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King Song 18a 1360wh top speed fall


Alex_U

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When a wheel is anounced with 40 kmh....i would think that the "lift off" cut off is 50 kmh at least...

But: Is it possible that because of the 1200W Standard or 3000W Max the safety margin has been cut down to a "Minimum"???

i could be totally wrong...just a thought......

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Hi,

It might no also depend on the energy that is required to go over that top speed, for example if you do a fast acceleration if your wheel is capable of achieving 40kmh top, it migh shutoff on you just a few kmh after its top speed if you accelerate hard, or if the battery is low. Might depend on the model though.

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23 hours ago, WaveCut said:

KingSong has some poorly designed algorithms about dealing with uphills/downhills and tilt-back.

 When torque is not enough to stabilize new setting, then wheel thinks that rider pushing it hard and constantly accelerates to stabilize, unsuccesfully, which results in over-speeding cutoff.

It's definitely an awful software bug, and personally I think that it's very hard to fix, because controllers are not capable to compute such complex criteria... Just don't push it to the limits for your safety, please.

I would not say it is that dramatic. IMHO, KS wheels do deal up/downhills and tilt-back well enough, at least I did not had any problems with it at 20 km/h. The mistake is not in software, it is too low safety margin between maximum speed you can manually set and cut-off speed (in my case - 40 and 45 km/h, but it should be 40 and 50 or 35 and 45, i.e. 20% reserve). And this margin was preset by manufacturer and cannot be overridden by user.

So can someone help me find an email of KingSong, so that I could contact them, describe the case and ask to re-establish the correct 20% safety margin between max (allowed to set) speed and cut-off speed? I could not find their contacts anywhere, just a hot line on official site.

P.S. My condition is better, today I did not cover wounds with pads, no more blood or moisture coming out, wounds completely dried out. And I could take a usual shower this evening for the first time after the crash without any problems. Huge plans for the weekend, body protection has arrived ;o)

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@Alex_U I am feeling the pain just seeing your photos for the first time. Nasty! So glad you are OK. Do keep an eye on those wounds for any signs of infection. Unfortunately I have nothing to offer in terms of the technical difficulties you experienced. Looking at all of the posts and comments you are in excellent hands! Be well!

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I wonder if we can think of things theoretically this way.  These are all hypothetical numbers I'm using for example.  Keep in mind I may be way off base here as I'm no expert.  Please correct me if I'm wrong any where.

Going on a level surface with a 100 kg weight the wheel can go at a maximum safe speed of 40 kph with a terminal speed (where faceplant occurs at any speed over this) of 45 kph and has a lift test speed of 50 kph.  It's just dealing with frictional forces from the road, wind, axle bearings, etc.  If you put two people on and have a 200 kg weight on it, the maximum safe speed might drop down to 30 kph with a 40 kph terminal speed.  If there is a 1000 kg elephant riding it, that maximum speed might drop down to 10 kph with a 20 kph terminal speed.  So I think it's quite weight dependent. 

I remember I had a remote controlled car as a kid.  It would zip around happily at a certain speed.  When I placed some action figures on, it wouldn't go as fast.  When I put a really heavy toy on it, it would move but go at a crawl.  So I think an electric motor's maximum speed that it can go under load depends on the weight it is carrying.  When a manufacturer says my wheel can go a maximum 40 kph, that could be for a certain test weight and not an elephant, but I think you get where I'm going.  Even with cars, say a Porsche can go a maximum of 200 kph with one driver.  Put 3 elephants in the backseat, and that maximum speed might not be the same.

Back to having one 100 kg weight, and going up a hill the wheel is fighting gravity so to the wheel it feels like there is an increased weight of say 150 kgs on it so that maximum safe speed might decrease down to 35 kph and the terminal speed could be 40 kph instead.  Ever push a cart with a huge load of carrots on a level road?  Ever push that same cart up a hill?  It feels a lot heavier going uphill or as if you had a lot more carrots going on a level road.

