The Gotway Gods Destroyed My ACM

[Xima Lhotz]

4 hours ago, who_the said:

Relieved you are OK, Marty. Your wheel will be better than new soon, ready to roll for many more miles.

Reality dictates that our wheels have limits. My MSV3 1300-84W overheated close to 70º C during a steep climb on a public road (Quinby Road) toward Mt. Hamilton on a group ride last month. I was able to complete the ride, and my temperature never got anywhere near the peak on the rest of our ride. But when I got home and inspected my wheel, the solder joints before my board had clearly boiled and melted, but (thank goodness) had not breached. Other wheels on the ride did not reach the temps my wheel did. My reseller (Tec-Toyz) repaired the damaged wire and replaced the soldered connectors. On a hilly ride last weekend my temps got nowhere near overheating.

Be safe everybody.

Did it throw you off or did it beep and forced you to stop?

 

A perfect example of the board coped with the overheat situation perfectly (if it didn't throw you off) but the wires aren't up to the task at hand even with the 84V version. (no surprise there)

(Oh, so that tape and plastic sleeve is Ok for 200C is it, as the silicon cables? If designing around a 200C cable then ALL components must handle 200C in that chain) My guess is that the sleeve of the motor cable is not silicon and so that has an even lower temp rating.

This situation has alway been about the cable and will continue to be about cables ( the solder melted in the connectors due to heat from the cable (16awg motor cable)

The bullet connectors are fine, and are much larger than 14 awg and can easily handle the current (have not sen spec so guesswork based on size).

Even with the "new and future proofing 14AWG motor cable" it will fail inside the motor cable where the cables touch in these situation, they are not in "free air". Or in the connectors/solder depending on the current in the cable and sourrounding temp.

Its so easy to calculate the size of that cable according to current, and heat!

 

A rider should NEVER EVER have to care about what the wheel does, then its always "Well I think this is fine, but you say its not" situation. Account for outside temp, previous hills, omg that its just not how it should work. And the constant worry "is this the hill, must i slow down, have the wheel been in the sun". Not a comforting enjoyable ride.

 

The wheel warns if its to hot and forces a stop, and so the cables and connectors must be designed around the maximum continous output from the control board.

End of story, problem solved.

 

[meepmeepmayer]

There's no excuse for constructing a wheel that can put out 60A or more with wires that are meant for 20A or 30A. Obvious what will happen if you have constant currents higher than that.

There's no excuse for constructing a car that can go 250 km/h and use tires that burst at 80 km/h. Obvious what will happen if you constantly drive faster than that.

The "oh the wheels aren't meant for that" people are missing the point. Nobody complains the wheels can't do everything. The problem is, the wheels won't tell you if they can't, they break instead and crash you. That's simply a complete design failure, especially for a single-point-of-failure device as a self balancing, one wheeled ridable. No need to excuse that.

[US69]

11 hours ago, jrkline said:

. @Marty Backe's failure is the first time I have actually seen the wires melt the insulation on the wires coming from the control board not due to a connector failure/fault.The wires on the motor side have a higher heat rated insulation and have never been reported to have melted the insulation to the best of my knowledge.I'm going to replace the board side motor wires on my ACM to circumvent any possible "BrokeBacke" experiences in the future.I don't think that it is fair to blame Gotway for all of these failures.After all,extreme hill riding is not exactly how EUC's are designed to be used.Those of us who choose to use them in extreme or cutting edge ways know this as does @Marty Backe.

Unfortunatly that had not been the first time we had seen melted wires here..  @meepmeepmayer 's wheel had the exact same failure, completly melted and shorted wires and it seams for me this is a General design fault and whom  to blame if not Gotway? Now after all the connector failures it seams to work out, that not the connector was the real culprit in These failure series, they were just -before the connector changes-  the weakest part in the wiring harness. Now it Shows up that the 14AWG wire after the board the whole time was the real weak Point......

Marty is a very light Person, and even if he was going on an extreme hill in this Situation, the ACM -Gotway claimed that it can carry a 100kg Person and that on up to 30° hills......So at which degree and what weight are the ACM's  "allowed" to fail then?

A heavier rider might have had this failure on a much less steepy hill...And if 14AWG wires are 20Amp capable or 15, what does that matter if GW/ACM is pushing up to 60Amp through it?

