Hollow bore motor bearing failure Thread

[StealthPhoenix]

10 minutes ago, Planemo said:

Yes, many motors could have a bit of debris floating about. And theres tight tolerances between magnets and stators in all wheels. This includes the RS, MSP and MSX.

The point is that any intolerance due to bearings shows up this issue. The real issue isnt debris, its bearing slop.

If the problem goes away without loads being applied to the bearing (as you suggest) then the problem absolutely points to the bearing being the problem. I am unsure how you say it isnt.

i get your point, as a point that everyone seems to be making repetitively. if that rationale was soundly deduced, the problem would get solved once anyone followed the solution (by the common rationale, the solution is to replace bearings = knocking sound gone). but that hasnt been the case as far as im aware. some people replaced their bearings, and the sound did not go away, or it came back. at this point they thought to double down on their rationale, and believe that the second bearing replacement failed. i entertain those possibilities myself, but..msp and msx dont have hollow bores, despite the same rotor/stator assembly. this is my assumption, im not well versed on those wheels but i believe they are similar. i dont know if those wheels ever had a noise issue like the one the RS gets. i digress. 

im not suggesting the problem (assuming we agree: is the noise) goes away on bearing decoupling. im suggesting that if a bearing spins freely without any noticeable warping, or binding whatsoever, upon decoupling,  then even if the bearing slop exists, it does not exist to cause the problem (noise), and can be omitted as applicably negligible, as the bearing itself seems to function fine. the problem (noise) is somewhere further down the mechanical linkage AFTER the bearing is coupled, toward the end result of the tire spinning. i should make a youtube video i guess, to document my own experience of things. but i am not that invested to edit things haha..typing is so fast! in any case, if you still disagree, im open to listen to your opinion, because i may learn something still. but otherwise, *shrugs* i guess you guys are right. appreciate the feedback though @Planemo

[Flying W]

My original rs knocked but it was replaced by eWheels so I didn't get to open it up. I don't think it was bearings as there wants a grinding noise and one foot riding on each side didn't make it go away. 

There was a pic of an excessive amount of white goop in the motor hanging down and hitting the coils. In my case this seemed to be the most likely cause as it was RPM dependent. 

My new RS has been trouble free but only has 200 miles on it. 

[Simply_Striking]

I potentially have a stupid question..... Why are they making the bore size so big? Is it not possible to have a smaller sized bore, thus smaller sized bearing and still be able to run thick cables through them? Making them less prone to failure or am I missing something?

[EMA]

the failure is not related to size, bigger bearing have lot of pros compared to old one, new hollow motors runs way more smooth compared to old generations.

We still don't know 100% what the problem is, could be bearing, mounting or something else, newest gotway wheels seems fine

[RagingGrandpa]

We're comparing two designs:

• MSuper with bearing size 6203
• MSuper with bearing size 61824

Everything else about the bearing loads are equal:

• Same rider weight
• Same pedal dimensions (critically: width)
• Same distance between bearings (motors did not get 'wider')

If we consider typical manufacturer ratings for those bearings, we see:

• 61824 has 3x the load rating of 6203
  (30kN vs 10kN)
• 61824 has 1/3 the speed rating of 6203
  (8kRPM vs 26kRPM)

EUC is overall a "low speed application": 30mph is roughly 500RPM. Therefore, bearing speed is not a concern.

For deep-groove ball bearings of this type, a "load factor" (de-rating multiplier) is applied according to the direction of the load. It means if the load is not in the radial direction, the maximum tolerable load value is decreased. But critically: it is a multiplier to the nominal load rating.

Since 61824 ("hollow core") has a 3x higher load rating than 6203, it can handle more axial load too.

... and because of the same system loads and bearing separation dimensions, the thrust loading should not be substantially different between the two designs. On paper, this means 61824 is 'stronger' in every way.

 

That seems to fit our observations too.

We're not seeing 'overloading' failure symptoms (excess heat, metal fretting, seizure, etc).

Instead, the problems with RS have been "contamination" and "excessive freeplay."

 

My take-away: the bearing itself is not the problem.
I think improvements to the housing design and assembly process can likely resolve the issues, without changing the bearing size.

[RagingGrandpa]

19 hours ago, StealthPhoenix said:

- feeling for any binding or feeling for amy warpage. But everything feels smooth and great. This was before i even cleaned the dust and small sandy particles between the bearing and motor cover that u can see in the video. 

https://streamable.com/4o0cze

All the garbage in that gap!

