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Cause of RS motherboard failure: the no-luck wheel.


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Posted (edited)

So the pedals on the RS broke and I ordered new ones. While it was down, I decided to do a tire swap. Bought two new tubes, one of which had a hole fresh from the factory (small, and I will patch it as a spare.) The bearings were making a bit of noise as well and are "binding." So I have new bearings arriving. They did not show the same "gunk" as others and visibly looked pretty good on inspection. The pedal hangars had three bolts that held the shell on that were cross threaded / stripped (those will also be arriving.)

 

Anyhow, the pedals arrived, and the tire was on. So I decided to assemble it and take it for a short spin while I waited for the new bearings. I put it together (all 3 power wires and the hall sensor), plugged in the battery, hit the power button and it "jumped" and made a grinding sound before there was magic smoke.

 

Now, I don't mind. I'll buy a new board. I know that it is always the fault of the user when it comes to electronics. However, I don't actually know what went wrong with it. If it is a wire in the motor or some other screwy thing, I really don't want to buy a new board and fry it as well. I have attached a picture of where the arcing appears to have occurred on the board. I'm hoping that somebody may have seen this and be able to diagnose the problem.

 

The stupid thing is that it was just fine before swapping out the tire. I am not an electrical idiot- I hooked up the wires in the order they came off. It does not seem that difficult (unless something fell from my desk into that board and shorted it?) This is getting frustrating. I don't mind doing some repairs. But bearings, pedal hangars, main boards, pedals. I may as well have bought parts and assembled it myself at this point...

 

If anybody has some reassurance that it is not the motor wires and a new board will fix the problem, I'm all ears. Short of that, I suppose I can bite the bullet, and hope... But if it's the motor then its going to be like $600 for two boards, and another $600 for a motor. And the time to get them here... I really just want to ride at this point.

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The motor is almost certainly not to blame. To convince yourself- The motor should spin freely when the phase wires are open-circuit. You should feel notable resistance spinning the motor

Haha. I was sure they were not. But my cobbled together spacer with a zip tie came out. (I picked a stupid time to have apparently ran out of tape...) Yes, two were, and now I don't feel so smart... I

Just as an update- you were correct. It hit failure mode. So I put in all 5 jumper cables to make measuring the voltage easier. It was a consistant0 - 3.3 volts for each hall sensor as the wheel rotat

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Posted (edited)

Based on the picture you posted, there appears to be something strange about the silicone heat transfer pad beneath the MOSFETs. Is it two smaller pieces instead of one large sheet like normal? If so, that could be the cause as the silicone pad also provides an electrical barrier between the MOSFETs and the heat sink so they may have had an opportunity to short themselves (I notice the damage occurred between a pair of MOSFETs that are responsible for different motor phases, so this is a possibility). If this actually does end up being the case and it isn't just discoloration from the heat/smoke/discharge caused by the failure then it is ABSOLUTELY not your fault and should be covered under warranty for bad manufacturing/assembly.

Edited by Arbolest
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Thanks. I appreciate the knowledgeable reply. I actually just unplugged the motor leads and turned the wheel on. To my amazement, it powered up (obviously without the motor trying to balance it.) For fun, I measured between the different legs. Around 80 V between "1 and 3" as well as "2 and 3" But only around 1.9V between "1 and 2". Hopefully that makes sense. I attached a picture for reference.

 

What you are saying does make sense. The fact that it occurred right after the wheel was apart has me unconcerned with paying for a board. It would be nice (and I'll ask) but my main concern is getting it working and getting back on it. I have pretty much resigned myself to deciding that this is a fair weather wheel and will be the "offroad rig" and possibly ordering a Sherman for the commutes and bad weather...

 

Thanks again for the reply.thumbnail_64102514790757038521.thumb.jpg.b06279059c0d6ec3ebbc1be916b5adb7.jpg

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Ha! what do you know. I get to learn something new today. If I "tip" the wheel forward and back, the voltage between the different legs changes. So, if I tip it backwards, the voltage increases from the 1.9V to 80, while the measurement between leg 2 and 3 reduces. I suppose that makes sense. Now it has me scratching my head again... But at least it makes sense how these contraptions operate...

