How do I know when I'm reaching the limits of my wheel?

[erk1024]

... when it dumps you off the front and you superman to the asphalt. 

Okay, I'd like to know *before* that point. (Apologies if this has been covered to death already.)

@stephen and @Marty Backe mentioned that they have an alarm set at 90 amps. Where does that number come from? Do I have that option on the iPhone?

I was climbing a hill at 30-35 kph (going over a bridge... there are no actual hills in 2D Florida) and the whine out of the motor was definitely louder. I checked on the app later and it said "6" for the current which I'm assuming is 6 amps. Doesn't seem like a problem. But who knows how much time that little bar graph represents? Each of the six battery packs should be able to put out 10A each (continuous) as @Jason McNeil pointed out, so I shouldn't be worried until the amps gets much higher?

What it seems like I need is the instantaneous number of amps, and/or watts. Darkness bot has both current and power (watts) numbers, so watch one of those and make sure they don't approach the 60amp or 2000watt limits? Also the board will get hot under heavy loads.

What does the wheel do if you are using too much current? Tiltback? I'm assuming that no alarms will go off because those are specifically for speed.

Now in terms of top speed, is it independent of the power limits (above 25% battery level)? In other words, the wheel just has a limited amount of torque at higher speeds that's independent of the power requirements?

In that thread Marty said don't "lean into the wheel", but you have to do some leaning to counteract the acceleration. I guess right now I just lean forward a bit--not enough to overbalance off the front. The wheel accelerates at a rate that's plenty fast for me (right now at least). And then I back off, because after a few seconds I'm hitting my 35kph speed alarms, and as I still have some speed wobble issues, I don't want to go faster.

Edited June 2, 2019 by erk1024

[Smoother]

26 minutes ago, erk1024 said:

... when it dumps you off the front and you superman to the asphalt. 

Damn it!!! You stole my thunder 

Unfortunately, I can't answer any of your questions, so for this reason I'm out.

[Marty Backe]

The WheelLog Android app has separate alarms for speed, temperature, and current. When combined with the Pebble watch you can get alarm notifications on your wrist.

You can easily exceed 90-amps on the flat and level. All it takes is to hit a good sized bump. Or when you start moving forward and you lean heavy - big surge in current. Current consumption has nothing to do with living near mountains or hills.

When a wheel consumes too much current either it blows a fuse (KingSong) and blows a MOSFET(s) (Gotway) and possibly melts wires. But these failure modes only occur when you consume excessive currents for a non-trivial amount of times. Momentary surges in powers are normally nothing to be worried about - otherwise all of our wheels would be dead.

Edited June 2, 2019 by Marty Backe

[Chriull]

1 hour ago, erk1024 said:

... when it dumps you off the front and you superman to the asphalt. 

Okay, I'd like to know *before* that point. (Apologies if this has been covered to death already.)

Getting this kind of feedback before is not available (by now). Manufactures have only implemented very easy/simple and not really "useful" alarms/limitations.

To stay on the safe side is not accelerating heavily at higher speeds.

Quote

@stephen and @Marty Backe mentioned that they have an alarm set at 90 amps. Where does that number come from?

Experiance, trial and error. Thats just a number which the Gotway wheels "survived" at low speeds and inclines/high burden situations. Once this "alarm" rings the chances for overheating/blown mosfets/etc are increasing.

Quote

Do I have that option on the iPhone?

Darknessbot? Could have alarms like wheellog on android?

Quote

I was climbing a hill at 30-35 kph (going over a bridge... there are no actual hills in 2D Florida) and the whine out of the motor was definitely louder. I checked on the app later and it said "6" for the current which I'm assuming is 6 amps.

Thats what its saying, but most presumably its just any number correlating somehow to the motor current...

Quote

 Doesn't seem like a problem. But who knows how much time that little bar graph represents? Each of the six battery packs should be able to put out 10A each (continuous) as @Jason McNeil pointed out, so I shouldn't be worried until the amps gets much higher?

