MCM5 sudden acceleration/cut out at 23 or 24 mph

[Marty Backe]

2 hours ago, Delmeekc said:

On the wheellog output file spreadsheet my MCM5 peaks at over 7000w (7kw), definitely enough power.

On the alarms, is it best to set in wheellog or the gotway app , are the settings stored in the wheel or would they change to whats in the wheellog app.

The Gotway alarms are fixed (unalterable). The first two occur at fixed speeds (those speeds are set differently for each type of wheel). The third varies based on speed and battery level, and wheel type (MCM5, MSX, etc.).

The WheelLog alarms are only based on speed and of course are maintained by the WheelLog app, within your phone memory.

[alcatraz]

Any motor is unlikely to have max torque at top speed.

I'm just saying that theres a difference between 4000w climbing (medium speed max torque) and 4000w flat riding (max speed medium torque).

It'd be nice to see some power/torque curves of these motors. At different rpms the values change a lot.

Edited September 29, 2019 by alcatraz

[maltocs]

On 9/29/2019 at 10:17 AM, Delmeekc said:

On the wheellog output file spreadsheet my MCM5 peaks at over 7000w (7kw), definitely enough power.

On the alarms, is it best to set in wheellog or the gotway app , are the settings stored in the wheel or would they change to whats in the wheellog app.

I usually use the gotway app personally, although wheellog shoudl work fine as well. The settings are stored in the wheel and should not change if you don't change it unless for some reason there is an issue with the wheel. ie, on the MTen3, when my bluetooth module popped out, it reset the settings when it popped back in. It would probably reset if all power was cut to the wheel, ie you pulled the battery out for whatever reason. 

[Chriull]

23 hours ago, alcatraz said:

Any motor is unlikely to have max torque at top speed.

The EUC motors (bldc) have max possible torque at standstill and zero torque at max (no load) speed.

So by constant acceleration == constant torque (in reality even increasing torque by air drag) one will hit inevitably rather sooner than later the motor limit (decreasing torque) and overlean.

 

23 hours ago, alcatraz said:

I'm just saying that theres a difference between 4000w climbing (medium speed max torque) and 4000w flat riding (max speed medium torque).

Power is speed times torque (and some constant factor, depending on "which" speed used).

The main difference between these two 4000W is that at low speeds on inclines the motor current is much higher and endangers the mosfets/motor wires.

23 hours ago, alcatraz said:

It'd be nice to see some power/torque curves of these motors. At different rpms the values change a lot.

Torque curve (in first approximation) is easy - a line starting at max stall torque at zero speed going (linearly) down to zero at max no load speed.

Speed over speed is a simple 45° line.

If one multiplies both to get the (maximum possible) power its an "hill" (parabola) beeing zero at zero speed and at max no load speed and having its maximum at half max no load speed.

This max no load speed is about the lift cut off speed (just a little bit higher in because of the bearing friction, etc) and depends directly proportional on the battery voltage. So, as simple example if it is 84 km/h at 84V it will be 66km/h at 66V. Maximum corresponding possible output power will be in this example at 84/2=42km/h at 84V and 66/2=33km/h at 66V.

Motor current (as reported ?hopefully/more or less? by GW wheels) is (in a first approximation) proportional to the motor torque.

The motor generates a voltage (back emf) beeing kv times rpm. This back emf times motor current is the motor output power (== torque times speed time some constant factor).

A bit of the difference between this back emf and the battery voltage is the voltage drop at the ohmic resistance of the motor coils caused by the motor current. The rest of the voltage difference is "handled" by the motor driver and the coil inductance which act as a step down converter. So battery current is always lower than the motor current and battery voltage is always higher as the motor voltage. Just at max no load speed battery voltage is equal to motor voltage and both currents are by this zero. The lower the speed, the bigger the difference.

So all the reported power numbers like here this 7000W are just bullshit, as they multiply battery voltage with motor current, which are in absolutly no correlation. Like one has a desk lamp with a transformator/step down converter for a 12V bulb, taking lets say 1A. In the "logic" of the wheels reported number the power at the lamp would be mains voltage (230/110V) times this 1A - 230/110W! Which is absolut bullshit - the power dissipated by the lamp is of course only the 12V times 1A =12W!

Coming back again to the motor current, which is proportional to the motor torque: if one plots this (from wheellog logged data) in a graph over speed (as shown in https://forum.electricunicycle.org/topic/7855-anatomy-of-an-overlean/ ) for an overlean, one can see nicely how the current (=torque) decreases with speed along the motor limit while the rider overleans and faceplants.

