-"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-

Phil
If  We understand what you are wanting to do, build a counterrotating helicopter
using rotor rpm to produce the lift/thrust needed, without having any pitch
control on the blades?
If so here is some information.
Bensen did that with the "little zipster"

[Image]

It was mainly designed to be used to herd cattle, and as you can see from the
picture it wasn't intended to fly very high.
We have the plans for it. They are not complete in that some of the components had
to be purchased from bensen such as the transmission, and no details are given as
to how to construct it or even pictures, just how to bolt it together.
Since there is no way to control the pitch, it is not a feasable design. We
understand that you want to use two rotary engines for safety.  Even with the
rotary's being as reliable as they are, other problems can easily cause you a
literal headache. :-)
It can be controlled with the overhead stick, but tilting the whole rotor head and
shaft is  a very unstable way to get thrust.
If you are intent on building a coax, do it as a std helicopter with a swashplate
type control that changes blade pitch for thrust.
A coax is one of the most stable rotary wing platforms out there. Far more stable
than a tail rotor.
The next closest thing for stability is an intermeshing rotor system, like the
Kamax syncropter.
Gyrodyne built over 800 coax's for the Navy's drone program, and first built the
rotor cycle that used a pilot. They also built the first composite rotor blades.
Your question was on the material to make the rotor shaft out of, and most lite
helicopters use 4130 steel.
The Adams-Wilson Choppy, the Scorpion, the RotoWay exec's, the A/W 95, the
skytwister, the Helicycle, the Mini-500, the Aeros, the CommuterII, and several
others use a 1 1/2" shaft, usually 1/4 to 3/8 wall.
Some of the RotoWay 162's and exec's use a 1 3/4" shaft. Don't know the wall on
it.
Each of these helicopters are different weights, both empty, and loaded.
You should be able to get the specs from a shaft supplier for different wall
thicknesses for different stress levels.

Most of these helicopters have a proven track record, with many units flying and
having flown over the years since the choppy came out in around 1954. It was the
pioneer if you please.
If you would like further info lets do it off list so everyone doesn't have to
read all this helicopter stuff.
Royce

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