KingSong 16X 1554Wh 2200W 16*3in (Released July 2019)

[Chili D]

1 hour ago, Mike Sacristan said:

Doesn't the 16X have it's own alarms for this? Three rapid beeps in succession.

I hit it for the first time last week at a skatepark on FW 1.05. I was going to go up a 33 degree incline and I did the transition from flat to slope too hard.

I hit it again the day before yesterday on FW 1.07. I looked at Darknessbot and saw that I had hit slightly over 36.

Youtube link below embedded with timestamp at 15:15
Time of beep: 15:18
Time where I show Darknessbot graph: 16:20
Time where I measure slope: 16:48 (33 degrees or 65%)

I repeated the slope several times with smoother / more linear acceleration and got close to 36 but did not trigger any beep.

My riding weight was 69kg.

Other than these two instances I have never hit that alarm.

 

Thanks for the info on this. 36 would be great high end. nice analysis.  I haven’t heard those built-in beeps yet. I guess I prematurely set at 29amps in DB so I’ve been hitting the DB threshold and not the wheel’s even though I may be good in the low 30s. ill step the number up a little at a time and feel it out. 
 

@buell47

agreed on the wind and hearing. the reason I want to set in DB is the audible beeps from DB can be fed through the main speakers and controllable with the phones’s volume buttons vs the single onboard speaker that I can barely hear. Another bonus is that if music is playing the DB warning sounds are very noticeable because the music is overridden by the app’s beeps/voice. 
 

 

chili

[Mike Sacristan]

56 minutes ago, buell47 said:

Unfortunately hardly to hear at 45-50 km/h and on windy days even from 40 km/h. (without music) 

I was riding with Petra today. We switched wheels. She took off on my 16X.
She was doing 46kmh and the wheel was doing 5 beeps and also saying "please decelerate"... she never touched the soft tiltback though
Afterward I told her to look at the stats. They said 46.5kmh. She said that can't be me I didn't hear any alarms. 

I asked her what the hell is wrong with her ears because I can hear every single alarm lol. I guess we all have different ears and some ears cause more turbulence at speeds than others. I can barely hear my MSX beeping... she can hear her Tesla beep though. Strange.

Without those beeps though we are stuck at soft tiltback. But what we can do is play with the 4 beeps in slower scenarios to get a feel of the amount of lean possible.

For instance I was doing 35 and she was passing me at 45. I threw myself forward to match her speed and got soft tiltback at 44 because of the acceleration. Otherwise I would have gotten soft tiltback att 47 at that voltage. So the variable soft tiltback is a good feature. I did not get 4 beeps though. 

[BleepBloopBlop]

4 hours ago, Chili D said:

I’ve been searching keywords (16x/ alarm/amps/max), but not finding any details on the max amp threshold to watch for when accelerating hard on the ks16X. I currently have a 29Amp alarm setup in DarknessBot based on my accelerations that feel hard, but I tend to hit the alarm quite often. 

Anyone have any details or insight on how high it can go before possible overlean?

thanks,

chili

I have my alarm set at 60 amps and can hit that from a standing start on the flat but that rarely happens. FW 1.05

[EUC Custom Power-Pads]

3 minutes ago, BleepBloopBlop said:

60 amps and can hit that from a standing start on the flat but that rarely happens.

Aren't you the faceplant guy? 

[Mike Sacristan]

29 minutes ago, Chili D said:

Thanks for the info on this. 36 would be great high end. nice analysis.  I haven’t heard those built-in beeps yet. I guess I prematurely set at 29amps in DB so I’ve been hitting the DB threshold and not the wheel’s even though I may be good in the low 30s. ill step the number up a little at a time and feel it out. 
 

@buell47

agreed on the wind and hearing. the reason I want to set in DB is the audible beeps from DB can be fed through the main speakers and controllable with the phones’s volume buttons vs the single onboard speaker that I can barely hear. Another bonus is that if music is playing the DB warning sounds are very noticeable because the music is overridden by the app’s beeps/voice. 
 

 

chili

Try it at a skate park and ride like a donkey into a 33 degree incline like I did.  