Dont get me wrong, i love my Msuper V3, it's a nice machine, but to have this failures in mind/brain on every Kind of Little steeper hill? That really sucks.....And to top up the cake with a nice cherry Gotway now send out a Batch of wheels with a "bump cutout" automatic :-)

[DaveThomasPilot]

Sorry dude you're just wrong

On 6/19/2017 at 11:11 PM, Carlos E Rodriguez said:

No. All wrong. Motors are special animals and although the V=I*R principles are relevant, it is not adequate to make the inferences you make. This is because a motor has inductance, capacitance and resistance. Or reluctant since and resistance. As such the calculations are different that just using a purely resistive circuit. 

The motor is also a generator. So when it starts to spin it generates a voltage inversely proportional to the battery voltage applied to phase-a,b,c. The controller only applies enough current to the motor coils to induce enough torque to counter the tilt angle induced by the rider. 

So that being said, if I am going at fixed speed, fixed wind resistance and fixed grade the amount of current through the Motor will be the same no matter if the battery volts is 80 or down to 50.

so please understand motors before making stammers that are incorrect. 

Well I'm electrical engineer and designed power conversion products for decades.

Things like inductance and capacitance change the the in-and-out power  over their relatively short time constants.  But not over time periods long enough to be consistent with thermal time constants.

For AC Motors, (motors with AC input voltage) you can talk about power factor which is due to the phase difference between the voltage and current sinusoidal waveforms. So input power is not the RMS input voltage X input current.but that would just cunfuse what we're talking about here.

For the purposes of thermal analysis you can  use  average input and output power

It's pretty easy to demonstrate that the average input current must. vary if the average input voltage does ( assuming a constant load, like your example of going up a hill at a constant speed.)  Going down the hill is a negative load we have negative current from the battery (current going into the battery).

If you think the  average current doesn't change when the voltage is lower, where does the difference in input power go?

Boost and buck Regulators are good examples and a little easier to understand and motors. There are internal ripple currents and non Dc voltafend analysis you can do to determine duty cycle  for a given input and output voltage But always.

For motors  and switching regulators It is true that the current when the switches (FETs) are on doesn't very (much)when the input voltage changes. But the duty cycle (the time the Fets are on) does!

Lower voltage means longer duty cycle which is why the average input current increases.

 

[DaveThomasPilot]

8 hours ago, meepmeepmayer said:

There's no excuse for constructing a wheel that can put out 60A or more with wires that are meant for 20A or 30A. Obvious what will happen if you have constant currents higher than that.

There's no excuse for constructing a car that can go 250 km/h and use tires that burst at 80 km/h. Obvious what will happen if you constantly drive faster than that.

The "oh the wheels aren't meant for that" people are missing the point. Nobody complains the wheels can't do everything. The problem is, the wheels won't tell you if they can't, they break instead and crash you. That's simply a complete design failure, especially for a single-point-of-failure device as a self balancing, one wheeled ridable. No need to excuse that.

I absolutely agree with your point here. But for temperature rise in the wires, you have to consider what percentage of the time they're conducting that 60 amps.  Not sure if the wires in question were running that current at 100% duty cycle?

So you need to know the average current in the wires. You also need to know the peak instantaneous current for voltage drop considerations.

 

[DaveThomasPilot]

So that being said, if I am going at fixed speed, fixed wind resistance and fixed grade the amount of current through the Motor will be the same no matter if the battery volts is 80 or down to 50.

I suggest we have a different thread to discuss this, hopefully keeping it strictly technical and dispassionate. 

But, I do think it is a very important thing to understand, so I'm hesitant to "just let it go". 

I'll start the thread off and others can follow if they are interested.

[Marty Backe]

6 minutes ago, DaveThomasPilot said:

 

 

I suggest we have a different thread to discuss this, hopefully keeping it strictly technical and dispassionate. 

But, I do think it is a very important thing to understand, so I'm hesitant to "just let it go". 

I'll start the thread off and others can follow if they are interested.

What's the fun if we can't have passion 

[meepmeepmayer]

1 hour ago, DaveThomasPilot said:

I absolutely agree with your point here. But for temperature rise in the wires, you have to consider what percentage of the time they're conducting that 60 amps. 

