MSX motor break appart

[Slartibartfast]

My brother has an MSuper X which seemed to develop a small amount of slop when one transitioned from backwards movement to forwards and vice versa. Although noticeable, it was slight and didn't seem to be getting any worse so he continued to ride expecting he would need to find a way to torque up that main axle bolt if ever it started to get worse. Although it was fine for quite a while eventually, one day, it did suddenly get a whole lot worse and not being mechanically minded himself he freighted it to me to see if I could fix it.

When I received it there was indeed some slop in the axle but turning of the whole wheel itself felt strange and when I turned it on it shuddered violently back and forth then failed and started giving the "hall sensor" error beeping signal. It was then I new this was not going to be a simple axle bolt tweaking after all. After opening the shell and checking all the connections all seemed well and good so I removed the wheel to look for any signs of problems with the motor itself. From the outside the motor looked fine and it seemed those axle bolts were indeed done up plenty tight enough, so the only thing left to do was to crack open that motor housing and take a peek inside.

It is always with trepidation that I crack these housings open for on the most part they are best left un-tampered with but in this case there was no further options available so I bought a trusty "Flat ring" spanner and set about getting inside this badboy:


And when I opened it up was there a surprise awaiting me inside! It seemed the axle key had completely sheared off!!!

If you don't know, this is how the axle shaft is affixed to the inner part of the motor:


However this is what the "keyway" in the inside of his motor looked like:

 

This is the "keyseat" of the axle shaft:

 

And finally this is what's left of the axle "key" itself:

Has anyone else ever seen this on a wheel before? It seems highly unusual to me on a wheel that is less than a year old and only seen 1200km of use and, to be honest, it seems like down right shoddy workmanship.

Anyway, as it is, my brother is reluctant to try his luck with another Gotway product given how spectacularly this one failed and how non-existant support seems to be. Anyone know what went wrong?

 

All the best,
Slarti.

Edited April 24, 2020 by Slartibartfast

[EUC Custom Power-Pads]

36 minutes ago, Slartibartfast said:

seems like down right shoddy workmanship.

I don't know how sloppy you have to work to explain this?

37 minutes ago, Slartibartfast said:

Anyone know what went wrong?

It looks like substandard materials to me. 

[.....]

40 minutes ago, buell47 said:

I don't know how sloppy you have to work to explain this?

It looks like substandard materials to me. 

Substandard materials and sloppy tolerances. Its not shoddy work, it started BEFORE assembly, tho 'shoddy work' and poor QC could have also been a factor. I am not surprised at all. Opening both my wheels of different brands, pretty much told me what to expect. It is what it is, and what it is, cheap chinese manufacturing that ALL the current wheels are fighting against. Usually they get by with it, sometimes not. If i EVER saw a line of cars or 'quality' machines with this kind of quality, I'd also see them go out of business in the usa VERY quickly. But, theres a price to be met and a market to satisfy. So far we have seen that most people already bitch about the prices. Since batteries cost so much, they gotta scrimp where they can. Fwiw, my KS seems more thought out than my GW, but they are leagues apart in price. Even so, my KS is NOT made of hi quality materials NOR tight tolerances. Until we see people willing to pay a lot more for their wheels (in droves), manufacturers are going to do, what they have to do. Im betting that substandard metals are rampant in china. Not that they CANT make good alloys, its just that they CAN make cheap one's from recycled crap from all over the globe. I wonder which they are mostly choosing? You want quality, look at what a cars crankshaft puts up with, motorcycle axles, etc.. Even a tiny car with similar dimensions on the shaft as in these wheels, theres no damn comparison( I know a forged shaft may break as its too hard, but you get my point). It doesnt help, that 99% of us will never open a motor and see the slop they scrimp on. 99% of the time, it may not even be an issue. Its numbers my boy, not safety or quality. Paperclips vs forged and treated alloys..

Edited April 24, 2020 by ShanesPlanet

[Slartibartfast]

By "shoddy workmanship" I mean poor material selection, tolerance control and mechanical construction in general, not just the actual "workman" doing the assembly. In fact I suspect the actual "workman doing the assembly" was probably the least of the problems here.

Nonetheless, has anyone ever heard of this failure happening before?

Edited April 24, 2020 by Slartibartfast

[mrelwood]

The first I read about this issue was on an Inmotion (V8 or V10, not sure). Later I’ve heard for example  @Marty Backe mention it in his videos, regarding the larger GW wheel’s. None of this is to say which brands or wheel sizes the issue would be limited to though.

Sorry to hear that you have the issue, but good thing you guys found it before the axle was able to rotate freely! That could’ve hurt. It’s not a small task to successfully hunt down an issue like this, very well done!

 Worth mentioning that generally the EUC manufacturers do not make the motors themselves, so there doesn’t seem to be a reason to expect that a tendency to the issue would be manufacturer dependent. GW wheels are used for and are able to provide large amounts of power and torque, and on average they are ridden harder, so in that sense they may be statistically more susceptible for the issue. But a GW ridden like a KS shouldn’t be, based on what I understand.