Battery current is different to motor current and not reported by the app.

But 6A reported current, with all the uncertainties is with all the wheels not much, just if riding around maximum speed...

Quote

What it seems like I need is the instantaneous number of amps, and/or watts. Darkness bot has both current and power (watts) numbers, so watch one of those and make sure they don't approach the 60amp or 2000watt limits? Also the board will get hot under heavy loads.

The reported Watts are just some invalid meaningless number (but still somehow vaguely correlating to the burden) - its just multiplied battery voltage with motor current. But since motor voltage is not battery voltage and battery current not motor current it makes no sense to call this number anything with watts or power. And beside all of this the power advertised for the wheels is mostly also just some number...

Quote

What does the wheel do if you are using too much current? Tiltback? I'm assuming that no alarms will go off because those are specifically for speed.

The wheels have current limiting at lower speeds to prevent the mosfets from frying, overheat alarms which are some kind of accumulated current alarms. And then just as you mentioned speed related alarms.

Quote

Now in terms of top speed, is it independent of the power limits (above 25% battery level)? In other words, the wheel just has a limited amount of torque at higher speeds that's independent of the power requirements?

Maximum availavle torque decreases linear(?ly?) with speed. Maximum power is available at half maximum no load speed (~lift cut off speed). Available maximum torque, power is speed dependend and their relation not really intuitive.

If you're interested in more details you can read 

and the links mentioned there.

[Peter Q]

I knew the limit of my KS18AY with 1200W motor (factory said max speed at 40km/h)- 1680wh  and 100% charged last Monday and had a bad crash.

The wheel warning beep at 39 km/h, start tiltback at 40 km/h, tried to slow down but too late,  it did cut off before 42 km/h, then I was dumped to kiss the asphalt.

The wheel lift test cut off at  only 46.33 km/h, so little margin is not too safe.

My riding weight is about 200lbs, maybe I'm too heavy for the 1200W motor wheel to go 40km/h.

I'm ok due to my safety gears, only now knee and shoulder with a lot of pain. Maybe few week before anymore riding, but I will not ride close to factory said speed limit anymore.

Peter Q

[erk1024]

44 minutes ago, Chriull said:

If you're interested in more details you can read 

Wow. Thanks for the great information. I DID read that thread already, but I'll re-read it and I'll probably understand it better this time.   

[erk1024]

24 minutes ago, Peter Q said:

I will not ride close to factory said speed limit anymore.

I'm even heavier at 265 pounds, so I'll need to leave extra margin. But maybe the good news is that the wheels are getting stronger? If you decide 40kph is fast enough, then you're not close to the limit. The downside is that some people will always ride a wheel at its limits, and so people will be falling off Gotway Monsters 100V's at 65kph?

[Chriull]

On 6/3/2019 at 1:41 AM, erk1024 said:

Wow. Thanks for the great information. I DID read that thread already, but I'll re-read it and I'll probably understand it better this time.   

Fyi: There happened to be just another post regarding this topic:

 

[erk1024]

So I did some messing around tonight to collect more data. Things I learned on the KS18xl:

Leaning more doesn't make the wheel accelerate any faster. I've been doing mild leans to accelerate, so I tried leaning a bit more than usual. It didn't appear to make the wheel accelerate any faster. With my previous lean angle, I was already getting all the power that the wheel had. I have the ride mode set to medium.

I hooked up DarknessBot for the first time and watched the Current number. With a hard acceleration with flat ground, I was able to get it up to about 32 (amps presumably). As @Chriull said, this is probably "just a number" output by the control board.

I think on the KS18xl, if you do slow turns, the pedals do dip or angle forward, and it seems like it's part of the wheel's algorithm. I didn't notice it on faster turns. Maybe pedal dip is just part of the formula used by the manufacturers. It doesn't bother me. It's probably good to have some acceleration coming out of turns anyway.

