Welcome Inspire Pilots!
Join our free DJI Inspire community today!
Sign up

Bearing Replacement How To Video

Joined
Oct 5, 2014
Messages
171
Reaction score
55
Location
Connecticut, USA

From my understanding, the only real preventative maintenance that can be performed on our Inspires that would be considered critical to a continued flight, are the 4 motors and props. Prop replacement is a no brainer. The landing gear transformation drive-train isn’t critical. The electronics are obviously critical, but the only preventative maintenance you can do on these is to replace each and every circuit board. After all, how can you predict which electronic circuit will go bad. You are basically at the whim of good/bad luck if any one of them fails. So, motors should be the focus of a good preventative maintenance program in which there are two options. First option would be to replace the entire motor after some pre-determined number of flight hours. The second option would be to replace just the bearings in the motors. Since the Inspire motors are brushless, the only thing that could experience wear, under normal circumstances, are the bearings. Since replacing bearings is significantly cheaper than replacing the entire motor, it was my choice for my Inspire.

As it turns out, replacing the bearings is pretty straight forward as long as you have a reasonable amount of mechanical skill. In fact, I think it is less involved than replacing the entire motor. Since I could not find a decent video that focused on the Inspire motors, I decided to create one and share it with the members of this forum. I hope some of you find it helpful. The video is about 17 minutes long and covers the tools, disassembly and re-assembly.

There are 2 bearings on each motor. Start to finish, each motor took between 18 and 30 minutes. I chose to replace the steel bearings with the ceramic hybrid that I purchased from Boca Bearing (part # BMK-013C-OS). Less expensive bearings are available from Boca. The proper size is: 5mm Bore, 11mm Diameter, 5mm High.

All the tools required are pretty standard and covered in the video. One of the 2 bearings needs to be driven out with a drift (punch), but the remaining bearing removal, and the installation of both bearings is handled by a tool I built which is nothing more than a 2 inch #10 Allen head bolt fitted with a nut and a couple of washers. When removing the bearing, just the head of the bolt will work in most cases. However, something that is not covered in the video, but could happen in some cases, is the situation where in the process of removing the first bearing with the drift, only the inner race is punched out. Not the entire bearing. In this case, you need to remove the opposite bearing using the bolt/washer combination. You will find that with the inner race missing, the Allen head bolt can now be used on that second bearing. After that bearing is removed the tool fitted with a washer slightly under 11mm, can be used to extract the partially removed (broken) bearing.
 
Last edited by a moderator:

The Editor

Moderator
Staff member
Joined
Aug 7, 2013
Messages
10,303
Reaction score
5,413
The link to the video is: https://youtu.be/cWs1BrE8iUA

From my understanding, the only real preventative maintenance that can be performed on our Inspires that would be considered critical to a continued flight, are the 4 motors and props. Prop replacement is a no brainer. The landing gear transformation drive-train isn’t critical. The electronics are obviously critical, but the only preventative maintenance you can do on these is to replace each and every circuit board. After all, how can you predict which electronic circuit will go bad. You are basically at the whim of good/bad luck if any one of them fails. So, motors should be the focus of a good preventative maintenance program in which there are two options. First option would be to replace the entire motor after some pre-determined number of flight hours. The second option would be to replace just the bearings in the motors. Since the Inspire motors are brushless, the only thing that could experience wear, under normal circumstances, are the bearings. Since replacing bearings is significantly cheaper than replacing the entire motor, it was my choice for my Inspire.

As it turns out, replacing the bearings is pretty straight forward as long as you have a reasonable amount of mechanical skill. In fact, I think it is less involved than replacing the entire motor. Since I could not find a decent video that focused on the Inspire motors, I decided to create one and share it with the members of this forum. I hope some of you find it helpful. The video is about 17 minutes long and covers the tools, disassembly and re-assembly.

There are 2 bearings on each motor. Start to finish, each motor took between 18 and 30 minutes. I chose to replace the steel bearings with the ceramic hybrid that I purchased from Boca Bearing (part # BMK-013C-OS). Less expensive bearings are available from Boca. The proper size is: 5mm Bore, 11mm Diameter, 5mm High.

