Scatcat

Strange oscillation in GT16

106 posts in this topic

3 hours ago, meepmeepmayer said:

Pretty sure the cause are the metal pieces. No reason to assume anything else, especially now that the behavior has changed after you got some out.

My guess is, the wheel must be absolutely still (aka on the ground) and maybe also the tire a bit arrested (aka on the ground) so the "bad firing" of the motor due to the metal pieces cannot start any new oscillations.

I think I know how you feel. Heartbroken (a bit). Literally heartbroken. Like someone who just found their partner in bed with someone else (I assume). Trust gone, disappointed, sad, why, etc.

Had a bit of the same when my ACM died, but you certainly have it worse.

Well, good luck in getting all that stuff out! Wondering if you'll have to disassemble the motor in the end (separate stator and magnets so you can get in between).

Yeah, I worry that I will have to dismantle the motor totally in the end. Getting rid of metal shards in a magnetic environment is not exactly trivial.

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45 minutes ago, Marty Backe said:

Glad that you seem to have found the problem. As someone who seems to be inching closer to buying a GT16, this post is not very encouraging to me. Seems like it'll happen to every wheel eventually.

I don't understand where this came from. Was it on the axle?

Keep us updated as to your progress.

If it's the seal for the bearing, it might be an aberration. But then again, it might be one possible explanation for those high speed crashes. While a shard lodging between magnets and stator probably won't be enough to stop the wheel abruptly, it might be enough mechanical resistance to create a short hesitation in the wheel. That is not something you'd find comfortable when at high speed, leaning forward. :blink1:

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I was thinking of getting a GT16 instead of the KS for a while there, as I saw the 858Wh -version for sale at around 990€ or so, taxes & shipping included... I backed off in the end, as at that point there were so few riders with them (which still seems to be the case) and pretty much nothing was known of the quality or durability, except that some of the early boards had failed in France. Guess it was a good call.

Hope you get your motor fixed... maybe a high-power industrial vacuum cleaner might be powerful enough to get the shards out, maybe also while dragging a playing card or something between the stator and the magnets to loosen the small shards? The cardboard + tape -trick might help there also.

Edited by esaj
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16 minutes ago, esaj said:

I was thinking of getting a GT16 instead of the KS for a while there, as I saw the 858Wh -version for sale at around 990€ or so, taxes & shipping included... I backed off in the end, as at that point there were so few riders with them (which still seems to be the case) and pretty much nothing was known of the quality or durability, except that some of the early boards had failed in France. Guess it was a good call.

Hope you get your motor fixed... maybe a high-power industrial vacuum cleaner might be powerful enough to get the shards out, maybe also while dragging a playing card or something between the stator and the magnets to loosen the small shards? The cardboard + tape -trick might help there also.

Well Ferraris are also known for breaking down spectacularly from time to time. :D

The vacuum cleaner idea may be worth a try, especially if i combine it with a playing card to nudge the stuff at the same time.

Edited by Scatcat
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3 hours ago, Scatcat said:

Well, I got the tools and opened up the other side, which took some doing as there was a layer of rubbery silicone glue that held it together.

The first thing I found out was that the washers really where washers, not the seals integral to the bearing. On the other side there where no less than two of them. If there were two on the first side where there now are none, I still have shards from one whole washer in the wheel!

The second thing I found out is that the hall sensors are in a configuration that got me scratching my head:

hall-sensors-n-washers.thumb.jpg.767fe4413caee7a9ed6c40d8cf9788fa.jpg

Note that it seems the sensors are buried in the coils, which kind of makes sense, but makes a visual inspection rather difficult. If anyone sees something that looks wrong in the picture please holler. Tomorrow I'll go over the cables and solder points, to make sure nothing is detached.

Note on the right how thin the washer is, I'm kind of curious why they're there, and why if present, they're not a bit beefier? I suppose they're meant as some kind of seal/buffer anyway, but it seems like a strange solution.

I did find more debris, I haven't even tried to pry it out yet, will wait until I have the time and concentration to do it right. I also need a multimeter to check all cables to make sure there are no shorts or bad connections.

debris.thumb.jpg.82f920667e4a7d5d606ccaf3950c22c7.jpg

I've marked what looks like shards with arrows. There's more in other places, I just found a place where they're obvious.