[NordEstEuc]

I try to report my experience: as soon as my RS was delivered to me I got on it and after about 15km I started hearing the famous perfectly rhythmic tock tock rock.  At the suggestion of a friend, after returning home, I disassembled and pulled out some motor cable and the famous tock is gone!  Clearly I was happy and blamed the problem on the cable.  The fact is that the famous noise showed up three more times and finally disappeared.  (for the moment ?!) My RS took no hits, no water, nothing ... That's are the fact... Meaby we are all talking about two or more different problems with one only true: poor quality! Poor quality control, poor material, poor building process, poor customer assistance. 

[pontoonpete]

I think I figured out a better way to explain what I was trying to say. Forgetting about the size of the bearings imagine you moved the smaller bearings much closer together so that the space between the bearings is equal or less than the diameter of the bearing. Now you have no torsional stability because the bearings just want to twist out of place. They proportionally reduced the space between the bearings drastically by increasing bearing diameter so much and not increasing the space between them.

It's almost like there's just one big bearing now and every time you step on 1 foot plate and not the other the bearings try to twist out of place. To create the same stability with the big bearings as there is with the small bearings they would probably have to be spaced a foot apart LOL. 

I'm not sure why they went so big with the bearings? I thought it was just to accommodate larger wires? They could've accommodated larger wires with just a slight increase in axle and bearing size.

I hope they come to their senses with this hollow motor thing sooner than later. 

If you look at motorcycles, they are much heavier and go much faster, they have smaller bearings that are proportionally spaced much further apart. 

Edited January 7, 2021 by pontoonpete

[pontoonpete]

6 hours ago, NordEstEuc said:

I try to report my experience: as soon as my RS was delivered to me I got on it and after about 15km I started hearing the famous perfectly rhythmic tock tock rock.  At the suggestion of a friend, after returning home, I disassembled and pulled out some motor cable and the famous tock is gone!  Clearly I was happy and blamed the problem on the cable.  The fact is that the famous noise showed up three more times and finally disappeared.  (for the moment ?!) My RS took no hits, no water, nothing ... That's are the fact... Meaby we are all talking about two or more different problems with one only true: poor quality! Poor quality control, poor material, poor building process, poor customer assistance. 

Poor engineering!

[pontoonpete]

8 hours ago, RagingGrandpa said:

All the garbage in that gap!

Now mix some water in with that sand! I would say that some extremely abrasive paste! That has nowhere to go except into the bearing! Especially when under centrifugal force during high speed!

[Flying W]

I'm sure mines collecting garbage in the same place, I like riding off road more than on road. 

Now I understand why holes drilled there to let the crud, amd water drain out while the wheel is spinning makes sense. Ray Rokni has a video up on youtube showing the holes. 

 

[Planemo]

On 1/7/2021 at 3:41 AM, pontoonpete said:

If you look at motorcycles, they are much heavier and go much faster, they have smaller bearings that are proportionally spaced much further apart. 

I really dont think the distance between the bearings makes any real difference whatsover. The problem is not having an axle linking them.

On the hollow bearing, any weight which is placed outside the centreline of the bearing will try to rip the inner race from the outer race. See my first crude drawing:

 

If there was an axle linking the two bearings, this angular force would pass along the axle and be supported by the opposite bearing. Crucially, this force is now transferred into a radial load, which is what the bearing is designed for. See my next crude drawing:

 

The only long term solution is to use a bearing designed for axial loads eg a conical roller bearing.

Edit: Pics removed - having a cull of my uploads to retrieve space.

Edited March 4, 2022 by Planemo

[Chriull]

1 hour ago, Planemo said:

If there was an axle linking the two bearings,

if one looks at the video linked in https://forum.electricunicycle.org/topic/20744-hollow-bore-motor-bearing-failure-thread/?do=findComment&comment=344887

one sees the inner stator from the coils to the "inner axle" were the 4 threads to screw the pedalhangers are. The bearing from this open side fits on the "outside" radius of the axle and then connects over the motor casing to the stator (the many thread holes outside of the permanent magnets).

So the two bearings are already linked by an axle!

1 hour ago, Planemo said:

The only long term solution is to use a bearing designed for axial loads eg a conical roller bearing.

That seems not beeing used?

[Planemo]

1 hour ago, Chriull said:

So the two bearings are already linked by an axle!

Yes @Chriull, you are absolutely right! Thats a good vid to show the layout. Sorry guys, forget all my previous posts on this. I assumed the hanger bolted to the inner race without a central through-hub or 'axle' being involved.

1 hour ago, Chriull said:

That seems not beeing used?

They are not using conical bearings, but I am now not convinced they need to. So it seems we are back to the problem being simply poor quality bearings, an ingress of water/dirt or a combination of all three.