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Well, this seems like as good a place as any to drop a couple more pictures. Hopefully they help somebody in the future... I think I can spot the problem with this board...

 

I will update when I get a new board and hope that it is not the motor that is shorted somewhere. I will pull the cover off and take a quick look for any signs. Or maybe I will run it up to Terry at Complete electric (a great shop in town that I use for all of my industrial motor repairs...) I'm sure he can do a quick test and let me know that it is all good before I risk a new board.

 

 

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:shock2:

Fascinating! The damage is not exactly where I expected it to be based on the first picture you posted (on a different FET entirely)...

Also yes, I think you found your problem.  :laughbounce2:

While I don't think that the issue is based in the motor, I'm not an expert on them and taking it to someone qualified to do a quick inspection sounds like good peace of mind indeed. Let us know if you learn anything further on that end!

Also, maybe take one last reeeeeally close look at the chips on the front of the board. Sometimes damage to a leg of one of the controller ICs can lead to a FET getting stuck "on" and blowing a leg or two...

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Posted (edited)

Well... I think this is one of the more sloppily wound motors that I have seen. I wonder if the wire making contact between the rotor and the stator might have been responsible? I think this one pretty much is touching, there are a few others that look pretty shoddy as well. So far, I believe my unicycle was built on a Friday. The last one to roll off the line before quitting time...

 

I think I will end up asking my motor guy if I get a chance to get out of the office tomorrow...

 

I probably should not be surprised. I don't know of any industry or product where workers take pride in what they do. But I would be embarrassed to send that out the door (even if it ran and nobody was expected to see the insides.)

 

RS windings.jpg

rs winding 2.jpg

rs winding 3.jpg

rs winding 4.jpg

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57 minutes ago, DWOTR said:

Well... I think this is one of the more sloppily wound motors that I have seen. I wonder if the wire making contact between the rotor and the stator might have been responsible? I think this one pretty much is touching, there are a few others that look pretty shoddy as well. So far, I believe my unicycle was built on a Friday. The last one to roll off the line before quitting time...

It's called hand made craftsmanship, china style! or maybe its the Uighurs slave laborers fault! Kiddin' ofcos....err I think.

All jokes aside, sorry to hear bout all your troubles bud. I was there when you unveiled it for our epic rides. I was there when you showed me the cracked pedals. I was there when you told me bout the incoming Clark pads & pedals. 

Now, I wish I wasn't here to see your mobo gettin the egg fried rice treatment!!! O well, I know it hurts but its always darkest before dawn (or something like that). You'll be back out in no time doing the rough stuff on the RS & spanking my ass on asphalt with your new Sherm!

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When you get your replacement bearings check the grease. If it's packed with petroleum jelly (Vaseline) repack them with marine grease. My original and replacement bearings were packed with petroleum jelly. I think that's one of the causes of failure. My bearings went out at around 160 miles. I now have 590 miles and no problems. I only had dust in the right side, the left side was clean. I opened it up yesterday to give everything a once over.  I've been cought in some heavy rain. I also run the MTB trails near my house daily. Begode quality control is shit. My wheel has been decent but other wheels are totally screwed. I need to come up with a waterproofing solution for the top. I need quick access to the trolley handle and power switch. I use the wheel for last mile commuting.

If the new control board has a cover on it I would remove the cover. It's a source for overheating the board. Also conformal coat the daughter board. Mine was not but the main board was.

 

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1 hour ago, DWOTR said:

Well... I think this is one of the more sloppily wound motors that I have seen. I wonder if the wire making contact between the rotor and the stator might have been responsible? I think this one pretty much is touching, there are a few others that look pretty shoddy as well. So far, I believe my unicycle was built on a Friday. The last one to roll off the line before quitting time...

:facepalm:

 

1 hour ago, DWOTR said:

I think I will end up asking my motor guy if I get a chance to get out of the office tomorrow...

:thumbup:

 

1 hour ago, DWOTR said:

I probably should not be surprised. I don't know of any industry or product where workers take pride in what they do. But I would be embarrassed to send that out the door (even if it ran and nobody was expected to see the insides.)

