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speed for riding up the hill


ubertoad
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Hi,

I wonder is it safe to run up the hill as fast as I can. And if not, how fast can we ride?

As the limits seems to be based on speed, but cut out is based on power consumption. So riding up the hill you probably can use all your power having speed way less than limit and do a faceplant. Is this the case or it still will beep based on power consumption?

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32 minutes ago, ubertoad said:

Hi,

I wonder is it safe to run up the hill as fast as I can. And if not, how fast can we ride?

As the limits seems to be based on speed, but cut out is based on power consumption. So riding up the hill you probably can use all your power having speed way less than limit and do a faceplant. Is this the case or it still will beep based on power consumption?

Just an overheat cut-out is power related (or cut-out due to wires/connectors melting or mosfets frying).

then there is the overcurrent cutout of the bms (which gw does not have) and which does not really happen anymore with modern wheels.

and then is the last reason for a "cut-out" when one hits the motor limit - thats the most counter intuitive. This is not a real cut-out but an overlean - from a certain speed on the motor can only deliver decreasing torque, so is not able to keep one upright by accelerating.

If you take look at the graph ( motor current in A (which is proportional to motor torque) over speed in km/h):

And look at the line "current for incline 5 degrees and acceleration 1 m/s^2" (some grey-magenta color) - if you imagine one "rides" along this line and accelerates. If the speed reaches one of the "max limits" lines - depending on the actual battery voltage - then the motor suddenly cannot deliver the needed torque (not enough current possible to flow) anymore and if the rider does not brake/balance himself immedeately he faceplants...

Edited by Chriull
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32 minutes ago, ubertoad said:

Hi,

I wonder is it safe to run up the hill as fast as I can. And if not, how fast can we ride?

As the limits seems to be based on speed, but cut out is based on power consumption. So riding up the hill you probably can use all your power having speed way less than limit and do a faceplant. Is this the case or it still will beep based on power consumption?

To properly answer your question we would need to know to what extent the hill is a hill. There are shallow hills and very steep hills.

In addition to the slope of the hill we need to know what wheel you are riding because the power capabilities of the wheel will determine how much you can safely push it.

Edited by Marty Backe
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I'm riding KS 16A (probably rather B). I ride different hills (probably 15% is effectively the maximum where it can be really dangerous) and it's not that easy to estimate their incline and my speed while riding. And it is not really something to learn by trying and failing. So I'd like to know if there's some good strategy and if it is a problem.

As if it beeps at some power/heat, whatever, before the cut out it is unlikely to be a problem, I'm not gonna ignore beeps.

Edited by ubertoad
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24 minutes ago, ubertoad said:

I'm riding KS 16A (probably rather B). I ride different hills (probably 15% is effectively the maximum where it can be really dangerous) and it's not that easy to estimate their incline and my speed while riding. And it is not really something to learn by trying and failing. So I'd like to know if there's some good strategy and if it is a problem.

As if it beeps at some power/heat, whatever, before the cut out it is unlikely to be a problem, I'm not gonna ignore beeps.

As far as i know no wheel has until now warnings (beeps) before it reaches the torque limit. Somehow i managed it to stay well below the limits ( if you look at the blue dots in the graph). Also like it was written around here with the power abilities of the modern wheels and the pedal length (lever) it is hard to reach the limits?

i don't know if i have a certain strayegy - i just don't want to faceplant. Maybe its something one learns over time - maybe at one of my next uphill rides i have my first real faceplants...

you could just log your rides with either wheellog (android) or Gyrometrics (ios) and put your data into this limit excel sheet and check after your ride in which "regions" you where riding.

ps.: gyrometrics has a small fault in the actual version - for ks it shows the current by the factor 100 to low.

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40 minutes ago, ubertoad said:

I'm riding KS 16A (probably rather B). I ride different hills (probably 15% is effectively the maximum where it can be really dangerous) and it's not that easy to estimate their incline and my speed while riding. And it is not really something to learn by trying and failing. So I'd like to know if there's some good strategy and if it is a problem.

As if it beeps at some power/heat, whatever, before the cut out it is unlikely to be a problem, I'm not gonna ignore beeps.

During the last year, while I became more and more trustful with my KS16, I drove some rather steep hills up quite fast at the (as I call it) beeping limit (I set the 3 alarms and ollie/tiltback to 0,0,30,30).

I never had a problem until now, also not during a long offroad drive on partially very steep trails through the wood.  Though that doesn't mean much, because a cutout due to overheat may happen suddenly, but at least the wheel beeps some time before, so it should not take you by surprise.