If the wheel (batteries) can produce some current constantly, it needs to be considered. You design for worst case, not average. Either by bigger wires (or maybe some cooling solution/heatsink for the wires? Not sure how that could look and if it would make much sense...), or by the wheel stopping you with 100% guarantee and saying "Hey, keep it down!". Preferably the first, if you have the battery power for higher inclines/weights, why not make it usable? (assuming the rest of the wheel can keep up)

As soon as the manufacturers design their own motors without the thin e-bike part axles, I guess using arbitrarily big wires will be no problem at all. That's simple and cheap. So the ultimate issue are these thin axles. In the end, this problem and its solution seem to be quite simple.

Starting at the post in the link, some nice pictures of EUC specific motors by the Rockwheel guy, showing where the journey needs to go: click.

1 hour ago, DaveThomasPilot said:

You also need to know the peak instantaneous current for voltage drop considerations.

This is a completey different topic, but what exactly do you mean? Voltage drop causing cut outs? Blowing mosfets? What does it do? Would be happy to hear more. (Maybe some other thread if this is too offtopic,)

[Hunka Hunka Burning Love]

16 minutes ago, Marty Backe said:

What's the fun if we can't have passion 

That's right!    This is what I tell all my first dates!    Strange though why there seem to be no second dates.  

[meepmeepmayer]

6 hours ago, KingSong69 said:

Unfortunatly that had not been the first time we had seen melted wires here..  @meepmeepmayer 's wheel had the exact same failure, completly melted and shorted wires and it seams for me this is a General design fault

For the interested: the (old 16AWG) wires and the old connectors (now replaced by unproblematic connectors) are approximately the same strength. Whether one or the other fails is close to each other. Here's a post with the connector problem where the wires were really close to shorting (heat damage starting), too. So the (now fixed) connector issue just hid this issue of too hot wires:

The newer 14AWG (~30A) wires will be better, but in the end 30A still isn't enough if the wheels can produce a higher constant current.

[DaveThomasPilot]

1 minute ago, meepmeepmayer said:

If the wheel (batteries) can produce some current constantly, it needs to be considered. You design for worst case, not average. Either by bigger wires (or maybe some cooling solution/heatsink for the wires? Not sure how that could look and would make much sense...), or by the wheel stopping you with 100% guarantee and saying "Hey, keep it down!". Preferably the first, if you have the battery power for higher inclines/weights, why not make it usable? (assuming the rest of te wheel can keep up)

As soon as the manufacturers design their own motors without the thin e-bike part axles, I guess using arbitrarily big wires will be no problem at all. That's simple and cheap. So the ultimate issue are these thin axles. In the end, this problem and its solution seem to be quite simple.

Starting at the post in the link, some nice pictures of EUC specific motors by the Rockwheel guy, showing where the journey needs to go: click.

This is a completey different topic, but what exactly do you mean? Voltage drop causing cut outs? Blowing mosfets? What does it do? Would be happy to hear more. (Maybe some other thread if this is too offtopic,)

Maybe another whole section on brushless motor power and efficiency analysis, but briefly---

Some of high current paths don't conduct the current 100% of the time.  The speed controller is probably running around 100 Khz, or at least 10's of Khz.

So, the off and on times are in the sub-millesecond range.   For thermal analysis, you average those together, or if the current is on D (duty cycle) part of the time and off the rest of the time (1-D), then you just multiple the current times the duty cycle.

However, for calculating voltage drops, you use the maximum instantaneous current in the wire/FET/connector when its conducting--it helps not at all that isn't conducting all the time.

 

 

 

(Very) sim

[meepmeepmayer]

Thanks. Looks like more details really are for another topic.

About thermal analysis, I'm wondering if (simply due to the wire geometry) even bigger wires can melt (collect enough heat) if the heat can't dissipate fast enough. So even bigger wires might not help? In the end, the heat is there so where can it go?

[DaveThomasPilot]

Wires have a rated ampacity for a given temperature rise.  Here's an example:

https://www.powerstream.com/Wire_Size.htm

There are additional tables for bundles of wires together. 

Also, different wire insulations have can widely varying allowable wire temperatures--if you know the specific wire used, you can determine how much current the wire can handle without compromising the insulation.

Quote

In the end, the heat is there so where can it go?