There is nothing cutting out, shutting down or by firmware limiting anything (1) - it's just the motor not beeing able to deliver the torque necessary to counter the forward leaning rider. If one leans forward hard enough and the wheel accelerates so strong to keep the rider balanced everything happens so fast that it justs feels as if suddenly the motor would "cut out" as one "hits" the limit.

 

(1) there is just an exemption with the Z10 which limits the motor current by firmware to 110A and one can overlean this wheel by hitting this firmware current limit at "about any speed" without reaching the motor limit. (https://forum.electricunicycle.org/topic/8014-ninebot-one-z-z6-z8-z10/?do=findComment&comment=268477 

)

[Mono]

On 9/27/2019 at 5:04 AM, maltocs said:

now I don't want to ride it knowing that if I touch that magic 23mph or 24mph, it will speed up and dump me. 

LOL, AFAICS is the experiment is consistent with tiltback which sets in at the speed where you get the sudden acceleration. Nothing wrong with it. This is exactly what tiltback is doing: forces you to tilt the wheel far more back to maintain the same speed. Otherwise the wheel accelerates. Think about it: the sudden acceleration of the wheel will dump you to the back, not to the front. I assume that is not what happened, right? I am glad though that you decided to stay below 20mph for now.

Edited October 1, 2019 by Mono

[maltocs]

4 hours ago, Mono said:

LOL, AFAICS is the experiment is consistent with tiltback which sets in at the speed where you get the sudden acceleration. Nothing wrong with it. This is exactly what tiltback is doing: forces you to tilt the wheel far more back to maintain the same speed. Otherwise the wheel accelerates. Think about it: the sudden acceleration of the wheel will dump you to the back, not to the front. I assume that is not what happened, right? I am glad though that you decided to stay below 20mph for now.

I DO plan to stay below 20 now, but I did figure out to just turn off till back and it won't dump me again while I'm accelerating. I'm pretty the wheel wouldn't have acted that way if I just got 23 if I was very slowly accelerating, but it was a normal to hard acceleration in my case.

Behavior of this wheel I think. I know I never had any problems with actually being tilted back on my V10F. 

[Chriull]

5 hours ago, maltocs said:

I DO plan to stay below 20 now, but I did figure out to just turn off till back and it won't dump me again while I'm accelerating.

Sorry no. The tiltback had nothing to do with your accident(1). It will happen the same with tiltback disabled - please be careful!

Quote

I'm pretty the wheel wouldn't have acted that way if I just got 23 if I was very slowly accelerating, but it was a normal to hard acceleration in my case.

Exactly - the solution is to accelerate slowly and carfully at higher speeds!

Quote

Behavior of this wheel I think. I know I never had any problems with actually being tilted back on my V10F. 

If you accelerate hard to the limit with the V10 you'd most probably won't get/notice any tiltback before overleaning. Like with the last reported KS18Xl overlean...

Edit:

(1) In reality there are three different scenarious:

-1- One accelerates so hard, that one hits the motor limit below tilt back speed - then there is not tiltback starting and hence nothing happening by/beeing influenced by the tiltback. One just overleans....

-2- For less accelerations but still high burdens there is a "small" area, where tiltback speed is very close to the motor limit. If one "accelerates" into this "area" the tiltback tries to accelerate the wheel (so the pedals tilt up) and by this the motor limit is hit a fraction of a second earlier. But one would have hit it anyway just this fraction of a second later by accelerating. So no real difference... If one is very "sensitive/experienced" and feels this extra acceleration by the tiltback starting to do this extra acceleration one could see this as last warning and try to break immedeately. Could give one a last chance - maybe everything is happening too fast and imperceptible in such a situation that it just doesn't matter

-3- One is in the region with enough safety (torque) margin once tilt back kicks in. Then one just gets a tiltback. Nothing more, nothing less. The reason many GW drivers disable the tiltback (beside wanting to reach new speed records) is because the faster one accelerates into the tiltback the stronger it tilts the pedals. This can be very discomforting, especially at higher speeds. On the other side on should consider that without such a discomforting tiltback with such accelerations an overlean is just some seconds (if even a full second) away...