Going down a hill gravity helps so the wheel is happy that it feels like there is less weight, say 50 kgs so it needs less power to move.  Maximum safe speed might still be 40 kph, but the terminal speed has a ceiling of 45 kph or slightly higher due to what feels like a lighter weight for it to move.  If the hill is quite steep (eg. edge of cliff falling 90 degree angle) the terminal speed would be the same as the lift test speed as there would be as if no weight is on it (free fall).  Going down a typical hill because of gravity it's so much easier to accelerate to that maximum speed that you have to be especially cautious because the wheel thinks it only has a 50 kg weight on it now.  Leaning forwards at your regular lean to speed up will have that gravitation acceleration added to it making the net acceleration higher.  Zipping to 40 kph quickly then to 45 and over ends up with a splat as there's only about 5 kph of safety which is hard for a rider to gauge and difficult for the wheel to provide a tiltback in time for.  If a manufacturer could make a wheel with a "safe speed" of 40 kph and a terminal speed of 100 kph there would be no problem for the wheel to tiltback in time.  Some wheels like the Solowheel tilt back so much that it's impossible to over-ride it.  I don't know how much room they have between maximum safe speed and the terminal speed so maybe really fast accelerations might be able to over come it?

I wonder if a weight sensor might help the wheel in determining when to set the tiltback.  If the weight is constant the tiltback could be safely set at 40 kph.  If the weight is constant and the acceleration speed is high then it could drop the tiltback down to 35 kph to give some added rider response time.  If the acceleration is low there are no adjustment is needed.  If the weight suddenly increases that could mean the rider is going uphill so the tiltback could be adjusted down to 35 kph as the wheel needs more power reserve to climb.  If the weight is detected to decrease that could mean the rider is going downhill so the tiltback could be lowered again.  A floating tiltback setting adjusted by the control board might be a safe way to approach it, but the wheel would need to be able to sense when that adjustment is needed.  Perhaps a better sensor might be some sort of resistance to rolling sensor.   Maybe using the current level would work?  Going downhill the current reverses and goes into regeneration mode with an increase in voltage while uphill there is a rise in current and drop in voltage?

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I'm not convinced that the wheel detecting a climb or drop when I'm already in it is going to help. Terrain conditions make a big difference in safe speed. There's a trail near BWI Airport that's nice, flat, and straight, I can average 25kph for long distances. Around my house I can only manage about 19kph average speed because of all the potholes, dips, sidewalk heaves, and such. Those all come up suddenly over and over during the ride, there's no time to get to top speed because almost immediately you're braking and need to slow down right at the torque limit of the Firewheel. It's also exhausting because you have to pay a lot more attention!

38 minutes ago, HunkaHunkaBurningLove said:

I wonder if a weight sensor might help the wheel in determining when to set the tiltback.

The rider's weight is constant during the ride. An accelerometer could determine the vertical rise/fall, but only at the point where it has already happened. Based on what I described above with sudden obstacles, it would be super helpful to have that data a few seconds in advance of the change. :D By the time you've hit an incline, bump, or drop, the wheel may be in a situation where any safety reserve is spent.

I could see the software doing something simple like adjusting the margin of safety based on the rider's weight though, you could just enter it manually and it would set the recommended warning levels based on the torque it would need to balance the rider based on that weight. Letting people pick their own warning points without any guidance, right up to the point of shutoff, seems like it will get these wheel makers in trouble.

 

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I think my old physics teacher would be rolling in his grave if he saw how much I've forgotten over the years.  Apparent weight does change with acceleration in an upwards or downwards direction if I Googled that correctly (see elevator physics examples). 

I think you're right in that the manufacturers might be better off picking a well defined maximum safety speed well below the terminal velocity taking into account various downhill grades, maximum rider weights and maximum acceleration requests from the user.  Increasing the terminal velocity capability of the motor to keep a greater reserve of wheel power available would also be wise.

