ALERT! Used P4 yaw motors sold as new.

[jiminyfixit]

Attention "Pilots". With all the posts on yaw issues in the P4's, I have probably solved one of the mysteries. Anybody who has purchased "new" yaw motors from 2 companies that I know, "Flyfuntech2014" and "Extremediy", both Chinese sellers on eBay, buyer be beware! These are NOT new motors. They are obviously obtained from service centers that have been purchased, maybe given to, these 2 outfits, and sold as new. I even think they are the same outfit with 2 names, as their "thank you" messages are identical. When they say they have been "tested", THAT is a bad sign. Why would ANYBODY "test" a new motor?
After going to all the trouble to replace the yaw motor, with what you think is a new one, reassemble, install back on the drone and find out there are still "issues" with the yaw, I decided to remove and pop the housing off the "new" motor. To my surprise, one of the sensor chips had deep scoring in it. This is one of the signs of a bad motor. This happens in a crash when the housing touches the sensor. There is very little clearance between the two. The gold contacts also had excessive gouges. I checked the other 3 motors I bought form these 2 scoundrels and found; blue lock tite in the 3 mounting screw holes, divots in the gold contacts on all motors, and 3 motors with scores in one or both sensor chips.
I have contacted the sellers and await their response. I wanted to alert Pilots to this as soon as possible. I had a problem with a Chinese seller a few years ago, who was selling counterfeit ribbon cables. I guess they figure a person who buys just 1 will be reluctant to return it and might think there is something else wrong with the camera beside the ribbon. Well, I purchased 10 ribbons and returned them, after testing 3 of them first, but the seller NEVER reimbursed me for $19 postage. Another reason they think you won't return a bad product. We'll see how they handle these bad yaw motors.

As difficult as it is to evaluate and determine the causes of issues with these fussy cameras, it's a shame less honorable sellers take advantage of unknowing DIYer's. I'm fortunate that I have the ability to test with multiple components and have no reluctance in taking motors and other items apart. This is why I will always share what I know with fellow "Pilots". Thank God for this forum!

Cheers,
Jim

 

[Sprtbkryder]

Thank you! Two thumbs up to Jimmy!!

 

[jwt873]

What are 'yaw motors'?

 

[John1960]

What are 'yaw motors'?

yeah what are yaw motors ??????????????????????????????

 

[macoman]

Motors that don't work properly... I assumed!

 

[With The Birds]

What are 'yaw motors'?

By definition a motor installed in the AC with rotation in the yaw axis- the only place you might find one of those would be in the camera gimble assy.

 

[jiminyfixit]

By definition a motor installed in the AC with rotation in the yaw axis- the only place you might find one of those would be in the camera gimble assy.

Excellent definition! All of DJI's gimbaled cameras, and others like Zenmuse, have small, 3-phase "motors" that control gimbal motion and are fed by electronic signals from the A/C's accelerometer and processed by circuitry in various circuit boards. The motors do not perform full rotation like we think most motors do, but are "indexed" to limit rotation. "Indexing" is established with the combination of 2 evenly spaced sensors on the motor base and evenly spaced magnetically dense spots in the black "race" in the drum. I take a small metal screwdriver and position it in the race area to determine where these "spots" are and mark them with a felt marker, (see photo). I will do this when I remove a yaw motor from a crashed drone and "reuse" it in the same drone. I have found every drum has slightly different orientation of the magnetic "spots", relative to the mounting holes. I have NO idea why they vary and this may be the reason different new motors may not center properly, as Ted mentioned in one of his posts.

The "yaw" motor is attached to the upper portion of the.....you guessed it, the yaw arm and controls left and right motion, with the "centered" position as the starting point. Pitch and roll have similar motors with different mounting drums, but function in the same manner. Any disturbance in the delicate electronic components, will alter the normal function of any of the gimbal motors. In order to determine if a motor has been compromised from a crash, you have to remove the "housing", "drum", whatever you want to call it, to see if the 2, very tiny, sensor chips are damaged. I use a small machinists punch and a small machinists vice to tap the shaft out of the drum. If they have even a slight scrape or gouge in one or both sensors, they will function erratically. Varying depths of the scrape are determined by what the forces were from the crash. There is a certain amount of "flexing" of the shaft with a very small gap between the drum and the motor base and a crash of any amount can eat up the gap. Another DJI design flaw. I have attached a photo showing the 2 different versions of the yaw mounting drums, early, with no "ears" and the new version. I have also shown the marks I made in the drum indicating magnetic spots and where they are oriented in relationship to the mounting holes. I don't have a camera capable of zooming in to get a good shot of the tiny sensor chip that got knocked out of position, but at least you have an idea of what the motor looks like without the drum in the way. Note: When I reassemble the drum to the motor, I first use silly putty, yes, silly putty to remove any dirt or metallic grit from inside the drum and on the motor. These components need to be very clean to function properly. I have had to disassemble motors before that were functional, but were full of dirt from a crash.

I am starting to go round and round with Flyfuntech and Extremediy who sold me the used motors. This is a stall tactic, especially when they keep asking similar versions of the same questions.

