Hi
I've been lurking here for some time now. Got my Inspire 1 pro for aerial photo- and videowork in 10/2016. First problem was after total of 2hrs of flight I noticed one motor was making a clicking sound when rotating. While running without props on a table it vibrated audibly and the table amplified the sound. Bearings of this motor were going bad. I also checked all the other motors and one more felt loose.
Now here comes the real problem: My Inspire also experienced the harmonic vibration other users have posted here. It only vibrated when raising the landing gear. I originally thought it was because the T-joints are loose as in other cases. They were sufficiently tight. I was even worried about the servo motor because the joints felt so tight when removing the smaller arm and rotating the motor arms.
I sent the inspire for maintenance to DJI through our retailer in Finland so they could address the vibration and bearing fault. It took 3 weeks and DJI had replaced 2 motors though the other motor they replaced wasn't the additional 'loose' one but another. I went for a test flight and the vibration was still there when raising the landing gear. The drone was dead still when landing gear down.
Now it gets interesting. I thought that it must be something else than the T-joints and went for the propellers. I have the quick lock-type props. As I don't have a balancing device I measured all the propellers from the center point to the tip (they were equal to 0.5mm). Then I measured the vertical distance from table top to the both tips of all propellers and looked for balance(so that one tip is not lower or higher than another in one prop). I have in total 12 props and only 4 of these were < 0.5mm. Others were 2-3mm off. Then I collected these 4 good props and measured again. They were off by 1-2mm!? Turns out that if I install prop 1 to motor 1, it is good when installing one way and bad when installing the other way around(keep the motor still and rotate prop 180deg before installing again). This was the case with all the props thus rendering my previous test useless.
I read the post about propellers in which the op said that it's crucial that you don't scratch or bend them in any way. I have also a long background in RC flying and agree with this. I have been extremely careful with the expensive Inspire and the props. Anyway. I set, measured and installed the props so that everything was in balance and the vibration was still there. I still didn't believe that the props would be the cause of this because me and my business partner have bent, scratched and sat on so many props with our previous self-built rc-planes, zagis, quads etc. in 20 years with no problems at all.
Here is a video of the continuing problem:
The video is slow-motion video from LG 5X, around 100fps -> 24fps
I continued to look for the cause of the oscillation and realized that the Inspire + gimbal is a spring-mass-system. I looked into harmonic vibrations theory and it seems that the inspire's motors seed an oscillation to the frame(propably normal for drones) which is amplified in a resonant frequency when the gimbal(X5) is attached. I came to a conclusion that DJI has had bad luck with these masses and the rubber dampers in between them... Maybe not enough testing but the whole combo seems to be too near to the resonant frequency straight out of the package.
I went to prove this and changed the resonant frequency by squeezing the damping rubbers a little bit with zipties. -> No oscillation at all. I mean dead still.
Next thing I did was contact the retailer again with my testing results and he suggested that I should test without the gimbal and check that the plate into which the gimbal connects is securely attached to the Inspire. I did and everything was fine and the bolts tight. I took a test flight with no gimbal (1st time without) and no vibration. Then I measured the weight of the gimbal (534g) and cut a small block of wood about the same weight (539g). Strapped the wooden block with zipties under the gimbal plate being careful not to squeeze the gimbal's wiring on top of the plate and also making sure that the gimbal plate can move freely from the rubber dampers. This time with no zipties on the dampers and a similar weight hanging from the plate -> vibrating again.
This has (at least to me) proven that there is "nothing wrong" with the inspire but it's just poor choise of masses and wrong stiffness in the rubbers between. I still don't rule out that the Inspire wouldn't be in specs and is faulty in some way that I can't measure. They had one situation like this with a phantom 3 and the whole combo had to be replaced before the vibration went away.
So all in all:
- Harmonic oscillation problem when landing gear up -
-> faulty bearing in motor was not the cause of the problem
-> looseness in T-joints was not the cause of the problem
-> propellers being off balance were not the cause of the problem (ALTOUGH may seed the vibration, but still 12 props tested, should brand new props work..?)
Problem is presumably: mass(inspire) + spring(rubber dampers) + mass(gimbal X5) being too close to the resonant frequency of the system into which the motor+prop-combination feeds small vibration. Little reservation still for something else being faulty in the combination.
(Effective mass (spring–mass system) - Wikipedia)
I will now contact DJI directly and try to solve this by presenting all evidence from these tests and hoping that they have a solution for this oscillation. If they have, I think it's new, stiffer rubber dampers for the gimbal plate because you really can't alter the weights of these parts. But if they don't and this is not a common problem (retailer knew about only one other case) I think they have to exchange the drone and X5 for new ones. In the meantime we're losing customers(again), yay...
Any ideas, comments and experiences about these vibrations and your own tests are appreciated. I may have missed something. Also if you have this vibration problem, I can take photos of the DIY solution with the zipties and/or the wooden block test. Going to send an e-mail to dji now->
I've been lurking here for some time now. Got my Inspire 1 pro for aerial photo- and videowork in 10/2016. First problem was after total of 2hrs of flight I noticed one motor was making a clicking sound when rotating. While running without props on a table it vibrated audibly and the table amplified the sound. Bearings of this motor were going bad. I also checked all the other motors and one more felt loose.