My friend set his Nikola 100v at 90A to follow Marty's overheat hill methodology and Wheellog beeped all the time. In the end the beeps will just turn into background noise and lose meaning if we hear them too often.

Bumping it up a bit sounds like a good idea. A DB 4 beep 88% power translation would be nice as well.

51 minutes ago, BleepBloopBlop said:

I have my alarm set at 60 amps and can hit that from a standing start on the flat but that rarely happens. FW 1.05

Does the wheel do 3 beeps in quick succession as per my above clip? What are you using to read the amps?

[BleepBloopBlop]

19 hours ago, buell47 said:

Aren't you the faceplant guy? 

I'm the hand plant guy, My face is fine haha. I've put another 1000 miles on my 16X since that accident with no issues.

 

I use WheelLog for amperage alarming. I used this more as a method for testing to see the maximum power I could get the wheel to draw without overpowering it. Here is the most I've logged to date. I dont really see a point in doing this as honestly the wheel doesn't accelerate much faster leaning so aggressively. 

[JonnyBonz]

20 hours ago, Mike Sacristan said:

Bumping it up a bit sounds like a good idea. A DB 4 beep 88% power translation would be nice as well.

Does the wheel do 3 beeps in quick succession as per my above clip? What are you using to read the amps?

By DB I’m assuming you are referring to DarknessBot.  Are you able to set the alarms with the latest version?  I am running DarknessBot on IOS have not been able to set either of the 3 alarms or the Max Speed.  Just wondering if anyone else is having the same problem. 

[Mike Sacristan]

3 hours ago, JonnyBonz said:

By DB I’m assuming you are referring to DarknessBot.  Are you able to set the alarms with the latest version?  I am running DarknessBot on IOS have not been able to set either of the 3 alarms or the Max Speed.  Just wondering if anyone else is having the same problem. 

Yes I mean DarknessBot.
Nope I can't set the alarms with it. They fail to set. So I set them with the Kingsong app and leave them there.
If I use any alarm on Darknessbot I use the alarm at 45 kmh but at application and not device level.

I'm sure it will be fixed in a future version. I just want the 45 kmh alarm because at that speed I have longer braking time, less time to react, etc.
If I want to ride at or past 45 kmh it will be with my alarm blazing. Whether I am on my MSX or 16X.

[Chili D]

6 hours ago, BleepBloopBlop said:

I'm the hand plant guy, My face is fine haha. I've put another 1000 miles on my 16X since that accident with no issues.

 

I use WheelLog for amperage alarming. I used this more as a method for testing to see the maximum power I could get the wheel to draw without overpowering it. Here is the most I've logged to date. I dont really see a point in doing this as honestly the wheel doesn't accelerate much faster leaning so aggressively. 

My viewing on the amp alarm wasn’t so much about leaning to go faster, but to have confidence in how hard I can lean.  I mentioned I had a DB alarm setup at 29amps and you and @Mike Sacristan are showing the ceiling of the wheel’S built in alarm is much higher than that. Now I can push more confidently. Appreciate everyone’s input here. 
 

chili

[mrelwood]

 

On 11/17/2019 at 7:53 PM, Chili D said:

max amp threshold to watch for when accelerating hard on the ks16X.

Don’t get confident accelerating harder! There isn’t a fixed amperage threshold that when exceeded causes an overlean. An overlean can be caused by many factors the amperage does not take in consideration. Don’t rely on just an amps warning to save your face.

[Aneta]

13 hours ago, BleepBloopBlop said:

I'm the hand plant guy, My face is fine haha. I've put another 1000 miles on my 16X since that accident with no issues.

 

I use WheelLog for amperage alarming. I used this more as a method for testing to see the maximum power I could get the wheel to draw without overpowering it. Here is the most I've logged to date. I dont really see a point in doing this as honestly the wheel doesn't accelerate much faster leaning so aggressively. 

