phil wrote:
Would seamless pipe (4130) be a proper "tube type" material to
use
for a shaft turning max 2000 RPM @ 200hp, 300 hp max? The ends
need to
be splined to slip onto a gear.
If seemless pipe won't work, what might do the trick? It must
be
hollow because I need to run a tube through it.
Dimensions are everything. Do you have a sketch?
What RPM is the engine generating 300 HP? Also what type of
engine?
Four cylinder piston engines at 200 HP have much worse torque
pulses than 2 rotors or a six cylinder piston engine.
What is on the end of the shaft?
Paul Lamar
Since no one answered, I'll give my two cents:
1. I would suggest to use seamless mechanical tubing of near
90,000 - 110,000 psi tensile or higher, such as 1340, 3140, 4140,
4340, etc.
Even 1050 or 1060 might do. The higher steels are better against
corrosion.
Do not use "pipe" per ASTM specs.
2. A quick calculation at 8000 psi stress and 300 hp shows that
you need about 19,400 mm3 polar section modulus Zp.
Suitable tubing is 2.5 in OD with 1/4 in wall (29,600 mm3),
or 3 in OD with 3/16 in wall (35,800 mm3)
Using a spline at the ends makes the 1/4 wall better suited.
A 3" OD Tube with 1/4" wall has 44,900 mm3 which might be
overkill.
This is of course a rough calc for a reasonably short shaft,
without
any consideration for vibrations and assuming a fairly even
torque.
Instead of steel you may want to use seamless Alu-tubing that is
lighter.
I am not sure what stress is used for Aluminium. Perhaps 4000 psi
for 6061 T6
or of the 7 series Al. With Al the polar moment should be near
40,000 mm3.
A 4" tube with 1/4 wall has ~85,000 mm3. Quite safe.
A 4" tube with 3/16" wall is ~67,000 mm3.
No responsibility, of course, just a suggestion of the approximate
size
required.
Rolf Pfeiffer
I can see I'm way over my head here. :) But it's a learning
experiance
at the least.
I'll assume aluminum would be an easier material to learn with.
Within
the next 6 months, I want to buy a lathe and small mill. I've seen a
3
in 1 mill in kitplanes that is CNC ready but the lathe is a bit
short
for long term goals. I've been looking at a few Grizzly models that
won't bust the bank also(G3617 horizontal/vertical mill for $3000.00
and
the G4016 lathe for $2700.00).
My little "Evans Handbook" has charts up to 3" inch tubing, with a
wall
thickness no greater than .250". I'm guessing I'll need something
closer
to .500" at the least.
Can I turn pipe down so I have a shoulder for a bearing to come up
against to transfer the load? I have a very rough drawing I'll
send. I
have no ideal on where to place the bearing properly, so I just
guessed.
I'm open for any suggestions. :)
Max weight of aircraft would be about 2000 lb. I'm doing some rough
rounding, 500lb. passengers & "extras", 500lb of engines (two
13b's,
most likely turbocharged) 500 lbs of fuel and 500 misc for frame
etc.
Very rough but at 2000 I'd still have only 10 lb per HP on one
engine
(assuming 200 hp per engine).
Anyhow, attached is a sketch of the mast.
You are way over my head too. You need help from an experienced
helicopter design engineer. These things are not trivial.
Paul Lamar
I figured I could play around with the idea (just the mast and
gearbox, NO ROTORS!)
in my backyard to see what it would take to bust it. :) I figured I
could bolt it
into a jig, then power it with a pair of 3 hp. AC motors I have. The
plan was to
use hydraulic jacks with guages to measure the radial and thrust loads
before it broke.
How does one find a design engineer? Megga bucks? Just looking in
the
Portland yellow pages gives me nothing. If my idea would work, am I
not just handing someone a "Why didn't I think of that" game plan? I
know this sounds a bit lame, but in my mind, I think I'm on to
something. :) I've searched and searched the internet and have come up
with nothing close, as far as small coaxial helicopters go. Yaw
control
in a hover is what I *think* is different with my idea. No
swashplate,
no tip brakes, no tilting rudders to vector rotor downdraft. Also, no
auto-rotation...thus the two 13b's. BUT, a hollow rotorshaft for a
ballistic recover system...just in case.
Thanks
Phil Williamson
Advertise in the back of EAA Sport Aviation. "Help wanted. Retired
helicopter design engineer."
The wonderful thing about the internet is he could live anywhere.
Paul Lamar
Phil, why don't you look at what Bell has built over the years, the 47,
and the Jet Ranger in
particular.
You can find the mast (rotor shaft) sizes, material from a web search.
Bell's site used to have the specs for the Jet Ranger and the Huey, but
when they upgraded the
rotor system they changed the web site as well.
Could not find much but advertising the last time we visited it.
4130 is usually the material used. Diameter and wt will depend on your
rotor system and gross
weight.
The Jet Ranger is limited in max continious torque because of bending
the rotor shaft. When they
upgraded to the higher powered engines, they may have changed the mast
specs to sustain the higher
power ratings of the new engine.
Royce
Thank you Royce. I'll go poke around. I always seem to get a bunch hits
on RC model stuff.I need to learn to search better. :) I found a book in the
back of my 'Aircraft Spruce' cat. by Dr. Eric Hollman and Martin Hollman
called "Modern Helicopter Design" I'll be ordering. It comes with several
programs as well. I hope it'll be a good source of information.
Phil
-"Steven E. Odle" wrote:
Might want to check out 4340 it is superior in that app. able to take torque
and shock,( WHEN),
properly heat treated!
It is widely available at a price!
N34FR-
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