Mark Rober - Amazing Invention- This Drone Will Change Everything
Also see the novel rotor design at this timestamp .
Amazing - I am totally blown away!
I couldn’t get through more than 5 minutes of his rambling. Does he get to some kind of point?
Here are some good criticisms of drone delivery, although even though a thing can be criticized does not mean it can’t be commercially viable:
Summed up: Safety regulations will not allow it in urban environments, the cost per package will be high because only one package can be carried at a time, the claims of the tether length presented is unrealistic, the payload is limited, the range will be limited, and so on.
The only way zipline can work is because it is payed for by the taxpayers, and because it has a niche market in medical delivery in a rural setting with bad road infrastructure in a place with little regulations.
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Free pdf download of referenced study:
Reduction of Tonal Propeller Noise by Means of Uneven Blade Spacing
Reduction of Tonal Propeller Noise by Means of Uneven Blade Spacing
An experimental study was conducted on the noise characteristics of four-bladed general aviation propellers with uneven blade spacing. The subscale propeller designs were inspired by the fourbladed McCauley propellers used on the Beechcraft King Air 350 series aircraft. The 4-inch diameter (1:22.5 scale) propellers were manufactured using high-resolution stereolithography and were powered by a high performance, radio controlled brushless electric motor. Acoustic measurements were taken with a 24-microphone array. The use of uneven blade spacing created additional tones over which the acoustic intensity was distributed. Large amounts of acoustic intensity were shifted into the lowest frequency tone (occuring at half of the blade passage frequency of the propeller with evenly spaced blades), resulting in reductions of A-weighted overall sound pressure levels of up to 5 dB for polar angles near 90. These reduction are partly offset by increases in A-weighted overall sound pressure levels of up to 4 dB at polar angles less than 50. Although the theory used to predict propeller noise does not show good agreement with experiments, it does show this trend of increasing noise at low polar angles. Since noise at low polar angles are weighted less in noise metrics such as flyover noise, the use of uneven blade spacing has potential for providing noise reduction without adding excessive complexity to propeller design.
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