Do you have a sketch, please?

Someone build a radio controlled copter with little propellers on the ends of the two or three main blades, place at 90º to "drive" the main blades. The energy needed to sustain hover was said to be considerable less than for a similar craft with only blades in the horizontal plane. A bunch of videos on YouTube but I can't remember the account name or any keywords.

Would anyone please draw a sketch for me? Thank you in advance!

Would anyone please draw a sketch for me? Thank you in advance!

Something like this. Only instead of fingers, airscrew.
   

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I'm afraid you guys are not quite with me. Hi

Let me make my idea more understandable.
The design is like an electric bicycle that does not have an electric motor, but is driven by the recoil of an electric fan mounted on the luggage rack behind the rider.

When the windspeed (against the direction of motion) reaches the speed of the air being pushed through the fan: no further air can be pushed through the fan.
This is not a function of design, but an operational condition of the fan itself.


Do a search for ‘wind powered car that drives itself upwind’
you will find that in order to do this you mist gear the wheels to a higher ratio than the fan.
The reason behind this is exactly the same but in the opposite direction.


This is how fans work, and one of the reasons wind turbines have to be turned off above a certain wind speed. Not only is it dangerous, but the generator cannot operate under these conditions.
Sure the fan will turn
But the speed of the wind is the same in front of the fan as it is behind it. So torque, pushing power, pulling power, all scale off once the condition is broken.


This is not a problem, as long as that condition is handled.


As for the axial torque (considered ‘roll’ in the forward (x) vector) is still present if you mount the fan to the rack instead of the tire. This removes most of the gyro torque, but unless the fan is completely horizontal, there is still an upward torque placed upon the rear of the bicycle.
Enough to lift your tail off the ground? Probably not, but definitely must be considered on something like a drone or aircraft. And in the case when the fan IS horizontal: gyro torque appears on the axis of rotation of the fan. Counter rotating fans could be used to cancel this out.


With fins placed on the tire such that the fan actually spins the tire (rather than simply pushing the bike with a fan): direction of rotation of the tire means the fan is facing forwards. (Assuming that is the direction you wish to move in)
In this scenario you are directly fighting the wind as in the example at the top.
And again here, once the windspeed reaches the output speed of the fan, it stops providing forward acceleration. Also heavy losses appear from wind currents that are not dissipated hitting the fins.


The idea of driving the wheel from a fan on it’s’ rotating peripheral is probably the best of these scenarios, notice how the direction of rotation of the wheel is complementary to the direction of force applied by the fan.
however the system constraints must still be considered.

Why do you imagine such a device would be OU?

The mathematics involved are the inverse of jet nozzle physics,
Which are not bound by closed-system constraints.


Leaving a possibility for exploration.

We should remember that, in a sailing boat, one can be pushed into the wind.

Yes and its’ the same range of angles. The sail acts as a single propeller blade or wing of an aircraft