Edited October 1, 2019 by Chriull

[Marty Backe]

9 hours ago, maltocs said:

I DO plan to stay below 20 now, but I did figure out to just turn off till back and it won't dump me again while I'm accelerating. I'm pretty the wheel wouldn't have acted that way if I just got 23 if I was very slowly accelerating, but it was a normal to hard acceleration in my case.

Behavior of this wheel I think. I know I never had any problems with actually being tilted back on my V10F. 

The biggest take away for others reading this is, only do hard accelerations (if you must) at very slow speeds. If you've never truly learned your wheel, monitor the currents for awhile to learn the extreme power demands that your wheel requires when you do a hard acceleration.

I know I'm missing out on some of the fun of EUCs by never doing hard accelerations, but I just don't want to be dumped even at the starting from standstill stage.

[maltocs]

14 hours ago, Chriull said:

-2- For less accelerations but still high burdens there is a "small" area, where tiltback speed is very close to the motor limit. If one "accelerates" into this "area" the tiltback tries to accelerate the wheel (so the pedals tilt up) and by this the motor limit is hit a fraction of a second earlier. But one would have hit it anyway just this fraction of a second later by accelerating. So no real difference... If one is very "sensitive/experienced" and feels this extra acceleration by the tiltback starting to do this extra acceleration one could see this as last warning and try to break immedeately. Could give one a last chance - maybe everything is happening too fast and imperceptible in such a situation that it just doesn't matter

If these were the only three scenarios, then I would have to go with #2 that happened to me. I was accelerating , not any harder than i've done before, but I probably got to a slightly higher speed. The incline was very slightly downhill, it was VERY little grade, but worth mentioning, but even a very little amount with my 210lbs that day helped me to accelerate a tiny bit faster. It all happened in a split second, but it pretty much tossed me off in the forward direction or cut out, i dunno, it was so fast. There was no chance to brake. I did not hear any beeps until I was tossed. I react very well to beeps. it was not noisy and I was not wearing a helmet, so I would have heard them.

I don't know that the V10F would do this as it doesn't accelerate that fast. I mean it's fast, but the MCM5 accelerates like no other wheel I've tried. Not that I'm a super hard accelerator, but I do do a LOT of hills, and at times I feel like i'm on my tippy toes getting V10F to go faster. I would never do that with the MCM5 as it would actually go!

Edited October 1, 2019 by maltocs

[Mono]

On 10/1/2019 at 8:51 AM, Chriull said:

-2- For less accelerations but still high burdens there is a "small" area, where tiltback speed is very close to the motor limit. If one "accelerates" into this "area" the tiltback tries to accelerate the wheel (so the pedals tilt up) and by this the motor limit is hit a fraction of a second earlier.

How is this any different from initiating to break in this very situation?

What does "hit the limit earlier" even mean? I don't see any logical way how tiltback can lift the pedal in exchange of giving up torque that is needed to keep the rider from overleaning. Overlean means the pedal drops, tiltback means the pedals lifts. If the wheel can provide sufficient torque it can lift the pedal (or keep it straight). If the wheel cannot provide sufficient torque, it will drop the pedal forward. The idea that trying to lift the pedal could reduce the applied torque seems just a non-sequitur.

[Mono]

On 10/1/2019 at 7:07 AM, maltocs said:

I DO plan to stay below 20 now, but I did figure out to just turn off till back and it won't dump me again while I'm accelerating. I'm pretty the wheel wouldn't have acted that way if I just got 23 if I was very slowly accelerating, but it was a normal to hard acceleration in my case.

The wheel did dump you forward, not backwards, right?

[Chriull]

1 hour ago, Mono said:

How is this any different from initiating to break in this very situation?

What does "hit the limit earlier" even mean? I don't see any logical way how tiltback can lift the pedal in exchange of giving up torque that is needed to keep the rider from overleaning. Overlean means the pedal drops, tiltback means the pedals lifts. If the wheel can provide sufficient torque it can lift the pedal (or keep it straight). If the wheel cannot provide sufficient torque, it will drop the pedal forward. The idea that trying to lift the pedal could reduce the applied torque seems just a non-sequitur.

With my point 2 in regard of tilt-back influencing overlean i meant the small area, just below the "crossing" of tiltback speed and the motor torque over speed limit.

One can accelerate into this "area" and still just have enough torque so tiltback can start. By the starting tiltback, trying to tilt the pedal up by accelerating a small oncrease of burden and speed happens, so one reaches the motor limit/overlean a little bit earlier...

