Msuper v3 top speed crash - wrecked shell

[US69]

1 hour ago, Greg Spalding said:

I'm glad you brought this up because I don't understand why the only way King Song is dealing with their safety issues is to have the wheel cut its power significantly when the battery drops below 50%, which seems ridiculous to me.

Sorry, i really do not understand that...ridiculous?

on one way !!everyone!! is screaming for safety...then when a company implements a restrict on a certain batterie it is called ridiculous? i have another word for that: responsibility, as this is what all want?! a restriction that stopps (stupid) riders, to request more power than the batteries are able to give......

All older gotways and other wheel just shut off, if you request highspeed on ..lets say 40% batterie...

its just how it is with batteries...they go done...the power goes down....and when i see on this board here...i can not say the userrs are always "in mind" of that...pushing and pushing on the limits as long as it is possible.......

 

[Cloud]

49 minutes ago, Greg Spalding said:

I should not have been stated my point in that way. Obviously, safety is first.

My point is that I believe reducing the maximum allowable speed by forcing a tiltback earlier should occur when there is 25 or 30% of battery power left and not 50%.  That's all I meant.

I think @Greg Spalding explaind above what he meant.

he meant to say that 50% is too conservative to start reducing the max speed

 

[Keith]

15 minutes ago, Cloud said:

Exactly - this illustrates my point above. Where do you guys see Torque decreasing with speed? Torque increases with speed during riding, as more power is demanded from the motor

That graph is a graph of actual power and torque demanded by a rider during a ride, it's very undulating nature shows this. 

What is being referred to is maximum torque. Had the rider leaned forward as hard as he possibly could and accelerated at maximum possible then the graph would have shown a steadily decreasing torque. So torque only increases in this graph because the rider is demanding less than maximum. In fact the point where demand hits maximum available can clearly be seen from 18kph onward where torque then decays fairly linearly. 

Don't forget back EMF is countering the applied voltage as RPM and speed increases, maximum  torque is found at zero RPM, effective maximum voltage (applied voltage-back EMF) can only get lower as speed increases.

[US69]

@Greg Spalding

Sorry, i read your explanation, that you find 50% to high after my post above!

and i did not want to accuse you of something :-)

i brought this behaviour up, and i only find negativ, that KS has not done from the beginning and marketed their wheel as 40kmh wheel...

unless that, i find the 50% mark also a bit high, but it seams to be needed!! as 50% is less or even just 60volt...and with that much less watts available...

dont get me wrong... i just missunderstood your "ridiculos" announce :-)

 

Another thing: today i drove both wheels: V3 AND Ks18... and they are both...ABSOLUT fantastic...and such an improvement over earlier wheels!!! And as i said often: i am 100kg and i am living in a region called "hilled land"...and both wheels bring me everywhere i want to go... so i can only say that your concerns about a wheel that can carry your weight for 40km plus....here they are: Ks18 and v3!!! (as long as younnot ask for 45kmh :-). )

[Greg Spalding]

1 minute ago, KingSong69 said:

@Greg Spalding

Sorry, i read your explanation, that you find 50% to high after my post above!

and i did not want to accuse you of something :-)

i brought this behaviour up, and i only find negativ, that KS has not done from the beginning and marketed their wheel as 40kmh wheel...

unless that, i find the 50% mark also a bit high, but it seams to be needed!! as 50% is less or even just 60volt...and with that much less watts available...

dont get me wrong... i just missunderstood your "ridiculos" announce :-)

 

Another thing: today i drove both wheels: V3 AND Ks18... and they are both...ABSOLUT fantastic...and such an improvement over earlier wheels!!! And as i said often: i am 100kg and i am living in a region called "hilled land"...and both wheels bring me everywhere i want to go... so i can only say that your concerns about a wheel that can carry your weight for 40km plus....here they are: Ks18 and v3!!! (as long as younnot ask for 45kmh :-). )

i'm appreciative for your post and information

i never thought you accused me of anything.... i am learning new things here every day and that makes me extremely happy

glad to hear about the 40km+ on the KS18 and V3

again, thanks

[Cloud]

6 minutes ago, Keith said:

That graph is a graph of actual power and torque demanded by a rider during a ride, it's very undulating nature shows this. 

What is being referred to is maximum torque. Had the rider leaned forward as hard as he possibly could and accelerated at maximum possible then the graph would have shown a steadily decreasing torque. So torque only increases in this graph because the rider is demanding less than maximum. In fact the point where demand hits maximum available can clearly be seen from 18kph onward where torque then decays fairly linearly. 

Don't forget back EMF is countering the applied voltage as RPM and speed increases, maximum  torque is found at zero RPM, effective maximum voltage (applied voltage-back EMF) can only get lower as speed increases.

Hmmm...i understand that torque would be gradually descreasing from the moment someone starts accelerating to the moment he reaches the costant elevated speed. This makes sense. But i am not talking about torque during acceleration.

I believe the overall increase in torque shown in the graph illustrates the power/ torque demand with speed increase. ( i am discounting the multipke spikes due to accelerations to a higher speed) .

i see that torque slightly decreases with speed higher than 18kph, not sure why - i will need to read the description of the experiment to understand why this happened.

 

 

[EricGhost]

31 minutes ago, Cloud said:

Exactly - this illustrates my point above. Where do you guys see Torque decreasing with speed? Torque increases with speed during riding, as more power is demanded from the motor

1rst there are motors and there are motors, electrical or not and they have their own curve not all the same, but all of them must follow the power definition, I.e: power=torque x angular speed, as power has a limit Named max power it is clear that if you run at max power the higher the speed the lower the torque. But when you start your run you do not start at max power therefore torque & speed can increase both

This does not mean that your available torque increase with speed, it means you're reaching the max power point once you reach it on plain terrain at a certain speed go uphill and try to keep the speed let's see if torque will increase  

http://lancet.mit.edu/motors/motors3.html

[Cloud]

43 minutes ago, EricGhost said:

1rst there are motors and there are motors, electrical or not and they have their own curve not all the same, but all of them must follow the power definition, I.e: power=torque x angular speed, as power has a limit Named max power it is clear that if you run at max power the higher the speed the lower the torque. But when you start your run you do not start at max power therefore torque & speed can increase both

This does not mean that your available torque increase with speed, it means you're reaching the max power point once you reach it on plain terrain at a certain speed go uphill and try to keep the speed let's see if torque will increase  

http://lancet.mit.edu/motors/motors3.html

I understand the formula for the power per torque, and i understand that once you reach maximum power, with additional speed increase power will decrease. I also agree with the curves above.

however, i still believe the curves above are applicable to a situation different from the regular riding scenario. I believe these illustrate the torque , and power per different speed, as the angular motor speed would change per the varied motor loading ( or resistance) . You apply more resistance to the motor, the speed decreases and the torque increases. You let the motor spin free - the speed increases and torq decreases.

but in the riding conditions its the opposite. When you increase the speed you you increase the loading / resistance and provide the increased power ( volts x amperes) and i believe you increase torque to meet the demand. 

Sorry if i am saying nonsense, i just dont know how to see this differently right now

 

[Raptor]

7 hours ago, Cloud said:

Exactly - this illustrates my point above. Where do you guys see Torque decreasing with speed? Torque increases with speed during riding, as more power is demanded from the motor

The test is based on the maximum capacity of the largest permanent power ! Be seen that the top of the curve in the maximum speed, they can withstand the maxloads .That 40 km h smooth surface road is not really a max load ! But at this 42kmh, my KS18a me 92kg yet pedals by raising the air throw my. Wheel did it with very great force and four times . Did not feel the force weakening for 40kmh ! However, the ECM will limit is ourselves very Strongly ! But I've traveled 44kmh once and did not feel any restriction on ?  Reason for shutting down must be something else .Possible weakness batteries that i'm meet RC airplane hobby continually ! Voltage drops and load amps go up and the controller gets confused !       I'm very accepted  opinion KingSong69 ,until 40kmh MSuperv3 and KS18 are very good wheels ! Above this speed are still problems. I too would like to try instead 65c-130c LiPo batteries, their very weak Li-Ion Battery. The problem is connection to the controller, because they require very precise balanced to for drive time  if  braking ( long downhill braking and braking, charging the batteries back but i don't know how this control this current mainboard charging system ) .

[Chronic]

 

My friend was a battery low voltage(50%) 48 km/h cutoff.

I'm very sad ..

 

[Greg Spalding]

HOW IS YOUR FRIEND?

the wheel looks horrible

but, HOW IS HE?

[Marty Backe]

34 minutes ago, Greg Spalding said:

HOW IS YOUR FRIEND?

the wheel looks horrible

but, HOW IS HE?

I think by 'friend', he meant the MSuper.

[Greg Spalding]

24 minutes ago, Marty Backe said:

I think by 'friend', he meant the MSuper.

yes, perhaps the translation was a such

then.... HOW IS HE? 

i hope he spent DISPOSABLE income on that wheel

[zlymex]

There are two basic principles(actually there are more) for the type of motor that EUC uses.
1. The torque is proportional to the armature current
2. The counter electromotive force is proportional to the speed.
https://en.wikipedia.org/wiki/Brushed_DC_electric_motor#Torque_and_speed_of_a_DC_motor

Look at the simplified model of a DC motor

Where Rm is the internal resistance, which can be regarded as a fixed value for a given motor for the argument.
Eb is the counter EMF, proportional to the speed, let's say 1V for 1km/h, and 40V is equivalent to 40km/h.
Vin is the input voltage, which may vary because of the control board, but the max value of Vin is the battery voltage(minus some voltage drops)
Ia is the armature current, which is proportional to the torque.

According to Ohm's Law, (Vin-Eb) = Rm * In
This can be expressed as:
In = (Vin - Eb)/Rm = Vin/Rm - Eb/Rm
If express it graphically, we will get this well-known negative-slop straight line of torque/speed 'curve'

If the motor is stalled, speed is 0 and so is Eb, In = Vin/Rm which is the max current(25A) so we get the max torque of the motor at Vin.
If we lift test a motor(no load, torque=0), Eb will be 50V and the speed is 50km/h
If the speed is 40km/h, Eb=40V, Ia = 10V/2 Ohm = 5A, which means we get 1/5th of the max torque
If the speed is 45km/h, Eb=45V, Ia = 5V/2 Ohm = 2.5A, which means we get 1/10th of the max torque
If the speed is 49km/h, Eb=49V, Ia = 1V/2 Ohm = 0.5A, which means we get 1/50th of the max torque.

Three things worth noting: 
One is that the max torque of the motor(stall torque) depend on Vin thus depend on battery condition(whether its full or not).
The second is that the negative-slop straight line is the max torque line for different speed at a give Vin. If the battery condition changed(such as from full to near empty), Vin will become smaller, and the line will shift inward(towards the origin, the bottom-left corner)
The third is that the actual torque the motor produces when people riding an EUC is seldom reached the max torque line(unless may be faceplant).  The max torque line is the limit line, it is NOT something like the load line or working line, we should stay away from the limit line as far as possible(below the line, towards the origin), leaving enough safety margin as green shaded area. 

When people do experience high speed crash, it often happens at the red point of above graph, where speed is high and the max torque the EUC can produce is low.

[checho]

3 hours ago, zlymex said:

There are two basic principles(actually there are more) for the type of motor that EUC uses.
1. The torque is proportional to the armature current
2. The counter electromotive force is proportional to the speed.
https://en.wikipedia.org/wiki/Brushed_DC_electric_motor#Torque_and_speed_of_a_DC_motor

Look at the simplified model of a DC motor

Where Rm is the internal resistance, which can be regarded as a fixed value for a given motor for the argument.
Eb is the counter EMF, proportional to the speed, let's say 1V for 1km/h, and 40V is equivalent to 40km/h.
Vin is the input voltage, which may vary because of the control board, but the max value of Vin is the battery voltage(minus some voltage drops)
Ia is the armature current, which is proportional to the torque.

According to Ohm's Law, (Vin-Eb) = Rm * In
This can be expressed as:
In = (Vin - Eb)/Rm = Vin/Rm - Eb/Rm
If express it graphically, we will get this well-known negative-slop straight line of torque/speed 'curve'

If the motor is stalled, speed is 0 and so is Eb, In = Vin/Rm which is the max current(25A) so we get the max torque of the motor at Vin.
If we lift test a motor(no load, torque=0), Eb will be 50V and the speed is 50km/h
If the speed is 40km/h, Eb=40V, Ia = 10V/2 Ohm = 5A, which means we get 1/5th of the max torque
If the speed is 45km/h, Eb=45V, Ia = 5V/2 Ohm = 2.5A, which means we get 1/10th of the max torque
If the speed is 49km/h, Eb=49V, Ia = 1V/2 Ohm = 0.5A, which means we get 1/50th of the max torque.

Three things worth noting: 
One is that the max torque of the motor(stall torque) depend on Vin thus depend on battery condition(whether its full or not).
The second is that the negative-slop straight line is the max torque line for different speed at a give Vin. If the battery condition changed(such as from full to near empty), Vin will become smaller, and the line will shift inward(towards the origin, the bottom-left corner)
The third is that the actual torque the motor produces when people riding an EUC is seldom reached the max torque line(unless may be faceplant).  The max torque line is the limit line, it is NOT something like the load line or working line, we should stay away from the limit line as far as possible(below the line, towards the origin), leaving enough safety margin as green shaded area. 

When people do experience high speed crash, it often happens at the red point of above graph, where speed is high and the max torque the EUC can produce is low.

I would like to add that max safe speed for a heavy rider is lower than max safe speed for a light rider since the heavier rider to be safe will requiere greater torque than the light rider, which means the heavier rider will have to significantly reduce the speed more then the light rider to have more torque at the same power. So a speed that could be consider safe for a 60kg rider could be very dangerous for a 120kg rider on a bad road and a windy day. The minute you go over a bump on the road the extra power is needed otherwise it is a faceplant.

[Mistagear]

On 10 October 2016 at 6:48 AM, Marty Backe said:

 

Doesn't your dyne graph show max power and torque @ 18 kph declining power and torque beyond 20 kph culminating in tilt under load @ 28 kph ?

[Chriull]

22 hours ago, Tilmann said:

...The big difference: if the wheels logic "decided" to shut down, it has access to telemetry data, that allow to anticipate what's coming, but it is not telling me.

+1. Thats really a major lapse in the "state of the art" firmewares!

Until now i have found/thought of 2 such warning cases that would be a great safety improvement for us riders:

- overtemperature: The firmware nows the telemetrie data and just has to look at the temperature gradient and can warn a couple of seconds before the max temperature may be reached! A more sophisitcated way would be to measure the ambient temperature and emulate the "heat flow" - the firmware knows the Energy "burnt" in the Mosfets (~I²*R DS on) and then there is just some "thermal capacity" of the heatsink/motherboard compartment and the thermal conductivities. Should be a quite simple simulation.

- hard accelerating "through" the tilt-back directly into the "cut-off": There were quite some reports that harsh accelerations can lead to direct cut-off without the tilt-back getting triggered. As the firmware nows the actual speed and the acceleration it could warn quite immedeately that cut-off will be reached soon by starting the tiltback not at a fixed set value but already at much lower speeds.

Both of these cases could be also covered by Wheellog/9BMetrics. In combination with a pebble/apple watch a vibration alarm would be a sufficient last warning before the wheel cuts off. Once i have some nice logs and enough spare time i plan to start some of these "analysis" - but maybe @JumpMaster and/or @Paco Gorina are already working on something like this or could easily implement this more or less "adhoc"?

Quote

...On the subject of heat: does anybody know for sure, which components are at risk of overheating? MOSFETs, battery, BMS, motor, CPU?

Mosfets should be the first to burn and they produce most of the heat in the compartment. But also allmost all other electrical components producing heat will get problems over the time in a 60-70°C compartment with almost no air-flow...

Quote

 And: which temperature is/are measured? With MOSFETs, is the temperature measured inside every one, or by just one external sensor on the heat sink? 

 

The used Mosfets have no build in temperature sensor. I havent seen till now any temperature sensor on the heatsinks. Imho it is a seperate sensor somewhere on the PCB or maybe also just some sensor build in some IC used on the motherboard...

19 hours ago, Cloud said:

Exactly - this illustrates my point above. Where do you guys see Torque decreasing with speed? Torque increases with speed during riding, as more power is demanded from the motor

19 hours ago, Keith said:

That graph is a graph of actual power and torque demanded by a rider during a ride, it's very undulating nature shows this. 

What is being referred to is maximum torque. Had the rider leaned forward as hard as he possibly could and accelerated at maximum possible then the graph would have shown a steadily decreasing torque. So torque only increases in this graph because the rider is demanding less than maximum. In fact the point where demand hits maximum available can clearly be seen from 18kph onward where torque then decays fairly linearly. 

Don't forget back EMF is countering the applied voltage as RPM and speed increases, maximum  torque is found at zero RPM, effective maximum voltage (applied voltage-back EMF) can only get lower as speed increases.

I tried to read and understand how the chart @Raptor posted was made. (google translate of a russion forum needs much fanstasy and creativity to understand...;( )

The graph was created by accelerating a ?1 ton? barrel by the wheel. From the acceleration of this barrel the computer calculates power and torque over the speed. The wheel was "pitched" forward to accelerate this barrel. Some "frame" helped holding the wheel in position. The initial acceleration (something like up to ~10 km/h) was not the maximum the wheels could "deliver", since quite some fuses burned/overpower warnings where given.

I don't know exactly what happened after the max power was reached - either the "dynamometer" stopped, the tester stopped accelecating/testing or the wheel cut-off?

Anyway - it was not a measurement of the power/torque over speed but only the max power the wheel could produce - and this is not limited by the motor but by the electronics. (quite sure but still imho;) ) This is imho also shown by the "undulating nature" of the graph - this could result from the regulating mechanisms in the firmware. Or could also be from the "soft" tires coupling the wheel with the barrel - or maybe a combiation of both?

This max power measurement has (as good as) nothing to do with the torque capabilities when riding at around 40/45 km/h.

 

19 hours ago, Cloud said:

Hmmm...i understand that torque would be gradually descreasing from the moment someone starts accelerating to the moment he reaches the costant elevated speed. This makes sense. But i am not talking about torque during acceleration.

I believe the overall increase in torque shown in the graph illustrates the power/ torque demand with speed increase. ( i am discounting the multipke spikes due to accelerations to a higher speed) .

i see that torque slightly decreases with speed higher than 18kph, not sure why - i will need to read the description of the experiment to understand why this happened.

 

The "used" torque is direct proportional to the acceleration of the wheel. So if one "asks" the wheel for a specific acceleration by leaning forward the controller lets a current flow through the motor which generates this torque. So current is direct proportional to the torque which is direct proportional to the acceleration. (The controller can regulate the current by the duty cycle of the PWM pulses).

This is true as long the torque (~current) and speed of the wheel is within the borders of the torque/speed limit chart. Once one "hits" this limit one start to overlean!

If you look at the last "D.C. motor torque/speed curve" @zlymex posted (with the red dot) and imagine you start driving by leaning forward constantly so the wheel starts a constant acceleration with exactly the torque of this red spot. Then one "moves" in this chart on a constant line (parallel to the "rotational speed"/x-axis) until one reaches the speed indicated by the red spot. This is exactly the last moment where the motor can deliver this torque. After this spot the torque decreases and as one still leans forward this means the wheel does not accelerate enough anymore to balance the driver and a faceplant happens (if the rider cannot react fast enough and balance himself again by leaning back)

As already mentioned before by some posters, in this case the torque cannot be delivered anymore after the "red spot" because the difference between the battery and the "motor generated voltage" is too low to let a current flow which could "induce" this torque.

18 hours ago, Cloud said:

but in the riding conditions its the opposite. When you increase the speed you you increase the loading / resistance and provide the increased power ( volts x amperes) and i believe you increase torque to meet the demand. 

Exactly - as long as you stay within the limits of this torque/speed curve. In this area you can increase torque to accelerate to higher speeds and vice versa as you want. It is just the moment you "touch" this limit line and try to cross it, then the torque decreases and you overlean.

Edit: (inserting new lines did not work anymore - so i stopped writing and resumen now with an edit...)

These "mechanics" descriped above are only regarding the motor capabilities. You still have additional limits introduced by the firmware like power/current limits, for some wheel some max speed where a immediate cut-off is triggered or some temperature limit. These additional limits make the possible operating area in this torque/speed chart even smaller.

Edit2: repaired @ notifications, since they also did not work before while writing this post...

Edit3: I just found another way of hopefully clarifying the torque/speed chart: The line does not show the only possible operation "points" the motor can handle, but the limits! So the real duples of torque/speed this motor can handle is the whole area within the triangle (0,0)-(no load speed,0)-(0,max torque(stall torque))

[Dancer]

4 hours ago, checho said:

I would like to add that max safe speed for a heavy rider is lower than max safe speed for a light rider since the heavier rider to be safe will requiere greater torque than the light rider, which means the heavier rider will have to significantly reduce the speed more then the light rider to have more torque at the same power. So a speed that could be consider safe for a 60kg rider could be very dangerous for a 120kg rider on a bad road and a windy day. The minute you go over a bump on the road the extra power is needed otherwise it is a faceplant.

That is why the Gotway 80% alarm is a power alarm and not a speed alarm. At a lower battery level the alarm will go off at a lower speed.

[US69]

12 minutes ago, Dancer said:

That is why the Gotway 80% alarm is a power alarm and not a speed alarm. At a lower battery level the alarm will go off at a lower speed.

I have asked "Linnea Lin" from Gotway exakt this question, if the 80% Alarm is in any way Batterie related!

Her answer was: No, the 80% Alarm just rings when the Motor is on 80%...nothing to do with Batterie!

[Dancer]

12 minutes ago, KingSong69 said:

I have asked "Linnea Lin" from Gotway exakt this question, if the 80% Alarm is in any way Batterie related!

Her answer was: No, the 80% Alarm just rings when the Motor is on 80%...nothing to do with Batterie!

Strange. I have done over 4000 km on my ACM v1 now and I always get the alarm on a lower battery at a lower speed. Could the motor be on his 80% at a lower speed on a lower battery level ?

[Paco Gorina]

In enclose s .pdf explaining why sometimes wheels fall down with no apparent cause which is related to the torque / speed question. There is also a Mathematica file so you may play a little.

 

english.pdf

Model_2.nb

[zlymex]

That saying of '80% of power' warning is wrong!

As a matter of fact, Gotway don't care or know about the instant power at all. On the very first app interface, I know the commands, getting voltage and current are separate, one have to switch mode in order to get them both to calculate the power. Has any one seen any of the Gotway apps that show Power? If the app or the wheel don't know the instant power, how comes the 80% power?

As someone already pointed out, the 3rd alarm always comes at 37-38 km/h. I also confirm this because I tested the wheel at half empty battery and full battery. Therefore, the 3rd alarm is a speed related alarm, not power related alarm. It is not 80% of some top speed either, because physical speed limit is always battery related. 

[Chriull]

9 minutes ago, Paco Gorina said:

In enclose s .pdf explaining why sometimes wheels fall down with no apparent cause which is related to the torque / speed question...

Seems very interesting, but unfortionately the labels of the charts in the pdf are not readable (at least using windows)... So it's hard to follow/understand ;(

[Dancer]

12 minutes ago, zlymex said:

That saying of '80% of power' warning is wrong!

As a matter of fact, Gotway don't care or know about the instant power at all. On the very first app interface, I know the commands, getting voltage and current are separate, one have to switch mode in order to get them both to calculate the power. Has any one seen any of the Gotway apps that show Power? If the app or the wheel don't know the instant power, how comes the 80% power?

As someone already pointed out, the 3rd alarm always comes at 37-38 km/h. I also confirm this because I tested the wheel at half empty battery and full battery. Therefore, the 3rd alarm is a speed related alarm, not power related alarm. It is not 80% of some top speed either, because physical speed limit is always battery related. 

Now I am confused. I just went for a test.

My battery is at 60 %. When I accelerate hard the alarm goes off at 30 km/h. When I accelerate slow I can go to 35 km/h without alarm.

[Paco Gorina]

In word format t in this link. Better graphics

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