Faceplant because of overleaning is a different story, but as Chriull wrote above I think one gets a feeling after some time. I also believe that such an overlean accident could only happen to me offroad, not on asphalt.  Maybe I'm just to anxious offroad to ride the wheel to it's beeping limit.

Only once until now I had a problem, where the wheel beeped at me for another reason than reaching maxspeed:  I accidentally fully charged the wheel before a very long downhill drive, where the wheel started beeping and tiltback after some 100 meters, so it was impossible to proceed. I had to drive back up a while, before I could go down completely.

Edited by HermanTheGerman
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I think it's a good idea to watch the power consumption from the KS app every once in a while. The goal is to familiarize yourself with the power needed for certain hills at certain speeds, and for acceleration at a level ground and various degrees of uphill.

When riding a few crazy steep uphills for the first time with my KS-16S, I was very cautious as I had learned from my Lhotz. Next time when I looked at the app I was maxing out at around 1200W. The peak power on the KS-16S is more than twice that. Now I know that on full battery the KS-16S torque will conquer any uphill I dare to try. As long as the tire still has grip ofcourse.

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2 hours ago, Chriull said:

As far as i know no wheel has until now warnings (beeps) before it reaches the torque limit.

Oh! I guess technically this may not be so easy (to not do too conservatively) but it's still disappointing.

21 minutes ago, mrelwood said:

I think it's a good idea to watch the power consumption from the KS app every once in a while. The goal is to familiarize yourself with the power needed for certain hills at certain speeds, and for acceleration at a level ground and various degrees of uphill.

When riding a few crazy steep uphills for the first time with my KS-16S, I was very cautious as I had learned from my Lhotz. Next time when I looked at the app I was maxing out at around 1200W. The peak power on the KS-16S is more than twice that. Now I know that on full battery the KS-16S torque will conquer any uphill I dare to try. As long as the tire still has grip ofcourse.

@ubertoad This is a great idea of what you can do if you're worried. Just check a hill like described, increase your speed going uphill as long as you're in the motor envelope, and see what wattage you actually have.

In general, it will be nearly impossible to overlean a 1200W nominal wheel (same with the 1500W Gotways) unless you're extremely fat or going above the speed beeps.

One thing you can do, is to slow down when you approach a increased demand situation like when a hill starts. Aka do not go 35 km/h right when the hill suddenly starts (or a big bump or whatever), but slow down a bit before.

On hills, you will most likely get a overheating or overcurrent warning looooong before you reach the motor limits of a 16S.

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2 hours ago, mrelwood said:

I think it's a good idea to watch the power consumption from the KS app every once in a while. The goal is to familiarize yourself with the power needed for certain hills at certain speeds, and for acceleration at a level ground and various degrees of uphill.

The power consumption of the app is just a house number - at low speeds it can be easily twice or triple of the real value.

2 hours ago, mrelwood said:

Now I know that on full battery the KS-16S torque will conquer any uphill I dare to try. As long as the tire still has grip ofcourse.

+1!

also on a straight road once when i did not watch the surface there was a small ditch which made me "fall" forward - i was already sure that i have my first high speed faceplant on asphalt, but the ks made it to accelerate again under me so nothing happened other then a bit of adrenaline!

1 hour ago, ubertoad said:

Thanks, so looks like there'll be some beeping at least before the cut off.

No. Beeps are Only for slow speed overpowering, overheating and the fixed speed alarms. 

1 hour ago, meepmeepmayer said:

Oh! I guess technically this may not be so easy (to not do too conservatively) but it's still disappointing.

Thats very easy to implement, needs almost no cpu resources and would be a real usefull alarm.

a 30 km/h alarm and tiltback is extremely conservative with full batteries and useless if one accelerates a bit more on not so full batteries - then a below 30 km/h "cut-out" is easily possible. Without any beep or tiltback.

@ubertoad- maybe thats my strategy to stay safe: the faster i go the less i accelerate!

 

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On 7/21/2017 at 0:10 AM, Chriull said:

The power consumption of the app is just a house number - at low speeds it can be easily twice or triple of the real value.

No doubt. Presenting a wildly fluctuating value only a few times in a second is bound to be inaccurate. But it's something, and I feel it's still a good learning point.

Quote

also on a straight road once when i did not watch the surface there was a small ditch which made me "fall" forward - i was already sure that i have my first high speed faceplant on asphalt, but the ks made it to accelerate again under me so nothing happened other then a bit of adrenaline!