I now realise that I've had two events with strange noises that I though was debris stuck in the wheel, but that might well have been debris stuck in the wheel. :D

You have to laugh about it, the alternative is to bawl my eyes out. I've ridden this wheel like 600km, and here I stand not knowing if I can fix it or need a new motor and maybe a new controller...

If there's nothing wrong with the hall sensors and cables, the only thing left is the controller. But if I clean this, test the connections and still have the vibrations, then how should I know? That's the downside of choosing Rockwheel instead of Gotway or Kingsong, there's no servicing available on this side of the planet. Shenzhen is seven time-zones away.

Sorry to sound down, but I feel a bit deflated. I've contacted the guy selling the wheel to me, to try to trace who sold it originally to see what they say about it. But I can't say my hopes are very high.

Well the only thing I can do is try. I bloody love the ride, so at least I'm motivated. Right now I've made it into the worlds heaviest pizza. :D It's in a bag meant for pizza, since my poor lovely woman found the odour of silicone, plastics, resin, grease and oil less than thrilling.

The most frustrating part is that I don't get to ride it, until I'm done. The withdrawal symptoms are a bitch, I itch all over and it's just two days. :cry2:

This really has me doubtful about buying a Rockwheel now. If all their wheels use these thin low quality washers than this failure will probably be common. Unless you can recover all the pieces necessary to reconstruct the washers than your wheel will forever be in doubt. Not a good feel I'm sure.

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On 7/15/2017 at 10:00 AM, Scatcat said:

@陈小杰 I really hope not using the washer won't introduce instability to the wheel.

Actually I'm rather pissed off right now, because the idea of putting a big f-ing steel-washer that may be all of 0.25mm thick in a wheel with a shit-load of strong magnets and electromagnets seems... well... interesting.

Had this been a Swedish company, I would have demanded my money back right now - or a new wheel with reassurances that this was a one-time event. Yes we have that kind of extensive consumer protection in Sweden.

A washer in the motor should be good for more than 550 km, it should be good for ten, twenty or fifty times that much - at least.

I had to use a f-ing tooth-pick and a ceramic tweezer to get some of the shards out from between the magnets and the stator. I guess they WOULD introduce interesting effects when the magnetism in the stator moves the shards from the magnets to the stator.

Those look like shims, and possibly there were two on one side and one on the other.  I wonder if the axle nut loosened on one side, allowing some play, causing the shim to break?  Not a good scenario.  But maybe you could retighten the axle nuts and the wheel would be rideable, even without replacing the broken shim.  I have no idea, just putting some thoughts out there that might give other possibilities, and trying to look on the bright side.  I hope you get this sorted out.

Actually, after rereading this post and looking at the pictures again, I take back what I just wrote.  You probably need a new motor, and the mainboard looks like it has some cold solder joints on it.  

Edited by steve454
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Those look like wave washers.

https://www.fastenal.com/products/fasteners/washers/wave-washers?r=~|categoryl1:"600000 Fasteners"|~ ~|categoryl2:"600089 Washers"|~ ~|categoryl3:"600106 Wave Washers"|~

Maybe they are meant to fill in the gap between the bearing and stator to offer support to the motor cover when the pedal support bolt is fastened.  As Steve mentioned maybe if one side was not tightened enough that might have allowed the washer to spin about explaining the scratches and eventual fracture.  It's probably meant to remain stationary through friction?

Do you have a photo of how the washer sits on the axle or in relation to the motor cover inner surface?  More photos would be helpful.  If you have a caliper, take some measurements to try to get some replacement washers.

http://www.ebay.com/bhp/wave-washer

I don't think audio speakers use neodynium magnets.  You may need to remove the outer hub from the stator to get access to clean properly.  Be careful not damar any copper coils.

It's good to see the hall sensor legs insulated and mounted to a small support PCB that appears to be glued to the stator.  The metal shards could be throwing them off or might have damaged something.

Edited by Hunka Hunka Burning Love
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5 minutes ago, Hunka Hunka Burning Love said:

Those look like wave washers.

I've seen those before but didn't know their purpose until following your link. 

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Those are not low quality thin washers. They are spring washers. It looks like they are using them to absorb in-out stator gap play. The most likely reason is that there is a machining mistake and tried to use the spring wager to fill the gap. If they had made the pieces correctly, the bearing inner race and outer race must be tight after assembling and mating with the respective static piece mating with the race. If you need washers a machining error occurred. And the spring washer broke because it is most likely rubbing on a spinning race or assembly and wearing out. 