This is a very wrong and very dangerous misconception - that "as long as my drawn power does not exceed the max power I ever recorded during aggressive accelerations at some speeds, I'm safe". The term "power" for us probably does more harm than good, we should always think in terms of thrust (or torque, for a given wheel diameter), and most importantly, thrust margin - a leftover from motor's thrust after air drag and rolling resistance take their mighty bite. All this is brilliantly illustrated in @zeke's "The Holy Bible of EUC Rider" post:

I'll use my little crafted example from here:

By moving the black vertical dashed line, we can inspect what would happen if the rider accelerated "full throttle" from that speed towards the "terminal" speed of 53.8kph. For example, if we move it to 42 (this is the answer to the question of the Universe, right?) - 42kph, we can see the battery power of 4473W (or 62.6A of battery current). That's how much power would be drawn if we were at 42kph and we leaned forward at exactly 100% duty cycle. Of course, that's impossible - that would be a faceplant, so we lean a bit less, and suppose, the power was... 4258W, as in your spreadsheet. Now, let's go back to my 50kph example. At 50kph the max battery power is only 3266W, much less than 4258, so we're totally safe, right? WRONG! And why, is shown in my example linked above: at 50kph a little unevenness on the surface with only a couple of inches rise in 1 yard of distance, will overthrust the motor and result in a faceplant!

We should just forget about this word "power", it's useless for us... and dangerously misleading.

Edited November 19, 2019 by Aneta

[Harvey Pooka]

1 hour ago, Aneta said:

This is a very wrong and very dangerous misconception - that "as long as my drawn power does not exceed the max power I ever recorded during aggressive accelerations at some speeds, I'm safe". The term "power" for us probably does more harm than good, we should always think in terms of thrust (or torque, for a given wheel diameter), and most importantly, thrust margin - a leftover from motor's thrust after air drag and rolling resistance take their mighty bite. All this is brilliantly illustrated in @zeke's "The Holy Bible of EUC Rider" post:

I'll use my little crafted example from here:

By moving the black vertical dashed line, we can inspect what would happen if the rider accelerated "full throttle" from that speed towards the "terminal" speed of 53.8kph. For example, if we move it to 42 (this is the answer to the question of the Universe, right?) - 42kph, we can see the battery power of 4473W (or 62.6A of battery current). That's how much power would be drawn if we were at 42kph and we leaned forward at exactly 100% duty cycle. Of course, that's impossible - that would be a faceplant, so we lean a bit less, and suppose, the power was... 4258W, as in your spreadsheet. Now, let's go back to my 50kph example. At 50kph the max battery power is only 3266W, much less than 4258, so we're totally safe, right? WRONG! And why, is shown in my example linked above: at 50kph a little unevenness on the surface with only a couple of inches rise in 1 yard of distance, will overthrust the motor and result in a faceplant!

We should just forget about this word "power", it's useless for us... and dangerously misleading.

I love this post. Not because I understand it . . . I don't. But you sneaked in a Hitchhiker's reference which is awesome. I showed the above linked discussion you had with @zeke to a friend of mine with a physics degree and asked him to explain it. His summary was, "Never mind. These people are smarter than you. Just do what they say."

[zeke]

1 hour ago, Harvey Pooka said:

I love this post. Not because I understand it . . . I don't. But you sneaked in a Hitchhiker's reference which is awesome. I showed the above linked discussion you had with @zeke to a friend of mine with a physics degree and asked him to explain it. His summary was, "Never mind. These people are smarter than you. Just do what they say."

Lol, sorry for being pedantic! This is the short of it.

The faster you go, the more thrust is needed to maintain your speed because drag force is rising.

The faster you go, the less thrust the EUC is capable of providing (this is a characteristic of all electric motors).

The difference between the thrust the EUC can provide, and the thrust you're already using, is how much leftover thrust is available for you to do as you please like trying to speed up or whatever. If there is zero thrust available, or if you suddenly lean forward and create a need for thrust that exceeds what is available, then you can't launch the EUC in front of you anymore so you can't slow down. (And then you apply the skin brakes.) It's clear that the point where available thrust reaches zero is a very critical, very important point. A hard limit. You could call this the wipeout point.

As you can imagine, the available thrust drops very quickly as you go faster, because the thrust needed to maintain speed is rising at the same time that the thrust the EUC can provide is dropping. At low speeds there's tons of thrust available, but at high speeds there's very little. And eventually, at some high speed, there's zero thrust available. This means that although you might be able to accelerate super quick from a standstill, if you try to pull the same G's at full speed, or even at half speed, you'll nosedive.