This actually happened to me just two hours ago! I've been afraid of tree shadows on the road, since they can hide huge holes and bumps. A transition from dirt to pavement had a ~6cm step I didn't see because of the shadows. The KS-16S (in hard mode) bounced up, but the landing was smooth enough, and all went well. Man I love this wheel!

Now I wish I had had Gyrometrics running!

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  • 2 weeks later...
On 20.7.2017 at 5:50 PM, Chriull said:

As far as i know no wheel has until now warnings (beeps) before it reaches the torque limit. Somehow i managed it to stay well below the limits ( if you look at the blue dots in the graph). Also like it was written around here with the power abilities of the modern wheels and the pedal length (lever) it is hard to reach the limits?

I am not so sure about that. I rode a NB1 E+ for more than 2000km (a 500W nominal / 1500W peak wheel), and when I drove up a steep hill, it would start to beep at me at 10kph with the apps power meter reaching almost 1500W, while it normally started to beep at 23kph. So I am pretty sure the NB1 did monitor power output and issued an audible alarm when reaching the power limit. I also experienced beeps due to overheat after a long and steep climb. Never had any cut-out. Now riding a KS16S and even on my steepest hill, I can't seem to push it hard enough to even reach the power limit, so I did not hear any low speed beeps so far and can't say if there would be any. The pedal length simply is too short to push the wheel forward hard enough to get anywhere near the peak power limit.

Edited by Christoph Zens
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9 minutes ago, Christoph Zens said:

I am not so sure about that. I rode a NB1 E+ for more than 2000km (a 500W nominal / 1500W peak wheel), and when I drove up a steep hill, it would start to beep at me at 10kph with the apps power meter reaching almost 1500W, while it normally started to beep at 23kph. So I am pretty sure the NB1 did monitor power output and issued an audible alarm when reaching the power limit. I also experienced beeps due to overheat after a long and steep climb. Never had any cut-out. Now riding a KS16S and even on my steepest hill, I can't seem to push it hard enough to even reach the power limit, so I did not hear any low speed beeps so far and can't say if there would be any. The pedal length simply is too short to push the wheel forward hard enough to get anywhere near the peak power limit.

Yes - nb e+ has a power warning, also the ks16 - as you mentioned this ks16 overpower warning is hard to reach. Also overheat warnings are normally implemented.

but no wheel has a warning for the torque limit (torque over speed chart). This can quite easily be the reason for an overlean while staying far below the overpower, overheat or speed limit.

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1 hour ago, Chriull said:

but no wheel has a warning for the torque limit (torque over speed chart). This can quite easily be the reason for an overlean while staying far below the overpower, overheat or speed limit.

That should not be the case. The motor should have been designed such that its operating point at the maximum rated speed of the wheel (35kph for the KS16S) is near the maximum power output of the motor. At this operating point, the motor delivers its peak power and there is still 50% of the motors stall torque available, which should have been used as the rated torque when designing the wheel, meaning that all calculations regarding the ability to balance the rider under various conditions should have been done with 50% of the motors stall torque. Also, slowing down the motor (bump, increased incline) will immediately result in more torque anyways. From an earlier post of a KingSong employee in this forum, I gathered that KS designed their wheels using exactly this approach. From my own experience, I can say that the KS16S is pretty good in building up torque to pull itself out of pot holes. It feels like one would fall off, since the wheel suddenly slows down being stuck in the hole, but the stalled motor suddenly delivers a lot of torque and pulls the wheel out again before the rider loses balance.

I think such under-torque situations mostly happen on wheels which have a mismatched combination of motor characteristics and speed limit, such that they operate the motor beyond its maximum power output. On a well designed wheel, such a warning would never fire under normal riding conditions. To cover the unexpected, such a warning could be implemented and issue a beep or two before the rider falls off, but I don't think that the beep would help to prevent the faceplant, because once the rider entered an extreme pot-hole at high speed with not enough torque to get out again, there is no way to correct the situation. So that's probably why no one bothered to implement it in the first place.

Another thing to remember that moving at high speed, a lot of energy is available as momentum, stored in the mass of around 100kg moving at 30kph. This momentum adds to the reduced torque of the motor to cover bumps and medium sized pot-holes.

There was a link to a Russian website on this forum, where they tested a number of wheels on a dynamo-meter. From the resulting power output measurements, it looked like most wheels (but not all of them) hit their speed limit before the power output went down. I don't remember which wheels showed decreasing power before hitting the speed limit though.