Tonight was all about trying different tire pressures to see the effect on comfort and speed wobble. Keep in mind that I'm 265 pounds without equipment on (120kg). Truth is that it was hard to notice any difference in the frequency or strength of speed wobbles. Maybe the strength of wobbles was worse at the very low pressure? hard to tell.

45psi - very comfortable but the wheel feels kind of flat, and squishy.

50psi - still comfortable and not as squishy. This pressure is probably OK for me to ride at

53psi - seems like the right tire pressure. Still comfortable but the tire feels more solid

57psi - tire is getting pretty hard. Bumps are more of a jolt

60psi - harder, less forgiving on the bumps for no real advantage.

Seems like the right pressure is in anywhere in the 50 - 53 range. It would be good to try the MSX with the larger and fatter wheel. I could run it at a lower pressure, so I'm assuming it would be more comfortable.

Edited June 5, 2019 by erk1024
fixed text issues

[MaxLinux]

1 hour ago, erk1024 said:

Seems like the right pressure is in anywhere in the 50 - 53 range.

I like 50 for my 18XL.

Edited June 5, 2019 by MaxLinux

[erk1024]

I should have mentioned that this conclusion agrees very well with the article on the eWheels site on tire pressure. If you extend out the lines in this graph, then at my weight the tire pressure should be 53'ish. With all the 3" tires coming out, it would be great to add lines for those tires to the graph. The forum could collect data for it.   

https://www.ewheels.com/guide-tires-appropriate-pressures-electric-unicycle/

Edited June 5, 2019 by erk1024

[mrelwood]

7 hours ago, erk1024 said:

I tried leaning a bit more than usual. It didn't appear to make the wheel accelerate any faster. With my previous lean angle, I was already getting all the power that the wheel had.

That’s not quite how the physics at play here work. The wheel responds only to the location of the rider’s Center of Gravity. If the CoG is placed too much forward, you crash due to over-lean. Up to that point the wheel uses as much power that is needed to keep you upright. This is an universal rule with all EUCs. How much the CoG can be put forward depends on the wheel, battery level, incline, etc, so it varies constantly.

Some time ago an afvanced skiier started EUCing, but couldn’t get his new Tesla to go faster than 3km/h, no matter how much he ”leaned”. Turns out his ”lean” was the downhill skiing pose, which actually aims to keep the CoG centered under your feet.

Instead of leaning, move your hips forward/backwards while keeping your upper torso close to vertical. That is a command that the wheel understands very well. 

 

Regarding the topic title. By the time I’ve gotten well familiar with my wheels, I have started accelerating a lot faster. I still don’t know the actual limits as I have never over-leaned. But I believe that increasing the acceleration slowly enough (both every time and incrementally as you get familiar with the wheel) might give you the chance to react if you feel the slightest amount of dip in the pedals, hear burdening sounds from the wheel, or see even small bumps ahead. That has kept my 94kg (+ gear) upright so far, but I of course don’t know if my fastest accelerations are still slow by some standards.

Just don’t go much past your comfort level, a tense rider is a bad rider and doesn’t sense the situation very well.

[erk1024]

3 hours ago, mrelwood said:

Instead of leaning, move your hips forward/backwards while keeping your upper torso close to vertical.

Yes. Right I agree. Moving hips forward while keeping torso mostly upright is the way to go. It's much easier to shift your CG back if you need to.

All I was saying is that as you lean (shift your CG forward), the wheel responds to that input. But there is a point where the wheel is already accelerating as much as it's going to. So at that point, there is no sense in leaning more. Adding more input doesn't add more power. Probably on the "hard" ride setting, you could lean even less to get that same amount of power. This makes sense from the perspective of controlling the wheel safely because it discourages over-leaning. Mild CG shifts achieve the same result.

Edited June 5, 2019 by erk1024

[meepmeepmayer]

As @mrelwood says, if the wheel doesn't react (differently), you're not leaning (differently). Which is as good as a definition of "leaning" as one can have for EUCs, because that's the lean that controls them. Maybe you have a different definition of "leaning"? Personal perception of how much you "lean"? Nothing wrong with that, but it can be misleading.

