- Join
- Nov 16, 2017
- Messages
- 46
- Age
- 59
with the battery in, the centre of gravity is perfectly in the middle of the spark as I've just balanced it. But it did surprise me as you would have thought it was heavier towards the rear but it's not
Stopping the props mid-flight
- Thread starter rich777
- Start date
polish_pat
Member
- Join
- Sep 21, 2018
- Messages
- 11
- Age
- 40
And even if it was heavier in the back it would be a simple countermeasure of spinning the front props faster (to a certain degree) because this is not a helicopter so it doesn't rely only on one Centre Force pulling it up. I know that folding propellers might be counterintuitive but it's the same reason that if you start spinning in a circle really fast on yourself your arms will move out. my only question is friction going to prevent in keeping the propellers from spinning fast enough to sustain a safe landing? the friction of the motors to free spin versus the size of the propellers because electrical power will overcome this but perhaps not gravity alone.
The battery is 96g and i think the drone alone is ballpark 260g. Its 1/4 of the weight
The battery is 96g and i think the drone alone is ballpark 260g. Its 1/4 of the weight
Last edited:
I agree that folding props work just fine with the motor spinning them. I disputed the claim that they would counter rotate after a loss of power. I was able to get the ol' leaf blower out today. Unless the Spark falls level at something approaching 200mph, relying on spinning props to get you down gently is not gonna happen. They would start to turn kind of in a unbalanced way. As soon as I changed from aiming straight at the underside of the prop they fluttered and stopped.
My advice is don't lose power
I agree that folding props work just fine with the motor spinning them. I disputed the claim that they would counter rotate after a loss of power. I was able to get the ol' leaf blower out today. Unless the Spark falls level at something approaching 200mph, relying on spinning props to get you down gently is not gonna happen. They would start to turn kind of in a unbalanced way. As soon as I changed from aiming straight at the underside of the prop they fluttered and stopped.
My advice is don't lose power
There's also a misconception that the unpowered props will 'autorotate' on the way down and help with some lift, but they won't.
As any RC or full size heli pilot knows, to autorotate you have to be able to change the collective pitch so that the leading edge of the blades have the correct angle of attack to generate lift on the way down, basically by applying negative pitch.
The Spark props are fixed pitch and would try to rotate backwards on the way down. As the prop would be spinning backwards (which it can't anyway, see below*) it wouldn't generate appreciable lift because the airflow over it is in the wrong direction and wouldn't generate any appreciable pressure difference.
*This is all moot anyway, as the coreless motor magnetic resistance is too high to allow the airflow to spin the motors.
It's an expensive brick guys.
I have seen a spark falling, and it falls like a brick. Props don't autorotate.
If you think that it will fall with props up and autorotating (braking the drone), try it and upload the video here. But I don't recommend it, at all.
If you think that it will fall with props up and autorotating (braking the drone), try it and upload the video here. But I don't recommend it, at all.
polish_pat
Member
- Join
- Sep 21, 2018
- Messages
- 11
- Age
- 40
Yes, and as any heli pilot knows, you can land safely with total engine loss and "glide" down, but that is possible only because the rotor never stopped spinning and has little need of force to continue spinning...not sure if in the improbable situation where the rotor was static and had to gain momentum to stop the stall the helicopter wouldn't also be a brick falling from the sky...id be curious how much altitude would it require to save it.There's also a misconception that the unpowered props will 'autorotate' on the way down and help with some lift, but they won't.
As any RC or full size heli pilot knows, to autorotate you have to be able to change the collective pitch so that the leading edge of the blades have the correct angle of attack to generate lift on the way down, basically by applying negative pitch.
The Spark props are fixed pitch and would try to rotate backwards on the way down. As the prop would be spinning backwards (which it can't anyway, see below*) it wouldn't generate appreciable lift because the airflow over it is in the wrong direction and wouldn't generate any appreciable pressure difference.
*This is all moot anyway, as the coreless motor magnetic resistance is too high to allow the airflow to spin the motors.
It's an expensive brick guys.
Nothing will save it unless the rotor airfoil is able to generate lift, and that can't happen with the Spark because the pitch is fixed.
polish_pat
Member
- Join
- Sep 21, 2018
- Messages
- 11
- Age
- 40
if you go on YouTube look for DJI F550 crash, he loses all his engines at about 9 minutes into the video and you can see at that point the Drone stabilizes and ends up somehow Landing in trees with much less impact then if it would just fall from the sky and I understand that the spark doesn't have four extra propellers but at that point it doesn't matter it just needs more velocity...this is the typeof situation that I can only settle on a solution when a specific test proves the Siri because your intuition says one thing your knowledge of aerodynamics has another and yet some videos going towards one side others towards another and others to a theory that you would not even imagine I would be really curious to see a real life test
- Join
- Nov 16, 2017
- Messages
- 46
- Age
- 59
It wouldn't actually creates lift it would just create a drag almost like a parachute coming down. And I don't think the magnetic resistance in the Motors has an effect on how fast the props rotate because if you power off your spark they rotate freely without any magnetic feeling as they are brushless Motors.
- Join
- Nov 16, 2017
- Messages
- 46
- Age
- 59
Mine is green just like a floating leaf[emoji849]My spark is red, just like a flying brick!
I have a fast way to get the drone down, you put it in landing mode while having the stick all of the way down and I can get it down 8.6 to 9 mph
Old thread, but I have seen a youtube video of a guy doing this with a mavic. He did a shutdown midair and the drone recovered before hitting the ground. Fun watch ! Ive imagined trying it with my spark, but never did since, like mentioned above, it wont start the props from an inverted position. I havent checked the actual speed, but can say my drone comes down super fast with the nld mods.
DJIBILL
Well-Known Member
- Join
- Dec 21, 2018
- Messages
- 54
- Age
- 68
i agree that there should be a faster way to descend. in Sport mode it is slightly faster. The Spark will land plenty fast though on it's own, when you have only 5-10% of the battery left and the app says "LANDING" Seems twice as fast if you are over water...probably not just seems like it.
i have heard that all around speed is increased. not sure NLD is a good idea. I have thought about it. i live in a NFZ . i can't even fly my drone in my yard or house. I have to go 10 miles to fly. maybe in an area away from everything NLD is good, not in a crowded metropolis or a NFZ . they have satellites that can track your coordinates and they can zoom in and follow you to your house they can even go back days and look they do it all the time to criminals.
Last edited:
Similar threads
