> > 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?
Tony
Tony,
I have several disjointed comments to make. So, there is no particular
order here. Do you know what procedure Dave uses to apply his resin?
The middle layers of carbon would pretty much be wasted in a structure
like this. Having a core is a good idea. I would suggest using a core
mat and introducing the resin via vacuum infusion. This is not the
lightest way to do it, but, it would give plenty of time to lay up the
cloth carefully and the core mat can be made to conform to the shape.
Paul, as Bill suggested, your most recent drawing with the mount
integral to the housing is going to be difficult to lay up on a male
buck. I would prefer to follow through with the Schertz beam ideas and
keep the mount separate from the bell housing. I'm also a little
concerned that those long through bolts will be subjected to some
cantilever loading off the front of the housing. A conical shape or a
shape like the small end of an egg would transfer loads directly to the
engine housing. It would be important to put some uni cloth running
helically at about 45 degrees in the outer layers around the bell housing
to make sure the carbon feels only tension. Dave does beautiful work,
but I'm not sure he would want the responsibility of the engineering
design on this thing. I became disinterested in his airplane when I
saw the indentation in his firewall that formed less than a 1" clearance
around the hot end of the turbocharger. :-)
I'm not a candidate for one of these. I'm planning to use the Ross unit.
Aubrey
The Ross unit is a very fine design with the exception of the lack of the helical
gear thrust bearing. The very latest versions fixed that oversight. It is about
ten pounds lighter than Tracy's. Only towards the end did the quality control go
down the drain. Too bad they are not still around. I would love to know what
happened to the casting patterns.
Paul Lamar
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