Boca bearings upgrades for Tiger(Avroto) motors.
- Thread starter redridinghood
- Start date
DucktileMedia
Drone Enthusiast
montorc has replacements for $7. I just bought the boca bearings as my tiger bearings are already screwed with less than 2 hours of flight time if that. They say EZO but I wonder as well to their authenticity. My Avrotos however have much more use on them and have had no issues. I will mention that I had to crash the heli to avoid a further danger and it is possible that this is the cause of all this. Still wish there was a better way to remove bearings without sticking them in the oven.
The bearings on my Tiger MT4008's come out with a VERY light tap with a plastic rod from the back. But, for sure, if you crashed it, the bearings won't have liked that at all. I just took the shields off an old bearing - as I've said elsewhere, it's factory greased, so it should never be "oiled". Unfortunately the shields are not designed to be removed - removing it destroys it - so you can't clean and re-grease.
It seems to me that Boca Bearings money just isn't worthwhile, considering that the majority of damage seems to be caused by blade strikes. I pay £1.38 (US$2.25/€1.73) each for EZO originals - as a "consumables" cost that's pretty reasonable IMO - any doubts, change 'em! The only alternative that might be worthwhile would be a rubber shielded version if you fly in particularly dusty/sandy conditions. I have a blue plastic tarp in the car - if the take-off spot looks dusty, I spread the tarp out (with some tent-pegs or rocks) and take off from that.
It seems to me that Boca Bearings money just isn't worthwhile, considering that the majority of damage seems to be caused by blade strikes. I pay £1.38 (US$2.25/€1.73) each for EZO originals - as a "consumables" cost that's pretty reasonable IMO - any doubts, change 'em! The only alternative that might be worthwhile would be a rubber shielded version if you fly in particularly dusty/sandy conditions. I have a blue plastic tarp in the car - if the take-off spot looks dusty, I spread the tarp out (with some tent-pegs or rocks) and take off from that.
DucktileMedia
Drone Enthusiast
The bearings actually did pop out pretty easily i just had to make a nice wood block with a 1/2" hole to punch it out using a blunt tipped nail. I used a mchine screw and nut with washers to drive them back in. i agree with you that it would have been better to buy more EZO replacements than the $10 boca's. I didnt really think about it when buying them. but the good news is that the sound went away so it was indeed the bearings.
Bartman
Welcome to MultiRotorForums.com!!
Brushless motors and bearing issues
Hi everyone,
I've been swapping out bearings a little bit lately and I've got two observations to share.
First is that the top bearings on the bottom motors of my coaxial quads seem to wear out first. I think the reason for this is that these bearings are the most exposed to collect dust and I also think that the washers are very soft and that as they wear away the tiny filings are falling into the bearings causing them to wear more quickly. In diassembling the bottom motors to do the bearings the bottom bearings are fine but the tops are worn out (These motors are inverted in the lower position so the top bearing is the one on the opposite side from the propeller).
Second, the inner races of these little bearings seem to be very prone to damage from prop strikes. When the prop hits something the motor shaft will pivot on the bearing just under the prop and deform the inner race of the bearing on the other side. Once the inner race is deformed even a tiny amount the bearings will start to wear against the surface and you'll hear things making noise while you're flying.
To prevent this it seems like it's good practice to not bang your props against immovable objects or surfaces
and if you're using your motors in an inverted position, blow some compressed air across those upper bearings to keep tiny dust and metal particles from working their way into the bearings.
I'd be curious to hear anyone's take on this.
Bart
Hi everyone,
I've been swapping out bearings a little bit lately and I've got two observations to share.
First is that the top bearings on the bottom motors of my coaxial quads seem to wear out first. I think the reason for this is that these bearings are the most exposed to collect dust and I also think that the washers are very soft and that as they wear away the tiny filings are falling into the bearings causing them to wear more quickly. In diassembling the bottom motors to do the bearings the bottom bearings are fine but the tops are worn out (These motors are inverted in the lower position so the top bearing is the one on the opposite side from the propeller).
