Correct motor mount angle

[Jeff48]

I’ve been scanning threads throughout cyberspace for a definitive answer to the question of rotating motor mounts and the subsequent “disasters” that await the unwary. Since it is The RPIC’s responsibility to ensure the sUAS is Flightworthy before every flight it seems to me DJI has neglected to provide us with a critical indicia of flightworthiness, the proper angle for the motor mounts. Since they seem to be unwilling to provide it, I think we can get a decent idea by pooling our data and deducing that angle.
I propose we measure (in landing mode, not travel mode) the distance in millimeters between the surface on which the AC is placed and the outer tip of each of the two front propellers when the prop ends point to one another while being 90 degrees to the plane of the airframe. Ideally these measurements should be approximately the same. Any significant deviation from identical would be an indication that one of the CF tubes had rotated (either between the CF tube and the motor mount itself or, more likely, the entire CF tube has rotated at the “T” connector on the boom).
I am including photos of my bird for reference.

 

[slim.slamma]

View attachment 20296 View attachment 20297 I’ve been scanning threads throughout cyberspace for a definitive answer to the question of rotating motor mounts and the subsequent “disasters” that await the unwary. Since it is The RPIC’s responsibility to ensure the sUAS is Flightworthy before every flight it seems to me DJI has neglected to provide us with a critical indicia of flightworthiness, the proper angle for the motor mounts. Since they seem to be unwilling to provide it, I think we can get a decent idea by pooling our data and deducing that angle.
I propose we measure (in flight mode, not travel mode) the distance in millimeters between the surface on which the AC is placed and the outer tip of each of the two front propellers when the prop ends point to one another while being 90 degrees to the plane of the airframe. Ideally these measurements should be approximately the same. Any significant deviation from identical would be an indication that one of the CF tubes had rotated (either between the CF tube and the motor mount itself or, more likely, the entire CF tube has rotated at the “T” connector on the boom).
I am including photos of my bird for reference.

I Found a good thread on this subject on another forum. I’ll dig it up and post the link.

The NBA Finals is on so give me some time dig to it up Jeff. I’m pretty good when it come to digging through cyberspace.

 

[slim.slamma]

problem with arms

I hate to post up other forum material but I think you guys are on to something.

 

[Florida Drone Supply]

View attachment 20296 View attachment 20297 I’ve been scanning threads throughout cyberspace for a definitive answer to the question of rotating motor mounts and the subsequent “disasters” that await the unwary. Since it is The RPIC’s responsibility to ensure the sUAS is Flightworthy before every flight it seems to me DJI has neglected to provide us with a critical indicia of flightworthiness, the proper angle for the motor mounts. Since they seem to be unwilling to provide it, I think we can get a decent idea by pooling our data and deducing that angle.
I propose we measure (in flight mode, not travel mode) the distance in millimeters between the surface on which the AC is placed and the outer tip of each of the two front propellers when the prop ends point to one another while being 90 degrees to the plane of the airframe. Ideally these measurements should be approximately the same. Any significant deviation from identical would be an indication that one of the CF tubes had rotated (either between the CF tube and the motor mount itself or, more likely, the entire CF tube has rotated at the “T” connector on the boom).
I am including photos of my bird for reference.

Yes, if your aircraft was involved in a crash there are certain dimensions which are usually left for the repair stations to correct. There may be some threads on this subject but possibly no definitive threads, including this one.

We have found that just a slight grasp of the booms (as we do during a preflight) will change the measurement you show to either equal the dimensions out or make them totally different. We do this regularly to assure there are no weak engine mount to boom connections with regards to the glueing process.

That being said the relationship between landing mode and flight mode regarding propeller orientation would be hard to compare and really do not compare. All the forces of flight will change the measurements of the props and booms depending flight loads. The IMU and ESC's will control the motors speed and compensate for most irregularities. There are so many different ways for the systems to compensate for slightly out of "Tune" arms and motors that would prevent us from saying that "This or That" was the cause for poor performance of a flight.

