I seem to remember a discussion about the need to oil the motor bearings every 6th flight.
OMG!
I was on the phone with 3DR about another subject and when finished I said "oh by the way"
blah, blah, need to Lube? and the answer was yes, I will send you the directions.
I did not receive the information as of 2 weeks later.
How often to do oil the bearings?
with what oil?
and how?
Decades ago I built anemometers for a research project and calibrated them in a wind tunnel. I found that
it was better to run the bearings dry as it did not collect dirt as well. The bearings were very lightly loaded
so it seemed to work. It seems to me that when I fly and apply vigorous attitude adjustments the bearings are sufficiently loaded to require Lubrication.
Can I get a witness?
How about, how often and the technique.
Safe landings
Dan
Replies
Almost none of the bearings used in multicopter motors have removable shields and many of them are not simply shielded, but in fact sealed.
The thinner oil or grease - (Superlube) I have recommended will in fact penetrate most shields, but generally not sealed bearings (and you do not want to inject through or under a rubber sealed bearing.
So far the only company I have seen that has any data regarding their bearings is Tiger Motor who have a bearing replacement schedule for their large motors based on hours of use.
Basically most manufacturers of quality motors supply replacement bearings and expect you to simply replace them when they become worn out (ostensibly due to the fact that they are not disassembleable).
Older motors like Scorpion recommended lubricating (and even had their own lubricant).
But almost all bearings have shields or seals now and information about lubrication has become very sparse.
I am actually glad to see the response you got from 3DR, at least they also appear to have figured out this isn't as simple as they thought it was.
KDE motors have the biggest, best bearings they can stuff in them and most of them have a 3 bearing stack (which is pretty much unique).
Some of them especially their bigger ones are sealed and the rest are shielded.
KDEs motors will outlast (and outperform) any other motor in the same size and weight class, period.
So far none of the motors have adopted proper thrust bearings which is what is really needed for multicopter use, so the best we can do is get ones with the highest quality largest conrad style ABEC bearings we can.
It is possible that ceramic or boron nitride like are available from Boca Bearing might provide extended life, but they can be fussy too.
http://www.bocabearings.com/bearing-applications/rc-bearings
Or these hybrid ceramics
http://www.trbrc.com/category-s/364.htm?gclid=Cj0KEQiAsdCnBRC86PeFk...
Best regards,
Gary
Don't know if this helps but I have successfully used the following on various RC bearings for a number of years. It works with very small to large bearings and no need to remove the shields. I think the product and recommended grease was aimed originally at high load RC helicopter bearings.
http://peteshobbies.com/prcp/Greaser/grindex.htm
http://peteshobbies.com/prcp/Greaser/PRCPbuy_greaser.htm
Hi Whooper,
That first link is a really excellent and thorough article.
The article is 12 years old however and is referring to the bearings used in RC fuel engines.
Circumstances for fuel engines are quite a bit different.
Most bearings in those motors are open and those that aren't are almost always shielded - not sealed.
He speaks of sealed bearings, but does not differentiate between sealed and shielded bearings and the bearings he is referring to that his greaser can grease are really shielded, not sealed.
You really couldn't grease actual sealed bearings with that technique, it would simply compress the seal against the side of the bearing and no grease would enter the bearing.
That said, it is a cool device and for those beartings where it would work where you have removed them from the motor, you could use it.
However,. by the time you have removed a bearing from the motor, it is probably a better idea to replace it anyway.
Also, he is talking about heavy lithium based greases, which would work fine for highly stressed fuel engines, but really are not well suited for our electric motors.
Generally you need a lighter grade grease or oil for our motors and modern Teflon additive is in such small micro particles it definitely does not produce a gritty condition for even the tiniest of bearings and it is an excellent - probably the best additive for our use.
Teflon micro lubricants really weren't yet commercially available when he wrote that article.
RC fuel engines are also subject to bearing wash-down from the solvent type fuels used, our electric motors are not.
It is possible that there are some bearings for some motors that would benefit from this, but mostly, if the lubricant won't wick into the bearing while it is still in the motor (open and many shielded bearings), I would generally recommend simply replacing it if you need to remove the bearing.
If I were using fuel RC motors with ball bearings I would probably buy one of these, otherwise probably not.
Tiger motor recommends a "small drop of lubrication oil on each bearing every 5 or six flights".
