How common are motor bearing failures?

[DJtoad]

I'm still learning on my two month old Blade 450 and spend most of my stick time doing figure eights in the front yard. Although I've had a few minor mishaps I've never had any major crashes and have only had to replace a few inexpensive parts. Recently I noticed an unusual humming noise coming from the heli and black dust on the main gear. I checked the gear lash and it seemed fine but then noticed the top of the motor appeared loose. I took out the motor last night and discovered that the bottom bearing is completely shot, so much so that I can move the pinion gear from side to side. I'm not sure what would have caused that. Does it have to be oiled regularly? I ordered some good replacement bearings last night (Boca SMR73C-YUU NB2) and they've already shipped so I shouldn't be out of commission for long. But I was wondering how common bearing failures are with these motors.

[FuntanaS]

They are pretty common. The side to side play is most likely from the shaft being worn out sad to say.

[buddha2490]

Is there an alternative?

[jdFin]

Ah, motor bearings. If you search this forum, you'll find guys that have flown the stock motor hundreds of flights without issue. You will also find guys that have had problems with the motor. I might be a category all to myself; I burned out the bearings in three e-flight motors before getting a scorpion.

I would suggest calling Horizon (do the callback thing) and telling them exactly how long you have flown it and such, and they will probably take care of it for you. If they do, put in the new one, and keep flying. If it goes out again, you decide if you want to change paths or not.

Some guys lube their stock motors. I never did, abiding the official HH position that lubing is not necessary. I do lube the scorpion (since they say to), so I will never have an apples/apples comparison.

The third stock motor I put in had ceramic bearings from boca, and it did not seem to last longer.

[sarah1097]

well i have had a my share of flights with a blade 400.i always had issues with the 420 motor but never the 440 motor. now if your nice and what not, more then likely hh will send you a new motor for free, and or replace it for free. They did it for me three times. One of the main reasons that motor goes out is if your belt tension is too tight. i burned a motor out in one flight due to that, and it did the same thing yours did. I then really lubbed the belt and made it looser and never had a problem with it. good luck with it.

[DJtoad]

Originally Posted by FuntanaS

They are pretty common. The side to side play is most likely from the shaft being worn out sad to say.

That's exactly what it was. I assumed it was the bearing but last night I pulled the motor apart and found the shaft had worn down significantly and it doesn't appear to be a replaceable part.

The bearing seems to turn fine so why would the shaft wear like that? I did a temporary fix by sliding down the shaft 3/16" inch so that it made direct contact with the bottom bearing again and placed another thin washer between the bearing washer and the c-clip to fill in the gap. I also put some silicone grease in there for a little extra insurance. It probably won't last that long but the heli spun up nice and smooth and was much quieter than before. I guess I'll call my LHS today and see if they have a new motor in stock and if not, have them order one. Since I've already got new ceramic bearings on the way I'll probably replace the stock bearings in the new motor with the ceramic ones with the hope that it will keep the same problem from happening again.

[2cants]

This has been a problem in the past for some, including me...

Several things to do to fix this...

1 - the bearing is liekly ok - to check, remove the pinion, circlip, and most likely the main motor shaft is worn
2 - if so, use some JB Weld to fill in the wear spot, let is harden and sand/file back the hardened JB weld to match original shaft diameter.
3 - I superglued the shaft to the inner race of the bearing - but this is not 100% required.
4 - This is important... Use a 5mm wide piece of A4 print paper, and loosen the motor in it's mount. Slide the paper between the pinion and main gear. Push the motor in tight - so that the paper is between the main gear and pinion. Tigthen the motor mounts (4 x scres - use loktite). The gear mesh distance will now be spot on (an over tight mesh causes the shaft to wear).
5 - make sure the bottom shaft bolt (3mm) is not too tight - I tighten then back off 1/2 turn. If too tight then the tail gear (below the main gear) gets squeezed and make the main gear/tail gear oblonged. (this is evidenced by wobbly main gear).

Once all done - then motor pinion/ main gear sweet. All set to fly. Goodluck.

[DJtoad]

Thanks for all the info, everyone! I think my gear lash may have been a little tight from the factory. I adjusted it using the paper trick once I noticed the black dust on the main gear. Maybe that's what caused the shaft to wear but it still seems odd to me that it would happen unless the bearing was bad. The belt tension seems fine so I don't think that was the cause.

I'm going to send a picture of the shaft to HH and see what they say. Maybe they'll send me a new motor, maybe not, but to be honest I'd just assume pick one up at my LHS than be out of action for weeks waiting on a replacement. If this is a somewhat common issue, I'm not sure why they don't sell replacement motor shafts or a rebuild kit with a new shaft / bearings. BTW, I never thought about trying JB Weld. I might give that a shot...

I considered upgrading the motor but since I just invested $20 in new bearing and, being a noob, the additional power would probably just get me in trouble faster, I decided to stick with OEM for now. I was hoping ceramic bearings would fix the issue but if it happens again, I guess I'll have no choice but to upgrade.

[Scammer]

The 440 was the same price as the 420 at my LHS.
Yes another shaft/bearing problem.
Replaced with the 440 and since my flying skill have a long way to go, I keep the throttle curve lower until my skills reach the level that I can use the extra power.

[InFocus]

No one has yet commented on the black dust..

Could the black dust be residue from the belt? Sarah mentioned above that if the belt tension is too tight, it could cause the motor to wear out faster.

[buddha2490]

Originally Posted by InFocus

No one has yet commented on the black dust..