The insulation will likely melt or be destroyed before the wire acts like a fuse.  The copper in the wire is a really good conductoer of heat (far better than the thermal path through the insulation), so much of the heat will be conducted to whatever the wire terminates on.  Typically a heat sink on the control board.

The motor windings might get a lot of airflow--I have no clue about that.  But, if they do, that convection would be excellent for dissipating much of the heat.

I'm not looked at the motor in EUC, so I don't know any real details, just general principles.

 

[meepmeepmayer]

Thanks! Uh yeah, that table, I've seen it before

Does this mean, using big wires is most likely enough to solve this problem, as the heat will go away then? Great!

[DaveThomasPilot]

Here's a thread I started after being challenged by my assertion that at a given output power (like going up a constant slope at a constant speed), more current will result than at a higher voltage:

 

[DaveThomasPilot]

1 minute ago, meepmeepmayer said:

Thanks! Uh yeah, that table, I've seen it before

Does this mean, using big wires is most likely enough to solve this problem, as the heat will go away then? Great!

yes.  But, there may be another weak link that pops up.   Needs to be tested for a rated continous power!

[Rehab1]

On 6/19/2017 at 0:11 AM, Marty Backe said:

Yes, maybe the new motors are better, but I think their existing wiring harness still scares me a little. They needs bigger axle wheels so that they can use beefy wires and lots of heat insulation. I still feel fine about my Gotway wheels under less strenuous conditions.

OK, so you've hinted at your problems in this thread twice. I'm now off to find what misery you've written about elsewhere. I may be afraid to look 

WOW...Do I need to catch up! It sounds like you are going to splice together new motor wires. That should work! Use a 14 or 12 awg silicone wire where you spice. Given all of the wire melting issues I wished I could have finished my ACM mods with the silicone wire. GW should use the same 14 awg silicone wire coming out of the board for the motor which would then have less resistance (= less heat), a higher temperature insulation rating (200 degrees c) and 10 times the number of strands! Just look at the comparison between of 14 awg standard wire and silicone! 

The new 14 awg standard motor wire that GW upgraded to, in my opinion,is still suboptimal! . Given all of the melted wiring issues that have been taking place if I had the guts I would rip my new GW motor apart and replace it with the silicone wires. Unfortunately it is such a tight fit feeding all of the wires through the shaft!  GW needs a larger axle!

 

If you do splice the motor wires it might be prudent to go with the silicone. Also check closely where the wires enter the shaft. Remember that I had some rough burrs. The new GW motor wires are wrapped.

Another thing to consider when replacing your wires and board is upgrading the bullet connectors to 4.5mm. The current bullet connectors are only 3.5mm. The less resistance the better!  I was going to use a hefty 5.5 mm bullet connector but they were too large!. Well good luck buddy!

 

 

[Marty Backe]

37 minutes ago, Rehab1 said:

WOW...Do I need to catch up! It sounds like you are going to splice together new motor wires. That should work! Use a 14 or 12 awg silicone wire where you spice. Given all of the wire melting issues I wished I could have finished my ACM mods with the silicone wire. GW should use the same 14 awg silicone wire coming out of the board for the motor which would then have less resistance (= less heat), a higher temperature insulation rating (200 degrees c) and 10 times the number of strands! Just look at the comparison between of 14 awg standard wire and silicone! 

The new 14 awg standard motor wire that GW upgraded to, in my opinion,is still suboptimal! . Given all of the melted wiring issues that have been taking place if I had the guts I would rip my new GW motor apart and replace it with the silicone wires. Unfortunately it is such a tight fit feeding all of the wires through the shaft!  GW needs a larger axle!

 

If you do splice the motor wires it might be prudent to go with the silicone. Also check closely where the wires enter the shaft. Remember that I had some rough burrs. The new GW motor wires are wrapped.

Another thing to consider when replacing your wires and board is upgrading the bullet connectors to 4.5mm. The current bullet connectors are only 3.5mm. The less resistance the better!  I was going to use a hefty 5.5 mm bullet connector but they were too large!. Well good luck buddy!

 

 

Hey @Rehab1, nice to see you again  

No, I'm not planning on splicing new wires to the motor. I'm not crazy like some people around here 

I'm still waiting to hear from Ian. I know that I need a control board, but I may be getting a new motor too since I see evidence of melting/softening insulation on the wires closer to the axle. If I get a motor/control board combo I'll just go with the defaults. If I only get the control board and decide not to pursue a new motor then I'm going to solder the wires together and bypass the connectors altogether.

