Im a new drone pilot. Ive had my MM for a couple weeks now, and am having a blast. I have noticed that the MM struggles in any kind of wind, and has caused a few fly away situations that ive read about. Just curious, has anyone tried installing slightly oversized propellers, or even propellers with a more pronounced pitch? this would help develop slightly more thrust, possibly saving a MM in a fly away situation caused by windy weather. Anyone tried this?
Anyone tried oversized propellers
- Thread starter rjhat3
- Start date
I can tell you that the MM's front props are already maxed out lengthwise. Mine has the black skid marks along the edge of the fuselage to prove it. I don't know but it's logical to assume it happens when climbing or descending fast, maybe both. Maybe other situations as well like tight banked turns. Hard to know for sure.
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Size and/or pitch increases that provide increased thrust must operate at a lower RPM which will move the designed operating characteristics of the propulsion system and flight controller algorithms. Increased current demand, perhaps approaching the design maximum is possible. The rate of RPM change will also be reduced which could actually reduce performance (reaction time to changing wind loading being an obvious potential consequence).
bumper
Well-Known Member
I'm not an engineer, or propeller designer, just an airplane pilot and owner. It's been said that propeller design is part science and part black art, but here's a few rules and thoughts:
Think of prop pitch like transmission gears. A flatter pitch is like low gear, faster to accelerate and quicker to respond, but with lower top speed and less efficient in cruise. Conversely, a coarser pitch will be less responsive to power input changes and will have a higher top speed. My airplane gets around this problem by having a variable pitch prop, analogous to the transmission in a car. For take off, a flatter pitch is used for faster acceleration, and for cruise,, a coarser pitch for higher top speed and efficiency. Another rule of thumb is that a longer, slower turning prop is more efficient than a shorter, faster turning prop. Higher prop tips speeds generate more noise. As prop tips approach the speed of sound, noise increases dramatically and efficiency drops.
Your drone has limited room and clearance for a longer prop, the tips need to clear the drones structure. The props are designed with flexible blades, to a degree this allows the prop to behave like my airplane's variable pitch prop, but it also means they prop needs more clearance to avoid striking the structure.
Prop pitch and length will also needs to match available motor power. Too much prop (pitch and length) will bog down a lower power motor, yet an undersized prop, or one with too flat a pitch, won't be able to harness and use more power from the motor.
Prop tip vortices detract from efficiency, the swept, thinner tips are designed to help improve efficiency, reduce tip vortices and reduce noise.
For the larger DJI drones, like my M2P, "Master Air Screw (MAS) makes slightly larger props that eek out a small increase in efficiency - they don't yet make them for the Mini.
Think of prop pitch like transmission gears. A flatter pitch is like low gear, faster to accelerate and quicker to respond, but with lower top speed and less efficient in cruise. Conversely, a coarser pitch will be less responsive to power input changes and will have a higher top speed. My airplane gets around this problem by having a variable pitch prop, analogous to the transmission in a car. For take off, a flatter pitch is used for faster acceleration, and for cruise,, a coarser pitch for higher top speed and efficiency. Another rule of thumb is that a longer, slower turning prop is more efficient than a shorter, faster turning prop. Higher prop tips speeds generate more noise. As prop tips approach the speed of sound, noise increases dramatically and efficiency drops.
Your drone has limited room and clearance for a longer prop, the tips need to clear the drones structure. The props are designed with flexible blades, to a degree this allows the prop to behave like my airplane's variable pitch prop, but it also means they prop needs more clearance to avoid striking the structure.
Prop pitch and length will also needs to match available motor power. Too much prop (pitch and length) will bog down a lower power motor, yet an undersized prop, or one with too flat a pitch, won't be able to harness and use more power from the motor.
Prop tip vortices detract from efficiency, the swept, thinner tips are designed to help improve efficiency, reduce tip vortices and reduce noise.
For the larger DJI drones, like my M2P, "Master Air Screw (MAS) makes slightly larger props that eek out a small increase in efficiency - they don't yet make them for the Mini.
DJI's propulsion engineers have already done the work matching motors, ESCs and props.
Post #4 explains why you can't just slap on some bigger props and expect improved performance.
Post #4 explains why you can't just slap on some bigger props and expect improved performance.
If you put your drone some distance downwind in a wind that's too strong for it to get back against the wind, the drone didn't "fly away".
I think as the other commentors have said the MM is maxed out. The real simple solution is to get a bigger and more powerful drone. I went from the MM to the MA 2 and have loved the extra stability and power ; and have just started experimenting with the upgraded technical capabilities such as higher resolution pictures and 4k video. Good luck and keep flying!!!!
Changing props doesn't change the wind penetration on any drone, as long as the motors don't max out.
The only thing that helps is more attitude or weight.
For example, on the air2 adding 200gram weight makes a huge difference, almost get as good as mavic 2 in high winds.
Just think about it, the forward driving force can be written (a little bit simplified, not include wind drag increases with attitude):
F=m*sin(attitude)
The only thing that can increase F is attitude increase or mass increase.
The only thing that helps is more attitude or weight.
For example, on the air2 adding 200gram weight makes a huge difference, almost get as good as mavic 2 in high winds.
Just think about it, the forward driving force can be written (a little bit simplified, not include wind drag increases with attitude):
F=m*sin(attitude)
The only thing that can increase F is attitude increase or mass increase.