On top of it all, when you start throwing in other variables (like hitting different size bumps, going up inclines, fighting a headwind, or low battery), the wipeout point changes. It's super tricky to know how much thrust you have available, or how much faster you can go until you reach the wipeout point, because currently the feedback from the EUC doesn't give enough information to know it. The only way to really know the limit is to reach it and see what happens.

With the current generation of EUCs, the only thing you can do that's safe(ish) is to trust the alarm, and as you go faster, accelerate sheepishly.

Oh, and if you do hit the wipeout point, bend your knees really fast to unload the EUC so it has an easier time getting ahead of you. It's kind of a last-ditch effort, and it won't work in all circumstances, but it can save your skin.

Edited November 19, 2019 by zeke

[Harvey Pooka]

5 hours ago, zeke said:

Lol, sorry for being pedantic! This is the short of it.

The faster you go, the more thrust is needed to maintain your speed because drag force is rising.

The faster you go, the less thrust the EUC is capable of providing (this is a characteristic of all electric motors).

The difference between the thrust the EUC can provide, and the thrust you're already using, is how much leftover thrust is available for you to do as you please like trying to speed up or whatever. If there is zero thrust available, or if you suddenly lean forward and create a need for thrust that exceeds what is available, then you can't launch the EUC in front of you anymore so you can't slow down. (And then you apply the skin brakes.) It's clear that the point where available thrust reaches zero is a very critical, very important point. A hard limit. You could call this the wipeout point.

As you can imagine, the available thrust drops very quickly as you go faster, because the thrust needed to maintain speed is rising at the same time that the thrust the EUC can provide is dropping. At low speeds there's tons of thrust available, but at high speeds there's very little. And eventually, at some high speed, there's zero thrust available. This means that although you might be able to accelerate super quick from a standstill, if you try to pull the same G's at full speed, or even at half speed, you'll nosedive.

On top of it all, when you start throwing in other variables (like hitting different size bumps, going up inclines, fighting a headwind, or low battery), the wipeout point changes. It's super tricky to know how much thrust you have available, or how much faster you can go until you reach the wipeout point, because currently the feedback from the EUC doesn't give enough information to know it. The only way to really know the limit is to reach it and see what happens.

With the current generation of EUCs, the only thing you can do that's safe(ish) is to trust the alarm, and as you go faster, accelerate sheepishly.

Oh, and if you do hit the wipeout point, bend your knees really fast to unload the EUC so it has an easier time getting ahead of you. It's kind of a last-ditch effort, and it won't work in all circumstances, but it can save your skin.

Thank you for the lay person summary. I liked yours and @Aneta's discussion (and a couple of other people) because you guys went into the science of what's happening. And because you guys were discussing the science behind something and often confirming the theories, it was like a peer reviewed journal report. Often people here post suggestions based on personal experience, which is still valid, and if I try it, it often works, but it's nice to know the why the suggestion works. It also lets me adjust my techniques or habits or extrapolate.

So for example, extrapolating your last statement about bending your knees to unload the EUC. So bending your knees pulls your torso back which I am assuming is the unloading that you are referring to? Does this mean riding with bent knees with your body more over wheel all the time result in needing less power at a given speed over riding by leaning forward at the same speed? The EUC needs less power to "catch" you so has more power available for sudden bursts if you need it (to accelerate, compensate for rough terrain, etc).

If so, that would mean modifications to allow you to accelerate without leaning as much (ie. power pads, foot pedal/toe modifications, raised front calibration) would give a slightly greater available power safety margin no matter what speed you are travelling. Would it also reduce the drain on your battery? (ie. travelling 35 kph with your knees bent requires less power than travelling the same speed by leaning forward.) I know it's the same speed so it sounds as if the power drain should be the same, but does the unloading make a difference?

I'm not a speed rider so I'm not worried about crashing while trying to go fast. But I do like riding farther so my battery does drain down.

Again, thanks for the theoretical information.

Edited November 19, 2019 by Harvey Pooka

[Qarky]

The 16X has held up fairly well thus far.

