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Which Propeller to replace?

Waseem

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Hi, I am totally new to drones, so sorry if my question is silly. I have tried searching this forum but couldn't t find an answer.

My Mavic Mini showed up a Motor Speed Error, I brought it down immediately, and turned it off. How do I know which propellers to change? The warning said something like replace propellers on beeping ESC or something to the effect. What does that mean? It was just a general beep.

Apologies again if the question is silly, and thanks for your help.
 
Hi, I am totally new to drones, so sorry if my question is silly. I have tried searching this forum but couldn't t find an answer.

My Mavic Mini showed up a Motor Speed Error, I brought it down immediately, and turned it off. How do I know which propellers to change? The warning said something like replace propellers on beeping ESC or something to the effect. What does that mean? It was just a general beep.

Apologies again if the question is silly, and thanks for your help.
When the propellers are bent or damaged, the aircraft propulsion may be reduced and not perform as intended. The new Mavic Mini propeller safety inspection feature is capable of detecting this and sending a notification to the pilot with a “Motor Speed Error” message.
and in Drone world, there are no silly questions, just silly actions that could have been pre-resolved with a question :)

check the props, they may also be unbalanced
the new folding props are much more difficult to balance unlike the older straight ones,where a little sandpaper could balance them, IMHO, better to just get new ones as the folding ones are not easy to balance
but if you get ambitious, here is a video

 
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If you can't see any with obvious external damage, when in doubt replace all of them
 
The current version of the firmware directs the mini, after landing, to 'twitch' the props and sound a buzz on the arm associated with the error. So it's easy to pretty easy to determine the props concerned. Maybe you turned it off too soon.

I know this for a fact having seen it on mine.
 
The current version of the firmware directs the mini, after landing, to 'twitch' the props and sound a buzz on the arm associated with the error. So it's easy to pretty easy to determine the props concerned. Maybe you turned it off too soon.

I know this for a fact having seen it on mine.

Thanks Rehkram, that’s the answer I was looking for. Yes, I switched it off immediately and was wondering how others were talking about definitively Knowing WHICH prop to change ... now I’ll look for the twitching motor. ??
 
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When the propellers are bent or damaged, the aircraft propulsion may be reduced and not perform as intended. The new Mavic Mini propeller safety inspection feature is capable of detecting this and sending a notification to the pilot with a “Motor Speed Error” message.
and in Drone world, there are no silly questions, just silly actions that could have been pre-resolved with a question :)

check the props, they may also be unbalanced
the new folding props are much more difficult to balance unlike the older straight ones,where a little sandpaper could balance them, IMHO, better to just get new ones as the folding ones are not easy to balance
but if you get ambitious, here is a video


Thanks Torkan, I’ll replace the rear ones. There was a very slight tear on one edge of one rear prop and that must have been from one instance where it clipped some leaves on a tree. Didn’t realize even that brief and light an encounter could damage a prop.
 
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T
If you can't see any with obvious external damage, when in doubt replace all of them

Thanks Iannes, 1/4 props at the rear had, what I thought, a slight rough edge. I’ll replace the rear 4 and see, if the problem persists, will replace front ones too ??
 
check the props, they may also be unbalanced
the new folding props are much more difficult to balance unlike the older straight ones,where a little sandpaper could balance them, IMHO, better to just get new ones as the folding ones are not easy to balance
but if you get ambitious, here is a video


While I don't think prop balance was at issue for the OP's "overspeed warning", I think a precision jig is a better way to position blades for balancing, rather than the variable speed electric drill shown in the video. I use a jig to straighten my M2 props for balancing with the Dubro. Three equidistant pins, installed in a straight line, position the prop blades perfectly for balancing.

Some may note that the prop hub could be rotated a bit - in either direction. However, this will have no discernible effect on prop balancing so long as the blades are clocked identically relative to the hub shaft hole - this, the jig achieves with ease.

Shown is a Master Airscrew prop for my Mavic 2. I find MAS props to be out of balance slightly more often than OEM DJI props. I can improve balance on about 20% of either DJI or MAS props. I don't sand off material to achieve balance, but rather add tape weight near the hub.

y2TCywD.png
 
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Zbip57, very helpful, thank you, got it ??

I was planning to replace my props today, flew the drone with the intention of setting off the alarm and find out the offending prop/motor, but two full batteries flown, and couldn’t get the warning activated.

I think ill keep flying the drone until the next time it warns me.
 