Thanks for your thoughts and creating a great conversation that will most likely continue!

 

[Jeff48]

problem with arms

I hate to post up other forum material but I think you guys are on to something.

Yup. That’s the best thread so far. I also posted a similar reply there. Thanks

 

[Raphael Dahan]

View attachment 20296 View attachment 20297 I’ve been scanning threads throughout cyberspace for a definitive answer to the question of rotating motor mounts and the subsequent “disasters” that await the unwary. Since it is The RPIC’s responsibility to ensure the sUAS is Flightworthy before every flight it seems to me DJI has neglected to provide us with a critical indicia of flightworthiness, the proper angle for the motor mounts. Since they seem to be unwilling to provide it, I think we can get a decent idea by pooling our data and deducing that angle.
I propose we measure (in flight mode, not travel mode) the distance in millimeters between the surface on which the AC is placed and the outer tip of each of the two front propellers when the prop ends point to one another while being 90 degrees to the plane of the airframe. Ideally these measurements should be approximately the same. Any significant deviation from identical would be an indication that one of the CF tubes had rotated (either between the CF tube and the motor mount itself or, more likely, the entire CF tube has rotated at the “T” connector on the boom).
I am including photos of my bird for reference.

Hi Jeff, you meant landing mode ? Because as I see in the pictures, the craft stand on his legs.

 

[Jeff48]

Hi Jeff, you meant landing mode ? Because as I see in the pictures, the craft stand on his legs.

Yes. Thanks Raphael. Nomenclature error on my part. I appreciate the correction. I will correct it in the original post to avoid further miscommunication

 

[EpicJib]

Sorry missed the proper height. What should they be at the tips of the propellers?

 

[Jeff48]

Sorry missed the proper height. What should they be at the tips of the propellers?

We actually don’t know that number DJI doesn’t provide it to end users. We are trying to figure out, based on member reports of their own numbers, what appears to be a reasonable assumption.

 

[Phil DeVore]

Yes, if your aircraft was involved in a crash there are certain dimensions which are usually left for the repair stations to correct. There may be some threads on this subject but possibly no definitive threads, including this one.

We have found that just a slight grasp of the booms (as we do during a preflight) will change the measurement you show to either equal the dimensions out or make them totally different. We do this regularly to assure there are no weak engine mount to boom connections with regards to the glueing process.

That being said the relationship between landing mode and flight mode regarding propeller orientation would be hard to compare and really do not compare. All the forces of flight will change the measurements of the props and booms depending flight loads. The IMU and ESC's will control the motors speed and compensate for most irregularities. There are so many different ways for the systems to compensate for slightly out of "Tune" arms and motors that would prevent us from saying that "This or That" was the cause for poor performance of a flight.

Thanks for your thoughts and creating a great conversation that will most likely continue!

Should this issue that concern me? Seems like there’s always something to worry about when it comes to the I2 from people who take everything to extremes. I check the tightness of the CF tubes prior to every flight even though I have installed motor clamps. I just don’t want anything to happen when I am up in the air.

 

[Jeff48]

I’m just spitballing here Phil.
Even if the aftermarket CF clamps are tight and keep the individual motor mounts from rotating on the CF boom (as would be the case if the glue on the motor mount to CF tube were compromised), the OEM design could still allow the entire CF tube to rotate inside the tee connector and offset both the front and rear motor mounts from the intended plane and therefore the left side and right side motor mounts would be at different angles and the props, when attached would not be level when pointing at each other. I know this can happen because while mine was in for unrelated service the tech spotted the inequalities and corrected the problem by loosening the tee connector screw and by turning the CF tube and retightening the screw returned the mount angle to the like new position.
Like I said, I’m just spitballing ideas but I’d still like to know the “ideal” angle or range of ideal angles for my own peace of mind.