Imo just a non issue but i mentioned this point, because there are/were always rumours that the tiltback is so dangerous because he can cause an overlean.

Edit: A try to show this 3 cases in a torque over speed diagramm:

Edited October 2, 2019 by Chriull

[Mono]

1 hour ago, Chriull said:

By the starting tiltback, trying to tilt the pedal up by accelerating a small oncrease of burden and speed happens, so one reaches the motor limit/overlean a little bit earlier...

This I don't understand. The only thing the motor can do is put more torque or less torque. If the motor is at its limit torque it doesn't matter whether the controller asks for tiltback, the motor will stay on its limit torque and not be able to speed up (i.e. lift the pedals). If it is not at its torque limit it will increase the torque which can only prevent an overlean. Only this added torque can then lead to a speed up (of the wheel, not of wheel and rider) which only then will decrease the torque limit while already more torque was applied. What am I missing?

1 hour ago, Chriull said:

Imo just a non issue but i mentioned this point, because there are/were always rumours that the tiltback is so dangerous because he can cause an overlean.

Then why would you even fuel these rumours? Surely enough @maltocs chose exactly this scenario as the only possible cause of his overlean.

Edited October 2, 2019 by Mono

[Chriull]

12 minutes ago, Mono said:

What am I missing?

I don't know - i can't really follow your points.

If you look at the graph above at the (constant) torque line number 2 - this constant torque is acceleration the rider & wheel until tiltback speed is reached. This torque was choosen that this happens just before reaching the motor limit. So without tiltback the rider would overlean in lets say 0.1 seconds, by the starting tiltback which gives a bit more acceleration one would reach the motor limit in a little bit less like 0.08 sec.

1 and 3 cover almost all cases, and with case 2 one would overlean anyhow...

[Mono]

4 minutes ago, Chriull said:

i can't really follow your points.

Where did I lose you?

5 minutes ago, Chriull said:

If you look at the graph above at the (constant) torque line number 2

The point is that in the tiltback scenario we would not go along a horizontal constant torque line and then magically tiltback appears. The only way tiltback could happen is that we also have a vertical change thereby increasing torque.

[erk1024]

On 9/26/2019 at 11:04 PM, maltocs said:

I KNOW, NOT WEARING PROTECTION IS STUPID

I was wearing boots and knee pads, but no shin guards. I was riding at night ran off into the grass because the sidewalk abruptly ended. I bogged down and had to bail ... and one of the pedals hit me in the shin. Um, ya, I deserved that...

Basically you had no protection, no alarms, and crashed and didn't get hurt = SUPER LUCKY

Edited October 2, 2019 by erk1024

[erk1024]

On 9/27/2019 at 12:56 AM, Marty Backe said:

I'm just going to stick with ~25-mph max regardless of how fast my wheel can go

I agree with this philosophy, although I've set my limit a smidge higher on the 100V Monster V3. I just leave on the 48kph tiltback on.

[Chriull]

2 hours ago, Mono said:

Where did I lose you?

From the beginning - i assume you wrote about something different or some special aspect of this issue i did not get...

Quote

The point is that in the tiltback scenario we would not go along a horizontal constant torque line

Constant torque (about constant acceleration) up to tiltback speed was just an assumption/condition i choose to show the three different possible scenarios. I could have choosen any other more complicated function to reach these three states, but why make it more complicated...

Quote

and then magically tiltback appears.

Tiltback appears deterministicly once one accelerated up to the threshold and had not enough torque to hit the motor limit (case 1 vs case 2&3)

Quote

The only way tiltback could happen is that we also have a vertical change thereby increasing torque.

Yes. That's what i tried to draw in my above sketch for case 2 - note the small line between tiltback speed and motor limit, a bit above the line before tiltback speed.

Edited October 2, 2019 by Chriull

[Mono]

@Chriull, if you agree that tiltback can only be initiated by increasing the torque, I don't understand how you can think that it can lead to an overlean. Increasing the torque is exactly the one wheel-side action that prevents overleaning.

1 hour ago, Chriull said:

i assume you wrote about something different or some special aspect of this issue

I wrote something entirely generic, starting with that the wheel can only either increase torque or decrease torque (given it provides a certain torque at a certain time) and do nothing else really.

Edited October 2, 2019 by Mono

[Chriull]

2 minutes ago, Mono said:

@Chriull, if you agree that tiltback can only be initiated by increasing the torque,

+1

2 minutes ago, Mono said:

I don't understand how you can think that it can lead to an overlean.

