRU on a piston engine has to be complicated.  It not
> > >only has to handle linear torque and thrust, but virtually any other
> > >imaginable angle as well. Then it has to be designed to avoid any
> > >resonances with those power train pulses AND take the positive and
> > >negative torque without beating the snot out of the gears which means
> > >next to nothing for slack (which brings its own set of problems).
> > >Helical, double helical, spur, planatery...each with it's own set of
> > >pluses and minuses.
> >
> > Most manufacturers seem to take the attitude that big is strong and
> > bigger is stronger.  In order to resist the impulses and resonances
> > you mention, they just design huge gears to take the load.
> >
> > >BUT, didn't  the big 12 and 16 cylinder Vs in WWII have PSRUs? Course
> > >those engines had very short TBOs too.  Then again they weren't
> > >exactly babied either.
> >
> > Yup, the Roll Royce Merlin uses a spur gear reduction drive, driven
> > off a torque tube.  Those gears are some big.  Every single one of the
> > big radials also used a reduction drive, but was a planetary type, not
> > spur.  I think the low TBO was more due to the nature of the treatment
> > of the engine during combat than something inherent in the design.
> > But come to think of it, they still don't have a very high TBO even
> > now, when they don't have to be run up to military power for every
> > takeoff.
> >
> > By the way, the Rolls Royce Griffon engine was sort of two 12 cylinder
> > engines siamesed together for a total of 24 cylinders.  I'd hate to
> > work on that thing.
> >
> > >Also...How did the guys make out using the Olds chain drive in the
> > >Legend?  It "appeared" to work great for at least a short time, but
> > >they were running 400 to 500 HP through a chain that was used in a
> > >drive train that only had about 200 HP on the other end.  When I
> > >talked to the one guy at Oshkosh some years back he thought it had
> > >plenty of reserve.
> > >I always like that airplane. Last I saw it had a turbine up front.
> > >
> > >>Sorry, that should be NSI.
> > >
> > >I know when he used the original "so called" chevy big block aluminum
> > >based engine he felt the front web was the weak spot. Course that was
> > >right after planting his IV_P off the end of the runway when the web
> > >broke. (or did he make it back on that one?)  At any rate the web
> > >broke and it was a high pucker factor.
> >
> > I hadn't heard that the web broke.  The story I got was that they did
> > some computer analysis of the engine design and factored in the prop
> > forces that would be transferred to the block by the PSRU and decided
> > to add material to the block where the PSRU bolted on.  Of course, Jim
> > could have told me this AFTER the engine broke, don't know.
> >
> > Corky Scott
> Corky,
> Sorry, but the Griffon was a V-12 like the Merlin, just BIGGER:
> 
> http://www.home.aone.net.au/shack_one/rolls.htm
> 
> Rick Pellicciotti
> http://www.spitfire.org

However, there were at least two variants of Rolls Royce Griffon engines:
1       On the Spitfire, it had a single five bladed propeller which 
        rotated in the reverse direction from the propeller on the
        Merlin engined aircraft.  I have been told that it killed a few
        unwary pilots who forgot and pressed the wrong rudder pedal on
        take-off.   :-(
2       On the Lancaster, and on at least one single engined attack
        aircraft (I can't recall the name), it was equipped with a pair
        of concentric contra-rotating propellers.  As you say, though,
        the engine itself was similar but BIGGER.

Regards,

Peter