One can do a simple test. Stand in the same position, but simply on the ground. Are you stable and not falling over? You're not leaning (in my sense).

And if you were to "lean more" but the wheel wouldn't react, you'd simply fall on your face. Just as you'd fall over when doing the same on the ground.

-

I'm pretty sure your pedal dipping is unintentional, simply a bad calibration/cheap sensor. Why? Because it's inconsistent between wheels of the same type. If all 18(X)Ls had pedal dip, someone would have complained. The fact that it appears less (or not) in faster curves is because there you're less tilted sideways. The more sideways the wheel is tilted, the more a badly calibrated sensor is thrown off from ground truth of what is horizontal in the direction of travel.

I hate dipping like nothing else, but if you like this "feature" (bug), good (I'd still try a fresh calibration and enjoy the always-level pedals as God intended)

[erk1024]

We might be getting lost in the semantics here. And I could be wrong about what I was feeling (it's not like I had instrumentation attached or anything). When I tried it I was going really slow, so maybe the wheel bogged a bit, or there was a little delay in power delivery--not sure.

2 hours ago, meepmeepmayer said:

Stand in the same position, but simply on the ground. Are you stable and not falling over? You're not leaning (in my sense).

You can lean forward, which moves the contact patch on your shoes forward (or at least the point where your shoes are putting the most pressure on the floor) and still maintain balance. This would put more pressure on the front of the EUC pedal. But in both cases (standing on the ground or standing on an EUC pedal) it doesn't mean you would necessarily fall forward.

Later, when I was using DarknessBot to check the "current" and was hitting 32, that felt like plenty of acceleration for me, and wouldn't feel the need to go above that. In fact, as the wheel speed increased, I'd probably have to back off.

Anyway, I think what @mrelwood was saying about getting an intuitive feel for the wheel as you ride it.... seems like a good approach. I'm going to stop overthinking it.

Edited June 5, 2019 by erk1024
added text

[mrelwood]

2 hours ago, erk1024 said:

We might be getting lost in the semantics here.

I’m sure we are not. The EUC as a device is mechanically so incredibly simple, that the pedals staying flat under almost all situations tricks the mind. I think I understand the feeling you get, but it is not related to the wheel running out of power.

Mechanically an EUC is just a spinning wheel. Nothing else. There is no separate mechanism adjusting the pedals. The only thing the wheel can do is spin the wheel with a speed that keeps the pedals flat.

If the power of the wheel is surpassed, the pedals can no longer be horizontal. Because the only thing that keeps them horizontal is the accelerating wheel.

Kind of like you can stay upright on the ground with a little forward lean, but as soon as your CoG goes past your toes, you tip over. Same thing happens with the EUC.

Spinning wheel. Nothing else. Mindboggling.

[Planemo]

I think I get what erk is saying.

He seems to be saying (and just pulling some random numbers here) that if he leans forward at 60% and the wheel accelerates at X speed, when he leans forward at 100% the wheel accelerates at the same speed.

Given this is happening at low speed, it's not an issue with the motor reaching it speed limit.

So the only thing that can be happening is that the wheel can't keep up with the amount of lean he is able to provide. Ergo, he has reached the wheels maximum torque (at the given test speed) and the only next step is that he overleans and falls forward off the front.

I have to say, I am only stating this from a theory pov as I have never overleaned, nor have I noticed the issue he is explaining, probably because I don't have the kahunas yet to push my wheels to the situation he describes!

[LucasD]

Recently I had a strange fall, after a phone started beeping of 25kmh I decided that I want to disable it so started to brake.

The next time I know I fell back on my butt and slide on my wrist protectors. Not sure if it was strange balance problems, wheel oscillations or I over-leaned in braking direction.

For lean control a good exercise is to hold something (pole, barrier), have a back straight and move the wheel forward & back (with a bent knees) yet the back and head stays in place. It can be done super fast and it allows fine control, however max angles would be limited but they can be adjusted by body lean. 