Zbip57, very helpful, thank you, got it ??
See also these three posts on;

What might be causing the propeller deformation leading to Motor Speed Error warnings;
mavicpilots.com/threads/motor-speed-error-mavic-mini.86130/page-13#post-1038101

A definitive test to measure propeller performance;
mavicpilots.com/threads/motor-speed-error-mavic-mini.86130/page-13#post-1038918

How to prevent further prop deformation;
mavicpilots.com/threads/motor-speed-error-mavic-mini.86130/page-14#post-1042991
 
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While I don't think prop balance was at issue for the OP's "overspeed warning", I think a precision jig is a better way to position blades for balancing, rather than the variable speed electric drill shown in the video. I use a jig to straighten my M2 props for balancing with the Dubro. Three equidistant pins, installed in a straight line, position the prop blades perfectly for balancing.

Some may note that the prop hub could be rotated a bit - in either direction. However, this will have no discernible effect on prop balancing so long as the blades are clocked identically relative to the hub shaft hole - this, the jig achieves with ease.

Shown is a Master Airscrew prop for my Mavic 2. I find MAS props to be out of balance slightly more often than OEM DJI props. I can improve balance on about 20% of either DJI or MAS props. I don't sand off material to achieve balance, but rather add tape weight near the hub.

y2TCywD.png
Interesting setup, but how would you use this to balance props for the mini?
 
Interesting setup, but how would you use this to balance props for the mini?
Exactly.

The Mini blades are sold by DJI as a matched pair, whereas most of the aftermarket ones I've seen on Ebay or Amazon are sold as a bunch of loose individual blades.

I've used the duBro balancer on my previous Phantoms which have rigid two-bladed props. It works great for that. But even there, it is only a static balancer. What's really needed is a dynamic balancer to measure the balance as the prop is spinning.

For example, each of the three examples in this image will balance perfectly in any position when the shaft is at rest. But they will each behave differently when the shaft is rotated at speed.

Image-B could represent a 2-bladed prop where the centre mounting hole is not perfectly square to the axis of the propeller blades, with one half of the blade bent up and the other half bent down.

Image-C could be a prop missing a portion of its tip on one side and thus less capable of generating lift, with weight added to the other side to make it balance "properly" using a static balancer. Or it could be a prop with one half having greater pitch angle generating more lift than the other half. Either way, that thing is going to vibrate when run at speed.

Dynamic-Static.jpg
 
We're going way off topic here, but I think the original poster's question has already been answered.

My old Phantom-1 had terrible vibrations causing awful jello in the GoPro video recordings. I bought a Du-Bro balancer and fixed all the props by adding small bits of tape to make them statically balance. The original props were all way off balance, and this made a huge improvement.

But then I discovered it was actually one of the motors that was out of balance. I think an earlier crash actually bent the motor shaft. If I ran the motors at the speed with props removed, the Phantom would walk around the tabletop just from the vibration.

Here's how I balanced that:

 
Interesting setup, but how would you use this to balance props for the mini?

With individual blades, I think your best bet is to use a small digital scale to weigh each blade, something like this:


This still leaves the possibility of uneven weight distribution, (e.g. a blade with more of it's weight near the tip would impose greater centrifugal force to cause and imbalance), but practically speaking, with a blade this small, that won't be much of an issue. Actually, I think being able to easily weigh each blade individually is somewhat of an advantage.

Best, of course, is being able to dynamically balance blades on the motor, as one can then also calculate adjustment weight for a given speed and it automatically takes any imbalance of the motor, ring gear etc, into account. When I balance full size aircraft props, that is most often done at cruise speed as that's where the system operates most of the time.
 
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Dynamic balancing. That brings back memories of dynamics lectures!
 
Hi, I am totally new to drones, so sorry if my question is silly. I have tried searching this forum but couldn't t find an answer.

My Mavic Mini showed up a Motor Speed Error, I brought it down immediately, and turned it off. How do I know which propellers to change? The warning said something like replace propellers on beeping ESC or something to the effect. What does that mean? It was just a general beep.

Apologies again if the question is silly, and thanks for your help.
An Electronic Speed Controller, or ESC for short, is the driving circuitry for the motors. In the event of an error, these ESCs can make their respective motors vibrate instead of spin.
Feel the motors and whichever one is vibrating with the beeps, change the props on that one.
Sometimes, you may see slight motion of the props on the motor as well.

Of course, if you can't tell, just replace them all.

Note: The Mavic Mini has a design flaw with its front arms that may sometimes cause the front props to hit the body of the drone.
 
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