Cheers,
Jim

 

[Droneted]

I bought a bunch of yaw motors but none from those companies. I have been traveling so i haven't had a chance to check them.

 

[jiminyfixit]

I bought a bunch of yaw motors but none from those companies. I have been traveling so i haven't had a chance to check them.

Hi Ted,

Where did you get yours?
I am now in need of a few, after waiting and then getting someone else's junk.

 

[Droneted]

I got some used ones from Wvon1124. I had good luck with these. I got some new ones, i hope, from another guy. I will check to see who thatvwas.

 

[Droneted]

The new ones were from the same guy you got them from.
I just got those so i will look them over carefully. I may send them back.

 

[Droneted]

They actually look new. I didn't take them apart

 

[jiminyfixit]

They actually look new. I didn't take them apart

Ted,
Even a used motor looks new, until you check the gold contacts on the ribbon cable to see if there are any "divots" made from the connector. New motors will not have any divots. There also should not be any evidence of blue Loctite in the mounting screw holes. I would also assume they would come in an official DJI bag with the customary DJI product card and part number. Then, take an eye loupe and look closely at the top of the 2 very tiny black sensors that sit at the edge of the motor plate to see if there are any radial grooves in one or both of them. The next step would be to remove the metal housing for a closer look at things and see if the black magnetic ring is free from nicks and gouges. In a crash, the shaft flexes and the armature lugs can dig into the race along with the edge of the housing, scraping across one or both sensors. One damaged sensor or nicks in the race will make the motor inop.
These P4's have a weakness in the yaw department. I realize DJI engineers are using the yaw arm as an impact link to help prevent more severe damage to the rest of the gimbal, but the motor is the weak link that DJI should be supplying. I have experienced more motor issues with the few P4's I have attempted to repair, than the dozens of P3's and P2V+'s that I have successfully repaired. Gram for gram, the P4 gimbal is almost twice the weight of the P3, utilizing the same size motor shaft. When DJI decide to change the yaw housing to the "new version", they actually increased the torque on the shaft instead of strengthening it. The "good" used yaw motors that I have come across were all the earlier version that I swapped housings on.

I just ordered another "New" motor form another outfit in China that promises that the motor is, in fact new. We'll see.

 

[Droneted]

You are right. Mine have marks on the connector. Very fait but there. I have been traveling buying used ones from Ebay that have for the most part been ok. At least I know what i am getting with used.

 

[eric148]

Attention "Pilots". With all the posts on yaw issues in the P4's, I have probably solved one of the mysteries. Anybody who has purchased "new" yaw motors from 2 companies that I know, "Flyfuntech2014" and "Extremediy", both Chinese sellers on eBay, buyer be beware! These are NOT new motors. They are obviously obtained from service centers that have been purchased, maybe given to, these 2 outfits, and sold as new. I even think they are the same outfit with 2 names, as their "thank you" messages are identical. When they say they have been "tested", THAT is a bad sign. Why would ANYBODY "test" a new motor?
After going to all the trouble to replace the yaw motor, with what you think is a new one, reassemble, install back on the drone and find out there are still "issues" with the yaw, I decided to remove and pop the housing off the "new" motor. To my surprise, one of the sensor chips had deep scoring in it. This is one of the signs of a bad motor. This happens in a crash when the housing touches the sensor. There is very little clearance between the two. The gold contacts also had excessive gouges. I checked the other 3 motors I bought form these 2 scoundrels and found; blue lock tite in the 3 mounting screw holes, divots in the gold contacts on all motors, and 3 motors with scores in one or both sensor chips.
I have contacted the sellers and await their response. I wanted to alert Pilots to this as soon as possible. I had a problem with a Chinese seller a few years ago, who was selling counterfeit ribbon cables. I guess they figure a person who buys just 1 will be reluctant to return it and might think there is something else wrong with the camera beside the ribbon. Well, I purchased 10 ribbons and returned them, after testing 3 of them first, but the seller NEVER reimbursed me for $19 postage. Another reason they think you won't return a bad product. We'll see how they handle these bad yaw motors.

As difficult as it is to evaluate and determine the causes of issues with these fussy cameras, it's a shame less honorable sellers take advantage of unknowing DIYer's. I'm fortunate that I have the ability to test with multiple components and have no reluctance in taking motors and other items apart. This is why I will always share what I know with fellow "Pilots". Thank God for this forum!

Cheers,
Jim

Hello and thanks for all the information. I'm just looking for a yaw motor. So I understand that you need to contact the seller and make sure it's really new and not used. Is there a store you recommend that can be trusted to sell a new product ?. Second thing. I understand that even if the yaw motor is new there is still a problem. Sure you all saw the video on YouTube that the guy returns the old magnet housing and puts it on the new motor. Has anyone tried it? Does it really work? And what is the logic of this? Maybe you can fix the circuit board. If it is really only two burned sensor chips that cause the problem. So I believe that anyone who understands electronics can fix it. If anyone has any practical advice, I'd be happy to know. Why be dependent on dji. The profits from the parts of the product are greater than the profits from the sale of the product. This is the big money of all companies. So you have to find a solution to the problem without hurting you in your pocket. Thanks