[Chriull]

7 hours ago, Planemo said:

I think I get what erk is saying.

He seems to be saying (and just pulling some random numbers here) that if he leans forward at 60% and the wheel accelerates at X speed, when he leans forward at 100% the wheel accelerates at the same speed.

That's how i'd interpret @erk1024s posts, too. But that's not physically possible - imho he for him leans forward (lets stay with your numbers) 60 to 100%, but in reality he has the same shift of the CoG. If the acceleration is the same the shifted CoG (leverage of the body over the pedals) has to be the same, or one would fall off the wheel...

[Planemo]

Im not saying you're wrong, I am just going to try and present this in a way that erk is trying to describe and I am trying to understand. How about this:

Standing on the floor, we can remain upright with our weight evenly spread over our feet, front to back.

1. We can lean foward, say 2 deg, and we end up with more weight towards the front of our feet.

2. Lean a bit further, and we can put virtually all our weight on the balls of our feet. We still havent fallen over, but we are close.

I think that what erk is saying is that it doesnt make any difference in acceleration for his euc whether he is at 1. or 2.  Surely the only reason this can be so is because the wheel cant provide the extra torque required to accelerate the wheel faster and therefore ease the weight off his poor tootsies.

I think you can probably work out what I am trying to explain, and I am willing to be corrected but I just cant see it!

 

[erk1024]

@Planemo understands what I was saying.

I was thinking the different riding modes interpret the tilt of the pedals as input. If you put pressure on the front of the pedals (trying to tilt them) the wheel responds by accelerating. You can apply pressure (moving weight towards the balls of your feet) without necessarily falling off the front. The wheel can respond aggressively to that input (hard riding mode) or less aggressively (soft riding mode). I think on a harder mode, you can get more response out of the wheel with less input. And at some point, it's responded as much as it's going to.

I'm not sure but maybe some riders think it's the opposite. That hard riding modes "resists" the rider leaning? That soft riding modes let you tilt the pedals (lean more) before it responds, and then the wheel accelerates to get back under you. Maybe it depends on how much you weigh? Just things I was mulling over.

I could be completely wrong (it's happened before!) and I only tried it once, so you guys would know better than me.

[mrelwood]

29 minutes ago, erk1024 said:

@Planemo understands what I was saying.

We all do. But you and @Planemo don’t understand that

4 hours ago, Chriull said:

that's not physically possible

 

1 hour ago, Planemo said:

Lean a bit further, and we can put virtually all our weight on the balls of our feet. We still havent fallen over, but we are close.

We haven’t fallen because our CoG hasn’t surpassed the area we stand on. Just like with EUCs, the area we stand on representing the available torque range.

Quote

I was thinking

...

You can also read in detail all about the riding modes, over-leans, torque curves, riding dynamics, lean positions etc right here at this forum. Nothing wrong with pondering about things by yourself, but if you actually want to learn how stuff works, you can find posts from guys with degrees on or otherwise advanced in electronics, physics, mechanics, and even programming self-balanced robots, right here at this very forum.

Again, your wheel did not run out of torque, power or speed. When it does, it cannot catch you or keep you upright, so you crash. End of story. I have no doubt that you felt what you felt, but in reality, it can not happen in our existence as we know it.

We have already explained a few times why. If you are interested, read them again. A few times if you need to.

[erk1024]

5 hours ago, Chriull said:

That's how i'd interpret @erk1024s posts, too. But that's not physically possible - imho he for him leans forward (lets stay with your numbers) 60 to 100%, but in reality he has the same shift of the CoG. If the acceleration is the same the shifted CoG (leverage of the body over the pedals) has to be the same, or one would fall off the wheel...

I think I get it now.

When you stand on the ground, and you shift your weight, the floor pushes back by the same amount no matter where you push on it (infinite mass and all that) But what you're saying is that if you shift weight to the front of the pedal, the wheel has to counteract that exact pressure on that point on the pedal, or you are no longer supported and you fall. Right?