Edited by Christoph Zens
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47 minutes ago, Christoph Zens said:

That should not be the case. The motor should have been designed such that its operating point at the maximum rated speed of the wheel (35kph for the KS16S) is near the maximum power output of the motor. At this operating point, the motor delivers its peak power and there is still 50% of the motors stall torque available, which should have been used as the rated torque when designing the wheel, meaning that all calculations regarding the ability to balance the rider under various conditions should have been done with 50% of the motors stall torque. Also, slowing down the motor (bump, increased incline) will immediately result in more torque anyways. From an earlier post of a KingSong employee in this forum, I gathered that KS designed their wheels using exactly this approach. From my own experience, I can say that the KS16S is pretty good in building up torque to pull itself out of pot holes. It feels like one would fall off, since the wheel suddenly slows down being stuck in the hole, but the stalled motor suddenly delivers a lot of torque and pulls the wheel out again before the rider loses balance.

I think such under-torque situations mostly happen on wheels which have a mismatched combination of motor characteristics and speed limit, such that they operate the motor beyond its maximum power output. On a well designed wheel, such a warning would never fire under normal riding conditions. To cover the unexpected, such a warning could be implemented and issue a beep or two before the rider falls off, but I don't think that the beep would help to prevent the faceplant, because once the rider entered an extreme pot-hole at high speed with not enough torque to get out again, there is no way to correct the situation. So that's probably why no one bothered to implement it in the first place.

Another thing to remember that moving at high speed, a lot of energy is available as momentum, stored in the mass of around 100kg moving at 30kph. This momentum adds to the reduced torque of the motor to cover bumps and medium sized pot-holes.

47 minutes ago, Christoph Zens said:

There was a link to a Russian website on this forum, where they tested a number of wheels on a dynamo-meter. From the resulting power output measurements, it looked like most wheels (but not all of them) hit their speed limit before the power output went down. I don't remember which wheels showed decreasing power before hitting the speed limit though.

Yes and no ;)

The russian website is http://airwheel.ru/test-monokoles-na-dinostende/ - for the KS16B/C it showed ~2,2kW at ~24 km/h.

But one can quite easy run into an overlean at around 26 km/h with this wheel - also it "just" uses ~1,7kW at this moment (the max possible power with this battery voltage and speed)... (http://forum.electricunicycle.org/topic/7855-anatomy-of-an-overlean/)

Once one hits the torque limit for a given speed no (forward) balancing is possible anymore...

But as said - these limits are quite well choosen for the KS16B/C (and for quite sure also for the KS16s). Without the 30 km/h limit one could hit with just 800W output power at ~36 km/h the torque limit and easily overlean.

Regarding the momentum: With the high center of gravity and the instability it just creates a lever with a forward torque, which the wheel has to "outaccelerate". Just the normal balancing. The more momentum (mass/speed) is involved (and the higher the the center of gravity) the more balancing (torque, acceleration) is needed from the wheel.

 

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23 hours ago, Chriull said:

Regarding the momentum: With the high center of gravity and the instability it just creates a lever with a forward torque, which the wheel has to "outaccelerate". Just the normal balancing. The more momentum (mass/speed) is involved (and the higher the the center of gravity) the more balancing (torque, acceleration) is needed from the wheel.

 

Yes, it would help if the wheel would weigh 80kg and the rider 15... Since that's not the case, the momentum of the rider probably does more harm than good.

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  • 2 weeks later...

Dear @ubertoad

you asked:

On 20.7.2017 at 4:30 PM, ubertoad said:

Hi,

I wonder is it safe to run up the hill as fast as I can. And if not, how fast can we ride?

As the limits seems to be based on speed, but cut out is based on power consumption. So riding up the hill you probably can use all your power having speed way less than limit and do a faceplant. Is this the case or it still will beep based on power consumption?

The following thread took a closer look on that subject, including a mathematical estimate of "save" speed going uphill at a given weight and slope:

PS.: There are also a number of other threads mentioned in that topic that discuss various aspects of this issue:

On 6.11.2016 at 10:42 PM, RenaissanceMan said:

For the benefit of myself and more recent visitors to this forum (and this thread in particular) I collected a few references on previous posts to this subject matter by a forum search for "motor yield". These I found anticipating the discussion at hand and in general substantiating the findings presented here. They all emphasize the inherent safety speed limits based on battery level and other factors. Enjoy the reading AND speed conscious riding :rolleyes:!

 

 

 

 

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