D Hillberg
Well-Known Member
That's why you need more studies, Rotorcraft History is everywhere
Help Support Homebuilt Aircraft & Kit Plane Forum:
- Status
dong090909
Well-Known Member
i have been learning
Sorry for the late chime-in...
60 km/h only translates out to 32 knots, brother... almost right on the design stall speed of the An-2. A conventional rotorcraft such as a Sikorsky S-70 or a Bell 525 can push 160 knots plus. The tiltrotor I test fly for a living can push 300...the next one I will be testing will exceed that!
At 32 knots, the rotor system has just barely passed through what we rotary wing jockeys call "effective translational lift" (around 16-25 knots) and the transition into transverse flow (around 10-30 knots). Aerodynamically, alot of changes begin happening across the rotor disk during this transition.
My recommendation going forward is to define your expected operating envelope, set your thresholds, and design to them, doing research along the way. All current rotorcraft, be they traditional, tandem, intermeshing, compound, coaxial and tiltrotor configurations, are designed the way they are for a reason. Learn their lessons, and if you have something better, go for it- I am anxious to see what you come up with!
My retractable rotors are based on roll up party whistles -
Extension relies on high pressure air and weights in the outer tips of the rotors.
I haven't decided whether to keep the whistles. On the one hand rotary wing aerocraft are more than sufficiently rackety. On the other, whistles add a degree of psyops in some operations.
Extension relies on high pressure air and weights in the outer tips of the rotors.
I haven't decided whether to keep the whistles. On the one hand rotary wing aerocraft are more than sufficiently rackety. On the other, whistles add a degree of psyops in some operations.
D Hillberg
Well-Known Member
Most rotor craft have a minimum rotor starting wind speed . If started above the rotor system limit you get excessive flapping, mast bumping, rotor blade deflection and rotor blade collision, Navy had flap stops to limit blade sailing to vertical heights.
30 kts for the Bell line of helicopters, Sikorsky had start cycle limits [Keep em turning even in loading]
Good info...but I was not planning to go there yet. Startup wind limits (it is 45 kts from all quadrants on the Bell-Boeing V-22) are too far into the weeds with the OP so far...he has many other things to consider with his design process before he starts thinking about startup/shutdown wind limits.
Also, some Army, Marine, Coast Guard and Air Force rotorcraft (namely the H-47, H-60, H-64 and H-53), have flap restraints in the rotor systems. The V-22/AW609/V-280 do not. All have wind limits.
dong090909
Well-Known Member
I very much agree with this statement:
"We must discard the idea that past routine, past ways of doing things, are probably the best ways. On the contrary, we must assume that there is probably a better way to do almost everything. That we must stop assuming that a thing which has never been done before probably cannot be done at all."
-Walter & Reimar Horten
The reason why I set such a low cruising speed during the landing phase is to reduce the risk, because I think: increasing the forward speed when the rotor is working is to make a great trouble and solve it.
The ultimate goal, of course, is to go above and beyond all the great, high-speed rotors you mentioned at fixed wing speeds.
Otherwise, this kind of thinking has no meaning to exist.
You are here at the right time, as long as it is valuable technical content, you will not be late
thanks.
dong090909
Well-Known Member
As for my follow-up work, I am happy to communicate with you
constantly with toys
Improve the structure
Hear opinions from judges around the world
If this step has reached the bottleneck and it is difficult to improve, I start to enter a new stage: advanced toys
this stage:
Catapult for takeoff and parachute for landing, in order to reduce the cost of playing
The most important thing is: test the diamond jack of the rotor in the air, the conversion function
Of course, at this stage, I will let the whole world participate in the way of open source patents.
This is a design that is different from all great airlines, and the only reason is: I think the benefits of owning this patent （For example: commission, dividend）are already satisfied, and the other benefits can be shared globally.
I am sure that I will not take the road of Sikorsky's development of rigid rotors, the second successful rigid rotor scheme in the world. The design idea is: win-win
It is efficient because from the beginning, the whole world is involved
constantly with toys
Improve the structure
Hear opinions from judges around the world
If this step has reached the bottleneck and it is difficult to improve, I start to enter a new stage: advanced toys
this stage:
Catapult for takeoff and parachute for landing, in order to reduce the cost of playing
The most important thing is: test the diamond jack of the rotor in the air, the conversion function
Of course, at this stage, I will let the whole world participate in the way of open source patents.
