Good afternoon Paul

There is my revised design i tend to use Tracy prop shaft
who as been tested for several hours, i know i will have some
weight but for the first test i will go this way and then i can
redesign or improve after testing for several hours and
different rpm.

The main trust line can be located inside of spool bolts surface
and back plate, the way i locate it will be hard to install it.

The second trust bearing between prop shaft and spool can be
omitted and use the bushing only what you think

The back plate will be perforated at 4 points to received the
rubber bushings mount and each side of front part with 4 gussets
and 2 of them will have 2 rubber bushing mount
I know you are in favor of carbon fiber tubing but at this speed
we need a good lubrication bearing with oil circulation and
cooling and carbon fiber resin are not good friend with oil.


I will draw on drawing board on my return to USA.

If someone have comments about this design they are free to let me know.


Jean Prudhomme

Tracy says his output shaft is not suitable for a 50 pound constant
speed prop. I agree.

Are you still placing the engines nose to nose in the tail?
The fuselage will have to be 80 inches wide.

Paul Lamar

The engine lenght at flywheel is about 23"
23" plus 2" space between approx plus 23" equal 48" this is the
actual size of the velocity at firewall but i will see what i
need extra.

If it work fine i will have to built the other housing for the
opposite hand with the pinion shaft at lower the centerline and
both driving shaft s will be close to bottom wing skin and the
propshaft is located above the wing trailing edge.

From the flywheel is the driving shaft with taper housing with
starter may be part of transmission 2nd generation housing and
will blend with the high of the airfoil at this position maybe
with a little reset serve as a scoop for cooling .

The Tracy shaft will be use as ground ajustable propeller same
as been design by Tracy and is easyer and faster to built the
gearbox..

The constant speed prop it will be in future if the the gear box
work fine  and i will see what kind of design i will need at
that time,

I just want to ground test for the first design and see how
this concept will work on stationary stand and if i have good
result it can be modified to save weight.

Installing the engines on wing will bring some extra
weight,double spars,extra structure , more surface drag, fuel
cell in the strake if leaks it will be a real danger with
engines located  behind the fuel cells.

I see lot of advantages regarding weight closer to cg and
rolling axle,stronger engine mount attachement at firewall,only
one fire proof wall,small engine mount attached to the main spar
,reverse prop rotation,oil cooler in front of the propeller
box,water cool radiators below engines,shorten and easyer to run
engines controls ,electronic wiring ,ect

With a single spar wing we have to keep the full wing assembly
for the strenght behind the spar and with this design i do not
alterate the bottom skin only beefee up and the upper skin will
be altered and reinforced to receive the prop shaft located just
above the trailing edge.

It,s a new idea and concept and it worth to try it


Jean Prudhomme


At the end of the engine you need a bell housing and a bearing
to support the U-joint. That is another 5 inches minimum each engine
or 10 inches total. Maybe not 80 inches but a pretty wide fuselage
never the less. Get Bill Jepson to draw this up for you to scale.

If you used conventional twin nacelles and Tracy's gear boxes the
props would be 50 or so inches closer together. You could slim down
the entire fuselage in the area of the nacelles. It is called
a pressure recovery fuselage shape.

http://tinyurl.com/klropu
http://preview.tinyurl.com/klropu

Paul Lamar