My experience with the Mini is that whilst it doesn't cope particularly well with strong winds, it does a good job in moderate winds as long as you're sensible about what you do with it. For example, avoid flying a long way downwind from the home point (ideally, position yourself so you fly upwind for most of your flight), generally fly as low as you can to achieve what you want and set the RTH height so that it's the minimum required to safely clear local obstacles. Most flyaways aren't really flyaways, they're blowaways - the Mini doesn't actually fly away, it just can't fly back against a strong wind. The Mini has a maximum flight speed of 29 mph in level flight so you can work out how fast (or not) the drone will be able to return to you if it's coming from a downwind position - if the wind is 30 mph, if you maintain height it will only ever get further away no matter how much you try to bring it back!
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Attitude (for a drone), yes. Weight - why?
Wouldn't that just apply to an aircraft in the glide? If you have 2 identical aircraft with the same power units and you increase the mass of one of them, there's no reason why it would penetrate the air any better in level flight - you'd just need more power to maintain the height at a fixed airspeed. There is no "wind drag" as such - aerodynamically, the aircraft doesn't know if it's windy or not. As far as it's concerned, it's just moving at a particular airspeed through an airmass. The fact that the airmass is moving (what we refer to as wind) doesn't change the amount of air moving past the aircraft at a particular airspeed, it just changes the groundspeed. Increasing the mass would just make it more stable in turbulence because it would have more inertia.
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The reason is that all mavics are attitude limted to about 30 degrees. It refuses to go more than that unless you hack some parameters. It also is ground speed limited (not so much in sport mode), which ever come first.
So for an aircraft that weight 500g you get a forward force like
F=0.5*sin 30 => 0.25N
For a 1kg you get
F=1*sin 30 => 0.5N
So you will have a stronger force to driving it forward.
Why you not see any speed increase in no wind is that the speed limit in firmware kicks in and lower the the attitude.
You get drag from the TAS, otherwise it would accelerate to infinity speed, which don't happen.
If you don't believe me, try it for yourself. You need an app that can show the attitude though, or use atti-mode
I think you mix up things since the mavic are booth attitude limited and speed limited which ever come first. Took me a while before I realized this myself. So you can't just calculate:
ground_speed = wind_speed - max_speed
its more like:
ground_speed > wind_speed - max_speed
since the firmware adds attitude to 30 degrees when going against the wind.
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Think of a weightless drone, will it get any forward speed when you tilt it
I always compares 0 and infinty to understand things.
I will try to do an video about it where I show the difference.
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Definitely ??
That sounds unlikely.
What made you think that the props made any difference in wind?
Did you do any testing?
Was the drone able to fly any faster (which is the only thing that would help it in wind) ?
Have you looked at recorded flight data to see what difference it made?
I flew my MM last week near my house in moderate winds that some may consider questionable. I received wind warnings suggesting it wouldn't be able to RTH, even though I was flying away from home into the wind, not going full forward stick, and still able to go at least 3mph. I was flying 90 to 120ft, enough to clear all trees.
Mass won't help thrust, but it will dampen it appearing to struggle as it compensates for constant wind changes.
The MM may sound horrible hovering in moderate and shifting winds, but it handles well for me. Just take it easy and gradually learn what it can and cannot handle.
The only no win situation I can think of is when you lose signal and RTH altitude and wind can't get it home. If you still have signal and you're drifting, lower altitude or just land. Point gimbal down while you land so you can see by landmarks where you're landing.
Mass won't help thrust, but it will dampen it appearing to struggle as it compensates for constant wind changes.
The MM may sound horrible hovering in moderate and shifting winds, but it handles well for me. Just take it easy and gradually learn what it can and cannot handle.
The only no win situation I can think of is when you lose signal and RTH altitude and wind can't get it home. If you still have signal and you're drifting, lower altitude or just land. Point gimbal down while you land so you can see by landmarks where you're landing.
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Wasn't this a defect early on with the Minis that they had to correct later (probably by changing the prop length).
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The length of Mini props has never been changed.
All that happened was releasing firmware 1.0.5
I would strongly recommend against using other than DJI oem props. They were developed the maximize the motors, and offer optimal performance without shortening the life of your drone.
You can’t get something for nothing.
Groundspeed limited? So you’re saying that if you had a 40 mph tailwind, the Mini would fly backwards at 11 mph to maintain a groundspeed of 29 mph (its maximum speed)?
I think you’ve oversimplified these equations to the point where they don’t really mean anything. Is F force required? It’s very difficult to see how any extra force is not just that required to maintain level flight with the extra weight. There’s too much missing from your equation.
Yes, but that’s simply drag caused by moving through the air. It’s not “wind drag” (which you mentioned earlier), which doesn’t exist.
Groundspeed=airspeed +/- wind speed component. However, the maximum speed is the maximum speed whether it’s windy or not. All the drone knows is that it’s moving through air - it doesn’t know that the air it’s moving through is also moving. When it’s in the cruise, it doesn’t automatically speed up if it’s flying into wind or slow down if it’s downwind.
Let’s call it 1g to get back into the real world. Yes, it would get forward speed. It would accelerate very quickly as it would have very little inertia but would be affected much more by turbulence as a result. The more you increase the weight, the more power you’ll need to make it fly forward at a constant height and speed but the more stable it would become.
Adding weight to an aircraft in level flight doesn’t make it go through the air any faster, it just needs more power to go at the same speed.
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