>> > > Vacuum bagging is no problem, we do it on
almost every part we  >> make.
>> >
>> >  > I don't think i'm too worried about fire
personally. The  >> general layout
>> >
>> >  > is important.
>> >
>> >  > The spacers need to be inserted prior to
thermal cure. The  >> mold would
>> >
>> >  > need to have
>> >
>> >  > the sides needed for a motor mount built in.
This part might  >> be best
>> >
>> >  > done male-molded.
>> >
>> >  > The vacuum bagging would give a super finish
anyway.
>> >
>> >  > Bill
>> >
>> >  >
>> >
>> >  > Good idea on the built in motor mount. We
considered this
>> >
>> >  > a long time ago sand cast in aluminum but
the heavy weight was
>> >
>> >  > discouraging.
>> >
>> >  >
>> >
>> >  > Carbon fiber would be another matter
entirely.
>> >
>> >  > Here are a few old dwgs. It would have to be
redesigned
>> >
>> >  > for carbon fiber. I'll work on it.
>> >
>> >  >
>> >
>> >  > -- Paul Lamar ...No rotor no motor.
>> >
>> >  >
>> >
>> >  > Paul,
>> >
>> >  > The motor mounts need not be actually made
from the mold. The  >> flat
>> >
>> >  > sides George did for the aluminum BH would
work too. That  >> said if the
>> >
>> >  > shape could be kept somewhat simple it would
be lightest to  >> mold them
>> >
>> >  > in. A thin rib is difficult to set up in the
mold of course.  >> A fluted
>> >
>> >  > shape is better while still being removable.
>> >
>> >  > Bill
>> >
>> This is an opportunity to separate the bell
housing and  motor  >> mounts.
>> As the design stands right now,  you would have
to pull the engine to
>> service the drive. Not too  slick in my opinion.   Jerry
>> I see what you are saying Jerry but it is not
entirely necessary.
>> One could use a bunch of 1/4 inch nut plates and
remove
>> the long 1/4 inches bolts when one wanted to
inspect or service
>> the drive.
>> I think I have come up with a way of reducing the
cost at the
>> expenses of a little extra weight. Back to some
sort of
>> sandwich. 13 layers of pure carbon would cost
about $600.
>> If you could cut that down to about 4 layers the
cost would
>> be about $180 for carbon. Wood is not the most
fireproof
>> material but it is probably no worse than epoxy
resin.
>> Flat sheets of 1/8 inch thick aircraft plywood
>> could act as the core in all flat surfaces as
there
>> are several in this design. Narrow strips of this
ply wood
>> side by side could be used in the curved
surfaces. In the radii
>> several more layers of scrap carbon could be
used. The labor would
>> be higher but several hundred dollars may be
taken out of
>> the cost.
>> Tony why don't you run this idea by Dave and see
what he says.
>> I also thought of using 1/8 inch aluminum as the
core but the weight
>> savings would probably not be justified by the
increased
>> cost of the carbon/aluminum bell housing. A high
pressure die
>> casting is already as little as 1/8 inch thick in
some areas.
>> Yogi's idea of sand cast magnesium is also a
pretty good idea.
>> I think the Mistral bell housing is cast in
magnesium.
>> Paul Lamar ...No rotor no motor.
>
>
> I'll run it by him, but look! lets try to stay
focused here. I wasn't
> suggesting a composite bell housing because I was
worried about the
> cost. Remember we are strapping the redrive to
this thing, short of
> an engine failure if the bell housing fails it's
just as bad and if
> it costs a little more to make sure I have an
adequate amount of  > carbon
> then so be it, it's still an airplane you guys
some things you don't
> want to skimp on, and for me this is one of those
things. I will have
> my wife and kids in my airplane at some point and
I really don't want
> wood in my bell housing. Why don't we just let
Dave design the thing
> as he has already offered to do that. I think the
most important thing
> that we need to know is how many people will be
interested in one?
> or will be willing to lay down a deposit for one.
I'll bet Dave could
> crank a few out in about 2-3 weeks and know doubt
they will be worth
> every penny. What say yee?
>
> TonyT

Tony,  I am in favor of a Composite Bell Housing if
it meets very
conservative engineering standards.  At this point
in time we don't
even have a "seasoned" design.  The drawings are
iteration #1 and
have along way to go.  I am totally opposed to
including the engine
mount in the bell housing.  A bell housing failure
could cause the
engine to depart the airframe!!!!!    We need to
stop, inhale a
couple of times and go through an orderly process
with plenty of time
for the design to improve.   Also,  I want to say
that while saving
weight is a normal fascination for the home builder
as well it should
be, adequate strength is much more fundamental and
important.  Given
the potential for income, Dave should be willing to make up a
prototype that we can weigh, and test to
destruction.  This is
something I have done more than once.  I know what a
pain in the ass
it is, but it is the only responsible way.......     Regards,  Jerry

one big downside to carbon is, if it does fail, it
fails completely. s glass and kevlar are more impact
resistant (and s glass is much cheaper presently).
race car design is obsesively oriented to saving
weight often at the expense of reliability (see
mcclaran in F1 the past few years). but ultimately if
you want something which can fail with out
neccesarilly complete failure, it's hard to beat
metal. how about a composite with a metal frame?

gary



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