Second, the inner races of these little bearings seem to be very prone to damage from prop strikes. When the prop hits something the motor shaft will pivot on the bearing just under the prop and deform the inner race of the bearing on the other side. Once the inner race is deformed even a tiny amount the bearings will start to wear against the surface and you'll hear things making noise while you're flying.
To prevent this it seems like it's good practice to not bang your props against immovable objects or surfaces
and if you're using your motors in an inverted position, blow some compressed air across those upper bearings to keep tiny dust and metal particles from working their way into the bearings. I'd be curious to hear anyone's take on this.
Bart
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Tomstoy2
Member
Bart, I think your observations are correct. It doesn't take much to damage these things.
I have to admit, I've had phenominal results with my mt motor bearings! I have had well over 150 flights on it this year, one serious crash, bounced off a set of stairs once and reciently flew up into an overhead power cable! Still running nice and smooth!
Still, think this winter it might be a good idea to change them out when the weather gets disagreeable.
I have to admit, I've had phenominal results with my mt motor bearings! I have had well over 150 flights on it this year, one serious crash, bounced off a set of stairs once and reciently flew up into an overhead power cable! Still running nice and smooth!
Still, think this winter it might be a good idea to change them out when the weather gets disagreeable.
tahoelight
Member
I've had the 2826 500kv T-motors for about 6 months. I have gone through bearings on pretty much every motor. I also just replaced two sets of motor bearings tonight with new T-motor bearings. One set came faulty in the package. I have been fighting vibes since day one. So, I am on the search for longer lasting bearings as well.
bocaaa expensive but the quality is very good!!
Were these new bearings marked "EZO"? And were they "faulty" right from the package, i.e. if you put a pencil in the bore and rotate the inner race you can feel a roughness?
I'm still trying to get to the bottom of this Tiger/EZO bearings issue. EZO bearings are a high quality product. I'm sure they will have received a 100% automated check in the factory (a very sensitive machine to do a final check equivalent to the pencil test) in addition to numerous other tests of the races, balls and cages before final assembly - so they really should not be "faulty" when you get them.
May I ask how you are fitting them? What exact procedure did you use to get them seated in the stator?
Bartman
Welcome to MultiRotorForums.com!!
are your motors all mounted upright?
this is the part number for replacement bearings i've been using in my tiger 2814 motors, from Boca, SMR694C-YZZ #5 NB
you have to use these washers from mcmaster, 98032A436
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i wouldn't try re-using the snap rings or the washers. The washers are very malleable and wear out.
also, i'm in the process of pricing out manufacturing for a small tool to press these bearing into place. i should know this week what the price will be. i'm going to make a tool for the smaller 2212 motors also.
bart
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I think that, of all the components on a multirotor, the bearings should be at the top of the "consumables" list and subject to a "planned replacement" policy. Bought in bulk, even high quality bearings are about $2 each or less. Replacing them every n flights or n hours would be cheap insurance, especially considering the potential damage/danger of an in-flight failure. They are effectively the only moving part in the entire machine - the sole mechanical contact point for the conveyance of hundred of watts of work from battery to propeller. To replace 16 bearings (for an octo) every, say, thirty flights is a consumables cost of about $1 per flight - insignificant!
Furthermore, they are exposed to the elements in a way and to a degree that invites early failure. They are shielded bearings, not sealed bearings: contaminants can and will get past the shields. This makes a strong case for using "contact sealed" bearings for this application - these have rubber seals that make contact with both inner and outer races, effectively preventing the ingress of any contaminants. The penalty, of course, is increased drag. But on a large engine the power loss (and additional temperature rise) will be completely insignificant. The cost is slightly higher but it would constitute an overall saving if it extends the planned replacement schedule from the above example of thirty flights to, say, sixty flights.
