- Jul 18, 2005
- Abu Dhabi UAE
- 582 Commander Elite
- Total Flight Time
- Stopped counting years ago after 5,000
So you've quit flying with major airlines (= not the ones which still use DC-3s or Martin 404s) 10-15 years ago? (by which time any modern passenger aircraft was exclusively controlled by the power of electrons..;-)Don Hillberg->....some times the electrons go on strike,what do you do? Go along for the ride?
What is more simple, push rods, dozens of joints and bearings or a tiny cable that runs from your stick straight to an actuator in the blade in a setup that even does away with a feathering bearing for the blade?Don Hillberg->..You have broken the First rule, Keep it Simple stupid
You can't repair a ball bearing either, you have to replace it. Same with a chip that quits.Don Hillberg->....only adds a piece that no one can repair
Bryan Cobb-> Looks like to tilt that much rotating gyroscopic mass would take a hydraulic cylinder with a 1" ram to me???
Tilting the head on a gyro is the functional equivalent of a swashplate control.
Let's say you want to roll the aircraft to the left. Tilting the head to the left applies a cyclic input to the blades when they are in the 12 & 6 o'clock position. The 12 o'clock blade starts to pitch down and the 6 o'clock blade starts to pitch up as they spin, assuming CCW rotation as viewed from above. No inputs are made at the 3 & 9 o'clock postion because of the teetering hinge (remember we are dealing with a left roll input only at this point). Although the actual pitch inputs are made at the 6 &12 position the effect isn't felt until 90º later due to gyroscopic precession. It takes a few revolutions for the blades to "fly" the rotor disc to it's new orientation.
To apply a pitch input, the same applies but the cyclic inputs are made at 3 & 9, and the effects are felt at 6 & 12 o'clock. Really no different than a Bell 206.
The reason you don't have to have Herculean strength is that it doesn't take much power to tilt the head and pitch the blades. Reorienting the rotor disc is done aerodynamically.
Heavier blades take a little longer to fly themselves to a new orientation vs. lighter or faster spinning blades so more feedback in the stick may be felt, but it's not a case of manhandling a 50 lb. spinning mass like a giant bicycle wheel.
Here’s a diagrammatic view of a Bell-47 and similar rotorheads. The feathering bearings are linked together in such a way that rotation is possible only for collective pitch application.
Cyclic pitch is accomplished by rocking the hub about the feathering axis; whether by single or double pushrods from a swashplate or by some other means is irrelevant.
Whatever the case, drive torque is isolated from the cyclic control system.
Thank you for confirming that cyclic is not controlled by feathering...helicopters beside Bell 47 and Scorpion use this method?
I never really timed it, I did not leave the Cable system on my Scorpion long after I got it. I would say it was at least 2 or 3 seconds.Thank you for confirming that cyclic is not controlled by feathering( no feather bearings, no pushrods to a swashplate) in this helicopter, but cyclic is controlled ala gyrocopter style. How many and which other helicopters beside Bell 47 and Scorpion use this method?
BTW, Animal, or should I call you Tim, concerning the lag in your heli, how big is it? split of a second, two seonds? does it feel so much.
thanks for the link to the Bee video,I have always thought that was a neat design and wondered what happened to it.Tom,
Here is a video of the Scheutzow BEE Helicopter that you mentioned.
Scheutzow BEE Promotional Video on Vimeo
The swashplate has been the preeminent means for helicopter flight control over the years, however, many are striving to eliminate it; and all its many moving parts.
Here is a proposed method for the flight control of a teetering rotor. It uses the gyrocopter method for cyclic control and power-change for collective control. Electrotor ~ Simplex
There appears to be no reason why the above hub mounted electric motor cannot be replaced by a fuselage mounted engine. This engine would drive the tilting rotor at a constant speed by locating a constant velocity joint between the motor and the tilting & teetering rotor.
The Bell 47 has feathering bearings. How else would collective pitch work? Rotor RPM remains constant while flying. Climbs and descents and accelerations/decelerations are done by collectively feathering both blades THE SAME AMOUNT in THE SAME DIRECTION.
The definition of feathering is "a blade's ability to rotate about its' chord axis."
For CYCLIC inputs, (Tilting the tip path) the Blades on a Bell 47 DO NOT pivot on their feathering bearings, THEY DO pivot about their chord axis AS A UNIT.
That is..In Unison... as one blade feathers toward a more positive angle, the opposite blade feathers toward a more negative angle, THE SAME AMOUNT in the OPPOSITE DIRECTION. Both blades are part of an assembly. Each blade is connected to the assembly in a way that allows collective feathering individually, and CYCLIC feathering as a unit.
The 47's head is a textbook example of a semi-rigid type.
If I understand you correctly, the tip path of a gyro is tilted aerodamically just like a helicopter? I totally understand this method. The Original Poster seemed to think that the tip path is tilted by MECHANICALLY tilting the AXLE (mast/shaft) that the blades rotate around?
Yes. A cyclic input causes the rotors to fly themselves to a new orientation.If I understand you correctly, the tip path of a gyro is tilted aerodamically just like a helicopter?
The axle, or spindle, is tilited mechanically. It it connected directly to the controls. Pushing the stick to the left makes the spindle (and rotor head) tilt to the left. Pushing it forward tilts the spindle forward, etc.I totally understand this method. The Original Poster seemed to think that the tip path is tilted by MECHANICALLY tilting the AXLE (mast/shaft) that the blades rotate around?
Nope. No swash plate necessary. The gimble mount serves the same purpose though.If control inputs are transferred to individual blades on a gyro, which "feather" to aerodynamically tilt the tip path, then there MUST be a swashplate, even if it's not called that!
Because the rotor hub and blades are not attached directly to the spindle. The hub bar is mounted using a teetering hinge. This allows you to only make a cyclic input. The blades are rigidly connected to the hub bar with no feathering hinges, so a nose down cyclic input on one blade is a nose up input on the other as the blades pitch on their spanwise axis as a unit.If control inputs on a gyro merely tilt the AXLE (mast/shaft) that the rotor spins on, then there is no swashlate and I do not understand why it doesn't take massive forces to do it?