This is my first EUC, and within 30 days of getting it, I had ridden in some wild places including down some train tracks in Amherst, MA as seen in this video.

Terrain:

Open Road

Fields

Meadows

Powerline-Gravel paths

Train Tracks 

 

I hope you all enjoy the shot of the Quabbin Reservoir that I got in the video, it really is a gift of nature and human engineering to the eye.

[JonnyBonz]

16 hours ago, Mike Sacristan said:

Yes I mean DarknessBot.
Nope I can't set the alarms with it. They fail to set. So I set them with the Kingsong app and leave them there.
If I use any alarm on Darknessbot I use the alarm at 45 kmh but at application and not device level.

I'm sure it will be fixed in a future version. I just want the 45 kmh alarm because at that speed I have longer braking time, less time to react, etc.
If I want to ride at or past 45 kmh it will be with my alarm blazing. Whether I am on my MSX or 16X.

@Mike Sacristan, I have the same issue where the alarms fail to set and also just set it using the Kingsong app, but you mention an application level alarm.  Which setting is that?  Where do you set it?  And is it audible through the wheel speakers as well?  In your vids, I do hear the 3 and 4 beeps and am assuming that is the device level alarms you set via the KS app right?

[Mike Sacristan]

1 hour ago, JonnyBonz said:

@Mike Sacristan, I have the same issue where the alarms fail to set and also just set it using the Kingsong app, but you mention an application level alarm.  Which setting is that?  Where do you set it?  And is it audible through the wheel speakers as well?  In your vids, I do hear the 3 and 4 beeps and am assuming that is the device level alarms you set via the KS app right?

The Darknessbot application alarm is independent of what you set the wheel at. The wheel alarms are in the actual wheel.

Darknessbot -> Settings -> Application -> Alarms -> Sound / 45 kmh.
And I have "on connection" set to on.

The Darknessbot application alarm is global for the app so if you connect to another wheel you keep the 45 kmh alarm.

As the audio is played on the phone and the phone can output it's audio to a bluetooth speaker then yes we can use the 16X bluetooth speaker for the alarm.
I prefer to use my little Bose micro.

Some things to think of though:

- the bluetooth speakers on the 16X go idle I believe and have a 1 second wake up time when receiving audio (if you are not playing music).
- Darknessbot and the 16X sometimes lose connection or have a delayed connection when reaching the alarm so it isn't 100% reliable although that might be because I tend to put my iPhone is battery saving mode.

[JonnyBonz]

 

1 hour ago, Mike Sacristan said:

The Darknessbot application alarm is independent of what you set the wheel at. The wheel alarms are in the actual wheel.

Darknessbot -> Settings -> Application -> Alarms -> Sound / 45 kmh.
And I have "on connection" set to on.

The Darknessbot application alarm is global for the app so if you connect to another wheel you keep the 45 kmh alarm.

Thanks Mike.  Good to know.  I did not have that alarm set.  I typically don’t play music when I ride so I’m guessing my watch and phone should notify me.  I guess I will play around with the Bluetooth connectivity on the wheel speakers to see how reliable they are. 

 

[mrelwood]

 

4 hours ago, Harvey Pooka said:

So for example, extrapolating your last statement about bending your knees to unload the EUC. So bending your knees pulls your torso back which I am assuming is the unloading that you are referring to? Does this mean riding with bent knees with your body more over wheel all the time result in needing less power at a given speed over riding by leaning forward at the same speed? The EUC needs less power to "catch" you so has more power available for sudden bursts if you need it (to accelerate, compensate for rough terrain, etc).

No... Think about it this way: Would you be easier to push around in a shopping cart if you kept your knees bent? Nope.

The point is to bend your knees (or crouch) quickly, and as your upper torso starts to drop downwards, less of your torso’s weight is weighing on the pedals. This is true for a very short time only, and once you have reached the crouched position, for a short moment the wheel carries more than your weight. And after that it’s just the same as originally. But hopefully the lighter moment was long enough for the wheel to be able to accelerate back under you. If it wasn’t, you just crash from the crouched position instead.

The stance/posture affects the thrust required to ride you around only via the smaller wind resistance. So yes, you will get better mileage riding crouched or seated.

