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Msuper v3 top speed crash - wrecked shell


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7 minutes ago, Chriull said:

Imho thats not possible. These actual high power wheel limit the current/power at low speeds to prevent the mosfets from dying. So they never reach the stall torque of the motor.

You are correct on this. I was drawing a limit chart included the board limit. As a mater of fact, the current limit is mainly to avoid the damage to the motor.

 

10 minutes ago, Chriull said:

On the other end of the chart (at least some of them) seem to never reach the no load speed. Someone here (imho @KingSong69) reported from one wheel (?ACM16 or Msuper V3?) that the lift-cut-off speed stays constant for full battery and battery with low charge - and this cannot be true for the real no load speed. So imho this wheel at least cut of by a fixed speed programmed in the firmware...

Could be the app's limit. The needle stops at 50 km/h always, but the digits not.

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5 minutes ago, Cloud said:

Why cant they gradually ( but still quickly) bring the wheel into the stalled condition ( by applying additional loading) until the wheel/ magnets start slipping

Because the electronics will limit the current and by this (current is directly proportional to the torque) one will never reach the stall torque of the motor.

5 minutes ago, Cloud said:

but the fuse wont burn yet as it requis a certain time to burn? Alternatively why cant they bypass the fuse for the purpose of the test?

They could bypass the fuse, but then its very likely that the Mosfets will die.

If you take another look at my chart (also it is for a hypotetical wheel since i don't know the exact characteristics of any real wheel) it could be hard to reach any point of the torque/speed limit line in reality.

One has the current limiting for low speeds. At medium speeds there is a power limit, and then there is a cut-off speed... Maybe inbetween there are same "leaks" within the firmware limit, where the motor limits could be "touched"

.... and if the test take to long the wheel shuts off because of over-temperature... ;)

1 minute ago, zlymex said:

You are correct on this. I was drawing a limit chart included the board limit. As a mater of fact, the current limit is mainly to avoid the damage to the motor.

And imho also to protect the mosfets?

1 minute ago, zlymex said:

 

Could be the app's limit. The needle stops at 50 km/h always, but the digits not.

Interesting idea - so this test should be repeated with the wheellog app! Unfortionately i don't remember exactly who tested with which wheel ;(

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@Chriull @zlymex. Ok, but why will they even need the stall torque and the no load speed points to establish the curve? If we assume the curve is a straight line, why cant they just test/ derive any 2 points on the curve and extrapolate the curve to find the stall torque and the max no load speed?

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3 hours ago, Chriull said:

You think you could implement some (maybe simplified) simulation like this in 9BMetrics to predict (possible) overleans and release a warning in time? Or is this already the reason you made the simulation, to identify "dangerous states" which will rise warnings in 9BMetrics? 

I think it is possible to detect dangerous states but usually the user is the one who must control it. You must know the future :)

For example I did the situation that has been talked in this thread, a descent and then a climb.

I selected a drive (a lean) that from stop would give you a constant speed.

Nothing here dangerous (2% descent, 1.5% climb, nothing near the speed but...

As you see, you increase speed in the descent to say 18 km/h and then begin to climb pushing harder just to maintain speed.

But just then the controller is not able to maintain speed as there is not enough torque at 18 kmh

So it is very difficult for an application to find dangerous situations because you must know there is a climb afterwards, etc. But you know it and if you are consciente of the situations which may be dangerous you may reduce speed before the climb. Just the opposite as if you go in a bike where you speed more to climb without effort. Here that is dangerous.

So the idea of the simulator is being able to detect situations that may be dangerous without the need of chrashing.

It needs some effort to set the parameters more exactly and built a good user interface but may be a good preventive tool.

down_up_word_pdf.pdf

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8 hours ago, Paco Gorina said:

In word format t in this link. Better graphics

http://www.gorina.es/9BMetrics/physics/english.docx 

As far as I understood the higher is your torque reserve the lower the risk to faceplant due to high acceleration or load increase such as steep hill or bumping or strong wind. So if I have two wheels one 800watt and another 1600watt both limited to let's say 30kmph, if their curve (torque,speed) are parallel whatever the torque limit of the 1rst wheel the second can have the double of torque limit provided the electronic can handle the double of current, imo the HT wheel is a safer wheel than an HS wheel, is it?

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I would say yes. But we should see the rest torque and the unloaded speed. Speed limitation is usually inferior and made by the software. And motor characteristics may be different. Power depends of the product of Torque by Speed at some point.

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Yes if we get into the tech details, but I wanted to point out a concept as new powerful wheels are getting out.

To make it simple with more power you can have more safety and you can have it by paying the price on speed, while if you want speed .....

Edit: btw "with more power ...." sound like spider man movie :) 

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28 minutes ago, EricGhost said:

....

To make it simple with more power you can have more safety and you can have it by paying the price on speed, while if you want speed .....

...

One can, or one drives a bit faster and has comparable safety and worse results in case of an accident..  ;(

 

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@nomad Just wanted to thank you for posting up the crash video.  I didn't want to come across as all preachy and whatnot, but often I do.  :rolleyes:  I think we're all glad to hear that you are safe and do sympathize with you for your crashed wheel.  Hopefully it just needs a new case replacement or some epoxy repairs.  I think these crashes just bring out the ohmigod :o response in me when I see a nice, speedy, powerful wheel end up dumping a rider.  It's good though that it does bring up healthy discussion of the consequences of getting too close to that upper limit which isn't a clearly defined point but rather a variable speed which depends on battery, rider weight, riding conditions, etc.