Could the black dust be residue from the belt? Sarah mentioned above that if the belt tension is too tight, it could cause the motor to wear out faster.

This I why I am keeping up with this thread. Over the past few weekends my main gear has got this black building up on it which I thought was odd because there is no wear patters on the gear that would indicate it was rubbing on anything. I have not removed the motor to see of there's a problem though, but after reading this last night I'll be checking it out.

[bradharvy]

I don't see how the dust could be from the belt. It looks like carbon/graphite dust. I believe my motor went bad from the pressure it took from my battery shoved up into it??? Makes since to me. I flew it 1 time and tore a battery up. Had all kinds a dust up front. Couldn't believe it didn't go up in smoke! The batt was a gonner. Thought I learned my lesson but at least 1 more battery got into it! I have since been really careful!
But the motor spinning at full speed with some force against it is what I think caused mine. It fell apart in the air....

[DJtoad]

Originally Posted by InFocus

No one has yet commented on the black dust..

Could the black dust be residue from the belt? Sarah mentioned above that if the belt tension is too tight, it could cause the motor to wear out faster.

I'm pretty sure it was from shaft wear, but I'll double-check to be sure. The bottom of the motor around the bearing was black with dust -- think it was escaping through the gap between the worn shaft and bearing race. It was only on the teeth of the main drive gear so I think it was "raining down" from the motor. The gear which drives the tail rotor is perfectly clean.

[ahahn]

I'm not sure what belt tension has to do with this motor failure.

The belt tension is handled by the main shaft bearings, not the motor bearings. I don't see why the motor bearing would fail. Actually on my Furion heli's, which have a similar tail drive, they recommend a very tight belt, "banjo string" tight!

I'd say the issue here is a common one for a lot of motors (just read some Scorpion motor threads). The motor shaft diameter is a slip fit into the bearing. When the motor is turning, the question is whether it is easier for the bearing to turn with the shaft, or for the shaft to spin inside the inner race. If the latter wins then the shaft will be rubbing against the inner race. The shaft always seems to lose this fight.

I'm not sure if a too tight main gear/pinion backlash is an issue for this or not. It could also be that the bearing itself develops too much friction due to too little lube, and the shaft again finds it easier to spin inside the race.

I know one solution is to glue the shaft to the inner race with a bearing retainer compound. The only problem there is getting the bearing out when you want to replace it. Perhaps if you glue, AND lube the bearing, this won't ever be an issue, but I am not sure.

[bradharvy]

I like your thinking! My traxxas wheels did the same thing, axle would spin inside the bearing, bearing would not turn, is just useless. On a truck, no biggie.
I never would of thought the bearing on my 450 would stick and win the fight over the shaft, but makes since. I don't want to tear up my motor, (that should b here tuesday) by yanking it apart. Can you tell me what I can tear apart on the old one? Is it possible it's still good? or can ya even put new shafts in? Probably no worth it...

[Scammer]

hmmm magic smoke & electronics....

it appears that black dust & motor shaft/bearing are also associated

https://www.helifreak.com/showthread.php?t=342881

I too had the black dust when mine failed

I still run the same belt at the same tension with no issues on new motor - but the new one is the 440

[FuntanaS]

On my second motor I carefully put a little bit of blue loctite on the shaft where the bearing rides on it. So far this has worked great. It makes it harder for the bearing to turn on the shaft but you can easily remove it if need be.

[Psuedo_Heli_Commander]

FWIW, I still have the original motor in my B450. I think the keys are, correct mesh, lube the bearings lightly about every 35-40 flights and silicon spray the belt. Getting a good motor...just luck I guess. Note: Make certain you only use a silicon spray brand that is safe on plastic. The silicon makes the belt quieter and preserves the rubber.

I have used silicon spray for many years on car door rubber, cv joint bellows and rubber hoses and have never had them go bad or stick in winter...oldest car still kept since new 88 CRX si. All rubber still like new, sprayed twice a yr. Car is not garaged, it's always in the sun and weather.


P_H_C
MCX2,MCPX,mSR,mSRx,MQX,SR,B450,550e 3gx

[sarah1097]

the black dust is from (unless there is something else in there that i dont now about) is from one the belt if it is to tight, it grindes it down and that is the black dust, i saw that when my 420 motor blew up. it also can be this, which is odd, I had a blade 400 so not sure in a blade 450 but if you look at the manual it shows the main gear then the auto gear right. If you pull them apart, it shows even in the manual that there is a washer that goes in there. Well unless they have updated this it is still wrong. the washer goes on top between the bearing, and the one way bearing. if you do not put the washer up there and you you have the shaft pulled up tight like you should, then the one way will hit against the top plastic and also cause the black dust. it will also melt your frame if you put the 440 in. how do i know, well it happened to me. put the washer on top and never had a problem, had proper belt tension and was fine. i no longer have a blade 400 but it was my first heli and probably the funnest.

[howboy]

Hello all,

This is my first post here. I have to go to work soon, so don't have time to elaborate right now.

My 420 motor shaft and bearing went bad after about two hours of practice flight (hop, skip, hover). I ordered a new 420 motor from a vendor, then contacted Horizon about my problem, and they are sending a replacement. The guy from Horizon said they were unaware of any problems with the bearing or shaft. However, two motors are on backorder until March 20, and an upgrade 440 motor is also backordered.

Does this sound alarms?

Also, check the Scorpion website. They warrant the motors for two years, but not the bearings.

I think the motor technology has overwhelmed the bearing technology.

Great site!

Howie