What do you think of having a small spare battery pack or large capacitor dedicated to emergency boost needs like hitting terminal velocity, excessive overlean/acceleration, and sudden potholes that require extra power to get out of?  Engaging it only in extreme conditions might allow the wheel to cope better with these issues when the main pack is fairly depleted or whenever the need arises.

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Something like infrared-, ultrasonic or laser-range/distance/obstacle detection sensor could be used to determine the angle of the ground (ie. place two sensors, one in the back, one in the front, with about 45-degree angle back and forth):

c5lDqys.png

Yeah, still can't draw worth s**t :D 

Of course, sudden bumps and street cornerstones could be detected as sudden steep uphill (or downhill), so probably they would need to track the average over a longer period to distinguish between them.

 

7 hours ago, HunkaHunkaBurningLove said:

I think my old physics teacher would be rolling in his grave if he saw how much I've forgotten over the years.  Apparent weight does change with acceleration in an upwards or downwards direction if I Googled that correctly (see elevator physics examples). 

I think you're right in that the manufacturers might be better off picking a well defined maximum safety speed well below the terminal velocity taking into account various downhill grades, maximum rider weights and maximum acceleration requests from the user.  Increasing the terminal velocity capability of the motor to keep a greater reserve of wheel power available would also be wise.

That would mean higher max speed for the motor, which would mean lower torque. It's always a tradeoff... unless you go really high power?

 

7 hours ago, HunkaHunkaBurningLove said:

What do you think of having a small spare battery pack or large capacitor dedicated to emergency boost needs like hitting terminal velocity, excessive overlean/acceleration, and sudden potholes that require extra power to get out of?  Engaging it only in extreme conditions might allow the wheel to cope better with these issues when the main pack is fairly depleted or whenever the need arises.

The capacitor would need to be really large to store enough charge. A spare battery pack could work, but it would still have to have at least as many cells as a single "main" battery pack, because it needs to be able to give out enough voltage. So if your main packs are 16S, the spare pack needs to be at least 16S. If the voltage from the spare pack is less than the back-EMF of the motor, it will actually start to brake when you switch to the spare-pack?

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19 hours ago, dmethvin said:

An EUC would seem to be further handicapped by the fact that the vehicle body doesn't have a natural "level" state to use in detecting when the vehicle is climbing.

That would be possible to solve by ("parking type") ultrasound proximity sensors on the front and back to calculate the current incline.

EDIT: @esaj beat me to it including illustration and more detailed explanation ;)

Edited by HEC
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2 hours ago, HEC said:

That would be possible to solve by ("parking type") ultrasound proximity sensors on the front and back to calculate the current incline.

EDIT: @esaj beat me to it including illustration and more detailed explanation ;)

link the wheel to the cellphone's gps and Google maps? Then it could use a predictive algorithm to slow down before the incline,

and maybe give some warnings like "mind your face" for those who keep pushing the wheel to the max :o

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7 minutes ago, Jurgen said:

link the wheel to the cellphone's gps and Google maps? Then it could use a predictive algorithm to slow down before the incline

Would be probably easier and more reliable to slap GPS module directly into EUC considering how cheap they're nowadays however I doubt Google or any other free(-ish) mapping tools includes such detailed inclination figures plus it will not know every ramp or bump in the road you might encounter anyway ;)

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2 minutes ago, HEC said:

Would be probably easier and more reliable to slap GPS module directly into EUC considering how cheap they're nowadays however I doubt Google or any other free(-ish) mapping tools includes such detailed inclination figures plus it will not know every ramp or bump in the road you might encounter anyway ;)

t if you plan your route in Google maps it should get some idea on hight differences along the road, and estimate inclines.

Of course it won't work if you decide to take to take a shortcut down the stairs with your 18"GW,

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I wonder if there is a way to do a combination winding to get both torque and high speed.  I've read that wire gauge size and number of windings result in the differences between high speed and torque.  Would it be possible to combine both in one wheel or would the space requirements make the wheel too large?  I mean wind larger gauge copper wire and also wind a separate circuit with thinner copper wire with more windings in an alternating pattern and create a control board that applies more power to one set for high torque requirements and gradually shift that power to the other windings for higher speed?  Or maybe that just doesn't work out?  I remember making an electric motor in industrial arts back in junior high where we wrapped some copper wires around some nails and completed the circuit which made the armature spin.  It was a very neat experiment on how electric motors work.

