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.
Paul Lamar
Good afternoon Paul
i really appreciate your help on my project
It seams to be about 75% as per my original design which i
include you may be able to open with your program.
I am looking to built 4 passenger back to back with front
passenger and enought room for two additional
rear passenger close to cg.
Let see what you came up at 75% and if we locate the engines
on wing they can be much forward back of the center wing
similar to the Piaggio and play with other components for
cg purpose.
I intend to built the outher skin straight on foam plug
so i can same money on moulding and it can be anytime to
make a mold after the airplane tested and with all futur
modification modifications
The foam plug can be pre cutted on a factory who are
specialised on foam moulding form for house and
commercial construction.
Jean Prudhomme
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