So difficult to say without close inspection. Without the spring washers you might notice a clanking sound when shifting left and right. Not sure if that would be a big problem. It might be ok. 

Edited by Carlos E Rodriguez
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Yi Chen on Rockwheel Store is helping me out right now, looking at pictures and giving advice. I can get whatever part I need from him it seems, but of course it will take a couple of weeks to reach me. That includes the wave washers.

He's worried though, that there has been a deformation in magnets or stator, and that it it what causes the vibrations. But I'll clean it out and test it, and if it's good I'll order replacement washers from him. Otherwise I'll have to order a replacement motor.

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1 minute ago, Scatcat said:

Otherwise I'll have to order a replacement motor.

Or for that matter a replacement EUC that f-ing works, if there is such a beast on this planet... 

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I just learned how to remove the stator from the magnets. That was interesting, and potentially dangerous for you hands if you do it wrong :D 

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Just now, Scatcat said:

I just learned how to remove the stator from the magnets. That was interesting, and potentially dangerous for you hands if you do it wrong :D 

You will need to be very precise when putting back together. The magnets will fight you to keep the rotor and stator the same distance all around (magnet stator gap). I don't have a link on how to properly align and maintain an even gap all around. 

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18 minutes ago, Carlos E Rodriguez said:

You will need to be very precise when putting back together. The magnets will fight you to keep the rotor and stator the same distance all around (magnet stator gap). I don't have a link on how to properly align and maintain an even gap all around. 

Yes, I think a bit of plastic sheet could be very helpful... But when you start putting the covers back on, the positioning will be OK. The hard part is getting it in place to align the screws without undue stress.

I think I'll have to get some silicone too, to make sure the seal is watertight.

Yi Chen is a goldmine of a seller. He advised me to take it apart, clean and inspect it, and then tell him what parts I need. From just the washers, the rim and magnets, the stator/hub assembly or the whole motor. That kind of service-minded seller is something to treasure.

While it will still take to f-ing long for my EUC addicted self, it still made me feel a lot better about my options.

Edited by Scatcat
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Yea, I'm getting the impression the "Rockwheel Store" is a great seller. More service than the manufacturer!

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44 minutes ago, meepmeepmayer said:

Yea, I'm getting the impression the "Rockwheel Store" is a great seller. More service than the manufacturer!

I dont know it exactly, but as i see it Yi Chen IS part of Rockwheel as producer..

But yes, plus one for him beeing a good seller!

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@Scatcat You have the photo in the gasket we have replaced, you can contact the seller Chen.

The phenomenon in the video, the gyroscope is shaken, try to fix the controller and the housing screws.

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9 hours ago, 陈小杰 said:

@Scatcat You have the photo in the gasket we have replaced, you can contact the seller Chen.

The phenomenon in the video, the gyroscope is shaken, try to fix the controller and the housing screws.

I think this means the control board might be loose causing the gyroscope to give bad signals. Make sure the control board is secure and the case is also secure. 

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2 hours ago, Carlos E Rodriguez said:

I think this means the control board might be loose causing the gyroscope to give bad signals. Make sure the control board is secure and the case is also secure. 

That makes very much sense. I will look into it.

12 hours ago, meepmeepmayer said:

So they sell their own wheels as well as the competition? Why not!

Exactly, why not?

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16 hours ago, 陈小杰 said:

@Scatcat You have the photo in the gasket we have replaced, you can contact the seller Chen.

The phenomenon in the video, the gyroscope is shaken, try to fix the controller and the housing screws.

It so happened that the board was very loose.

I have no idea why it happened now and not earlier. From what I could see, the screw to the right, MOSFETs upwards was loose, but the one in the middle was VERY loose.

Too loose to be explained by just vibrations, and also stuck. My guess is that the threads stuck when the board was screwed down originally, and the person attaching it thought that the screw was tight. I unscrewed it and got it to sit correctly in the threads, then it could be screwed down tight.

The other one seems to have been tight, but only when the edge of the board overlapped the edge of the rim with a few tenths of a millimeter.

My best guess is that the bump made the board move into its intended seating, thereby making both screws loose.

When I'm done cleaning and assembling the motor, I will assemble and test. It wouldn't surprise me if that did the trick. But I hope I haven't damaged any solder-points with the vibrations. If so, I may have to resolder or replace the board.

We'll see.

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