HSQE MANAGER

Hi JoeF,

In the photo of the Fluttermill that shakes a magnet back and forth, it is important to note that the clear plastic bell cranks used for that model, together, have much more mass and inertia than the magnet. So most of the energy of the blades is being used to shake the bell cranks rather than the magnet. The bell cranks need to be made as light at possible. They could be far lighter if made using two light rods joined at a right angle to each other, with a string between their tips of the rods.

Note that the two flutter blades do not oscillate in phase with each other. They oscillate 90 degrees out of phase with each other, regardless of which direction each blade is moving. So there are two power strokes per cycle from each blade, and four power strokes per cycle from the pair of blades.

With modifications, this particular configuration can be stacked vertically so that any number of blades could be made to flap at the same cycle rate, so that the power of all of the blades would combine.

It is also possible to use any number of blades in a horizontal row such that all of the blades work together to drive a common device. See my attached sketch of that type of proposed Fluttermill.

It should be possible to arrange this type of blade like the spokes of a bicycle wheel. They would all attach to the rim of the wheel, and to a one-way clutch bearing on the central shaft. The clutch bearing would use a return spring. When the blades flapped, they would flap at the same cycle rate. Twice each flap cycle, they would rotate the one-way clutch bearing a short distance with strong torque. Between pull strokes, the return spring would rotate the one-way clutch bearing backwards in preparation for the next pull stroke. So this Fluttermill would look like a multi-blade, horizontal axis windmill, but the rim would not rotate. Only the shaft would rotate.

PeterS

Hi DaveS,

With Fluttermills like the one shown in the photo by Dr. Hare, the blades are forced into synchrony (resonance) by each other. The wind direction doesn’t matter because it doesn’t change anything important. The blades must have the same size, mass distribution, and tension, and therefore the same natural frequency.

With a Fluttermill, the limits of the blade flutter are preset and all are the same. They have the same natural frequency. They are deliberately tuned that way.

With a Flipwing, the tether tension may vary a lot, so the natural frequency may vary a lot, so forced synchrony is not assured unless the design provides for it in some way.

With the Fluttermills I’ve shown, the design provides for it. It’s built in.

For a Fluttermill, paired vocal cords is absolutely not an accurate analogy because vocal cords vibrate 180 degrees out of phase, not 90 degrees out of phase (or in phase, like Fluttermill blades with a synchronizing cord).

Vertical or horizontal Flipwing blades might need to be mounted in a rigid frame in order to stay in phase with each other -- like the Fluttermill blades in a frame with a synchronizing cord.

Have you tried using two or more, vertical, Flipwing blades in a frame (with a synchronizing cord) to guarantee that their tension remains the same? The frame might need a tail vane to keep it facing the wind.

Have you tried using a pilot kite to support a horizontal beam, with two or more Flipwings connected to it, and to a horizontal beam below them, which connects to the tether to the ground, plus a synchronizing cord between the blades? The horizontal beams must stay horizontal.

Have you tried using a “T” frame arrangement similar to the photo of the Fluttermill by Dr. Hare? Two blades would attach to the top, horizontal arms of the “T”, and to a horizontal rocking bar below them that pivoted, at its mid-point, at the bottom of the “T”. A tether would attach to each end of the rocking bar, so two tethers would extend to the ground. That should produce 4 pull strokes per cycle.

The main point I’m making is that Fluttermills all use some sort of rigid frame to control the phasing of blade flapping. In most cases, the frame could be suspended from a kite and should still function in the same way as long as the movement of the frame was correctly controlled or limited.

It would be useful if Flipwing blades could be made to flap 180 degrees out of phase, like vocal cords, but I haven’t thought about how to do that.

PeterS

Hi DaveS,

The Fluttermills are pretty easy to understand, so I’m puzzled by your confusion. The cause of the confusion might be this: There is a difference in the way that a Fluttermill blade and a Flipwing produce a pulling force: The Flipwing, as I understand it, produces a maximum pulling force when the Flipwing is passing through its downwind position at roughly the middle of its stroke from one side to the other. In contrast, a Fluttermill blade produces its maximum pulling force when the Fluttermill blade is at the ends of its stroke and about to reverse direction.

When two Fluttermill blades are linked, as shown in the photo of the Fluttermill by Dr. Hare (see attached sketch), they almost instantly fall into 90 degrees out of phase because when one is fully contracted, the other one is fully extended, due to the linking mechanism, which is equivalent to a simple see-saw beam. A Fluttermill blade can be fully contracted (power stroke) only when its end of the see-saw beam is up toward the blade, which permits the blade to fully flex to the side. And conversely, a blade can be fully extended (vertical) only when its end of the see-saw beam is down away from the blade, which minimizes any flexing of the blade. So the see-saw beam functions as a “clockwork” phasing mechanism, to use your term. In the photo, the two bell cranks create the same phasing mechanism; they function like a simple see-saw beam. When one tips up, the other tips down, and vice versa. I hope that clarifies.

How to create stacked Fluttermills: To create a basic unit of 4 Fluttermill blades flapping in phase with each other, use a “H” frame (on its side) and pivot a see-saw beam at the mid-point of the “H” frame. Two blades are used on each side. And they both attach to their end of the see-saw beam. Then add two blades on the other side. All of the blades will control each other to create 2 power strokes per cycle. Then add another 4 blades above or below the first four, arranged in the same way. To connect the two sets of 4 blades, extend the two see-saw beams farther out to the side, then connect their ends on each side. Now all 8 blades will flap in unison to create 2 stronger power strokes per cycle. There is no inherent limit on how many “H” units can be stacked. The frequency of oscillation remains the same, but the pulling force is multiplied.

PeterS

Hi DaveS,

I looked at item number 72, but I didn’t see anything about kite launching.

PeterS