snips.....

I already contact a drive shaft manufacturer and i need a shaft of 24"
long for my drive
and they can make it for $600.00 for a ligt weight shaft with 1"dia gun
drill shaft
estimated at 8.5 lbs
with a 45mm bearings but if i can get to 1 3/8 shaft with tracy exact
bearing it will be
fine.

I already contact Tracy to have the shaft i need and he said it will be to
expensive .

I can reuse his housing to attach to the shock mount plate.

I do have all the parts on hand to built my angle drive at 3 to 1 ratio
and i should
assemble it as soon i solved my bearing and shaft problem
I do have an aluminum spool with 28 splines and i need to rebrouch to 31
or 35 splines.

I can buy a rought housing from Tracy and do some machining to suit my
shaft but i can by
pass his housing to have a lighter housing by using 2"I.D. x 3" O.D. and
weld stiffner rib
of alum 1/4 thickness to the gear end housing

and it will be on one pce instead 2 parts with Tracy Housing lighter.


Jean Prudhomme


You cannot put a prop on the end of a 24 inch shaft. It is against the
laws of physics. It is just not a bad idea it is the LAW. The penalty
for breaking this law is a crash and possibly death.

Jean,

Read these web sites.


http://www.epi-eng.com/mechanical_engineering_basics/torsional_vibration_int
ro.htm
http://en.wikipedia.org/wiki/Torsional_vibration


http://www.bksv.com/Products/LaserVibrometry/TorsionalAngularVibration.aspx


Paul Lamar



Yes i understand but if the shaft does have a bearing support at 11" or
12"
and have oil
circulation inside the shaft as return fluid can reduce enought the
oscillation .

Now how come on car and truck those axles shaft of 33" and over
unsupported
and with a
heavy load as tire does not break as you said in oscillations cycle.

On a copter they do have sometime shaft over 24"

Jean Prudhomme

The oil circulation and the intermediate bearings have nothing
to do with the torsional oscillations.

The moving rubber tires on automotive vehicles are in constant contact
with
the road and the friction in the rubber damps the low frequency torsional
oscillations. In some cases you can get severe torsional oscillation when
you break the tires loose on burn outs. I can do it in the RX8 any time
I feel like it.

Many air craft designers in the past have tried driving props with long
shafts. The vast majority have given up. One of the most famous was the
Bell P-39. The BIG difference is the gear box is right next to the prop.
The same thing goes for helicopter tail rotors. The shaft RPM is much
higher
than the prop RPM. That lowers the resonant frequency of the torsional
vibrations in the shaft so that range of RPM's can be avoided.

The only possibility for success and you will be the first in the world
is stiffen the prop shaft to raise the resonant frequency beyond 2700 RPM.
The way you do that and keep the weight down is use a large diameter,
very stiff, hollow carbon fiber shaft.


Here is the message I sent on this subject back in August 2009.


============================================================================
Here is a 3D of a traditional rear axle spool. It has a couple of features
we don't need. Namely there are two axles coming out. One on each side.
This means the bearings need to be rather small to support the axles.
This also means there is considerable bending loads on the spool due
to the gear separating forces. These must be reacted in the bearings
as shown by the red arrows. All and all a very heavy design.

We have a carbon fiber prop shaft coming out only only one side
so we don't need those bearings. The gear separating forces will be
directly
reacted by the large diameter thin section bearing in compression.
No bending moments. The shortest possible load path. Thin section bearings
are
a recent development. They are sometimes called helicopter bearings
because
light weight is every thing in a helicopter.

BTW The history of shaft driven propellers has not been good.
Every designer has had trouble from the P39 through the early Northrop
prop driven flying wings and the B36. Not to mention a bunch of small
aircraft designs. A prop at the end of a long shaft is a tough
engineering problem.

The reason I am undertaking this design is the advent of hollow large
diameter carbon fiber shafts could mitigate the problem due to the high
stiffness to weight ratio. We will use Tracy's design on the torque pulse
isolator or a copy of it which hopefully will allow us to tune out
the inevitable torsional vibrations.

I suggest Jean build a ground test rig to try this system out before
he builds an aircraft around this idea. You don't want to get it all done
and then find out you have a serious problem.

Paul Lamar
=========================================================================

End of quote.

Your goal appears to be building a canard pusher with lower drag.

The rotary engine has a very low frontal area for the amount of HP
it can developed. I would take the advice of NASA and put both engines in
long, low drag nacelles on the wing with the PSRU mounted on the
engine.

We have a big FBO here at Camarrilo airport that specializes
in Piaggio P180 Avanti II Twin-Engine Turboprops. These airplanes are
very very fast. I watch them fly over my house all the time
apparently on the way to Hawaii.

Pratt & Whitney PT6-66B engines give a cruise speed of 398kt at
altitudes over 35,000ft. The maximum range is 2000 miles.

I would scale this airplane exactly and use turbo charged rotary
engines with half the fuel burn.