4 hours ago, Harvey Pooka said:

If so, that would mean modifications to allow you to accelerate without leaning as much (ie. power pads, foot pedal/toe modifications, raised front calibration)

No mod really allows you to accelerate by leaning less or more than without the mod. To simplify a bit, the wheel can only sense your Center of Gravity, and it’s the only measure that tells the wheel to accelerate. Mod or no mod, you need to get the center of your gravity in front of the axle a certain amount to apply a certain amount of acceleration.

Wind resistance of course plays a part, but  short from carrying a huge cone shaped fixture in front of you, mods don’t have a notable effect in wind resistance. Your posture does though.

[erk1024]

12 hours ago, zeke said:

The faster you go, the more thrust is needed to maintain your speed because drag force is rising.

The faster you go, the less thrust the EUC is capable of providing (this is a characteristic of all electric motors).

I think you are counting the "load thrust" twice? If you're riding downhill, then the motor is not losing thrust just because it's spinning. When you look at graphs of electric motor torque, they *assume* the motor is under load (imagine an electric motor spinning a propeller on a drone). If the propeller spins faster, it creates more force which takes more power.

So there is a maximum amount of torque that the wheel can put out at any instant in time, and if you are going fast on flat ground, then you're using a bunch of that torque to counteract drag (wind, rolling resistance, etc.) If you run out of available torque, then the rider rotates forward, which results in a faceplant.

But you can run out of torque in other ways: going uphill, underinflated tire (more drag), headwind, overcoming obstacles ...

Does that sound right? (I'm happy to be wrong, as I'm also trying to understand it.)  

Edited November 19, 2019 by erk1024
clarification

[Chriull]

47 minutes ago, erk1024 said:

If you're riding downhill, then the motor is not losing thrust just because it's spinning.

By spinning the motor creates a voltage called back emf, by this "countervoltage" the voltage relative to the battery gets less and so less maximum current can possibly flow. So less maximum torque is possible the faster the wheel spins.

[Aneta]

1 hour ago, erk1024 said:

When you look at graphs of electric motor torque, they *assume* the motor is under load (imagine an electric motor spinning a propeller on a drone). If the propeller spins faster, it creates more force which takes more power.

Yes, the blue line ("the ever thinner ice") in the Motor Simulator and in @zeke's drawings is the maximum possible thrust the motor is capable of at that speed. The actual load is lower - until the max, "terminal"/overlean speed where they are equal. However, one can easily increase the load at any speed by accelerating or going uphill.

For example, in this spectacular spill the load was increased by acceleration, until at certain speed the ever decreasing torque became lower than the demand:

Fully expected.

Edited November 19, 2019 by Aneta

[Mike Sacristan]

4 hours ago, JonnyBonz said:

 

Thanks Mike.  Good to know.  I did not have that alarm set.  I typically don’t play music when I ride so I’m guessing my watch and phone should notify me.  I guess I will play around with the Bluetooth connectivity on the wheel speakers to see how reliable they are. 

 

I rarely use the speakers as I heard too much about pedal dipping and what not with the bluetooth speakers playing while riding.
I also had pedal dipping by 3 degrees in FW 1.05 below 505 battery when playing music.

Would be interesting to know how Darknessbot works with Apple Watch and if the vibration can be sent to the watch.

[zeke]

12 minutes ago, erk1024 said:

I think you are counting the "load thrust" twice here.

Nope, I wasn't double-counting.

Consider the force-velocity line of an EUC (or any electric motor):

 

You actually have a huge family of lines, virtually infinite in number, that are all parallel to each other and differ by the motor drive duty cycle, because duty cycle can vary continuously from 0% to 100% (it can also go to −100%, but I'll ignore that for now). I've illustrated only two lines: one at 100% duty cycle, and one at 50% duty cycle. Duty cycle cannot exceed 100%, so the top line is the most the EUC can possibly do.

 

Now, overlay the load force that you require while you're riding at steady-state on flat ground. As long as you keep the same profile, this is a fixed curve that rises quadratically because of air drag:

 

For illustration I've assumed you're riding at a speed that causes the motor to run at 50% duty cycle. Thus, the thrust available is equal to half of the stall thrust. At this speed, you can accelerate half as fast as you could from a standstill. You can still do some pretty sick moves, but not quite as aggressively as at zero speed. (What speed corresponds to 50% duty cycle? I don't have that information.)

