> > 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





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