In addition to a planned replacement schedule, one should have a strict policy for replacement after any "mechanical incident", whether it's an actual crash or just the slightest touch of a prop against the ground, a tree branch or whatever. In such an event the contact pathway for each bearing drops from the full complement of eight ball (in this size of bearing) to just one of those balls. That's potentially an immense load through a tiny contact area and is highly likely to cause damage to even the hardest ball and/or raceway. "Best practice" would certainly be to replace any bearing that has been subjected to such an event as a matter of course, rather than "hope it didn't do any damage". The damage may be microscopic in scale but it will develop into an eventual failure, so why wait? One interesting thought here is that if you are going to replace all bearings on a regular basis then there would seem to be little point in using stainless steel units. The justification for using this material is only resistance to corrosion - the penalty is that stainless steel is not as hard as the chrome steel (or other types) normally used in bearings. This suggests that chrome steel bearings would actually be the better choice (and they're cheaper!) - they'll be replaced long before they have a chance to go rusty!.
I've found myself that the circlips and shim washers factory fitted to my MT4008's are of relatively poor quality. You should have a plentiful supply of high quality steel (not stainless) replacements on hand. Both circlip and washer should be discarded whenever they are removed and new items used for re-assembly. The cost is so insignificant that to do otherwise would be careless.
One of the significant differences between different qualities of motors is the tolerances to which the parts are made. The most significant measurements are the diametral tolerances of the bearing seats and their circularity/concentricity, and the diametral tolerance, circularity and straightness of the shaft. Deviations in any of these will have significant impact on the performance of the motor and, particularly, the life of the bearings since they will experience the full consequences of any such errors. Also important will be the material of the shaft as it affects the torsional stiffness - subjected to constant acceleration/deceleration, the shaft will flex, especially within unsupported lengths. This will induce high frequency vibrations that will target the bearings (since they represent the only fixed support points), causing accelerated wear. Of course, prop balance will do the same but at lower frequency - all of which adds up to an "extreme environment" for the poor little bearings. After any prop strike it would be wise to replace the shaft as well as the bearings (and hope that the impact didn't distort the bearing seats as well).
Spending extra money on ceramic, hybrid and/or higher ABEC-rated bearings doesn't seem justified. Ceramic or hybrid ceramic bearings exhibit lower wear rates, but a regular replacement schedule negates that advantage. A higher ABEC rating could only be justified for use in a very high quality motor where the tolerances (as mentioned above) are so good that the bearing's improved performance would not be rendered irrelevant by the neighbouring components.
Such an approach might seem like overkill to some but it represents a trivial amount of work and expense compared, for example, to a single-rotor heli. The bearings are, as I said earlier, the only moving part on an MR and should be treated accordingly.
P.S. I haven't mentioned lubrication here at all - see this thread
Furthermore, they are exposed to the elements in a way and to a degree that invites early failure. They are shielded bearings, not sealed bearings: contaminants can and will get past the shields. This makes a strong case for using "contact sealed" bearings for this application - these have rubber seals that make contact with both inner and outer races, effectively preventing the ingress of any contaminants. The penalty, of course, is increased drag. But on a large engine the power loss (and additional temperature rise) will be completely insignificant. The cost is slightly higher but it would constitute an overall saving if it extends the planned replacement schedule from the above example of thirty flights to, say, sixty flights.
In addition to a planned replacement schedule, one should have a strict policy for replacement after any "mechanical incident", whether it's an actual crash or just the slightest touch of a prop against the ground, a tree branch or whatever. In such an event the contact pathway for each bearing drops from the full complement of eight ball (in this size of bearing) to just one of those balls. That's potentially an immense load through a tiny contact area and is highly likely to cause damage to even the hardest ball and/or raceway. "Best practice" would certainly be to replace any bearing that has been subjected to such an event as a matter of course, rather than "hope it didn't do any damage". The damage may be microscopic in scale but it will develop into an eventual failure, so why wait? One interesting thought here is that if you are going to replace all bearings on a regular basis then there would seem to be little point in using stainless steel units. The justification for using this material is only resistance to corrosion - the penalty is that stainless steel is not as hard as the chrome steel (or other types) normally used in bearings. This suggests that chrome steel bearings would actually be the better choice (and they're cheaper!) - they'll be replaced long before they have a chance to go rusty!.
