Weight of the Drone in total will be 240 Kg.

It Will be a quad copter drone setup but with 8 rotors(two on each corner) for redundancy purpose. Aim is achieve Thrust/weight ratio of 2. So need total needed thrust will be 500 KG. Considering 500 kg thrust by 4 rotors only(because the 2nd rotor on each corner if fails the 1st motor should be able to compensate thrust) , each should be able to produce 125 kg thrust. The propeller Diameter will be 1.2 m ( Total 8 propeller) Now coming to the question: What should be the power rating of the motor if i want 125 kg thrust from each Propeller (When running at 85%-95% of the max RPM.)

If you have any Doubts or any details please ask ,will reply as soon as possible.

  • $\begingroup$ If you want people to help you, could you invest some seconds to fix your text (or at least the typos?) $\endgroup$
    – FooTheBar
    May 11, 2018 at 13:48
  • $\begingroup$ Yes sure. Please tell. $\endgroup$ May 11, 2018 at 15:10
  • $\begingroup$ What should I tell you? $\endgroup$
    – FooTheBar
    May 11, 2018 at 15:16
  • 1
    $\begingroup$ For safety you better have all motors running at all times, otherwise failure detection + engagement time delay may result in uncontrollable flight. This means you have to optimize for 500kg thrust with 8 motors. Also, the thrust to weight of 2 is more than necessary for an emergency landing, but I’ll live with that as this is a theoretical study. $\endgroup$ May 11, 2018 at 19:06
  • $\begingroup$ Hi Cetin, All the motors will be running all the time. When all are running each motor thrust is only 125/2=62.5Kg. But if one motor on one corner fails the other one should be able to produce 125kg thrust(compensation), so il be taking motor which is capable to do that. $\endgroup$ May 12, 2018 at 4:17

1 Answer 1


Thrust vs. power is not constant -- it depends strongly on prop diameter (bigger diameter = more thrust/watt). It depends less strongly on a bunch of other factors that I would know in detail if I were an aerodynamics expert, which I'm not.

Getting that part right would be a huge part of a real design. I suggest, since this is a theoretical preliminary study, that you find some books on propeller design, and some on helicopter rotor design, and make a stab at estimating the prop size and motor power, with enough material for a section on the relevant trade-offs so that your instructors know you paid attention to it, and so that any follow-on researchers know where to look for more information.

  • $\begingroup$ I'm in contact with Propeller manufacturer and Motor manufacturer will be exchanging details with them and will be coming to a conclusion as to which will be the right propeller for motor. Will update the question once i get them. Propeller dia of 1.25 meter is restriction because of size constraints. The bigger the propeller the better because the DISK LOADING (en.wikipedia.org/wiki/Disk_loading) will be less , hence efficiency of the blade increases and less power is consumed . $\endgroup$ May 11, 2018 at 18:42
  • $\begingroup$ As per my calculation, the motor power will be approx to 13-15 Kw each. $\endgroup$ May 11, 2018 at 18:49

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