:eff04a58a6:

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Posted (edited)

I don't know about that. The worst motors I have ever seen come from Italy. (6X) 3/4Hp 600V 3 phase motors had their windings "melt" within a day. All of them were rewound by my guy at Complete electric... Any industrial equipment that is made in Italy can be assumed to be manufactured with parts that were rejected as inferior quality in China...

 

Speaking of which, I love having a "motor guy." Terry is going to try to get to it tomorrow. He agrees that it likely is not the bearing based on the feel of the motor. Without disassembly, his best guess is that one or more of the magnets may have broken lose form the epoxy. I'll try to get a video posted that I had taken from when I thought it was the bearing. Again, maybe it will help somebody in the future?

 

This also explains why the bearing was not contaminated by the same "gunk" that I had seen on failed bearings. Turns out that it may not be bearings after all, and that it might be a motor issue. Overall, very frustrating- but again, I'm very lucky to have a long standing relationship with a motor shop.

 

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16 hours ago, Unipilot69 said:

When you get your replacement bearings check the grease. If it's packed with petroleum jelly (Vaseline) repack them with marine grease. My original and replacement bearings were packed with petroleum jelly. I think that's one of the causes of failure. My bearings went out at around 160 miles. I now have 590 miles and no problems. I only had dust in the right side, the left side was clean. I opened it up yesterday to give everything a once over.  I've been cought in some heavy rain. I also run the MTB trails near my house daily. Begode quality control is shit. My wheel has been decent but other wheels are totally screwed. I need to come up with a waterproofing solution for the top. I need quick access to the trolley handle and power switch. I use the wheel for last mile commuting.

If the new control board has a cover on it I would remove the cover. It's a source for overheating the board. Also conformal coat the daughter board. Mine was not but the main board was.

 

Thanks for the advice on the board. The original bearings have around 800Km on them. I had avoided the rain pretty well, and they didn't look contaminated. I have some great grease here at work as well as a needle to fill it and displace the petroleum jelly. Right now, it is all going to come down to what caused the board to fry. To me, it sure sounded / smelled like a short. The only place I can see that happening is in the motor.

 

Like I said, assembled on a Friday right before quitting time. (Or being as it was China, maybe the joke should be modified to Sunday, just before supper...) I look forward to Terry's diagnosis...

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Wow those windings, that's just a time bomb, not sure I would ride that.

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On 5/12/2021 at 2:12 PM, RagingGrandpa said:

The motor is almost certainly not to blame. To convince yourself-

  • The motor should spin freely when the phase wires are open-circuit.
  • You should feel notable resistance spinning the motor when any 2 phase wires are connected together (just hold the terminals together by hand).
  • You should feel very strong resistance spinning the motor when all 3 phase wires are connected together.
  • You could also measure phase-to-phase resistance with a multimeter (but the DC resistance will be so low that cheap meters cannot distinguish it from a short).

And with the next board you try, perhaps it would be good to power it up with everything except the motor phases connected, upright it, and spin the tire to demonstrate that wheel speed is being measured smoothly (hall sensor check).
 

Bear in mind that a frequent issue with RS is bearing fit (mounting slop), not actual bearing wear nor corrosion. The bearing races may be moving in and out of their mounts on the hub and sidecover, due to improper dimensions of those parts...
 

If one of those loose wires were to become cut, it's not likely to result in cutout nor crashing- because these motors use (about 10) parallel conductors for the phase windings, and so the other parallel wires would still work.

(But it's still bad.)

 

Aargh. You appear to be correct. Maybe bearing slop. My motor guy did take a look at it and it does not appear to be a magnet- there are some wires that appear a little crushed, but whatever. It should work. He is going to put a little voltage through it and do a couple more tests. Then I am going to bring him the new bearings and he is going to install them. Then I will bring him a case of beer and pick up my motor. 

 

I had measured across for resistance with my Fluke thinking it would be better than my amprobe and got open on all. That said, I bought this model for working around 600V AC and not because it was good for much else... (there is only one setting for resistance. I really should have considered that.) But Terry is checking that as well before I see him tomorrow.

 

In short, it appears to be the main board (pun intended...) 

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Posted (edited)

When it comes to resistance, open circuit or closed... Who can tell the difference? Obviously, the circuit was closed and not open as I had mistakenly typed out above. But the Fluke could not measure the resistance.