Light machine oil (or super lube oil or light grease) will probably penetrate the shields that T-Motor uses on most of their bearings, a heavier automotive style grease (such as this tool is designed for) would not.
And a light oil or grease is what is needed for our motors.
Best Regards,
Gary
Just to clarify, the greaser is used for bearings on the helicopter drive train not the bearings in the glow engine. I have successfully used them in electric helicopters and cars.
All the motors I have seen have shielded/sealed bearings, even $10 ones from hobbyking.
Shielded bearings can be lubricated if the shields are removable like Steven Adams described. You can google "how to lubricate inline skate bearings". It's not a short process. It's probably more reasonable to buy new bearings.
Lubricating by letting oil wick into the bearing is a bad idea. It's pretty sure that you'll get some oil on the outside of the shield and this oil will only collect dust. This dust on top of the shield will unavoidably get into the bearing.
Just got a reply from 3DR
"In regards the motor lubrication; unfortunately we have no guidelines on this at the time, but I'll make sure to bring it up to see if there's any pointers we can share."
So my action item to find out what 3DR recommends is done, yet still no specific guidance.
I don't have much experience with the bearings in the brushless RC motors, only 608 size. Usually these have a circlip that can be unclipped to allow removal of the shields and then you can use acetone to properly clean the bearing and apply oil inside. I wouldn't apply oil to the outside for it to seep inside through the shields, unless you wipe the bearing dry before taking it out in the wild it'll just attract dirt/dust that sticks on to the oil.
If you can do maintenance on the bearings, I'd have two sets of motors to swap in and out as needed for maintenance without being grounded.
At conferences I go to, when a group explores a subject often times, a good deal of experience and knowledge happens rapid fire. At some point, the moderator or person who brought up the discussion, gives a first summary that may fire up some more exchanges or the group refines and agrees on the current understanding. Lets try this now.
The question: How often, with what lubricant, and technique should I tend to my Iris motor bearings?
Summary of discussion to date:
Not everyone in this group fly the IRIS and those who do, in time or have may already, switched to a different motor than stock.
The stock motor as supplied did not come with recommendations that I can find in writing yet some have suggested that a 6 flight maintenance schedule is best.
I do not know if over time, the stock motor has evolved and what the configuration is.
So, in general, depending on the specific bearing design, lubrication if at all, cleaning may or may not be required or in the case of some sealed bearings, not effective.
Experience has demonstrated particulate contamination in the motors..after they are forced air cooled.
Apart from a dynamic film that reduces the stress or working of the bearing material to prevent failure, Lubrication can also transport and retain material that interferes with the rotation..binds the bearing or increases the failure rate. The Crunchy Rotation Syndrome or CRS
It was pointed out that the ball bearings used in motors for aerodynamic propulsion in the direct drive configuration have mainly an axial or thrust load. Unless specifically designed for thrust load, bearing designed for radial loads will be compromised and thus have a reduced service life if the thrust load is above some fraction of the radial load spec. An Iris with battery weighs 1.3 KG thus for a Iris without a payload, the thrust at hover will be 1.3 Kg divided by 4 per motor...does not seem like much but the bearings are tiny.
Proposed Conclusions:
* We need what is specifically recommended by the motor manufacture and published in the user guides. By this I mean not just oil
* If a lifetime for the motor is specified then one needs to decide on the replacement interval
to satisfy lifetime requirements. This is complicated by the flight environment. Take off from a beach?
* Those who increase the acceleration of their drone by using different props or more battery cells should be aware that the bearing life time may not be as expected from lower thrust levels.
* number of flights may not be the best way of looking at this as for example flying at higher altitudes results in a higher rotation speed and we all know that given a bearing under a certain load, we can not increase the rotation speed above a point before the bearing fails.
Anything else?
Good summary Dan, I don't know If you can move the summary at first, under your topic presentation, A thing that I look important too, is to check each motor with the hand (as someone else explain to me in this forum, im goig to try to find)) periodically doing little force to one side, if you notice something different like a crispy bearing, not fly and try to replace as soon as posible, I think that this is common to any motors. It's great if manufacturers give this information but anyone do it because of different conditions, the only thing that we can have is changuing information here with owr different experiences.
Sorry my offtopic with my no iris cuad but I didn't find many discussions about this subject.
So really it not have sense to relubricate owr bearings? better to have a reposition stock and change when they go bad or change after X hours of flying time to avoid crashes? what do you think is better?
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