It appears that the windings are placed on the periphery of the internal armature in our EUCs while there is a lot of space from the axle to the periphery.  Could a design incorporate magnets mounted to both of the motor cover plates and have additional windings to power the motor from the inner part?  Or perhaps have a dual spin motor where a smaller electric motor hub spins inside the larger hub...

If you took this pancake motor:

http://www.qmed.com/mpmn/article/mighty-motor-flat-pancake

And used it as the armature for a larger motor with addition windings on the periphery to spin the inner motor, I wonder what the combined power would be like.  Image a motor that is spinning an axle.  Now imagine spinning that entire motor that is spinning that axle.  The combined effort would increase the rate of axle spin...

 

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9 hours ago, HunkaHunkaBurningLove said:

I wonder if there is a way to do a combination winding to get both torque and high speed. 

Well - in theory at least - you can wind the motor similar way like transformers with multiply outputs. basically you'll make windings with "branches" leaving out after specified amount of winds and then switch to which end "output" (input in case of motor though) to connect the second pole however it would be a bit tricky to make some smooth transitions between different lengths of the windings plus the whole winding would most likely need to by done with the wire of the same diameter making it less efficient for some sections / combinations.

Something like 3rd diagram on this page ...

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10 hours ago, HunkaHunkaBurningLove said:

I wonder if there is a way to do a combination winding to get both torque and high speed.  I've read that wire gauge size and number of windings result in the differences between high speed and torque. 

I'm pretty sure I can get a 10-15kw motor in a EUC for about the same weight as existing ones. But I can't do it until I can get a custom control board working. Some motor types also need between 50 and 100khz switching speeds depending on the design.

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26 minutes ago, HEC said:

Well - in theory at least - you can wind the motor similar way like transformers with multiply outputs. basically you'll make windings with "branches" leaving out after specified amount of winds and then switch to which end "output" (input in case of motor though) to connect the second pole however it would be a bit tricky to make some smooth transitions between different lengths of the windings plus the whole winding would most likely need to by done with the wire of the same diameter making it less efficient for some sections / combinations.

Something like 3rd diagram on this page ...

So what you want is two windings of the same diameter, but with the option to power them in parallel (for torque) or series (for speed)?

Even if you had to select the "mode" at power up, it would be a great option. 

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@HEC that's a very good site to learn / review about circuitry.  

It's interesting to see electric bike motors like these:

http://www.ebay.com/bhp/electric-bike-motor

in such a small form factor, but they are capable of high speeds using only 48 volts.  Are they lacking in torque and not suitable for EUC applications?  They don't look to be that large either...

I remember someone mentioning that they do use repurposed electric bike motors in EUCs, and they said the manufacturers need to design a better motor for them.  In what way would a better motor be made/designed?

 

Edited by HunkaHunkaBurningLove
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3 minutes ago, HunkaHunkaBurningLove said:

in such a small form factor, but they are capable of high speeds using only 48 volts.  Are they lacking in torque and not suitable for EUC applications?

Well - it's compromise between size, weight and cheaper components used. It's also geared unlike motors in EUCs and meant as assistance drive rather than full drive. Finally - it doesn't need to balance the rider upright ;)

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On 20.06.2016 at 1:04 PM, Jurgen said:

Swimming truncks at 45Kmh, really?!!! Man man man, you are one lucky bastard, it's a miracle you're still in one piece.

1 week after: pretty well healed and back to battle. In 2 weeks it'll be hard to see anything. Still do not know how to contact the manufacturer to ask them to increase the safety margin between max speed and cut-off speed, what was the only reason of my fall, except my own understanding of allowed risk.

1.jpg

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