[who_the]

14 hours ago, Xima Lhotz said:

Did it throw you off or did it beep and forced you to stop?

Neither. Wheel never beeped or stopped working. Did have a strong smell of electrical mischief though.  We pulled over for a few minutes until it cooled down. The wheel was good for another 35 miles of riding that day. Possibly not my wisest decision to keep going, but... We made it.

[Rehab1]

3 hours ago, Marty Backe said:

 

I'm still waiting to hear from Ian. I know that I need a control board, but I may be getting a new motor too since I see evidence of melting/softening insulation on the wires closer to the axle. If I get a motor/control board combo I'll just go with the defaults. If I only get the control board and decide not to pursue a new motor then I'm going to solder the wires together and bypass the connectors altogether.

If Ian does not have the main board and motor @Jason McNeil will set you up. I would like to know what changes have been made to the most recent batch of GW motors besides the upgrade to the 14 awg wires.

[Marty Backe]

1 hour ago, Rehab1 said:

If Ian does not have the main board and motor @Jason McNeil will set you up. I would like to know what changes have been made to the most recent batch of GW motors besides the upgrade to the 14 awg wires.

I'll post updates to this thread as I fix the ACM.

[TremF]

6 hours ago, Marty Backe said:

Hey @Rehab1, nice to see you again  

No, I'm not planning on splicing new wires to the motor. I'm not crazy like some people around here 

I'm still waiting to hear from Ian. I know that I need a control board, but I may be getting a new motor too since I see evidence of melting/softening insulation on the wires closer to the axle. If I get a motor/control board combo I'll just go with the defaults. If I only get the control board and decide not to pursue a new motor then I'm going to solder the wires together and bypass the connectors altogether.

 

3 hours ago, Rehab1 said:

If Ian does not have the main board and motor @Jason McNeil will set you up. I would like to know what changes have been made to the most recent batch of GW motors besides the upgrade to the 14 awg wires.

Looking at Ian's website it looks like he has stock of both the motor and board (if it's the S+ board that's required). 

I saw on another post that someone was being sent an MSuper V3(S+?) board for their ACM(S+)? If it works is it worth the try? Looking at the two boards on Speedy Feet they do look very similar if not the same.

[Marty Backe]

8 minutes ago, TremF said:

 

Looking at Ian's website it looks like he has stock of both the motor and board (if it's the S+ board that's required). 

I saw on another post that someone was being sent an MSuper V3(S+?) board for their ACM(S+)? If it works is it worth the try? Looking at the two boards on Speedy Feet they do look very similar if not the same.

Thanks. Right now I'm being patient. I assume some activity is occurring in the background with Ian and eventually I'll find out what's up. Or maybe a package will just show up at my front door.

[TremF]

1 minute ago, Marty Backe said:

Thanks. Right now I'm being patient. I assume some activity is occurring in the background with Ian and eventually I'll find out what's up. Or maybe a package will just show up at my front door.

Have you emailed him through info@speedyfeet.uk ?

I contacted him after my battery arced Tuesday evening and he responded mid morning yesterday. I sent a few emails yesterday and he responded to all that required a response. Depending on what time you contacted him it's currently 7:23am here so you can work out the time difference.

I hope you get it sorted soon but at least you have a few to fall back on in the meantime  

BTW my Monster looks great with the shiny new purple shell I can't wait to get it back & ride it again  

[Marty Backe]

21 minutes ago, TremF said:

Have you emailed him through info@speedyfeet.uk ?

I contacted him after my battery arced Tuesday evening and he responded mid morning yesterday. I sent a few emails yesterday and he responded to all that required a response. Depending on what time you contacted him it's currently 7:23am here so you can work out the time difference.

I hope you get it sorted soon but at least you have a few to fall back on in the meantime  

BTW my Monster looks great with the shiny new purple shell I can't wait to get it back & ride it again  

Yes. I didn't mean it to sound like Ian's not doing anything. He asked for my motorcode and opened a ticket, on Monday. I'm just waiting for the next step.

Glad you got your new shell back. Hopefully that first accident was a fluke and it'll stay pretty. Where is it? Did you opt to have Ian or someone else do the work?