This is a design that is different from all great airlines, and the only reason is: I think the benefits of owning this patent （For example: commission, dividend）are already satisfied, and the other benefits can be shared globally.
I am sure that I will not take the road of Sikorsky's development of rigid rotors, the second successful rigid rotor scheme in the world. The design idea is: win-win
It is efficient because from the beginning, the whole world is involved
D Hillberg
Well-Known Member
You can mount your test article on a car roof and film the action in the wind... A cheep wind tunnel
dong090909
Well-Known Member
Glad that our thoughts are the same,
It is the cheapest wind tunnel test.
thanks.
It is the cheapest wind tunnel test.
thanks.
dong090909
Well-Known Member
Dan Thomas
Well-Known Member
- Joined
- Sep 17, 2008
- Messages
- 6,986
But condemning the way things are done now, without understanding WHY they are done that way now, is foolish.
It's similar to the cheap-attitude-indicator discussion. One has to know WHY we have gyroscopic instruments in the first place, and not rocks on strings or bubbles in compasses.
Last edited:
dong090909
Well-Known Member
Therefore, we need a specific analysis of specific problems.
we start from beginning,
Please point out the fatal flaw of this scheme
Also, I've always believed that great companies bring the world into a swamp of difficult to advance and retreat, and the deadliest mistake is to use rotors for high-speed operation, self-made great problems, and then great solutions.
D Hillberg
Well-Known Member
13 minutes in...
Last edited:
dong090909
Well-Known Member
Futher more, after studying the coaxial anti-propeller rigid double rotor for more than half a century, even the most important lift balance conditions have not been summed up. Such a low-level mistake, whether it is a great company or not, should be reviewed.
I appreciate the kind words. But I am here to tell you that at those speeds, you are already in the Effective Translational Lift aerodynamic regime, and there is no need to solve it per se...the solutions are already out there. I want you to read up on the rotary wing principles and more. Things such as delta-P hinging, and how it helps compensate & control flapping & feathering of the blades, and the whole phenomena of gyroscopic precession and how it directly impacts rotary wing flight control design.
Again, I implore you to look at what has worked in the past, what works currently, and what has not worked....and why. Sometimes, some concepts never made it to reality, only because the state of the art at the time simply was not ready. For example, an old concept from the early 1960s, the folding proprotor, was not developed at the time. The state of the art in materials, flight control, etc, simply was not there. Today, that design is being explored once again, because it is now possible. Whether or not it becomes a reality will be left down to whether or not it could be practical...simply due to the inherent complexities of the problem.
If you think you have the solution to the physical problems inherent to the rigid coaxial rotor configuration, which first saw flight as the S-69 in the early 1970s, at high speeds, post your calculations here, now, then go work for the Sikorsky-Boeing team.
I personally know many people on the S-97 and SB-1 projects. They are all top-tier engineers who have taken great career risks to see their designs progress from idea to flight. To say they have failed without backing it up is incredibly ignorant on your part.
The physics of the problem will drive the solution, my friend.
If you think you have arm wrestled with Sir. Isaac and won you have a rude awakening.
Effective translational lift adds lift but not necessarily requires hinges at low speed. I think the V-173 had some problems with “rigid” props and they installed complex hinged rotors. Then it was cancelled. Just depends.
Correct. Large prop-rotors will inevitably need to flap & feather in response to any dissymmetry of lift situation, as well as to any roll/pitch/yaw modes introduced into the system as a result of maneuvering flight. If the prop does not have a way to move around to respond to these movements, dissipating forces in the process, those forces will be transmitted directly into the drivetrain & airframe. Rigid systems, as are seen in Sikorsky's coax demonstrators, feature incredibly stiff heads & blades. The blades cannot lead, lag, flap or feather naturally as a result of the aerodynamic & centrifugal forces that are being applied to them so as a result, those forces are transmitted directly into the drivetrain & airframe. These vibrations are dealt with by introducing even more energy into the system by way of an active force generation vibration suppression system. Everything is all well and good...until that system fails or otherwise goes out of phase. I know some of the SB-1 project pilots; they had such a failure at 180 knots...far short of its design airspeed. Both said the vibration was so violent that they thought the airframe was about to rip itself apart...one, who is a highly experienced XP in his own right, went as far as opting out of flying the aircraft anymore.
- Status
