Mavic Mini hoovering motor speed...is this normal?

[kamidoko1974]

Hi all,
I wanted to ask you if you ever had a look at your MM motor speed during hoovering...
Do you think this result is normal? What are you experiencing?
In the attachment the MM hoovering indoor without touching the RC. Propellers are new. Anyway changing propellers doesn't change the result.
Thanks for your feedback!
Federico

 

[sar104]

Take a look at this thread for motor speed data:

Mavic Mini uncommanded descent tests

After a little experimentation I was able to replicate the uncommanded descent problem under 0400 firmware by loading the rear props for a few hours as might happen in the flymore case. The props did appear slightly flattened compared to the front props. The problem quickly manifested itself in...

mavicpilots.com

 

[kamidoko1974]

Take a look at this thread for motor speed data:

Mavic Mini uncommanded descent tests

After a little experimentation I was able to replicate the uncommanded descent problem under 0400 firmware by loading the rear props for a few hours as might happen in the flymore case. The props did appear slightly flattened compared to the front props. The problem quickly manifested itself in...

mavicpilots.com

Hello @sar104 ,
thank you.
Yes, I spent some time on that amazing test you did... I couldn't understand everything but I thought it was a test about a MM with a special UD problem... I saw in your diagrams there is a difference between motors during hoovering time (if I'm right) but mine looks different. The fastest and the lowest motors are very different while yours look to be like 2 couples that have almost the same speed...Sorry for this terrible explanation...
Federico

 

[sar104]

Hello @sar104 ,
thank you.
Yes, I spent some time on that amazing test you did... I couldn't understand everything but I thought it was a test about a MM with a special UD problem... I saw in your diagrams there is a difference between motors during hoovering time (if I'm right) but mine looks different. The fastest and the lowest motors are very different while yours look to be like 2 couples that have almost the same speed...Sorry for this terrible explanation...
Federico

With identical props in still air they should be in pairs with regard to motor speed while hovering, but slightly mismatched props or any wind then you will see differences.

 

[scro]

Was there any wind/draught, or nearby objects that may cause downwash from the props to create turbulence around the drone?

There's loose correlation between diagonally opposite motors, indicating some stabilisation of heading going on. Also there's roughly 15% difference between the average speed of the fastest and slowest motors. Redraw the graph with the speed scale going from 0 to 12000rpm and it will "look" better.

 

[kamidoko1974]

With identical props in still air they should be in pairs with regard to motor speed while hovering, but slightly mismatched props or any wind then you will see differences.

Thank you @sar104 .
Ok...So I may have not perfect propellers even if they are new...or who knows...motors little differences... Anyway thanks a lot for your answer!
Federico

 

[kamidoko1974]

Was there any wind/draught, or nearby objects that may cause downwash from the props to create turbulence around the drone?

There's loose correlation between diagonally opposite motors, indicating some stabilisation of heading going on. Also there's roughly 15% difference between the average speed of the fastest and slowest motors. Redraw the graph with the speed scale going from 0 to 12000rpm and it will "look" better.

Hello,
no wind, it was indoor. I also made it hoovering in 4 different positions/orientations to avoid any input from the objects in the room but the result is the same...The difference from the extremes is between 15% and 20%... Thanks!
Federico

 

[scro]

Nice and scientific trying 4 orientations

There can be a surprising amount of airflow indoors, caused by warm/cool air flowing around, and windows/doors open. I have an ancient micro coaxial RC helicopter that has no fancy automatic position holding ability, and is useless in the slightest puff of wind. Indoors it drifts around even just from convective currents coming off the room heaters, and cooler air flowing down my stairway!

 

[kamidoko1974]

Nice and scientific trying 4 orientations

There can be a surprising amount of airflow indoors, caused by warm/cool air flowing around, and windows/doors open. I have an ancient micro coaxial RC helicopter that has no fancy automatic position holding ability, and is useless in the slightest puff of wind. Indoors it drifts around even just from convective currents coming off the room heaters, and cooler air flowing down my stairway!

hahaha...well... I don't have a wind tunnel for testing at home at the moment But I have a similar result outdoor...

 

[BokiFly]

I wanted to ask you if you ever had a look at your MM motor speed during hoovering...
Do you think this result is normal? What are you experiencing?

Yesterday I performed the same test as you, hover indoor, no sticks, just auto take off and auto land. I posted in another topic.
So I have the same question as you.
In some moments there is a 1500 RPM difference for rear motors. But so far no error messages, today I was flying a lot in the park, some of that was in S mode.
Considering tests that @sar104 performed about uncommanded descent I think that is a good practise to check our DAT logs from time to time, but I don't know what exactly we should see to decide to change the props. Hovering indoor tests? What difference in motor speed is tolerable?

 

[kamidoko1974]

Yesterday I performed the same test as you, hover indoor, no sticks, just auto take off and auto land. I posted in another topic.
So I have the same question as you.
In some moments there is a 1500 RPM difference for rear motors. But so far no error messages, today I was flying a lot in the park, some of that was in S mode.
Considering tests that @sar104 performed about uncommanded descent I think that is a good practise to check our DAT logs from time to time, but I don't know what exactly we should see to decide to change the props. Hovering indoor tests? What difference in motor speed is tolerable?

Hi, well in my case the difference can be until 2200-2500rpm but no issues at the moment... Unfortunately I haven't do a test when I had the ESC error a while ago but that time I even didn't know I could investigate about motor speed...

 

[Zbip57]

Just for comparison, this is my hover test with new prop blades installed on every motor except the right-front, which still has the original blades on it.

 

[BokiFly]

OK, then around 1.000 RPM (mine case too) should be fine.

 

[kamidoko1974]

Just for comparison, this is my hover test with new prop blades installed on every motor except the right-front, which still has the original blades on it.

View attachment 103598

mmm...far away better than mine... finger crossed!