You will save a lot of weight, cost and time.

Paul Lamar


"We have a big FBO here at Camarrilo airport that specializes in Piaggio
P180 Avanti II Twin-Engine Turboprops. These airplanes are very very fast.
I
watch them fly over my house all the time apparently on the way to
Hawaii."

I don't think a standard Piaggio has the range to make Hawaii west bound
from the west coast. It's over 2100 NM from Camarillo. Add a head wind and
they'd need ferry fuel tanks.

Jay

It is 3322KM. They may have added a bit of fuel.
That works out to 2076 miles at .625 conversion.

Paul Lamar

Paul tell me how i can find the informations and be able to
scale the Piaggio.

On the past i pick up a t tail design from someone on the group and i would
like to know more about it.

Sure i can buit a prop shaft with 3"dia carbon fiber which it have to run
on 4" dia housing it is possible to do the outside of end housing is already
4" dia a bit of machining and weld 4"dia aluminum tubing with reinforcing
gusset.

Like i told you on the past i am building one unit and do ground testing
prior to go further .

I know it will be easyer to install both engines on the wings

You see Paul the raison of building the drive shaft system is to keep the
engine away of the fuel cell strakes and i am aware of heat generated from
the engine to the composite wing.


Jean Prudhomme


OK I see what you are worried about. Things are making a bit more sense
now. Since you are starting from scratch we will see if we can come up
with some answers to those problems. Here is one idea. Stainless Steel
has low heat conductivity so a motor mount made from stainless tubing would
be better. The rubber motor mounts will also help. Boeing probably has
somewhat
the same problem on the 787 as the wing is made from composite.

I would put the fuel in the outer wing panels as that cuts
the spar weight. With the engines on the wings there should
be lots of room for fuel in the fuselage.

Just how big is this airplane? What do you figure on for
over all length?

Here is a good 3 view. You tell me how big you want it and
I'll do a 3 view so we can check interior space for people,
fuel and engines. The drawings appear to be in mm so the actual
full size airplane is over 36 feet long. One thing about
3 surface airplanes is they are not as CG sensitive as
canards.

Jean Prudhomme, see me at sun and fun, I go to forums and alternative
engine area, the computer lab, and composite shop and the ultralight flying
for the last hour. I can show you in minutes how to get a lofted fusaloge
shape with interior bulkheads etc in a day. I did a canard last week by
recycling my wing and its internal structure by adding the sweep and change
to dihedral, and the tail from my conventional airframe. The roncz 1145 ms
canard and the fusaloge are new, fit around the passengers, engine, avionics
bay, nose gear etc. The entire plane was lofted in one long day. The air
intakes and ductwork took an additional 1-1/2 days.. Some weight and balance
calculations run on the lofted plane will be necessary for the exact main
wing placement. If you have a cross section at both ends of the engine bay ,
the passenger compartment at the location a baseball cap would be worn and
a profile view of the side the rest can be generated. An overhead view
would be helpful.

For the passenger compartment lean two chairs against the
wall at the angle you want to recline the seatback and have someone measure
around you and your wife sitting in the chairs. The engine bay measurements
need reasonable allowance for cooling ducts and accessories. The cross
sections don't need to be the same shape. The posted examples are eliptical
with the top and bottom elipses different and joined at the widest point.
You can do circular, rectangular with rounded corners or something
constructed with arcs and lines. When you have the shapes rebuild the lines
with four points per inch and G3 continuity then loft it.
I will include the Trex airframe to show where the canard wing
started from then a view before adding the winglet tails and one with them.
If you have the airframe in your cad system you can do cross sections during
construction for the canard mount or landing gear reinforcement, or
firewall to scale and just cut them out of pvc foam. Also measuring the
surface area of the parts is necessary to calculate weight and balance. I
use 8 harness satin weave and add the weight of fabric plus 10 % for resin
weight. Add the secondary bonding material to the weight of the bulkheads to
make weight and balance less cumbersome.
I would like to dicuss with you what mix and type of plaster you
used building the plugs for the velocity moulds so I will be looking for you
also.
Are you still planning to have the engines end to end across the
fusaloge or are they one beside the other.

george grimes


    Hi Georges

I will be at Sun and Fun and will be happy to meet you there.

Like paul mention is two alternative, first i woulk like to finish my drive with carbon fiber 3"dia prop shaft and then ground testing and the other alternative is to install the engine on the wings .

Paul will work with me to redesign the piaggio at 75% scale by using the Mike James 1/6 scale cad design it will be much simpler and fasteron which my original project is close to Piaggio airplane .

I bought a new 250 amps tig inverter welder and still in the box for now ,i do have differential part from Lightspeed engineering and figured out how i will design the carbon fiber propshaft

Jean Prudhomme
        

If somebody brings a PC with Rhino on it to the work shop
tent I 'll share some of may dwg secrets :)

Paul Lamar