I've found myself that the circlips and shim washers factory fitted to my MT4008's are of relatively poor quality. You should have a plentiful supply of high quality steel (not stainless) replacements on hand. Both circlip and washer should be discarded whenever they are removed and new items used for re-assembly. The cost is so insignificant that to do otherwise would be careless.
One of the significant differences between different qualities of motors is the tolerances to which the parts are made. The most significant measurements are the diametral tolerances of the bearing seats and their circularity/concentricity, and the diametral tolerance, circularity and straightness of the shaft. Deviations in any of these will have significant impact on the performance of the motor and, particularly, the life of the bearings since they will experience the full consequences of any such errors. Also important will be the material of the shaft as it affects the torsional stiffness - subjected to constant acceleration/deceleration, the shaft will flex, especially within unsupported lengths. This will induce high frequency vibrations that will target the bearings (since they represent the only fixed support points), causing accelerated wear. Of course, prop balance will do the same but at lower frequency - all of which adds up to an "extreme environment" for the poor little bearings. After any prop strike it would be wise to replace the shaft as well as the bearings (and hope that the impact didn't distort the bearing seats as well).
Spending extra money on ceramic, hybrid and/or higher ABEC-rated bearings doesn't seem justified. Ceramic or hybrid ceramic bearings exhibit lower wear rates, but a regular replacement schedule negates that advantage. A higher ABEC rating could only be justified for use in a very high quality motor where the tolerances (as mentioned above) are so good that the bearing's improved performance would not be rendered irrelevant by the neighbouring components.
Such an approach might seem like overkill to some but it represents a trivial amount of work and expense compared, for example, to a single-rotor heli. The bearings are, as I said earlier, the only moving part on an MR and should be treated accordingly.
P.S. I haven't mentioned lubrication here at all - see this thread
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tahoelight
Member
No, my bearings were not marked EZO. They are unmarked and came in a T-Motor package via ClubHeli.
I am also fighting with dirt getting into the motors and melting to the green coated stators. I think this is what it is. Sometimes I need to take off or land in an area where dirt flies as I live in the mountains with dry soil. I think this is what is also causing some noise issues in my motors that are not necessarily bearing related, but can sound like it and create vibration. Anyone else having this issue of small build-up on the stators?
I agree that if I can find a reliable replacement set of bearings for a reasonable price, I would change them very often.
Bartman
Welcome to MultiRotorForums.com!!
Somebody's being naughty supplying unmarked bearings - not sure if that will be the dealer or RCTiger themselves. They may be good quality, but you have no way of telling until they fail early. EZO is a good brand to go for, widely available. Lots of big bearing brands - any one of them will do. You want ABEC 1 or 3 at the most. ABEC 5, 7 or 9 would be a waste of money IMO.
Based on what I wrote above, I'd get these contact sealed chrome steel bearings from Boca (or whatever size your motor needs), except I wouldn't pay their price! Any standard industrial bearing supplier should have these or be able to get them for you overnight. They are absolutely standard sizes - nothing special or unique to RC motors. A 4x11x4mm bearing is a "694" whoever and wherever its made.
Good suggestion to take off from a car roof - unfortunately my roof-rack would get in the way, so I have a blue tarp that I spread out and pin down with tent pegs or rocks.
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Bartman
Welcome to MultiRotorForums.com!!
what are you flying these days Jes? Last I heard you had something on the drawing board.
The Boca site had a promotion at the end of last year, 50% your whole order so I stocked up. If I have some time later I'll test your theory that they should be less money elsewhere but your Abec1 is the same price as the Abec5 I quoted. The difference is mine is shielded, yours is sealed. The only place I'm seeing a sealed bearing as possibly required is the top position on an inverted motor, everywhere else they're holding up fine.
Regarding your comment about our speed rating, by what I've been able to tell, ours is actually a low speed application for these bearings which should make the grease a lifetime lube. Out-of-round bearing races may make things heat up a lot more and make the grease melt out but lubrication shouldn't be necessary if everything else is normal.
Good discussion.
Bart