All the tools required are pretty standard and covered in the video. One of the 2 bearings needs to be driven out with a drift (punch), but the remaining bearing removal, and the installation of both bearings is handled by a tool I built which is nothing more than a 2 inch #10 Allen head bolt fitted with a nut and a couple of washers. When removing the bearing, just the head of the bolt will work in most cases. However, something that is not covered in the video, but could happen in some cases, is the situation where in the process of removing the first bearing with the drift, only the inner race is punched out. Not the entire bearing. In this case, you need to remove the opposite bearing using the bolt/washer combination. You will find that with the inner race missing, the Allen head bolt can now be used on that second bearing. After that bearing is removed the tool fitted with a washer slightly under 11mm, can be used to extract the partially removed (broken) bearing.
Don't forget to lube your landing gear worm drive as well - any decent RC grease will be fine. It prevents undue strain on the landing gear servo. :)
Also, for anyone doing this, be VERY careful with that threadlock - DO NOT get it on any of the plastic housing. It will eat thru plastic and your motor housings can crack/fail on you. Apply the tiniest drop with a toothpick into the thread of the screw.

P.S. Have embedded your video so people can play it straight from here. :)
 
  • Like
Reactions: ted35 and Phatzo
Joined
Jul 23, 2016
Messages
48
Reaction score
9
Age
54
Great video but personally I would rather replace the entire motor than just the bearings.

Sent from my XT1585 using Tapatalk
 
Joined
Jul 23, 2016
Messages
48
Reaction score
9
Age
54
Thanks, I really appreciate the video. It gave me good insight on the inners of the motor.

Sent from my XT1585 using Tapatalk
 
Joined
Feb 17, 2015
Messages
947
Reaction score
264
Age
38
Location
Hungary
Website
www.phat.hu
awesome video :) now i just have to find boca in hungary :D lol...
i am not sure how many hours i have on my bird as i falsley relied on the go app which turned out to be mess... so i am at about 40 something hours at the moment... could be true as i did a lot of flying last year...
thank you for sharing.
i love this forum :)


Sent from my iPhone using Tapatalk
 
  • Like
Reactions: John Archer
Joined
Oct 5, 2014
Messages
171
Reaction score
55
Location
Connecticut, USA
Great video but personally I would rather replace the entire motor than just the bearings.

Sent from my XT1585 using Tapatalk
As the editor said, they don't wear out. When I was comparing the options myself, I decided that going with new motors would not only cost me considerably more money, but also I would end up with motors that have the stock steel bearings. These are a lower grade then the hybrid ceramic bearings that I was able to install. But, obviously you do what you want. I only presented this video as an aid to anyone that may want to follow the same route that I took.
 
  • Like
Reactions: ted35
Joined
Oct 5, 2014
Messages
171
Reaction score
55
Location
Connecticut, USA
awesome video :) now i just have to find boca in hungary :D lol...
i am not sure how many hours i have on my bird as i falsley relied on the go app which turned out to be mess... so i am at about 40 something hours at the moment... could be true as i did a lot of flying last year...
thank you for sharing.
i love this forum :)


Sent from my iPhone using Tapatalk
Boca Bearings does ship internationally. I am not sure Hungary is one of them, but you could check with them to see. Also, I am sure there are additional import fees and so on. I found them to be a really good company to deal with.
 
Joined
Aug 3, 2016
Messages
35
Reaction score
14
Age
60
Excellent video! Many thanks for taking the time and trouble, Bob, to share this expertise here. I, for one, have bookmarked this thread and will be going this route when I feel it's time to replace the bearings.
 
  • Like
Reactions: ted35
Joined
Nov 28, 2015
Messages
481
Reaction score
193
Age
58
Do the standard bearings tend to show signs that they are about to fail (excess noise, free play, roughness when rotated, etc.) or can they fail suddenly without warning? Does anyone have figures for the flight hours they are good for?


Sent from my iPad using InspirePilots
 

The Editor

Moderator
Staff member
Joined
Aug 7, 2013
Messages
10,303
Reaction score
5,413
Do the standard bearings tend to show signs that they are about to fail (excess noise, free play, roughness when rotated, etc.) or can they fail suddenly without warning? Does anyone have figures for the flight hours they are good for?


Sent from my iPad using InspirePilots
Most (not all) multirotor bearings are good for around 100 hours. DJI do not really use very good quality bearings (cheap) so be mindful of that.
The first signs of deterioration will not really be noticable audibly or in flight but if you feel the temp of your motors on landing an elevated temp will be a sign of increased resistance and an indication to think about replacement.
 
