Mart,
The Constant Velocity Joint + Hub Spring rotor is a theoretically viable concept and it may be of interest to other developers of very-light rotorcraft. However, in my mind, it is only a progressive step in the movement toward an 'absolutely rigid rotor'.
Since there is no desire nor need for government funding or outside investors, I am afforded the liberty of striving for the whole enchilada. The risks are greater but the challenge is more exciting.
____________________________
Nick
Your postings and critiques are truly appreciated. However, your last one is disturbing.
I love the way you ....use past mythical helicopters as rationale.
The
Flettner Fl-282, the
Focke Fw-61 , the
Kellett ~ XR-8, XR-10 , and the
Sikorsky ABC were not "past mythical helicopters". The only mythical helicopter is the
Stepniewski (concept) and you have said in the past that Stepniewski was the aerodynamicist who you admired the most.
And you confuse the objections I raise as opinion, when all I ask is that you use some facts!
Dave can you define "absolutely rigid" and also describe the stresses in that rotor? Can you tell us what the vibration would be?
I defined
Absolutely Rigid Rotor for you. In regard to 'stress' and 'vibration', there is limited time available to deeply consider lower level details, at this stage of development. New concepts come from a top-down approach. A bottom-up approach can do no more than 'tweak' the existing.
While we are talking about mythical helicopters and facts; I have stated and provided a supporting argument on a valid concern about Sikorsky's latest concept, on my web page
Sikorsky's Reverse Velocity Rotorcraft Proposal. Your "factual" response will certainly add to the knowledge of the participants on this thread.
_______________________
slowrotor,
A few years ago Nick mentioned that the extremely high vibration of the
Hiller X-2-235 had even done damage to a wind tunnel.
The question then becomes; Why?
The answer is the 2/rev lateral dysimitry of lift during forward flight.
This craft has two blades per rotor, which ain't no big deal. However, these rotors are 'absolutly' rigid, and this is a big deal. The blades will be crossing each other at azimuths of 45º, 135º, 225º and 315º. In addition, because the blades are rigid they will be producing more thrust at the back of the craft then at the front. At one moment, two blades are providing high thrust in the left-rear quadrant, then a fraction of a second later two blades are providing high thrust in the right-rear quadrant. = 2/rev lateral shake rattle and roll
Please note that if the blades cross at azimuths of 0º, 90º, 180º and 270º the vibration will be longitudinal instead of lateral.
Even the three blade 'fairly absolutely rigid rotors'
on the
Sikorsky ABC created an
unacceptable lateral vibration around 225 knots. IMHO, a
four blade rotor should eliminate this lateral vibration.
Dave