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esaj

Does this count as a unicycle?

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OK, the same IPS now claims to build a complete 800 Watt wheel with 9.3kg weight. You also noticed that it says wheel/motor, which I guess means motor+wheel? It probably even includes tire and pedals and pedal mounts (as seen in the picture), as these are not listed otherwise.

Is there much weight difference between two different rated motors of same sized wheel? I do get that 16" rim + motor + tire etc. is going to weight more than 14", but is there that much weight difference in coils of two same sized wheels, even if the rated power is different? Or does the motor contain other parts that need to be bigger / heavier for more power? Although I'm not sure, I'd expect that the weight difference between, say, 500W and 800W motors of same size isn't that much, probably just more/bigger gauge copper wire in coils?

There are all sorts of new materials coming, but mostly they're still in the research stage, I think. Something like nano-ceramics or foam metals could probably drop the weight of the tire+motor+pedal -assembly considerably, but are probably still far away from commercial mass production.Of course, should you win a lottery, I'm sure Gotway or Kingsong or similar would build you a prototype wheel with pretty exotic parts, if you give them enough time and money... ;) 

 

Edited by esaj

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There are all sorts of new materials coming, but mostly they're still in the research stage, I think.

I don't think we are anywhere near to the situation where we would need genuine research into new materials to make current EUCs lighter. I could be wrong, but isn't what we have now rather using off-the-shelf products assembled together into a prototype-like device of 11kg?

Having said that, does anybody know whether the motors have been specifically designed for EUCs or are generic and used in other applications, and which applications in case?

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@robca, I like your style, well reasoned & presented arguments :) 

Even with 64cells, the battery pack is only 3kg compared to ~10kg for the direct-drive hub motor. If there is weight shedding potential, it will almost certainly have to come from there. It will be very interesting to see the tear-down individual component weight of the IPS zero, since they claim to be able to produce 800W of continuous power with 32 cells for a total system weight of only 9.3kg, which if true, is nothing short of miraculous.

Perhaps eWheel development will take two different courses: one catering for power-users & one for those who place weight saving at a premium. I could be wrong, but from all the technical materials I've read, I think the two requirements are mutually exclusive, either you have a beast of Wheel or you have a light one. 

The criticism about the capture rate is valid: the hardware allows one to set up to 50Hz, will see if this makes a difference in resolution for capturing swings in power output. 

 

Thanks for the nice words :) and, to be clear, I was not criticizing your data capture, just pointing out that it's very spiky even at what is a reduced rate, so the real graph would be even spikier. Your data proves my point: a EUC motor is under constant variable load, unlike what a e-byke or e-skateboard would show

 

Range and speed then don't sound much different from EUCs. 

I don't think anyone was claiming this. The question is: how much of the energy is purely "wasted" on balancing, and, how much energy needs to be necessarily wasted on balancing with the best-case controller implementation, and, whether this is a relevant factor in (a) the energy balance and (b) the necessary weight to carry. 

However, for some reason we don't notice all this accelerating and braking with our senses. Which seems to suggest that not so much movement is induced in the end, which suggests that not much energy is (at least in principle) needed in the end. (I do understand that the controller operates on time intervals that are not notable to our senses). We know that pole balancing can be done very smoothly with comparatively low acceleration forces applied, if the controller is smart enough and starts in the balanced position. 

Again, consumed energy is the integral, AKA average, am I wrong? From the graphs I can conclude that going uphill takes about 800 Watt and balancing takes less than 150 Watt (could be 100, could be 10, could be 1), assuming the wheel was balanced between time stamps 0.2 and 0.3. I can't see how to put a lower bound on the "balancing energy" from this data though. I would be delighted to learn how. 

That is definitely so and holds true for pedelecs as well. It means that battery size of comparable e-wheels must be larger than for pedelecs or e-skateboards, giving an e-wheel roughly a 1/2kg disadvantage (thereby added 10km safety margin range).

 

I never thought for a second that an e-skateboard would be my future transportation aid. But I immediately got suspicious when I first learned about e-wheels. One reason: any device with stand-alone wheel(s) that are smaller than, say, 12" has in my world only toy status, because it can be safely driven at moderate speed only on plain flat surfaces.

Right. Range and speed are the same, with half the weight and slightly more than half the battery size. Which is my point exactly :P. It's easier to build a lighter, longer range e-skate

An electric motor uses a lot more energy when changing speed. A lot more than running at constant speed. If you added Jason's logger to an e-byke or e-skate, you would see a relatively flat line, much, much lower as soon as they reach constant speed. Probably less than half on average. Hence the integral is much, much smaller, for the same amount of work.