[svenomous]

Let's remember that a human is very good at balancing on two legs and can do all kinds of things with legs, hips, torso, head, and arms to affect CG, and that the cerebellum does a pretty good job of making adjustments to try to keep CG "over the feet" so we don't fall over.  Therefore, I can hinge at my hips until my torso contacts my legs, and yet I'm still standing on my feet...because without even thinking about it my legs and hips flexed in such a way that my butt went backward to counteract the pivot.  My CG is essentially unchanged.  If I raise my arms in front of me, a small shift happens that also keeps me centered over my feet.  I can lift a leg and swing it forward and backward, and do all kinds of things while balancing on one leg, and my wonderful hindbrain causes all kinds of little hip and body shifts so my CG stays nicely centered over that foot.  So, often we think we're shifting CG by pivoting some part of our bodies, but in reality our CG is not moving at all, or only very marginally.  Otherwise we'd constantly be falling over.  The best way to "measure" our own personal CG is to pay attention to the soles of our feet.  If pressure is evenly distributed, our bodies are well centered over the feet.  If pressure is more on the balls/toes or heel, then CG can truly be said to have shifted.  A human standing on two feet without additional support has a very limited ability to shift CG without falling over.  Combine that understanding with the foot positioning on the pedals, and you can get a good sense for how rider CG is shifting in relation to wheel/axle.

That said, what some on this thread have explained, and which is very important to understand, is that a self-balancing wheel cannot "accelerate sluggishly" and still be self-balancing.  It just can't.  If you put CG forward of the wheel's axle, the wheel must move forward, very nimbly, to stay under your own CG and keep the pedals level.  The more the CG is put forward, the faster the wheel must respond to stay in place.  If you're truly "leaning harder" (as in "shifting CG further") during acceleration test B than you were doing during test A, and you didn't fall off the wheel due to "overlean," it means the wheel must have accelerated faster during test B than it did during test A.  If it seems that acceleration was the same between the two tests, there are only two possible explanations: either perception of acceleration was wrong, or perception of CG shift was wrong.

[Planemo]

9 hours ago, svenomous said:

If you're truly "leaning harder" (as in "shifting CG further") during acceleration test B than you were doing during test A, and you didn't fall off the wheel due to "overlean," it means the wheel must have accelerated faster during test B than it did during test A.  If it seems that acceleration was the same between the two tests, there are only two possible explanations: either perception of acceleration was wrong, or perception of CG shift was wrong.

And this is the statement that has cleared it up for me.

As mrelwood said yesterday - read, re-read then read again. I did but it didn't help much. But I find this stuff interesting so I carried on reading anyway and then your reply popped up which I think mrelwood had said in a similar way but yours seemed to work better for me.

I had put far too much emphasis on erks initial comment as being fact, and then going off on the path of trying to explain/understand why this would be so but in reality his belief of what was happening seems to be a red herring. To explain what he felt, I assume that maybe the result could have been based on his feet being further back during the second test...?

I thank you for your help mrelwood, svenomous and chriull (note I didn't add @ at the beginning of your names in case you are about to blow a gasket over this topic) and I know how frustrating it is when you are explaining stuff which people aren't getting. If any of you are still reading and are interested in replying (you really don't have too - I understand!) how about this as a spin-off scenario that I thought about during this thread:

2 wheels - both have an abundance of power/torque. For this example lets say 20Kw. Both wheels are identical. Test speed from say 0mph to 20mph.

One rider is a child, lets say 30kg. The other rider happens to be the heaviest man recorded - 635kg (these scenario wheels are strong).

Their foot placements (front to rear on the plates) are set up to be perfectly balanced on wheels which are switched off (perfect CoG).

The wheels are switched on and both riders are asked to accelerate as fast as they possibly can (the fat man is sweating a bit at this point).

Will the heavier rider rider accelerate quicker as his wheel will need to deal with a heavier mass to stop him faceplanting?

Or will it be identical - based on all objects falling at the same rate irrespective of mass?