I now dont think that axial loads are the problem here.

Sorry for jumping the gun people, I knew I should have looked into the hub design first 

[vladdark]

4 hours ago, Chriull said:

So the two bearings are already linked by an axle!

Yes, but this axle is made from poor quality materials. So i think that this is more "soft bed" for bearing than axle

[RockyTop]

@Planemostill has a point. The bearings might not be able to handle side force as well. 
 

With one foot on and one foot off:

It seems to me that on a smaller bearing almost all of the force is translated to up and down. The force on one side would be up and the other side down , while with the larger bearings ( same sized balls) more of the force is side to side. 
 

Maybe my thoughts are more psychological and the ratios are bothering me more than anything. 

Edited January 7, 2021 by RockyTop

[pontoonpete]

I've made a video to show visibly what I can't explain verbally LOL. I'm a shower not a talker

 

 

[WheelyBad]

Wow, I have a deposit down on a RS 19 HT that's scheduled ship in the next couple of days. This thread (among others) has me seriously second guessing that decision. I didn't go with the V11 because the tech hasn't had time to mature enough to warrant dumping my hard-earned cash into it. It really sounds like the same thing applies to these new hollow bore motors, be it in the V11 or the RS. Back to the drawing board I guess, and by drawing board I mean, trying to convince The Boss (wife) that I need to spend $2800 on a Sherman. Many thanks to everyone who's weighed in on this. It sounds like you saved me a bunch of headache.

[RagingGrandpa]

12 minutes ago, pontoonpete said:

https://youtu.be/ekJeqkMNZ0Q

Ah. But we disagree in two areas:

1. There is no 'pivot point' in the center of the bearings.
   Loads enter at the pedal, and leave at the tire... nothing dictates that the center of rotation be between the bearings.
    
2. Your example changes the spacing between the two bearings. But MSP vs MS-RS have the same spacing.

(For these two reasons, I think your motion arcs are misleading...)

.02

  

3 minutes ago, WheelyBad said:

Wow, I have a deposit down on a RS 19 HT that's scheduled ship in the next couple of days. This thread (among others) has me seriously second guessing that decision.
...
I need to spend $2800 on a Sherman.

Why not $1550 on a new, tried-and-true MSX?

https://forum.electricunicycle.org/topic/20801-msx-with-2500w-motor

Edited January 7, 2021 by RagingGrandpa

[WheelyBad]

5 minutes ago, RagingGrandpa said:

Why not $1550 on a new, tried-and-true MSX?

 

Believe me, I thunk the thought. If I could find one anywhere with any kind of a warranty like eWheels offers, I'd jump on it. Maybe I'm behind the times, but throwing $1500 at "green and fashion travaling" shop on aliexpress seems foolish. Am I wrong?

[pontoonpete]

7 minutes ago, RagingGrandpa said:

Ah. But we disagree in two areas:

1. There is no 'pivot point' in the center of the bearings.
   Loads enter at the pedal, and leave at the tire... nothing dictates that the center of rotation be between the bearings.
    
2. Your example changes the spacing between the two bearings. But MSP vs MS-RS have the same spacing.

(For these two reasons, I think your motion arcs are misleading...)

.02

I thought all your specifications on the bearings was great! And makes a very good point that there are more issues than just the bearings.

I do standby my thought process though.

I just want to highlight that something needs to be fixed so that we get reliable high-quality wheels because electric unicycles are just so awesome!

 

[RagingGrandpa]

6 minutes ago, WheelyBad said:

throwing $1500 at "green and fashion travaling" shop on aliexpress seems foolish. Am I wrong?

I purchased from this seller and had a good experience. What's even better is: they have US stock of 2021 MSX, so no 40 day wait!

https://www.aliexpress.com/item/4000959813329.html

[WheelyBad]

4 minutes ago, RagingGrandpa said:

I purchased from this seller and had a good experience. What's even better is: they have US stock of 2021 MSX, so no 40 day wait!

https://www.aliexpress.com/item/4000959813329.html

You, sir, are the man!

[AtlasP]

Why not MSP over MSX?--quite a bit newer/nicer while being just before the bearing issue introduced with the RS. My go-to advice until this gets resolved on the RS has been to look for an old-stock MSP (or buy a used MSP from one of the many people upgrading to Shermans).

Edited January 7, 2021 by AtlasP

[RagingGrandpa]

2 minutes ago, AtlasP said:

Why not MSP over MSX?

Pay more, get more... MSX -> MSP -> Sherman, all good wheels.