Electronics > Mechanical & Automation Engineering

Power to hover a 60kg drone?

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zenerbjt:
Dear Engineers,
For a battery powered drone of 60kg total , how much electrical power will be drawn from the battery to hover it?

There is an equation: P = K. m^(1.5)/r  (from the following website)
https://justdrones.com.au/how-much-power-is-needed-to-hover/

Where:
P =power
K=22.35
m = mass in kg
r = propeller radius (length) in metres.

However, I am speaking of a drone with 4 motors and each motor drives dual stacked propellors which rotate in opposite directions. (so eight sets of propellers in 4 "pairs")

Mechatrommer:
thats seems obvious... divide weight by 8 (m = 7.5kg), calculate for one propeller, and then multiply back the power by 8 (its in Gamera II - Can I build a human powered helicopter? example down below the linked website). do not add air turbulence effect or how much energy loss factor etc, we can discuss to no end... ymmv.

zenerbjt:
Thanks, i think those "dual stacked drone in opposite rotation" type  propellers  arent as good as two separate propellers....there's some physical phenomenon that stops it being that good....i mean, they are good in that it means they take up less space, but thats all.

I think "dual stacked propellers in opposite rotation" only give the thrust of something like 1.5 times  "two single  propellors in different places, spinning together"  ...but i'm not sure?

IanB:
You linked to an article that explains it all.

I'm not sure how anyone in this post can give anything more detailed than the article you linked? That article is already several screens long, and includes both formulas and derivation.

To summarize:

There is a theoretical minimum power required in the ideal case for a given propeller diameter.

This theoretical minimum power is inversely proportional to the propeller diameter, so the power increases for smaller propellers and decreases for larger propellers.

[Note: This is why modern aircraft jet engines have large diameter bypass fans to increase the effective diameter and improve the fuel efficiency. This is also why helicopters are much more efficient at hovering than VTOL aircraft like the Harrier jump jet. Helicopters have a way bigger "fan" to produce downward thrust than jet engines.]

Now, the theoretical minimum power is a law of physics, you can't do better than this. But you can obviously do worse. This will depend on the specific characteristics of the motor and fan. To learn about any specific case it will be necessary to look at the characteristic performance charts of a given fan or propeller arrangement, if such is available.  Or maybe do your own experiments and measure some results?

But the theoretical minimum should certainly get you in the ball park.

Mechatrommer:
oo ok i missed the stacked part if you mean stacked vertically one on top of the other sorry :palm: