Warnings should depend from current, not from speed

[esaj]

I was going to head to bed, but seeing this conversation, I thought I might add to the confusion

 

3 hours ago, John Eucist said:

Gotway and King Song apps show live monitoring of voltage and current.  I have noticed that when I do hard leans (hard pressure on front or back of pedals) the current would spike up while the voltage would suddenly drop (assuming the app readings were correct).  On a slightly different yet related topic, I was just looking at the Ohm's Law formula (I=V/R) which states that voltage and current are proportional to each other.  Doesn't that contradict the phenomenon I just described or am I just not understanding something correctly?  Could someone explain?

Ohms law still holds   Consider the following:

 

On the left-side of the image, there's a voltage source, the battery (BAT1) at 60V, the batterys' internal resistance (Battery_Internal_Resistance1) marked as a separate resistor (I used the value of 0.2 ohms as mentioned above by Keith), and a 10A current source (that's just for simulation purposes, to simulate the battery giving out exactly 10 amps).

When the wheels measures the voltage, it measures it "over" the battery, including the internal resistance of the battery. The "open circuit" (ie. no current flowing, the battery is disconnected or the circuit loop isn't closed) voltage of that battery is 60V. To my knowledge, "open circuit" voltage cannot be measured in real life, but I'll get to that in a bit.  Now, when 10 amps of current is flowing through the battery and its internal resistance, a voltage drop proportional to the current flowing through the resistance will cause a voltage "drop" over the resistance:

U = R * I, in this case U = 0.2ohm * 10A = 2V  (ohm = Volts per amperes). Like said, that's the voltage "drop" over the internal resistance of the battery when 10 amps of current is flowing through it. But then, how come we see a voltage of 58V (The "open circuit" -voltage of that battery minus the voltage drop of the internal resistance)? Like I said, you cannot (in real life) measure the open loop voltage, because you need a closed loop for measuring (current can be measured from magnetic fields without closed circuit, though). But, we have digital multimeters etc. that can measure a voltage. The "trick" is that the measuring circuit uses very high resistance (actually, the "more correct" term is impedance, but I'll get to that later ) to affect the measurement as little as possible. So basically, what you do when you measure the voltage is that you create a parallel circuit there, with very high resistance:

Now, the connected DMM (Digital MultiMeter) has created a parallel circuit "over" the battery (including it's internal resistance. Internally inside the DMM, there are voltage dividers etc. because the DMM circuitry would likely break or blow if you tried to measure something like hundreds of volts, and yet even the cheap ones can measure up to 200V or 600V or even thousands of volts. But the current flowing through the DMM is VERY small, because the input impedance is typically something like 10 MEGAohms (10 000 000 ohms), and thus won't affect the measuring (at least much).

Well, this actually didn't come out as clearly as I had envisioned... More helfpul (or less, but very relevant at least) stuff to look up could be something like Kirchoff's laws (voltage and current) and mesh network analysis... Moving on (for now, once I'm "more awake" tomorrow or some day, I can try my best to explain the above better )  More helpful (or less, but at least relevant) stuff to look up would be at least Kirchoff's laws (current & voltage) and mesh network analysis (and then you'll hit that pesky whatwasitcalled... Wheatstone bridge? that always threw me off in Circuit Analysis-courses )

But on the topic of this thread, let's take a look at a bit more realistic (but still far from real life) circuit of battery, motor drive & motor:

So here's pretty much the earlier circuit, except instead of a 10A current source, I've used some "more real" values. Other_res1 and Other_res2 contain resistances of the connectors, wiring, FULLY CONDUCTING mosfets (0.009 or 9 milliohms for 75NF75's, as per datasheet), so that the current can flow, and assumed that the wiring & connectors have very low resistance (1 milliohm). There are two separate "other resistances", because the circuit path goes like  Battery (+ it's internal resistance) -> wiring -> connection to mainboard -> high-side mosfet -> Motor phase A (wire + coil resistance) -> Motor phase B (coil resistance + wire back to mainboard) -> low-side mosfet -> battery negative terminal.

I measured the motor internal resistance from the Firewheel motor with a DMM, but because my meter isn't that good at low resistances, I wouldn't trust it blindly (the DMM showed 3.2 ohms when measuring, I then measured the internal resistance of the measuring probes, where it showed 2.6 ohms, so assumed it's 3.2ohm - 2.6ohm = 0.6ohm). I've also lately bought an LC (inductance/capacitance) meter, and measured the inductance between the two phases in series to be 0.52 millihenries (+- some percents of error), but I'll get to that, you guessed it, later 

Ok, so now we'll look only at the purely resistive circuit. Since all the resistances are in series, it's pretty easy just to sum them up to get the total resistance:

0.2 + 0.01 + 0.6 + 0.01 = 0.82ohms.

The "open circuit" voltage is 60V, so that must "drop" over the entire circuit, we can now calculate the current running through here:

I = U/R, here I = 60V / 0.82ohms = 73.17... A

That would be the theoretical maximum current at 60V battery voltage, assuming that the motor internal resistance would be that 0.6 ohms, which it probably isn't (And that my estimates of other resistances were correct etc). I'd need a real high quality milliohm-meter to know the real value.

Now we have some sort of a circuit where the battery is pumping current through the motor at "full blast". Of course that's not the whole story. Motors are difficult to understand (at least to me), because they aren't just resistance. To actually model a motor, you need to take into account that (in ideal component terms) it also has an internal voltage source (the back-EMF, when it's turning) and coils (which exhibit the beforementioned inductance). If there's no back-EMF, the motor is at standstill. So the above would mean a situation where the mosfets are fully conducting, full (theoretical) maximum current is flowing, but the motor isn't turning yet at all. So again, let's "complicate" our circuit a bit more:

Ok, so now our motor consists of internal resistance, the inductance of the coils (L1), and back-EMF. Here I've simply marked back-EMF as 60V, the same as the battery, so technically at this point no current is flowing, ie. the motor would be running at full speed and the voltages of the battery and the back-EMF match. Technically, due to friction etc., the back-EMF (normally) shouldn't be able to reach the battery voltage when running at flat, but stay somewhere slightly below (producing torque to overcome the friction & keep speed steady).

I mentioned "impedance" above. Impedance equals (ohmic) resistance + reactance

<this part of the post was somehow mucked up by the forum software as I was trying to add italics elsewhere... I'm tired, I'll try to finish the part some time later)

ow, as I've been writing this for a good 1.5 hours and want to wrap this up soonish and get to bed ). What that means is that the impedance of the motor changes when it's being run with PWM-pulses. PWM-pulses have frequency. That change in voltage/current is going to cause inductive reactance in the coils of the motor, which in turn affects the impedance of the motor. Not to mention that the mosfet-resistances will change, as when the mosfet goes from "fully conducting" to "totally not-conducting" it passes through (fast!) what is called linear region, where it's resistance will change (going towards infinity or some very large number before it totally stops conducting, and dropping from there to the minimal Rds(on) when starting to conduct).

Here's one last simulation picture, that I won't explain in detail (partially also because the magnetic field-stuff is way beyond me): 

EDIT: Actually, the gate-driving voltage in the above simulation is too low, so the results aren't exactly as expected... I'll rerun the sims at some point & post screenshots if someone's really interested   The point is that the back-EMF voltage actually fluctuates a lot due to the inductance and reverses itself all the time as the magnetic field expands / collapses

Basically, I've replaced "Other_res1" with a real mosfet (although probably not one which is actually used in wheels, just picked something with 80V Vds/ 10 milliohm Rds(on) fast...), and it's being driven by a 8kHz PWM-pulse from V1 with 50% duty-cycle and one microsecond (1µs) rise & fall-time. 50% duty cycle means that only half of the battery voltage is actually "applied" over the motor. The motor voltage is simulated as raising at a pace of 6 volts per second (like it was speeding up). Here's the voltage from the BEMF_measure -point in the above schematic over 10 second period:

Wow, that's all over the place... Actually, since in my simplified simulation the "applied" voltage only reaches around 30V (50% duty cycle), yet the motor back-EMF keeps increasing all the way to 60V (hitting that 30V value around 5 seconds), it enters a regenerative braking-phase around there... Sorry that I didn't include a graph of the current, but it actually shows some  very small negative (towards battery) spikes all over the places, before starting to feed the battery after that point...

But what are those weird "bulbs" at the beginning? This is to show what happens in a coil (L1, actually it's even more complicated, as in reality there are two phases with their own separate coils... ) when the current is suddenly interrupted or started (ie. the mosfet stops conducting/starts conducting), zooming closer:

The green graph is the voltage at the BEMF-measure, and the lower blue is the PWM-pulse. So what's happening? The voltage actually starts fluctuating back and forth and makes a kind of a spike when the mosfet again turns on (and then settles again). There's lots of stuff going here, and the simulation doesn't (always, depends on a lot of variables) even catch all the real-world phenomena. I was hoping to see large inductive spike, but didn't catch one now  But let's just say, that in real-life, I've seen a 1-phase motor cause spikes of 100-130V during running... and it was being driven by a 9V battery over similar mosfet-half-bridges as used in the wheels.

The point of this entire rant has been that it's "not that simple". Reason I haven't partaken much in the conversations about what the manufacturers should/should not do (other than just being otherwise busy) is that over the months of researching this stuff, it has dawned on me how complicated it all really is. Like I've mentioned in the motor drive-post I made some time ago, and that was already mostly written early this year, since then I've learned a lot, it is very simplified view of the entire motor drive and related phenomena. If it were "that simple", we'd all be designing and building our own wheels by now   This is not to disencourage conversation or anyone from learning this stuff, just that there's (much!) more than meets the eye... And don't even get me on started with ideal components in simulation vs. real-world components (hint: all real-world components exhibit SOME resistance, capacitance and inductance, unlike the ideal counterparts in simulation)....

 

[Tomek]

@esaj what a trip! (to a parallel universe, aaaarghhh .') )

btw. what's your take on the eternal question on full speed cutoff?

is it there just for user safety, or would you risk serious damage to the controller if the motor would be spinned (e.g. due to external forces) above its max rated speed when powered?

[US69]

 

@marc

as You See You got an answer from The tech pros :-)

to Stay at your 120 kg 35 degree 0-20kmh example:

just buy a New Kingsong :-)

it has a Warning ...Not Speed related...it's says:

"Caution! overpowering" in this Situation 

so i would say: (some of) The Wheel already have what You want

[Cloud]

To illustrate the points expressd in this thread, i "decided " to face-plant this monday at about 25kph right in the middle of an intersection. I ran off for a few feet but couldnt stay up and dove, rolled over my head or something like that, hard to remember. When i looked back the wheel was about 40 feet away behind me.  Luckily there were no cars rready to run me over and i only have a few bruises from the wall ( i was very lucky , as my only protective gear was bike gloves) . What i believed happened was, the battery was low, at about 20-25 %, and even thoug the speed wasnt as high as it could have been, i believe i accelerated too fast, and due to my 100kg and the low battery the wheel could not produce enough power to keep me up. I dont believe there was a shit down - i think i " overpowered " the wheel. There were no beeps or tiltback. It was a little strange as i had ridden at higher speeds and lower battery levels in the past - be careful at lower battery levels and high speeds especially during acceleration and always wear protective gear!

[Mono]

@Cloudwhich wheel was this?

[Cloud]

Just now, Niko said:

@Cloudwhich wheel was this?

Ks14 800w 840wh . But i dont want to make it sound like it's the wheel's fault. I dont believe the power cut off, i think the wheel simply didnt have enough juice to cope with the acceleration given an already decent speed. It was a little strange to me though, as i know i had been able to stay upright in similar situatikns in the past.

 

[who_the]

Glad you're OK @Cloud. Any hiccups or sputters before it gave out? I've slowly started to push my KS-14C 800w/840wh harder recently, and am interested if there are any warning signs. I'm about 70kg and average about 19kph during my 1/2-hour, 5.5 mile commute each way. I have my beep set to 30kph and usually hear it a few times each direction.

[US69]

2 hours ago, Cloud said:

To illustrate the points expressd in this thread, i "decided " to face-plant this monday at about 25kph right in the middle of an intersection. I ran off for a few feet but couldnt stay up and dove, rolled over my head or something like that, hard to remember. When i looked back the wheel was about 40 feet away behind me.  Luckily there were no cars rready to run me over and i only have a few bruises from the wall ( i was very lucky , as my only protective gear was bike gloves) . What i believed happened was, the battery was low, at about 20-25 %, and even thoug the speed wasnt as high as it could have been, i believe i accelerated too fast, and due to my 100kg and the low battery the wheel could not produce enough power to keep me up. I dont believe there was a shit down - i think i " overpowered " the wheel. There were no beeps or tiltback. It was a little strange as i had ridden at higher speeds and lower battery levels in the past - be careful at lower battery levels and high speeds especially during acceleration and always wear protective gear!

Sounds a Little bit  like my 30kmh faceplant with The KS16.....tiltback Set in...i was on a Little downhill accelerating to hard....and Overreacted in The tiltback....Wheel got wobly...and i fly....Batterie about 30%

since that i changed my Warning Settings :-)

before: 0 0 29 30

now: 26 28 30 30

settings before were to dangerous when accelerating to fast.....

[John Eucist]

12 minutes ago, KingSong69 said:

Sounds a Little but like my 30kmh faceplant with The KS16.....tiltback Set in...i was on a Little downhill accelerating to hard....and Overreacted in The tiltback....Wheel got wobly...and i fly....Batterie about 30%

How did you "overreact"?  By trying to slow down (leaning back) too fast?

[US69]

2 minutes ago, John Eucist said:

How did you "overreact"?  By trying to slow down too fast?

I think by Braking to hard, yep!

but like i Said i really accelerat much to fast/hard and that on a slightly downhill which got over into a horizontal...and The App in my (Broken) phone give me a Max Speed of 33 something....and As this was The First tiltback i got on that evening this was The Pace i had....i was Stupidly to fast pushing...

and The tiltback was ....don't Know how to say...Crazy hard!

much harder As when i accelerate slowly to Max Speed...

[John Eucist]

2 minutes ago, KingSong69 said:

and The tiltback was ....don't Know how to say...Crazy hard!

much harder As when i accelerate slowly to Max Speed...

So the tilt-back was "too quick and extreme"?  Was it possible to continue standing on the pedals or was it so tilted that there was no way to continue to stand?  Do you think you could have prevented your fall (after the tilt-back set in) knowing what you know now?

[US69]

3 minutes ago, John Eucist said:

So the tilt-back was "too quick and extreme"?  Was it possible to continue standing on the pedals or was it so tilted that there was no way to continue to stand?  Do you think you could have prevented your fall (after the tilt-back set in) knowing what you know now?

Yep! To quick and extreme!

i don't think i can prevent that in The SAME Situation at all....

i normally now The Limits.....but i oversaw The Little downhill Part (was on a Giant Gas Station)...which gave me too much acceleration....

so i THINK from 25 to 33 was in such a fast way that The tiltback was extreme and quick As i Never had such a "hard" tiltback before....

for me The Solution Is just Not to push to hard After 20kmh :-)

really: completly my fault....i did in NO way Blame The Wheel....

[John Eucist]

6 minutes ago, KingSong69 said:

Yep! To quick and extreme!

i don't think i can prevent that in The SAME Situation at all....

Hmm.  In that case I think the tilt-back programming could be improved.  It seems that the tilt-back function itself is what caused you to fall instead of a shut-down.  Maybe, ironically, it would be safer to disable the tilt-back and just rely on the beeps?

[SlowMo]

1 hour ago, John Eucist said:

Hmm.  In that case I think the tilt-back programming could be improved.  It seems that the tilt-back function itself is what caused you to fall instead of a shut-down.  Maybe, ironically, it would be safer to disable the tilt-back and just rely on the beeps?

Maybe @Jason McNeil already have tested the tiltback reaction of the KS-16? It should normally be the same as with the other models i.e. KS-14C and KS-18B.

[John Eucist]

1 hour ago, SlowMo said:

Maybe @Jason McNeil already have tested the tiltback reaction of the KS-16? It should normally be the same as with the other models i.e. KS-14C and KS-18B.

@KingSong69 said it's a case when accelerating very quickly instead of gradually.  Perhaps someone can do a test by setting the tiltback limit very low and then testing quick acceleration vs gradual acceleration. 

[esaj]

7 hours ago, Tomek said:

@esaj what a trip! (to a parallel universe, aaaarghhh .') )

Not my best idea to start writing that already half asleep after a long day, reading it back now, that post is just one mess

7 hours ago, Tomek said:

btw. what's your take on the eternal question on full speed cutoff?

is it there just for user safety, or would you risk serious damage to the controller if the motor would be spinned (e.g. due to external forces) above its max rated speed when powered?

I think hobby16 sometime mentioned that the cut-off itself is unnecessary (and he's an electronics engineer, so I believe he knows this stuff far much better and in-depth than me). So I'm not exactly sure why it is there, but I do think that the voltages play at least a role; if the motor would pass "super-synchronous speed" (or at least that's what I think it was called), ie. the back-EMF voltage would rise higher than the battery voltage, my understanding is that the motor would actually start to brake (not nice especially if you're leaning forwards ). The larger the difference between (applied) battery voltage and back-EMF, the higher the current, and thus either stronger acceleration or braking effect. If it's only "barely" above, the effect isn't very strong though...

Some people have reported on some wheels (don't remember which, MSupers maybe?) that you can feel the wheel starting to fall forwards when you're near the cut-off speed, ie. the motor hasn't cut-out yet, but it runs out of torque (coasting) or starts minimal breaking. Apparently, if you're fast enough, you can still save the situation if you're fast enough (move your weight back, to drop your speed).

So the cut-off might not be needed (at all), but that doesn't mean that the situation would (necessarily) be any more safe, to the rider at least. If you're going downhill and reach that "full speed", even if the wheel didn't cut-out, it would probably start braking, and if you were accelerating fast, it could just suddenly "slam" on the brakes. Likely you'd still fall, cut-off or not... tilt-back cannot be applied near the full speed, as it requires more torque (slight acceleration) to lift the pedals up, and to produce that torque, you need a higher voltage from the battery-side vs. the back-EMF, and if the back-EMF is near or at the battery voltage, that's not possible.

Seeing in real life how large spikes (to the tune of 10x the "input" voltage) the motor can kickback, that's what worries me right now, as it can go way above the rated voltages of the components. But there must be something in the wheels (either in the motors themselves or on the mainboard), like a snubber circuit or TVS-diodes or whatever, to "eat up" those high spikes. Or then they're just too low-energy (current) and short-lived (don't remember the details anymore, but probably the single spikes didn't last much more than microseconds, ie. millionths of a second) to actually harm the components. I really don't know (well, at least my H-bridge still works just fine despite those >100V spikes, even though the components are rated for something like 50-75V). But if the "ratio" is similar in the wheel motors, that could mean up to something like 600-800V spikes...

[Chriull]

5 hours ago, KingSong69 said:

Yep! To quick and extreme!

i don't think i can prevent that in The SAME Situation at all....

i normally now The Limits.....but i oversaw The Little downhill Part (was on a Giant Gas Station)...which gave me too much acceleration....

so i THINK from 25 to 33 was in such a fast way that The tiltback was extreme and quick As i Never had such a "hard" tiltback before....

for me The Solution Is just Not to push to hard After 20kmh :-)

really: completly my fault....i did in NO way Blame The Wheel....

 

5 hours ago, John Eucist said:

Hmm.  In that case I think the tilt-back programming could be improved.  It seems that the tilt-back function itself is what caused you to fall instead of a shut-down.  Maybe, ironically, it would be safer to disable the tilt-back and just rely on the beeps?

I had almost such a situation with my 9bot one e+ - accelerating a bit to hard and then having the tiltback kicking in too violently. Here you see the graph of the speed/pitch angle http://forum.electricunicycle.org/topic/3589-9b-metrics/?do=findComment&comment=39003. Unlike Kingsong69 i could not "overreact" and break to hard - i was quite surprised of the tiltback angle and tried everything to stay stable on the wheel - i could not decelerate and so the ninebot decided to even increase the tiltback angle! This whole fight took about 4-5secs until i regained full balance and could slowly start braking again - it felt like taking forever...

The harder one accelerates the harder the tiltback will kick in - or it would be useless. If one accelerated too hard you would be within no times way over the max speed and overlean/faceplant if the tiltback would be starting softly... If the tiltback is just before the maximum speed of the wheel (where there is still some torque left). In this case the "tiltback /no tiltback " question is just the choice of how one wants to fall...

The same is with the beeps - to give a warning for a reasonable reaction time one would need to set them at quite low speeds, so one has 0,5-1sec for stopping the acceleration (or even more if one needs time to evaluate if one wants to ignore the beeping or one should deaccelerated...) But this would lead to the wheel beeping all the time and making one crazy if one drives "normal"...

This situation should be a nice challenge for the firmware programmers - the wheel knows the actual speed, the pitch angle of the wheel (the driver pushing to accelerate) and the resulting acceleration to keep the driver upright -> so they could calculate if the actual scenario will "overshoot" the tiltback speed/maximum wheel speed whithin the next 1,2 or 3 seconds and immedeately start a (softer) tiltback/wild beeping!

2 hours ago, John Eucist said:

@KingSong69 said it's a case when accelerating very quickly instead of gradually.  Perhaps someone can do a test by setting the tiltback limit very low and then testing quick acceleration vs gradual acceleration. 

 

Whoever tries quick acceleration with a low tiltback be prepared to get an absolutely not nice experience...

[US69]

1 hour ago, Chriull said:

 

I had almost such a situation with my 9bot one e+ - accelerating a bit to hard and then having the tiltback kicking in too violently. Here you see the graph of the speed/pitch angle http://forum.electricunicycle.org/topic/3589-9b-metrics/?do=findComment&comment=39003. Unlike Kingsong69 i could not "overreact" and break to hard - i was quite surprised of the tiltback angle and tried everything to stay stable on the wheel - i could not decelerate and so the ninebot decided to even increase the tiltback angle! This whole fight took about 4-5secs until i regained full balance and could slowly start braking again - it felt like taking forever...

The harder one accelerates the harder the tiltback will kick in - or it would be useless. If one accelerated too hard you would be within no times way over the max speed and overlean/faceplant if the tiltback would be starting softly... If the tiltback is just before the maximum speed of the wheel (where there is still some torque left). In this case the "tiltback /no tiltback " question is just the choice of how one wants to fall...

The same is with the beeps - to give a warning for a reasonable reaction time one would need to set them at quite low speeds, so one has 0,5-1sec for stopping the acceleration (or even more if one needs time to evaluate if one wants to ignore the beeping or one should deaccelerated...) But this would lead to the wheel beeping all the time and making one crazy if one drives "normal"...

This situation should be a nice challenge for the firmware programmers - the wheel knows the actual speed, the pitch angle of the wheel (the driver pushing to accelerate) and the resulting acceleration to keep the driver upright -> so they could calculate if the actual scenario will "overshoot" the tiltback speed/maximum wheel speed whithin the next 1,2 or 3 seconds and immedeately start a (softer) tiltback/wild beeping!

 

Whoever tries quick acceleration with a low tiltback be prepared to get an absolutely not nice experience...

Again: my fault!!!

what should The Wheel Do better?

if You accelerate such hard The tiltback has to be hard....otherwise You would run into a Shut Off because The tiltback Is to useless....

no tiltback in that Situation would have bring The Wheel for certain Near 40kmh....

to tell The truth: i want to Show some Guys on The Gas Station how fast this Wheel Is ....and Overdone it completly ....

kind of : Look what i can! Stupidity at it's best...

 

[John Eucist]

7 minutes ago, KingSong69 said:

if You accelerate such hard The tiltback has to be hard....otherwise You would run into a Shut Off because The tiltback Is to useless....

I don't think that's necessarily true.  The only purpose of a tilt-back is to alert the user that you have exceeded a certain speed (in case you can't hear the beeps).  It should not tilt back to an extreme angle where you can no longer stand on the pedals to do a controlled slow down.  It should tilt to a maximum angle where you will definitely notice it as a warning but not so much so that the tilt-back itself becomes what CAUSES your faceplant.

[Cloud]

13 hours ago, John Eucist said:

I don't think that's necessarily true.  The only purpose of a tilt-back is to alert the user that you have exceeded a certain speed (in case you can't hear the beeps).  It should not tilt back to an extreme angle where you can no longer stand on the pedals to do a controlled slow down.  It should tilt to a maximum angle where you will definitely notice it as a warning but not so much so that the tilt-back itself becomes what CAUSES your faceplant.

 I have to agree with kingsong 69 here.

Tiltback has several purposes , most important being to make it impossible for the rider to continue going at the high speed and force him to slow down. Some riders will use it as an additional level of notification ( perhaps in a noisy environment where beeps cannot be heard), however the intent of the beeps is to notify, and the untent of te tiltback is to force the rider to slow down. It is there for the rider who chose to ignore all the warnings ( the last beep) and will therefore ignore all other beeps however many are set up to be the last ones, and continued accelerating. Tiltbqck therefore cannot be mild in a situation where the acceleration is too high, so as not to defeat the purpose of the tiltback , or it will be too late to tilt back after the fact

Unless the speed has reached a dangerous level, tiltback should be set up to be mild but noticeable. If the speed quickly reaches a dangerous level, tiltback has to be rather sharp. ( and this is how it works in ks14).  Perhaps after the rider falls off the wheel once caused by the severe tiltback, he will learn not to accelerate so fast when going already fast, rather than easily go thru a mild tiltback, learn to ignore it, reach an unsafe speed and pay for it one day.

if a safety feature makes the device more dangerous, it should be turned off. In this case , however, while there could be a situation where tiltback can cause the rider to fall, one can learn to continue riding through the tiltback, but one will never learn to stay upright if the wheel shuts down in the absence of said tiltback

[Cloud]

22 hours ago, who_the said:

Glad you're OK @Cloud. Any hiccups or sputters before it gave out? I've slowly started to push my KS-14C 800w/840wh harder recently, and am interested if there are any warning signs. I'm about 70kg and average about 19kph during my 1/2-hour, 5.5 mile commute each way. I have my beep set to 30kph and usually hear it a few times each direction.

No no hiccups, no warning. It all happened pretty fast though. Normally there are warning signs , speed beeps of course, sometimes if you are slowly pushing the wheel beyond its capacity, it will give out solitary beeps, or could tiltback depending on the situation. Long atory short , if you are 70kg, you should be in good shape, and almost outside of the risk zone riding normally on horizontal pavement on full battery. However it all depends on how hard you will be pushing the wheel. You can steel overlean, overspeed, overtorque, over anything. Knowing the perfect balance between overdoing and safely extreme-riding is a mark of a master  

 

 

 

[John Eucist]

37 minutes ago, Cloud said:

Tiltback has several purposes , most important being to make it impossible for the rider to continue going at the high speed and force him to slow down.

Actually when pedals are tilted back (up until a certain angle) it makes it EASIER to apply forward pressure on the pedals (hence acceleration).  Of course, if it's tilted back to an extreme angle where you can no longer stand on the pedals then the "make it impossible" scenario may be true, but then you would faceplant anyway since you can no longer stand on the pedals nor be able to apply backward pressure on the pedals to slow down.  I may be wrong but that seems to be my experience.  Would like to hear more comments regarding this from more people.

Additionally, I want to add that the tilt-back speed threshold should not be set at a level too close to "shut down" speed.

[Cloud]

1 minute ago, John Eucist said:

Actually when pedals are tilted back (up until a certain angle) it makes it EASIER to apply forward pressure on the pedals (hence acceleration).  Of course, if it's tilted back to an extreme angle where you can no longer stand on the pedals then the "make it impossible" scenario may be true, but then you would faceplant anyway since you can no longer stand on the pedals nor be able to apply backward pressure on the pedals to slow down.  I may be wrong but that seems to be my experience.  Would like to hear more comments regarding this from more people.

In most cases, before it becomes impossible to ride due to the extreme angle, the rider has a chance to slow down and let the tilt back go away. Upon getting the tiltback the rider will slow down immediately knowing what will happen if he doesnt.  My guess is you have been riding a wheel with very extreme tilt back once the critical speed is achieved, and in this sense i agree with you - tilt back should be gradual with slow acceleration - that is it should start prior to reaching the critical speed equivalent to a very steep pedal angle. You should probably change the wheel to kingsong  ks's tiltback is very mild unless you continue accelerating fast

[John Eucist]

1 hour ago, Cloud said:

You should probably change the wheel to kingsong  ks's tiltback is very mild unless you continue accelerating fast

I have four ks14 (800w) and two ks16

 

23 hours ago, KingSong69 said:

and The tiltback was ....don't Know how to say...Crazy hard!

much harder As when i accelerate slowly to Max Speed...

 

23 hours ago, KingSong69 said:

The tiltback was extreme and quick As i Never had such a "hard" tiltback before....

Based on what @KingSong69 said it appears that KS has the ability to have an extreme tilt-back when accelerating too fast.  And by that I do not mean "continue accelerating fast" but from no-tilt to a sudden extreme tilt.

[Mono]

10 hours ago, John Eucist said:

Actually when pedals are tilted back (up until a certain angle) it makes it EASIER to apply forward pressure on the pedals (hence acceleration).

applying forward pressure on the pedals, or leveling the pedals in the tilt-back situation, accelerates only the wheel. This moves the wheel in front of the driver, which in consequence either leads to reduction of velocity (principle of counter-steering or the inverted pendulum) or the driver loosing the wheel to his front.

This is why extreme tilt back makes it more and more difficult to accelerate: to initiate acceleration one needs to tilt back even further which at some point becomes very uncomfortable or even impossible.