5 ms·

From the way you worded this, I was expecting them to use the chair and sleigh as propellers. What's special about OP is that the propeller design is unusual, p

From the way you worded this, I was expecting them to use the chair and sleigh as propellers. What's special about OP is that the propeller design is unusual, proving that Leonardo wasn't that far off when he came up with the idea.

tshaddox 5y ago
Yeah, those YouTube videos really just demonstrate that...airplanes can carry things.
cobookman 5y ago
The report also shows it to have superior thrust to a traditional rotor for the same RPM. https://www.thedrive.com/content-b/message-editor%2F1643667998866-davinciscrewrotordrone.jpg?quality=60 https://www.thedrive.com/content-b/message-editor%2F16436679...
- dr_orpheus 5y ago
  Although a better metric might be to look at the thrust to motor power and get an idea of its efficiency relative to traditional rotors. I can put larger blades on the motor and will get more thrust at the same RPM but the motors will have to work harder to push those blades.
  - dTal 5y ago
    Indeed, the screw shape is essentially a large number of rotor blades, welded leading edge to trailing edge. Undoubtedly it produces more thrust for a given RPM, and undoubtedly the efficiency is horrifically bad.
    - adolph 5y ago
      Is the efficiency the number of amps required to gain/maintain a particular rotational speed? So given rotational speed 4k conventional is 50g thrust and DaVinci 75ish g, if conventional costs 10amp then DaVinci would be less efficient if it uses more than 15 amps?
      - Panzer04 5y ago
        Yep. Traditionally, drones use 2-3 bladed props, each additional prop blade increases thrust per rpm, but increases load by significantly more, hurting actual thrust per watt. I’d expect a screw to be the degenerate case and probably worse than a conventional many-bladed prop.
        zelphirkalt 5y ago
        In my imagination: Don't rotor blades also profit from air getting "in between" them, so that they have something to push against and thus push upwards? The screw relies on air getting in from the sides, while that air is being pushes outwards by the rotating screw. Am I totally off here?
        adolph 5y ago
        The authors did test having a "lip" around the edge of the screw: It was hypothesized that a down facing lip would prevent air from escaping radially outward from the rotor, but this was proven incorrect. All rotors tested (3,4 and 5 in Figure 2.2) have 1 turn, a pitch of 100 mm (3.94 in), a radius of 76 mm (3 in), and a 1:1 taper ratio. A downward facing lip showed reduced thrust and an upward facing lip showed negligible impact on thrust in Figure 2.7. Flow visualization conducted during this trial revealed that air was being ingested radially inward during operation of the no lip and up facing lip aerial screws, and that this flow was disrupted by the down facing lip. These results support the findings of the CFD studies detailed in Chapter 3. Figure 2.8 indicates that the presence of a lip in either direction increased the power requirement of the rotor. Figure 2.9 shows that the presence of a lip in either direction also reduced the FM of the aerial screw. Therefore, a lip is not a useful design feature at all, and was discarded. http://vfs.umd.edu/assets/downloads/2020_elico.pdf http://vfs.umd.edu/assets/downloads/2020_elico.pdf
        adolph 5y ago
        It would be interesting to understand why load increases more quickly than thrust for increasing blade counts. Do ducted fans have similar changes in load-to-thrust ratio given an increase in blade count?
  - whiddershins 5y ago
    There might be times where longer blades would be less desirable though, could this have some niche use? Also seems like the screw shape could be less prone to breakage.
    - dr_orpheus 5y ago
      True, they mention in the article some possible advantages of reduced noise and downwash.
- deleted 5y ago
  [deleted]
- walrus01 5y ago
  on a quadcopter or similar the useful metric is grams of thrust as measured instantaneously on a thrust stand vs watts consumed by the motor. see users guide here for details. https://www.tytorobotics.com/products/thrust-stand-series-1520 https://www.tytorobotics.com/products/thrust-stand-series-15... it's basically a load cell and an inline DC ammeter with some logging software. usually denoted as g/w or kg/w on big things.
matheusmoreira 5y ago
I thought the exact same thing. Clicked the link fully expecting to see chairs spinning at 7000 rpm. Was actually wondering if these objects could handle the forces involved without disintegrating.