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In the end I feel it doesn't matter much if the wheel cuts off at 45 or 50 km/h, as long as it warns you with a proper margin before that can happen, and I think it does in normal use. What really matters is what it can do safely without beeping. I knew a cut off around 45 km/h was a risk however I still thought this wheel could do 50 km/h. But it seems hoping didn't cut it for me, so out there in the moment I saw the coast was clear and the little devil on my shoulder said to me, just try it! Right after the crash I felt stupid and almost decided to not post the video, now I feel better about doing it.

I've got a price on a new shell and am thinking about repairing it or even selling the wheel as is. I've been busy and didn't have time to deal with this yet. The shell cracked a little along the top of the handle, more towards the back, the trolley was broken and the little rubber mudflap ripped off because of the split casing. Towards the front the head light hangs loose on one cable. The power button / USB port / charging plug and the pedals are all ok, tail light was not broken either.

I've actually not used the wheel since Sunday (crash day), I'm using my V5F+ instead and that's a better choice for my current everyday uses so I'm not sad really! My 2013 Moto X phone used for the recording only got some extra scratch marks in the corners and a tiny dent on the side, maybe a couple of very tiny scratches at the edge of the screen now that I inspect it, not sure if those were there before, no real issues. Just need to get some new clothes this weekend though, I did quite some gliding on my back there.. I've been needing to get a bigger backpack anyway so can't put off the shopping any longer now!

Anyway, just some material replacements needed here, nobody was really hurt so it ended ok this time. But of course falling at that speed should be taken seriously it could have ended much worse! I just still chuckle when I think about that moment, standing like a champ riding a single wheel passing 45 km/h - suddenly pedals go loose...

It's nice to know you people care and there's so many good points made, different viewing angles and lots of knowledge, it's great to see!

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You're a good sport for posting that up and putting up the video as a cautionary tale for others.  I often have two devil's sitting on my shoulders so I definitely know the feeling of okay let's do this even though it might not be the best idea!

It must have felt terribly embarrassing to crash and have that nice new wheel all cracked up.  :(   There's some repair threads in the Mod and Repair forum where people use some acetone and Lego blocks to make a plastic bonding material to fix plastic.  There's also some epoxy repair compounds that might help.  Maybe bonding some automotive fibreglass strips to reinforce the cracked areas underneath might help.  I am surprised that your MotoX survived that tumble!  That's pretty durable.

Anyways have a good weekend and safe riding! :D

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1 hour ago, nomad said:

Right after the crash I felt stupid and almost decided to not post the video, now I feel better about doing it.

Never feel stupid or ashamed for sharing your mistakes. Its a noble act that shows true strength of character. EUCs are in their infancy and unless faceplants are made physically impossible, there will always be someone out there who pushes the upper limits over the edge. My self and others have learned a lot and will take greater care after watching your video. I'd guarantee that you will have saved a few people in the future from serious injury or worse after seeing what can happen when these wheels fail. For that I thank you. 

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5 hours ago, 16bitSprite said:

Never feel stupid or ashamed for sharing your mistakes. Its a noble act that shows true strength of character. EUCs are in their infancy and unless faceplants are made physically impossible, there will always be someone out there who pushes the upper limits over the edge. My self and others have learned a lot and will take greater care after watching your video. I'd guarantee that you will have saved a few people in the future from serious injury or worse after seeing what can happen when these wheels fail. For that I thank you. 

@nomad More people see your post and learned a lot from the lessons learned video than indicated by the "likes" . Thank you from me and others not revealed. Glad you in one piece.

 

 

 

 

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On 10/13/2016 at 7:21 PM, HunkaHunkaBurningLove said:

It's good though that it does bring up healthy discussion of the consequences of getting too close to that upper limit which isn't a clearly defined 

This topic is a very healthy discussion and I am so happy @nomad was not injured. Be safe!

Unfortunately what is missing from this topic, and the other crashes or face plants stories discussed on this forum is the direct input from R&D and design engineers employed by Gotway, King Song, In motion and Segway, etc!

This forum has over 3000 members. In my opinion, this is a large enough audience to command that EUC manufacturer corporate executives provide our forum members occasional Q&A sessions with their engineers!  We need to get past the current paradigm that we are just a bunch of willing ginnea pigs performing ongoing safety and performance tests for these manufacturers every time a new wheel enters the market.  

There needs to be a conduit that provides a method for forum members to submit their questions directly to the manufacturer engineers. This conduit could consist of a designated group of 4 or 5 forum members. This special group should be proficient in EUC control dynamics and parameters, software firmware, control logic, inertial measurement, lithium ion batteries and power distribution to name a few. We are all of aware that there is a vast number of members that would meet or exceed these high standards! 

Additionally our group of experts representing us should be given a prestigious title that symbolizes strong solidarity, something like DEUCE (Designated Electric Unicycle Engineers)... just an idea?

In my opinion wheel manufacturer CEO's may be recalcitrant to provide representation on this forum due to legal repercussions or they just feel they do not have the resources to answer all of member's questions as a whole. Having our own select group of representatives submitting forum member questions to EUC manufacturer engineers in a highly technical context might open the doors for increased dialogue.

otor. The main 

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  • 11 months later...
On 11.10.2016 at 4:50 PM, Chriull said:

This was the graph for a fully charged battery at 67.2V. The same graph for 57V:

Nice graphs, thank you!
Did you consider, that with high current, the voltage will drop? That might have a severe effect for EUCs with less capable batteries.

 

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17 hours ago, caelus said:

Nice graphs, thank you!
Did you consider, that with high current, the voltage will drop? That might have a severe effect for EUCs with less capable batteries.

 

The "normal" voltage drop of a non ideal voltage source is considered (modelled by an ideal voltage source plus the internal resistance). But the additional voltage drop of batteries (by their chemistry) which partly recovers again not.

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