 The Inmotion I read about was fixed by welding the axle sections firmly in place. But a new motor doesn’t cost very much, and it would save you guys a lot of work.

Edited April 24, 2020 by mrelwood

[.....]

3 minutes ago, mrelwood said:

 The Inmotion I read about was fixed by welding the axle sections firmly in place. But a new motor doesn’t cost very much, and it would save you guys a lot of work.

The upside of cheap shit is that its also cheap to replace (catch22)! I too would just look for an entire motor, labor involved and risk to fix the old (this is a vehicle), is WAY not worth it imho. You could always try and modify the new one, or be VERY sure of assembly practices when you fix it. This should help. Just be aware, a new motor is more than likely more of the same.. I'm not picking on GW by any means. Not surprised they farm out the manufacture of the motors.

Edited April 24, 2020 by ShanesPlanet

[Slartibartfast]

5 minutes ago, mrelwood said:

...but good thing you guys found it before the axle was able to rotate freely! That could’ve hurt.

Oh, it was rotating freely (well sort of freely). It was the "free" rotation that caused the motor wires to sheer off (which can be seen in the 5th image), which is what caused the "Hall sensor" error beeps.

Edited April 24, 2020 by Slartibartfast

[yuweng]

From your photos, i can tell that the hub motor factory uses sub-standard key that leads to your problem.

Spoiler

From your photos above, the length, height & probably the width of the key is also wrong. On the middle photo, you can tell that this key doesn't have the same height, thats why it is crushing the metal on the left but not the right. Compare to the key in your hand with the last photo, it doesn't even shape like it.

 

If you opt for repair then as mrelwood has suggested, bring it to a good welder & your problem will be fixed though you won't be able to change the axle in case of future axle threads wear & tear. 

Edited April 24, 2020 by yuweng
typo

[Slartibartfast]

14 minutes ago, yuweng said:

If you opt for repair then as mrelwood has suggested, bring it to a good welder & your problem will be fixed though won't be able to change the axle in case of future axle threads wear & tear. 

I have no intention of repairing this motor.

The fact that the ring holding the "keyway" has split and that it is now out of round alone is enough to have me bin it, but added to this the way all the cables have been sheared off and not to mention the fear of it giving way at an inopportune time means I'll be seeking a replacement –thank you very much 

Edited April 24, 2020 by Slartibartfast

[yuweng]

Hopefully yours is a one case wheel problem, if its a batch problem then will Gotway send out axle set to the whole wide world MSX owners, just like they did for the 1st batch Nikola motherboard, we'll have to wait & see 

[Slartibartfast]

4 hours ago, yuweng said:

From your photos above, the length, height & probably the width of the key is also wrong. On the middle photo, you can tell that this key doesn't have the same height, that's why it is crushing the metal on the left but not the right. Compare to the key in your hand with the last photo, it doesn't even shape like it.

I'm trying to understand what you're saying there.

Correct me if I'm wrong but I had thought the the key, the keyway and keyseat were all reasonably well shaped to begin with. Although it's now broken in two I had thought the key would have once been more or less the right shape. Clearly the key has been sheared in half and the broken face looks pretty gnarly but that smooth face on the lower fragment in the photo is more or less the right shape is it not, or am i missing something? The fragment in the upper part of the frame has the smooth face down so you can't see it but if you were to place the two fragments together (rough sides facing each other) I think the key would be at least somewhat representative of the "correct" key you posted. In any event though, something clearly went catastrophically wrong as the key was sheared in half and in the process made an absolute meal of the other connecting pieces.

The middle photo is showing the way the keyway has been pulled open and actually split the ring into which it was cut:


In this photo the two points marked by the green circles once use to be joined however somehow that collar has completely split and that gap has opened up.

I suspect that collar actually failed first and a gap began to open (by just a small amount to begin with) and this is what caused the slop my brother felt at first. It seems this slight gap probably held for some time but eventually it failed properly and widened up to what it is now which is when the wheel became unrideable. Once the gap was as wide as it is now anything could have happened. One possible explanation is that one end of the key actually fell into that gap meaning only a tiny part was left protruding to mate with the shaft which lead to the burring we see around the slot in the axle shaft now.  Also, with one end "lying low" in the gap the other end would have been taking the full load of the connection which may have lead to the key shearing in half. I don't know: ¯\_(ツ)_/¯

Clearly though, regardless of what else was going on that collar should not have split and opened up like it has!

Edited April 24, 2020 by Slartibartfast

[Planemo]

Yeah I've seen woodruff keys cleanly sheared in half several times on race engines but never has the groove or surrounding metal split open! I think you're right, this may not have been a key or groove issue at all, and instead may be that the surrounding collar just split open which would cause imminent failure of the key and groove. Don't know how there was any room for the collar to 'open up' though...is/was the collar a smaller diameter than the disc it sits in?!

[yuweng]

Hmm, both of you do make a point & as Planemo has pointed out, could it be that your brother is riding his MSX like a race car that leads to such failure  i guess we'll have to wait for some one here that has more experience on motor axle & rotor to enlighten us but then again the MSX is the Porsche on our EUC world  

[Slartibartfast]

My brothers a heavy lad but if anything he's a moderately conservative rider. Definitely more of a cycle way cruiser than off-road thumper if you know what I mean.