 

As you push your speed higher though, the thrust available diminishes pretty fast (because the drive duty cycle required just to support your speed gets closer and closer to 100%). Once the available thrust hits zero, i.e. duty cycle is 100%, you can't accelerate anymore and you nosedive.

 

To make it clear, here I'll sketch the available thrust, which is the difference between the top red line and the green curve:

 

From this it's pretty clear: the thrust available drops like a rock with speed. 

 

If you want to talk about hills, this is what happens. Uphills shift the load curve up, and downhills shift the load curve down:

 

 

As a result, the available thrust also changes with incline. Going uphill, you have less available thrust at any given speed, and downhill you have more:

 

 

Oh, and what if you wear baggy clothing and stand up straight, versus wearing slick clothing? These make the load curve steeper.

 

 

As a result, for a given speed, if you wear slick clothing and reduce your aerodynamic profile, in theory your thrust margin is higher. (It's a bit more complicated that that, but to first order...)

 

 

1 hour ago, erk1024 said:

But you can run out of torque in other ways: going uphill, underinflated tire (more drag), headwind, overcoming obstacles ...

Does that sound right?

Absolutely. That's why you need to maintain a healthy amount of thrust available as margin to overcome these obstacles.

[Aneta]

2 hours ago, zeke said:

Nope, I wasn't double-counting.

Consider the force-velocity line of an EUC (or any electric motor):

 

You actually have a huge family of lines, virtually infinite in number, that are all parallel to each other and differ by the motor drive duty cycle, because duty cycle can vary continuously from 0% to 100% (it can also go to −100%, but I'll ignore that for now). I've illustrated only two lines: one at 100% duty cycle, and one at 50% duty cycle. Duty cycle cannot exceed 100%, so the top line is the most the EUC can possibly do.

 

Now, overlay the load force that you require while you're riding at steady-state on flat ground. As long as you keep the same profile, this is a fixed curve that rises quadratically because of air drag:

 

For illustration I've assumed you're riding at a speed that causes the motor to run at 50% duty cycle. Thus, the thrust available is equal to half of the stall thrust. At this speed, you can accelerate half as fast as you could from a standstill. You can still do some pretty sick moves, but not quite as aggressively as at zero speed. (What speed corresponds to 50% duty cycle? I don't have that information.)

 

As you push your speed higher though, the thrust available diminishes pretty fast (because the drive duty cycle required just to support your speed gets closer and closer to 100%). Once the available thrust hits zero, i.e. duty cycle is 100%, you can't accelerate anymore and you nosedive.

 

To make it clear, here I'll sketch the available thrust, which is the difference between the top red line and the green curve:

 

From this it's pretty clear: the thrust available drops like a rock with speed. 

 

If you want to talk about hills, this is what happens. Uphills shift the load curve up, and downhills shift the load curve down:

 

 

As a result, the available thrust also changes with incline. Going uphill, you have less available thrust at any given speed, and downhill you have more:

 

 

Oh, and what if you wear baggy clothing and stand up straight, versus wearing slick clothing? These make the load curve steeper.

 

 

As a result, for a given speed, if you wear slick clothing and reduce your aerodynamic profile, in theory your thrust margin is higher. (It's a bit more complicated that that, but to first order...)

 

 

Absolutely. That's why you need to maintain a healthy amount of thrust available as margin to overcome these obstacles.

This is the most excellent primer to date, in history of EUCs, on EUC Basics 101. It should be loaded into every EUC rider's brain like a firmware. Bravo!

To add, I encourage everyone to learn to use, understand, and play a lot with the industry-standard Motor Simulator:

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

It also supports simulation "sets" just like @zeke did: you can tell it to vary % grade or Cd in some range with certain step, and it will calculate each scenario. I only wish it would show Load curve (gray line) as thrust, instead of power. Would make it easy to see the thrust margin. But thrust can be calculated from power by simply dividing the latter by speed.

Edited November 20, 2019 by Aneta