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redfoxdude

KS16X Cutoff/Overlean - 29-30mph

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15 minutes ago, redfoxdude said:

I do think this is somewhat related to the previously documented reduced torque at higher speeds, and I certainly hope it could be improved with firmware updates.

It's not somewhat related, it's 100% absolutely related to EUC Physics 101 that has been discussed quite intensely recently. See e.g. this and links from there:

The manufacturer cannot do anything to circumvent the laws of physics.

Edited by Aneta

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17 minutes ago, redfoxdude said:

I don't recall even feeling the tiltback.

When speed is too close to "terminal", the wheel physically cannot do a tiltback, because for that it needs to spin faster under the same load to get ahead of the rider, but it can't, because the thrust margin is already pegged at near zero. Fully expected.

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@Chriull Yes, the back emf certainly reduces the available torque as speed increases. I would have hoped that King Song selected a battery/motor combination that yields enough torque at the desired top speed to maintain a good safety margin.

@Aneta I think you misunderstand. I feel that the hardware was not actually operating at or quite near its limit, and that, if the firmware commanded, there could have been more thrust. Utilizing more of the wheel's capable power is not circumventing the laws of physics. Thanks for your concern for my well being, though.

Edited by redfoxdude

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1 minute ago, redfoxdude said:

I am confident that the hardware was not actually operating at or quite near its limit, and that, if the firmware commanded, there could have been more thrust.

What exactly is this confidence backed up with, in technical terms (like log data)?

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Sorry this happen and I'm glad you are okay.  You are doing the right thing by lowering your tilt-back and warning and I would suggest 26mph.

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16 minutes ago, redfoxdude said:

I would have hoped that King Song selected a battery/motor combination that yields enough torque at the desired top speed to maintain a good safety margin.

Choosing a certain tiltback speed is a compromise - there always will be cases it cancels too "early" and cases one overleans without tiltback ...

Time will come (hopefully) when more sophisticated warnings will be implemented.

16 minutes ago, redfoxdude said:

I feel that the hardware was not actually operating at or quite near its limit, and that, if the firmware commanded, there could have been more thrust.

How to feel such if its near the limit? To get a real picture one should draw a current over speed diagram.

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Dang, sudden beeping heart attack and dropped you on the floor.  Glad you're okay!  My 16X w/1.05 is configured to last alarm/tiltback at 25 mph iirc.  What version control board you have ... I hear that you were using BT music.

Edited by xorbe

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Could you write you weight please? And if possible with and without gear?

Is everything ok with your wheel after crash is it functioning ok?

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51 minutes ago, redfoxdude said:

I would have hoped that King Song selected a battery/motor combination that yields enough torque at the desired top speed to maintain a good safety margin.

For given motor/controller/battery, that's just not arbitrarily possible (unless the manufacturer is intentionally throttling the system down). Back EMF is only determined by speed, nothing can be done about it. Battery voltage is whatever it is, nothing can be done about it. Windings resistance is fixed, nothing can be done about it. Then the max phase current at 100% duty cycle is Imax = (Vbatt - Vemf)/Rwindings and determines the max thrust the motor can output at this speed. The air drag is determined by your body position and velocity, nothing can be done about it (other than "chooching"/ducking to reduce Cd). The difference is the available thrust margin, and nothing can be done to make it higher.

The only way is to have a wider motor, with wider magnets/stator, to have proportionally more torque across the same speed range. But then riders will be approaching the terminal speed closer as they feel safer, doing more aggressive accelerations closer to the edge... and the end result will be the same. It's a well known phenomenon in extreme sports - "risk homeostasis": https://www.google.com/search?q=risk+homeostasis&oq=risk+homeostasis

If the ice on partially frozen river grows thicker, risky people will simply go farther towards the edge and snap the ice where it has the same thickness as before.

The only cure is self-discipline, period.

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1 hour ago, xorbe said:

Dang, sudden beeping heart attack and dropped you on the floor.  Glad you're okay!  My 16X w/1.05 is configured to last alarm/tiltback at 25 mph iirc.  What version control board you have ... I hear that you were using BT music.

Thank you! It was exciting, haha! It's the latest I think, 1.5? I replaced it during the investigation into the pedal flick thing. Haven't had any of the bluetooth related symptoms, I don't think. 

And haha, that music playing caused YouTube to warn me about the copyrighted content in my video. :P:rolleyes:

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2 hours ago, redfoxdude said:

According to the log, I wasn't even close to the max power output

What is the max power output of the 16X at 31mph?

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19 minutes ago, redfoxdude said:

I was well within the operating design limits of the wheel

What, in numbers, are the operating design limits of the wheel at this speed? And what was the margin over the limit you were trying to achieve?

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By the way, the numbers for current and power as shown in OP seem to be suspiciously low. As can be seen from Motor Sumulator, the mechanical power at speeds ~50kph is around 2kW, while battery power is in the upper 2000's, closer to 3kW:

https://www.ebikes.ca/tools/simulator.html?batt=cust_84_0.2_20&cont=cust_100_200_0.03_V&wheel=17i&frame=cust_1_0.01&hp=0&blue=Lbs&motor=M3540

10 amps/800W seems to be ridiculously low.

I've already raised this concern about possible bug in 16X telemetry here:

but people don't seem to care.

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@redfoxdude I am glad you are OK. Thanks for giving us this information. 

One more question. What temperature was it outside?

I had a similar cut out on a MSX. In my case the battery was low (35-40%)  I weigh 220 , I was going up a slight hill for an extended amount of time at 30 mph and the final straw was that it was 35 f degrees outside. I don't believe the battery could keep up with the demand at that temperature. 

Edited by RockyTop

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8 minutes ago, Aneta said:

but people don't seem to care.

it's because they just multiply by pi themselves :D

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7 minutes ago, RockyTop said:

I weigh 220 , I was going up a slight hill for an extended amount of time at 30 mph

What was % grade on that hill? (GPS coords would be sufficient - one can easily measure grades in Google Earth)

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8 minutes ago, Aneta said:

What was % grade on that hill? (GPS coords would be sufficient - one can easily measure grades in Google Earth)

An average of 3%  for a mile. 

As I said, everything was going against me at the time. I never heard a beep ....... but I had my ears covered because of the cold. Now I pay attention to all of the factors and I got a much loader beeper flush with but outside the wheel. I am not sure that it ever did beep but I know that I would not have heard it anyway. 

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21 minutes ago, RockyTop said:

An average of 3%  for a mile. 

As I said, everything was going against me at the time. I never heard a beep ....... but I had my ears covered because of the cold. Now I pay attention to all of the factors and I got a much loader beeper flush with but outside the wheel. I am not sure that it ever did beep but I know that I would not have heard it anyway. 

Well, 3% is nothing to sneeze at at these speeds, because for 100kg total weight that's 3 kilos of extra thrust needed which the motor may not have at these speeds.

Also, if 3% is the average slope, the road can easily have double or triple of that in some spots, it won't be even noticeable to the eye (i.e. 3% is only a rise of less than half-inch in one foot forward).

Edited by Aneta

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15 hours ago, Aneta said:

Well, 3% is nothing to sneeze at at these speeds, because for 100kg total weight that's 3 kilos of extra thrust needed which the motor may not have at these speeds.

At a flat road there is just thrust needed for acceleration friction, air drag and self balancing. Zero thrust needed to lift some weight.

So there is no "three kilos extra" for an 100kg rider at a 3% slope. "Just" the thrust is needed to lift the 100kg + the wheel against gravity at a certain rate, which is determined by the slope percent and speed.

Edited by Chriull

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