[Yxzygäilijä]

I had this exact same issue about one month ago with my 16x. I started to hear clicking sound from motor when accelerating or deaccelerating. 

I decided to open the motor. And I saw this

Fracture on both welds.

My solution to this was welding the axle to the place on both sides. It have worked very well without any problen since then.

 

Edited April 27, 2020 by Yxzygäilijä

[Declan acoustic-unicyclist]

On 4/27/2020 at 1:16 PM, Yxzygäilijä said:

I had this exact same issue about one month ago with my 16x. I started to hear clicking sound from motor when accelerating or deaccelerating. 

I decided to open the motor. And I saw this

Fracture on both welds.

My solution to this was welding the axle to the place on both sides. It have worked very well without any problen since then.

 

Damn homie, that looks like a broken axle. Kinda different, but just as big of an oof

 

This is why you inspect your wheels folks!!!

[.....]

6 minutes ago, Declan acoustic-unicyclist said:

Damn homie, that looks like a broken axle. Kinda different, but just as big of an oof

 

This is why you inspect your wheels folks!!!

Yup, new, used, you better have tools and be mechanically inclined. It really is too bad that the manufacturer dont go the extra mile as theyve got the tools and the wheel already open. Damn KS weld looks like my first day of welding class... Now that the axle is solid, how long until the motor deforms instead? Perhaps I need to make sure my welder is ready.

[Planemo]

All these collars should be welded the entire 360 deg from the factory. Just those 2 blobs of pigeon crap on each side could never be considered 'substantial'. Shocking.

[Slartibartfast]

5 hours ago, Planemo said:

All these collars should be welded the entire 360 deg from the factory. Just those 2 blobs of pigeon crap on each side could never be considered 'substantial'. Shocking.

They shouldn't need welding at all.

Just a shaft key should be plenty.

[Planemo]

I think you are missing the fact that the collar needs to be attached to the motor disc somehow. You cant key it because theres not enough material.

[Slartibartfast]

3 hours ago, Planemo said:

I think you are missing the fact that the collar needs to be attached to the motor disc somehow. You cant key it because theres not enough material.

Oh, fair enough.
Yes, I did miss that: 😊

My failure wasn't due to a lack of welding though, or at least I don't thing it was. I'm only guessing but it seems it was due to the collar itself simply not having enough integrity. True packing it with weld may give it more integrity but honestly, the collar itself should have been able to handle it with out being needed to be welded.

Edited May 1, 2020 by Slartibartfast

[Slartibartfast]

On 4/24/2020 at 9:52 PM, Planemo said:

Don't know how there was any room for the collar to 'open up' though...is/was the collar a smaller diameter than the disc it sits in?!

Just took some more photos of the failure and you can see that the collar just kind of "scrunched up" the sheet mettle of the disk part of the motor:

And here's another photo the split keyway just for good measure:

Edited May 9, 2020 by Slartibartfast

[Planemo]

Mad. Its almost like the disc just isnt strong enough to contain the expanding loads of the collar. Is the disc made from balsa wood?! Even then, I would still expect a key to simply sheer in half rather than the collar open up. They need to make the collar thicker (and full 360 welds to the disc of course)

I would imagine that the prime candidate for this problem would be when the wheel goes airborn for a period of time when riding, such as when doing big jumps/drop offs. Some slow motion vids actually show the wheel start to spin backwards before landing which must put massive stress on this area when the rider and wheel land.

[Slartibartfast]

 

37 minutes ago, Planemo said:

Its almost like the disc just isnt strong enough to contain the expanding loads of the collar.

To be fair, the disk isn't meant to contain the expanding loads of the collar, the collar itself should be more than capable of holding force from the key. As I understand it the disk is merely meant to stay attached to the collar and not allow the collar to "spin" inside the disk (which it actually did fine in my case).

Perhaps the collar is too thin around that keyway, or more likely this one had a manufacturing fault and there was a crack or something in that corner where it looks like the split began. In fact if you look closely at that last photo it actually looks as if there is a little rust inside the top part of that split indicating it had no doubt been "open" a while:

Edited May 9, 2020 by Slartibartfast

[Planemo]

38 minutes ago, Slartibartfast said:

To be fair, the disk isn't meant to contain the expanding loads of the collar, the collar itself should be more than capable of holding force from the key.

Oh I totally agree, the collar should not expand at all.

38 minutes ago, Slartibartfast said:

As I understand it the disk is merely meant to stay attached to the collar and not allow the collar to "spin" inside the disk (which it actually did fine in my case).

I didnt think it was fine though, it cracked the welds did it not? Are are you saying the welds would have held, had the collar not expanded? In any event I would still prefer to see a 360 weld at that section.

I agree, I think the collar is just too thin around the key area. The loads going through there are significant. There may have been a manufacturing defect as you say, but if the collar was thicker the crack may not have progressed to the point it did.