Scatcat

Strange oscillation in GT16

106 posts in this topic

Hi,

I agree with @KingSong69 It behaves like if the gyroscope was on a too high sensivity setting, it's a well known issue on some gyroscopes, in general this kind of issue could be answered simply by lowering the gyro sensivity, but I don't know if it's possible on a Rockwheel GT16 however :/

Maybe you could try calibrating your EUC and see if the issue is still here ?

Good luck !

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35 minutes ago, KingSong69 said:

Something with the hall sensors or a defect on the board.....As it seams to rotate as wild, and i did not see a defect like this on hall sensors before, so i would bet more on the board/gyro....

I would check the connections on the board...sensor wires from motor especially!

Well, it has never happened before, so the idea that something shook loose when I went over the bump is rather low hanging fruit :)
I suppose I'll have to dismantle the board housing and check if something went wrong in there.

Thanks for the input.

31 minutes ago, Pingouin said:

Hi,

I agree with @KingSong69 It behaves like if the gyroscope was on a too high sensivity setting, it's a well known issue on some gyroscopes, in general this kind of issue could be answered simply by lowering the gyro sensivity, but I don't know if it's possible on a Rockwheel GT16 however :/

Maybe you could try calibrating your EUC and see if the issue is still here ?

Good luck !

I already tried calibrating, also tried to change modes between "walking mode" and "playing mode" to no avail.

The funny thing though is that it still keeps the balance. It shakes like crazy but it doesn't cut out or spin freely.

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hey Scatcat,

can you turn off and lift the device in order to shake it? 
Does it sound like something lose is bouncing inside?
It almost sounds as if one of the magnets has lost its bond to the body of the motor. :huh:

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5 minutes ago, Spark said:

hey Scatcat,

can you turn off and lift the device in order to shake it? 
Does it sound like something lose is bouncing inside?
It almost sounds as if one of the magnets has lost its bond to the body of the motor. :huh:

Nope no sounds at all of that kind. The only sound when shaking are the normal creaks from the shell. If I bounce it while off, the only sound is rubber hitting the floor.

Aaand, if one of the magnets lost its bond to the motor... wouldn't the effect be a rather dramatic stop, as the magnet touches the stator?

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hmm, you might also want to check for loose bolts on the GT16.

I'm not sure wether loose hall sensor cables would let the wheel behave and sound like this.
a loose magnet that cannot physically leave its place due to its size can rattle like this,
at least in those muuuch smaller electric motor versions for drones I worked with before. :(

I hope you are still in warranty.

Edited by Spark
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If it's not loose bolts, connectors, shorted wiring, a loose control board shaking around (?), there is a slight chance it could be shorted wiring of the hall sensor legs or a blown sensor, but you would need to open up the motor to investigate that.  We've seen some Gotways which have wiring soldered directly to frail sensor legs without insulation.  Others use small circuit boards to attach the hall sensors to that act as a bridge onto which the wires are connected.

Considering these are Chinese "Toy Grade" electronics that have been suped up to go 40+ KPH, you're really relying a lot on how much they vibration and drop test their components if at all.  :innocent1: 

Edited by Hunka Hunka Burning Love
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Well, if it helps with the speculation, notice how the shaking stops if I physically hold the handle still. This makes me wonder if it's the board, since that part is what i hold still when I hold the handle. Best case would be a loose connector on the board, which would be fixable out of my own resources.

Thank you all for helping me speculate.

@陈小杰 Have you seen anything like this before?

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15 hours ago, Scatcat said:

@陈小杰 Maybe you know what's going on.

After going over a bump today the wheel started behaving strangely. It vibrated/oscillated violently and didn't stop until I physically grabbed it and held it still. I'm glad I wasn't going very fast, because I was able to stop in a controlled manner. I've opened the sides to make sure there are no loose cables, and everything seems in order. This is what it looks like:

 

I really hope there is an answer to this one. Any ideas and help would be appreciated.

Late to the party but it sounds like the member's have covered all of the bases. The hall effect sensors are small but mighty little beasts since they determine when the microcontroller energizes each coil along with indicating the exact rotor position. Like @Hunka Hunka Burning Love and @KingSong69 have mentioned it appears that a sensor might be faulty given your wheel cannot make this rotor positional determination. A faulty mainboard would be my second guess.

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@Scatcat Commendations for your great work here as involuntary beta tester for new wheels! Don't give up so others won't have the problems you have:);)

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38 minutes ago, meepmeepmayer said:

@Scatcat Commendations for your great work here as involuntary beta tester for new wheels! Don't give up so others won't have the problems you have:);)

Well, I feel a bit ill used...

We're not supposed to have to take our wheels apart to that extent. I don't really have the right tools. I need to get a new allen key as the one I have is not strong enough to get the other pedal assembly off. I got one side off with the bit-key I have and a lever in the form of a patent wrench, but the right side is even harder and I will break the key if I try.