 

[EpicJib]

We just need measurements from 10 new birds to get a good idea and average. Since these are on a spline you would only have 3 selections, the exact angles DJI intended one cog up or one cog down.

 

[Jeff48]

We just need measurements from 10 new birds to get a good idea and average. Since these are on a spline you would only have 3 selections, the exact angles DJI intended one cog up or one cog down.

Yup. My thoughts exactly.

 

[Phil DeVore]

I’m just spitballing here Phil.
Even if the aftermarket CF clamps are tight and keep the individual motor mounts from rotating on the CF boom (as would be the case if the glue on the motor mount to CF tube were compromised), the OEM design could still allow the entire CF tube to rotate inside the tee connector and offset both the front and rear motor mounts from the intended plane and therefore the left side and right side motor mounts would be at different angles and the props, when attached would not be level when pointing at each other. I know this can happen because while mine was in for unrelated service the tech spotted the inequalities and corrected the problem by loosening the tee connector screw and by turning the CF tube and retightening the screw returned the mount angle to the like new position.
Like I said, I’m just spitballing ideas but I’d still like to know the “ideal” angle or range of ideal angles for my own peace of mind.

I understand and agree with everything you said. All I was saying is that by installing the motor clamps I am doing anything I can to stop the problem from happening, hopefully.
Kinda like changing your oil at the correct time in your car.

 

[ElectricLife]

Fascinating thread...We've always tried to figure out how to get standard measurements, but so far we understand there's no official answer from the makers. Maybe we don't ask hard enough.

 

[mmarian]

We just need measurements from 10 new birds to get a good idea and average. Since these are on a spline you would only have 3 selections, the exact angles DJI intended one cog up or one cog down.

There is a picture in the Manual somewhere showing the Inspire from front with props lined up against each other. In my estimation the tips are pointing to about 1/4" above the bottom canopy dome screws in landing mode. I do not think this needs to be a pin point accurately set, a few mm up or down won't matter, as long as both prop tips are nicely alligned against each other. This can be achieved by loosening the screws on the clamps and then the angle of each arm can be minutely adjusted.That is how I have done it on my I2.

 

[Jeff48]

There is a picture in the Manual somewhere showing the Inspire from front with props lined up against each other. In my estimation the tips are pointing to about 1/4" above the bottom canopy dome screws in landing mode.

I think this is what you are talking about but still lacks specificity. The screen shot is from the I2 maintenance manual. https://dl.djicdn.com/downloads/inspire_2/20180223/Inspire_2_Maintenance_Manual.pdf

 

[mmarian]

View attachment 20351


I think this is what you are talking about but still lacks specificity. The screen shot is from the I2 maintenance manual. https://dl.djicdn.com/downloads/inspire_2/20180223/Inspire_2_Maintenance_Manual.pdf

Yes, thank you.

 

[Advexure]

Some additional info on this thread: Prop alignment - Inspire 2

There is a DJI repair fixture that our techs use that the aircraft goes on that properly aligns the arm angle. Without the fixture, the measurements above and schematic show the anhedral (opposite of a dihedral) of the propellers when in landing mode pretty well. Be on the safe side with additional outward tilt as too much inward tilt will result in a prop strike with the front vision sensor when you come in for a landing and bring the landing gear down.

Proper alignment in landing mode:

Proper alignment in flight mode:

 

[semiond]

Thanks guys this is rely interesting...

Can you give me two precisions please :


- @Jeff. Can you please tell in which condition you make your mesurement : 1 You take the drone in landing mode and you put it on a table or 2. you put it on a table in transport mode and active the landing mode and let the aircraft come alone in landing mode.

I ask this cause i notice there is difference from 5mm in the 2 different way, i suppose its due to when you let the aircraft come in landing mode there is some resistance on the surface (2).

- when you tight the screw adfter arm adjustement, did you put glue and how much did you tight it ? just a little hand resistant or you tight strong ?

Thanks