> Not a good design. Cantilever everything. Puts a side load
     > on the rear main that it is not designed to accept.
     > I am not talking about pre load tension. Has nothing
     > to do with pre load. Anytime you are transmitting HP
     > with a belt or chain there is a side load. Best to
     > straddle mount everything like this Ken Welter belt drive.
     >
     > Paul Lamar ...No rotor no motor.

    There's a lot of extra (and unnecessary) mass on the Welter
    drive.  He's
    got the right idea, though.

    A combination of Welter's and Valley's design is the best set of
    trade offs.  Add an outboard bearing straddle support to the Valley unit,
    made of a 1/2" x 2" bar that goes out past the big pulley to a
    couple of
    blocks bolted to the engine, and you have solved the problem without
    adding another 10lbs of dead weight.

    Drive designers usually base their stuff on auto designs.  Car makers
    have to over design, because they know that someone will take it to the
    limit and because a car takes many sharp shocks just in being driven
    around on the streets.

    Aircraft prop drives don't get those shocks.  If you study other, proven
    aircraft structures, you will see ways to design things which are
    nothing like the original (car-based) idea.  In the case of my
    suggestion, I remember when I was interested in Gyrocopters -- which
    hung the entire aircraft, fuel load and pilot from a rotor head attached
    by a couple of aluminum blocks such as I've described.  If it will take
    that kind of load, a similar structure will do just fine with any load
    your PSRU can generate.

    BTW, a large chunk of the planetary PSRU weight can be eliminated by
    some re-engineering.  Again, Ford designed it to allow a 300 HP engine
    to  push a 10,000 lb load over many years' worth railroad crossings,
    potholes, etc.  The prop load is less than about 250 lbs and all
    twisting forces on it are much longer and softer than just a drive to
    the grocery store.  The only inherently fragile parts of the whole drive
    are the gears, but there are extra pounds of carrier, housing and so on
    which could be rethunk.

    Consider that all you really need for a housing is a sealed "can" for
    the carrier assembly to spin in, that you pump cooling oil through.  The
    carrier itself can be lightened.  All you need for an output shaft is a
    SEAMLESS TUBE long enough to attach a prop mount to.  With a
    straddle-mounted bearing at the prop end of the output shaft, your
    housing could be a couple of layers of CARBON FIBER.  The common input
    shaft is likewise way to big and heavy, so go to seamless tubing for
    that, too.  *POOF* your 40 lb reduction is now a 20 lb reduction.

    Keith




The PSRU system either needs to make sure that all harmonic loads are
avoided (designed out of the operating points) or that the system can
absorb the harmonic loads with a wide strength/fatigue margin.  If the
sources of the loads is not well understood (rarely are they) it makes
sense to overbuild the system..


Regards,

Matt-

To a point.

What's on the market far exceeds that point.  Look at what's been done
elsewhere without failure -- at less weight.

Keith




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