I'm afraid I'll have to do it though, because while i scanned the whole left side for metal shards, even between magnets and stator, it seems I missed one or two. Getting most out helped a lot, it's a lot harder to provoke the vibrations.

But I can still provoke the vibrations in certain positions of the wheel and that is not acceptable. Going up a curb is not the problem, I usually don't do that at any speed where the vibrations could make me fall. But hitting a pot-hole or a speed-bump when going 15mph+ and getting the vibrations could be a disaster. Or getting them as I do a panik break...

After all, what seems to trigger them is high power. When I bounce the wheel slightly off center, the power when it lands is temporarily quite awesome. Same thing going up a curb when the wheel apply a lot of power to rebalance. Same thing if I'm at the end of a power break. I'm not sure if it's as bad at speed, but I really don't want to find out it is...

Edited by Scatcat
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@Scatcat

Did you try that behaviour on softer ride mode?

As in the other thread was said...it could also be just a tiny bit loose pedalarms, which then generate the vibrations in hard mode, the wheel trying to keep the pedals flat!

To be honest, i dont think that this tiny metal piece is/was the cause of that vibrations.....

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18 minutes ago, KingSong69 said:

@Scatcat

Did you try that behaviour on softer ride mode?

As in the other thread was said...it could also be just a tiny bit loose pedalarms, which then generate the vibrations in hard mode, the wheel trying to keep the pedals flat!

To be honest, i dont think that this tiny metal piece is/was the cause of that vibrations.....

The pedals are now screwed on like a rock, and the vibrations persist. I've tried all modes and also tried recalibrating.

When I can get myself a more sturdy allen key, I'll look into the other side of the wheel and check the hall sensors.

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Oh, just to add another little tidbit. You know I can stop the shaking by holding on to the handle hard. That however does not work if the wheel is not planted firmly on the ground. Getting it to spin in the air does nothing to stop the vibrations. At least not until it spins out and stops.

It must stop, upright, on the ground - as when you turn it on.

Edited by Scatcat
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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.

51 minutes ago, Scatcat said:

Well, I feel a bit ill used...

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).

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Idea: Can you use dental floss (or something similar) to clean the thin spaces between the magnets and stator?

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Good job on discovering the broken washer!  That was unexpected.  :blink: It's weird why it would need a washer there as no one else seems to have mentioned their motors have one that I know of.  @Rehab1 did your ACM motor have washers between the bearing and stator? 

It isn't a bearing seal cover is it?  Some have these coverings that help seal the grease inside with the ball bearings and cage.  The broken pieces look like they are painted or plated with a black covering.

Those metal pieces might be throwing off the hall sensors?  If you get a chance can you post some detailed photos of the motor covers, the hall sensor wiring and other areas in general?  I wonder if the noises other people have been mentioning could be related to similar pieces of broken washer.  This might explain the French users reporting random crashes at high speed?

Wow those are super thin motor cables soldered to the board... 

Edited by Hunka Hunka Burning Love
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5 hours ago, Scatcat said:

Well, well, well, look at what I found!

 @陈小杰 Take a good look at this:

metal-washer-shavings.thumb.jpg.140ca40b96fbc59d8600ea9f3eaa2cb1.jpg

Do you see the metal shavings? One stuck on a magnet, the other stuck between a magnet and the stator.

They're part of this:
the-washer.jpg.16c72f129952bb78b555d4c4bec57834.jpg

A washer that used to sit between the bearing and the stator. It was obviously wafer-thin and obviously broke after about 550 km...

Finding metal shavings all over the inside of the motor kind of explains why it behaves strangely. I really hope I've found them all.

I will have to do without the washer I'm afraid, because I really don't think there is a shop where I can find paper thin washers of that size...

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.

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30 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.

I think @Hunka Hunka Burning Love might be on to something, it would make more sense if it was part of the bearing that had broken and gotten loose.

Not a very good recommendation for that brand of bearing, if that is so...

2 hours ago, Hunka Hunka Burning Love said:

Good job on discovering the broken washer!  That was unexpected.  :blink: It's weird why it would need a washer there as no one else seems to have mentioned their motors have one that I know of.  @Rehab1 did your ACM motor have washers between the bearing and stator? 

It isn't a bearing seal cover is it?  Some have these coverings that help seal the grease inside with the ball bearings and cage.  The broken pieces look like they are painted or plated with a black covering.

Those metal pieces might be throwing off the hall sensors?  If you get a chance can you post some detailed photos of the motor covers, the hall sensor wiring and other areas in general?  I wonder if the noises other people have been mentioning could be related to similar pieces of broken washer.  This might explain the French users reporting random crashes at high speed?

Wow those are super thin motor cables soldered to the board... 

When I open the other side, I might be able to establish if there is a washer or a bearing seal on the other side. Whatever it is, it will be a bear to get rid of with those kinds of magnets inside the wheel. :(

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