 

Anyhow, bearings done, and now waiting on the board. But I have one last question. If I plug in the hall sensor- what am I looking at to be sure that it is correct? Am I simply measuring the voltage at the motor output plugs?

 

The more I think about it- the more I question the sensor. When I turned it on (before it released the magic smoke), it "cracked" like gears were slipping- very loudly. Of course, there are no gears. It was not trying to move forward or back in my hand that I felt- but could it have been slamming itself just a little forward and then a little back at high voltage, and could that be related to the hall sensor? Maybe. Or maybe it is time to just accept that it was the board. But if there is an easy test- I would like to do it...

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The hall sensors sense the position of the wheel, and any ongoing issues with them or their cabling tend to just make the wheel try to change the horizontal position very abruptly. Usually the fw recognizes this as an error and will turn off the motor with beeping and an error code.

 But the windings really are bad. Two pinched coil wires are enough to create a short. I would definitely put the rogue windings back in their place, with coil varnish or epoxy if need be.

 What the first photos made me think though was an actual physical short. I have seen rogue solder blobs on some GWs, and if there was one on the heat sink when you assembled the board, that could’ve caused the board to fry.

 

 The coils themselves can be measured by the resistance between the motor main wires as you turn the wheel, and the hall sensors can be measured from their connector when it’s plugged in and powered on. The five cables are common +, common -, and an output for each of the three sensors. The outputs switch between 0 and 5V in relation to their common ground as you turn the wheel. The motor main cables need to be unplugged as you measure.

 As you are measuring the hall sensor outputs, I’d also measure the voltages on the board at the unplugged motor outputs, which I understand you did before as well.

 

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9 hours ago, DWOTR said:

If I plug in the hall sensor- what am I looking at to be sure that it is correct?

I was suggesting: 

  1. (Leave the 3 motor phase wires unplugged)
  2. Plug the sensor connector into a working control board, and turn it on.
  3. Upright the EUC (with board installed), and spin the tire manually.
    If the hall sensors are working, there will be no error beeps, and your smartphone app will show the wheel speed.

Also if you unplug the sensor connector while the EUC is on, it should cause error beeps- good to recognize what those are, as you're ruling things out.

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Thank you both for your help and expertise. I will pick up the wheel (motor) on Tuesday and then just need to wait for the board. I will update once everything is installed.

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I can almost guarantee you mixed up the order of the phase wires. That explains burning a mosfet and the quick twitch of the motor. Did you take a picture before disassembly?

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On 5/21/2021 at 6:28 PM, DWOTR said:

Thank you both for your help and expertise. I will pick up the wheel (motor) on Tuesday and then just need to wait for the board. I will update once everything is installed.

You can't really mix up the hall sensor wires. They only plug in one way. The phase wires can easily be plugged in wrong however. And will definitely burn up a mosfet with any current applied to the motor windings (phase wires) when in this state. 

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Posted (edited)
On 5/24/2021 at 2:54 PM, Killian253 said:

I can almost guarantee you mixed up the order of the phase wires. That explains burning a mosfet and the quick twitch of the motor. Did you take a picture before disassembly?

I wrote the order in my notebook and transferred it directly on the wheel bearing cover in red paint marker for any future disassembly along with one alignment mark for the cover vs. the rim on one side and two on the other side to keep track of which cover goes on which side. I doubt assembly position matters in this case- but I'm used to doing that for industrial equipment.

 

I also checked several disassembly videos after it burned up wondering the same thing. All the videos have the wires in the same order that I wrote in the notebook and on the cover (Everything is at work and don't recall the order offhand.) Nope- they were plugged in the correct order... But I appreciate the thought- I had wondered the same thing. Enough to go over several youtube videos looking for confirmation of their order.

 

*Edit- I looked at the picture I posted earlier on in the thread. It looks like I had it as Yellow, Blue, Green...

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4 hours ago, DWOTR said:

Yellow, Blue, Green...

that's correct, yellow close to the battery plug

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1 hour ago, Jia Liu said:

For your reference. It's for the new black board, but the motor wire order should be the same.

image.png

That’s a way better board than the one I got. I just recently changed mine with a black board but it didn’t have that heatsinks by the fets but I’d did come with a inline fuse. I’d put up a photo but I’m not sure how. 

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