tshaddox 5y ago

Yeah, those YouTube videos really just demonstrate that...airplanes can carry things.

cobookman 5y ago

The report also shows it to have superior thrust to a traditional rotor for the same RPM. https://www.thedrive.com/content-b/message-editor%2F1643667998866-davinciscrewrotordrone.jpg?quality=60 https://www.thedrive.com/content-b/message-editor%2F16436679...

dr_orpheus 5y ago
Although a better metric might be to look at the thrust to motor power and get an idea of its efficiency relative to traditional rotors. I can put larger blades on the motor and will get more thrust at the same RPM but the motors will have to work harder to push those blades.
- dTal 5y ago
  Indeed, the screw shape is essentially a large number of rotor blades, welded leading edge to trailing edge. Undoubtedly it produces more thrust for a given RPM, and undoubtedly the efficiency is horrifically bad.
  - adolph 5y ago
    Is the efficiency the number of amps required to gain/maintain a particular rotational speed? So given rotational speed 4k conventional is 50g thrust and DaVinci 75ish g, if conventional costs 10amp then DaVinci would be less efficient if it uses more than 15 amps?
    - Panzer04 5y ago
      Yep. Traditionally, drones use 2-3 bladed props, each additional prop blade increases thrust per rpm, but increases load by significantly more, hurting actual thrust per watt. I’d expect a screw to be the degenerate case and probably worse than a conventional many-bladed prop.
      - zelphirkalt 5y ago
        In my imagination: Don't rotor blades also profit from air getting "in between" them, so that they have something to push against and thus push upwards? The screw relies on air getting in from the sides, while that air is being pushes outwards by the rotating screw. Am I totally off here?
        adolph 5y ago
        The authors did test having a "lip" around the edge of the screw: It was hypothesized that a down facing lip would prevent air from escaping radially outward from the rotor, but this was proven incorrect. All rotors tested (3,4 and 5 in Figure 2.2) have 1 turn, a pitch of 100 mm (3.94 in), a radius of 76 mm (3 in), and a 1:1 taper ratio. A downward facing lip showed reduced thrust and an upward facing lip showed negligible impact on thrust in Figure 2.7. Flow visualization conducted during this trial revealed that air was being ingested radially inward during operation of the no lip and up facing lip aerial screws, and that this flow was disrupted by the down facing lip. These results support the findings of the CFD studies detailed in Chapter 3. Figure 2.8 indicates that the presence of a lip in either direction increased the power requirement of the rotor. Figure 2.9 shows that the presence of a lip in either direction also reduced the FM of the aerial screw. Therefore, a lip is not a useful design feature at all, and was discarded. http://vfs.umd.edu/assets/downloads/2020_elico.pdf http://vfs.umd.edu/assets/downloads/2020_elico.pdf
      - adolph 5y ago
        It would be interesting to understand why load increases more quickly than thrust for increasing blade counts. Do ducted fans have similar changes in load-to-thrust ratio given an increase in blade count?
- whiddershins 5y ago
  There might be times where longer blades would be less desirable though, could this have some niche use? Also seems like the screw shape could be less prone to breakage.
  - dr_orpheus 5y ago
    True, they mention in the article some possible advantages of reduced noise and downwash.
deleted 5y ago
[deleted]
walrus01 5y ago
on a quadcopter or similar the useful metric is grams of thrust as measured instantaneously on a thrust stand vs watts consumed by the motor. see users guide here for details. https://www.tytorobotics.com/products/thrust-stand-series-1520 https://www.tytorobotics.com/products/thrust-stand-series-15... it's basically a load cell and an inline DC ammeter with some logging software. usually denoted as g/w or kg/w on big things.

matheusmoreira 5y ago

I thought the exact same thing. Clicked the link fully expecting to see chairs spinning at 7000 rpm. Was actually wondering if these objects could handle the forces involved without disintegrating.