Now here comes the real problem: My Inspire also experienced the harmonic vibration other users have posted here. It only vibrated when raising the landing gear. I originally thought it was because the T-joints are loose as in other cases. They were sufficiently tight. I was even worried about the servo motor because the joints felt so tight when removing the smaller arm and rotating the motor arms.
I sent the inspire for maintenance to DJI through our retailer in Finland so they could address the vibration and bearing fault. It took 3 weeks and DJI had replaced 2 motors though the other motor they replaced wasn't the additional 'loose' one but another. I went for a test flight and the vibration was still there when raising the landing gear. The drone was dead still when landing gear down.
Now it gets interesting. I thought that it must be something else than the T-joints and went for the propellers. I have the quick lock-type props. As I don't have a balancing device I measured all the propellers from the center point to the tip (they were equal to 0.5mm). Then I measured the vertical distance from table top to the both tips of all propellers and looked for balance(so that one tip is not lower or higher than another in one prop). I have in total 12 props and only 4 of these were < 0.5mm. Others were 2-3mm off. Then I collected these 4 good props and measured again. They were off by 1-2mm!? Turns out that if I install prop 1 to motor 1, it is good when installing one way and bad when installing the other way around(keep the motor still and rotate prop 180deg before installing again). This was the case with all the props thus rendering my previous test useless.
I read the post about propellers in which the op said that it's crucial that you don't scratch or bend them in any way. I have also a long background in RC flying and agree with this. I have been extremely careful with the expensive Inspire and the props. Anyway. I set, measured and installed the props so that everything was in balance and the vibration was still there. I still didn't believe that the props would be the cause of this because me and my business partner have bent, scratched and sat on so many props with our previous self-built rc-planes, zagis, quads etc. in 20 years with no problems at all.
Here is a video of the continuing problem:
The video is slow-motion video from LG 5X, around 100fps -> 24fps
I continued to look for the cause of the oscillation and realized that the Inspire + gimbal is a spring-mass-system. I looked into harmonic vibrations theory and it seems that the inspire's motors seed an oscillation to the frame(propably normal for drones) which is amplified in a resonant frequency when the gimbal(X5) is attached. I came to a conclusion that DJI has had bad luck with these masses and the rubber dampers in between them... Maybe not enough testing but the whole combo seems to be too near to the resonant frequency straight out of the package.
I went to prove this and changed the resonant frequency by squeezing the damping rubbers a little bit with zipties. -> No oscillation at all. I mean dead still.
Next thing I did was contact the retailer again with my testing results and he suggested that I should test without the gimbal and check that the plate into which the gimbal connects is securely attached to the Inspire. I did and everything was fine and the bolts tight. I took a test flight with no gimbal (1st time without) and no vibration. Then I measured the weight of the gimbal (534g) and cut a small block of wood about the same weight (539g). Strapped the wooden block with zipties under the gimbal plate being careful not to squeeze the gimbal's wiring on top of the plate and also making sure that the gimbal plate can move freely from the rubber dampers. This time with no zipties on the dampers and a similar weight hanging from the plate -> vibrating again.
This has (at least to me) proven that there is "nothing wrong" with the inspire but it's just poor choise of masses and wrong stiffness in the rubbers between. I still don't rule out that the Inspire wouldn't be in specs and is faulty in some way that I can't measure. They had one situation like this with a phantom 3 and the whole combo had to be replaced before the vibration went away.
So all in all:
- Harmonic oscillation problem when landing gear up -
-> faulty bearing in motor was not the cause of the problem
-> looseness in T-joints was not the cause of the problem
-> propellers being off balance were not the cause of the problem (ALTOUGH may seed the vibration, but still 12 props tested, should brand new props work..?)
Problem is presumably: mass(inspire) + spring(rubber dampers) + mass(gimbal X5) being too close to the resonant frequency of the system into which the motor+prop-combination feeds small vibration. Little reservation still for something else being faulty in the combination.
(Effective mass (spring–mass system) - Wikipedia)
I will now contact DJI directly and try to solve this by presenting all evidence from these tests and hoping that they have a solution for this oscillation. If they have, I think it's new, stiffer rubber dampers for the gimbal plate because you really can't alter the weights of these parts. But if they don't and this is not a common problem (retailer knew about only one other case) I think they have to exchange the drone and X5 for new ones. In the meantime we're losing customers(again), yay...
Any ideas, comments and experiences about these vibrations and your own tests are appreciated. I may have missed something. Also if you have this vibration problem, I can take photos of the DIY solution with the zipties and/or the wooden block test. Going to send an e-mail to dji now->
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. The video feed goes black and the software freezes on my Nexus 5X. First I thought that the Android on the Nexus was buggy because it had done it before and had to restart my phone. Turns out that the transmitter was faulty. Also the i1 went green light for about 2 seconds when powered on and connected to the transmitter. Then yellow continuous flashing. In the end the transmitter went dead with the video feed altogether. Tested with 2 nexus 5's, ipad pro 2007 and an ipad 2007. Transmitter master/slave and all possible combinations of transmitter+pad.