Joined
Oct 5, 2014
Messages
171
Reaction score
55
Location
Connecticut, USA
Most (not all) multirotor bearings are good for around 100 hours. DJI do not really use very good quality bearings (cheap) so be mindful of that.
The first signs of deterioration will not really be noticable audibly or in flight but if you feel the temp of your motors on landing an elevated temp will be a sign of increased resistance and an indication to think about replacement.
I would also like to add that you cannot just spin the motors and hear or feel for wear. Take an axle bearing from a car for instance. If you turn the axle and you feel resistance or a choppy kind of motion you know the bearing is bad. However, on the Inspire motors what you feel is the resistance caused by the very strong magnetic forces within the motor. Spin one of your motors and you will see what I mean. As the Editor points out above, testing for heat variations may be the only way to tell. As for changing them or not. Preventative maintenance is just that. Prevention. In the long run, it is cheaper to replace this wear point than replace the entire drone. And that's not even taking into consideration the damage that a failed drone may cause on property and people.
 
  • Like
Reactions: Phatzo
Joined
May 14, 2016
Messages
551
Reaction score
121
Age
41
Location
NM
Exactly when buying new motors your still getting 25¢ bearings in them an they are a moving part . Boca only way to go. I however have a different part # from them.
 

Attachments

Joined
Feb 17, 2015
Messages
947
Reaction score
264
Age
38
Location
Hungary
Website
www.phat.hu
ok, my brother lives in the US and is about to send me something :) i think i will pull the trigger and at least be prepared...
what is the life span of the hybried or full ceramic ones?
is there a "type" i will be able to have a peace of mind for a while?
i do have the corrosion block from the US for protection against water and wear as the lube puts a really thin film on and over the things you treat it with...

any feedback would be nice on wear numbers which are of course approx...

thanks
cheers
m


Sent from my iPhone using Tapatalk
 
Joined
Oct 5, 2014
Messages
171
Reaction score
55
Location
Connecticut, USA
Exactly when buying new motors your still getting 25¢ bearings in them an they are a moving part . Boca only way to go. I however have a different part # from them.
There are a lot of choices for bearings from them. I chose the ceramic hybrid "orange seal" in kit form. That means 2 bearings in a package which is cheaper than buying them as singles. You can get full ceramic, all steel and so on. I bought enough for 3 drones so I got them at a decent discount. Its best to talk to them about what bearing options there are and what quantity discounts they will offer you.
 
Joined
Oct 5, 2014
Messages
171
Reaction score
55
Location
Connecticut, USA
ok, my brother lives in the US and is about to send me something :) i think i will pull the trigger and at least be prepared...
what is the life span of the hybried or full ceramic ones?
is there a "type" i will be able to have a peace of mind for a while?
i do have the corrosion block from the US for protection against water and wear as the lube puts a really thin film on and over the things you treat it with...

any feedback would be nice on wear numbers which are of course approx...

thanks
cheers
m


Sent from my iPhone using Tapatalk
I think the Editor has stated 100 hours. But I don't know if there are any scientific studies that one can use as a guide. Now that I know what is involved, I figure I will include bearing replacement in an annual tune-up. After all, if only 1 motor fails, the Inspire is likely to be just a pile of scrap.
 
  • Like
Reactions: Phatzo
Joined
Feb 17, 2015
Messages
947
Reaction score
264
Age
38
Location
Hungary
Website
www.phat.hu
I think the Editor has stated 100 hours. But I don't know if there are any scientific studies that one can use as a guide. Now that I know what is involved, I figure I will include bearing replacement in an annual tune-up. After all, if only 1 motor fails, the Inspire is likely to be just a pile of scrap.
my understanding was that The Editor regarded to the original bearings. that is why i asked, but if the value of hours is for the hybrid ones then i will get a set :)


Sent from my iPhone using Tapatalk
 
Joined
Aug 3, 2016
Messages
35
Reaction score
14
Age
60
Here pilots your welcome it's good through the weekend
Thx Ftolino...... that discount has made me jump.. was going to defer further expenditure until next year but your kind sharing of the 35% discount was too good to turn down! .... and,only $7.95 shipping to France!
 
  • Like
Reactions: Ftolino

New Threads

Members online

Forum statistics

Threads
20,356
Messages
197,447
Members
29,900
Latest member
geoffedkins