It leads, just in this special case a bit earlier to an overlean than without tiltback. In normal scenarios like case 3 there is no leading to an overlean.

2 minutes ago, Mono said:

Increasing the torque is exactly the one wheel-side action that prevents overleaning.

?

Increasing torque increases acceleration and by this speed and hence brings one nearer to the motor limit.

?

[maltocs]

7 hours ago, Mono said:

The wheel did dump you forward, not backwards, right?

I was accelerating and it seemed to sudden accelerate me more until it cut out. I think in all cut out scenarios, one gets tossed forward, which is what happened to me.

4 hours ago, Mono said:

Where did I lose you?

The point is that in the tiltback scenario we would not go along a horizontal constant torque line and then magically tiltback appears. The only way tiltback could happen is that we also have a vertical change thereby increasing torque.

Honestly, I'm confused as well. I've experienced tiltback before on the V10F and Nikola+ when it overloads/overheats. They were usually when I was going at fairly slow speeds, under 12mph and always uphill. I sometime I even try to "ride it out" but it just keeps on tilting the pedals to such an extreme angle until I can physically no longer ride the device. I've also experience speed based tiltback on my old Ninebot S1 and MTen3 when the unit reset itself to the lowest tiltback speed. Again, it just tilted back until I was physically kicked off.

But on this forum, everyone is telling me that for a wheel to accomplish tiltback, the unit must accelerate. Due to my own test (the video), it seems that acceleration IS INDEED what happens when the MCM5 hits the tiltback setting. This is not the tiltback I'm used to nor anything that actually makes sense to me. I'm used to it quickly changing the baseline angle of the petals to tiltback to force me to slow down and eventually step off. 

But in the end, that is what happened and that was how I crashed on the MCM5. That is why I'm just turning tiltback off and not going that fast on this device. 

7 minutes ago, Chriull said:

It leads, just in this special case a bit earlier to an overlean than without tiltback. In normal scenarios like case 3 there is no leading to an overlean.

 

By special case, I assume you mean I just happened to meet all the the circumstances to cause the cut out that day. I felt I didn't ride any differently that day other than going a little faster. Now I feel like I have always been on the edge (2-3 mph) of it cutting out.

[Mono]

21 minutes ago, Chriull said:

Increasing torque increases acceleration and by this speed and hence brings one nearer to the motor limit.

It seems we have different models of what is happening when the wheel increases its torque without the rider having changed the input/position. I think that the wheel speeds up to the front of the rider, while you seem to think that wheel and rider will speed up. If only the wheel speeds up, it becomes impossible for the rider to fall off to the front of the wheel and it will initiate a slow down of wheel and rider (which is what tiltback is meant to do) or the rider will fall off to the back.

The only way to counteract an overlean on the wheel-side is to bring the motor closer to its limit. So bringing the motor closer to its limit cannot in itself make an overlean more likely.

Edited October 2, 2019 by Mono

[Mono]

12 minutes ago, maltocs said:

This is not the tiltback I'm used to nor anything that actually makes sense to me. I'm used to it quickly changing the baseline angle of the petals to tiltback to force me to slow down and eventually step off. 

There is no contradiction there. The only way to slow down is to bring the wheel further in front of the rider than it was before, that is, to speed up the wheel compared to the rider.

[maltocs]

1 minute ago, Mono said:

There is no contradiction there. The only way to slow down is to bring the wheel further in front of the rider than it was before, that is, to speed up the wheel compared to the rider.

I'm okay with the wheel speeding up to get in front of me, I just dont understand why it would do it to a point of cut out where there is a 100% chance of a crash. If the wheel just tilted the petals back (ie tiltback) or just stopped increasing the power (as in just maintain power) to a point of cut out, there would be a less than 100% chance of crash. I feel that's what it should be doing. But then again, it is just a basic mechanical device and probably doesn't employ that much smarts.  

[erk1024]

On 10/1/2019 at 4:49 PM, maltocs said:

If these were the only three scenarios, then I would have to go with #2 that happened to me.

That sounds right. Because the wheel was using most of the torque already to go close to max speed, it didn't have enough left to get back under you. And it didn't have time to warn you. As has been mentioned, you can't accelerate hard while going fast.

Because of the small wheel, the MCM5 has lots of torque / zippiness, but it's not built for speed. The other new wheels have more powerful motors, bigger batteries for more available current, and can handle higher speeds.