Our senses do not perceive anything, because the controller reacts in 1/200th of a second. And the motor has to apply a lot of torque (a lot!) to speed up and slow down. Having to react super fast, uses a lot more power than reacting slowly (since the rate of change depends on the amount of available current and the motor power). The faster it reacts, the smoother the ride. Early wheels and low end Arduino controller have very rough rides. Newer controller and more powerful motor, smoother ride. That comes at a huge cost in terms of used power. If you graphed an e-byke or e-skate, you would see a spike when accelerating, then slowly tapering off when desired speed is achieved (even going uphill). The motor operates at constant speed

I don't have a e-skate to instrument, but I know brushless motors very well. Take for example a quad (drone). on a quiet day, hovering uses a certain amount of power, not very high, because the brushless motors are operating at near constant output (not really, the PID loop still keeps changing speed, but relatively slow). The same exact quad on an even slightly windy day, hovers using 30% more power, at least. And balancing a quad is not as complicated as balancing a human being on top of a wheel, with the huge momentum of that inverted pendulum. Every time you have to change a motor speed, energy is wasted in the battery, mosfets and the motor itself. The faster and more powerful the change is, the more is wasted. A portion of that area under the spikes is wasted in heat, and not converted to range (a portion bigger than a motor coasting at normal speed)

Saying that skateboards are not a a viable transportation option might be true for you, but clearly proven wrong every day by the many thousands of people commuting on a skateboard (I see many more skateboarders in London than EUC-er :) ). People skateboarding safely since the early 70s in San Francisco, Seattle and other hilly cities also prove that skateboards can indeed safely go fast. As a matter of fact, on average e-skateboards have much higher safe top speeds than EUCs, and no need for tilt-back. Motor cutoff is also much less dramatic on a e-skate (you simply lose braking downhill, but it's easier to recover than a cutoff in a EUC)

I'm intrigued by EUCs and will get one as soon as I find the right combination of weight and battery (for airplane travel). But I recognize that there are more efficient solutions, and I encourage experimenting outside of the current form factor (which is the reason I posted my initial comments)

 

Edited by robca

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I don't think we are anywhere near to the situation where we would need genuine research into new materials to make current EUCs lighter. I could be wrong, but isn't what we have now rather using off-the-shelf products assembled together into a prototype-like device of 11kg?

Having said that, does anybody know whether the motors have been specifically designed for EUCs or are generic and used in other applications, and which applications in case?

At least Daao/XINAOMA (who has built motors for at least Firewheels, IPS and older Gotways) has a specific category for "self-balancing wheelbarrow motors" in their catalog, but the catalog does not for example contain the Firewheel motor, which may have been specifically built for Taizhou Wanchang Electronic Technology (the company manufacturing Firewheels).

http://www.daaomotor.com/html/Self-balancing_Wheelbarrow_Motor/

Edit: looks like their catalog has changed since the last time I saw it, there is now only one page of the motors, when before there were 3. And the images are no longer loading, earlier on there was at least one motor with the IPS -logo in the side.

 

DAAO Electric (Jiangsu) Co., Ltd. and Changzhou AOMA Technology Co., Ltd., established in 2006, is a technology institution and manufacturing enterprise specialized in researching and developing electromotor and controller of electric vehicles. Covering a floor space of 36,000m2 and having an annual production capacity of 3,500,000 sets, the company has developed into a leading enterprise in Chinese industry of electric vehicle electromotor since its foundation. Its products are used in provinces and cities all over China, as well as in many other countries and regions. 
Always maintaining the core concept of driven by technology and thriving on high-quality, the company persists in exploration and research, striving to launch onto the market more environmentally-friendly, energy-efficient, and economical high-tech products that are closer to perfection. Our company has successively passed the certification for ISO9001 and ISO14001 systems. In addition, our products have passed national and international certifications such as CCC and CE. Thanks to the comprehensive management system and standard, mature production techniques, thorough testing methods, and precise and effective quality assurance system, XINAOMA & DAAO brand enjoys high prestige in domestic and overseas markets. 
 
My Firewheel motor has the marking A16AMK27C1412048393 and XINAOMA logo in it. Never identified the motor further than that. Probably the motor designation is A16- (for 16-inch?) AMK27-C, the rest is probably date & serial (4th of December 2014, 8393).

Oh, right, when the first mainboard of the Firewheel burned, vee73 (who back then owned it) tore open the entire wheel, including the motor. The pictures are here:  http://forum.electricunicycles.info/forum/viewtopic.php?f=23&t=1848

 

Edited by esaj

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 Right. Range and speed are the same, with half the weight and slightly more than half the battery  size. Which is my point exactly :P. It's easier to build a lighter, longer range e-skate

well, I meant range and speed are the same with about the same size battery (while the device is heavier, that's what we can agree upon). The typical claim is 24km range (sometimes even more) for 240Wh, where 20km are apparently a quite realistic number for most EUCs. EDIT: IPS and Solowheel users have been reporting ranges at and above 10km/100Wh in this forum. 

An electric motor uses a lot more energy when changing speed. A lot more than running at constant speed. If you added Jason's logger to an e-byke or e-skate, you would see a relatively flat line, much, much lower as soon as they reach constant speed.

I would be interested in seeing it, even much more than being told what I would see :P 

Probably less than half on average. Hence the integral is much, much smaller, for the same amount of work.

I would be in for a bet against this claim. That is, I bet that on 15km/h constant-speed flat or uphill rides at most 33% of the energy is used for balancing (with reasonable controller design) against at least 50% is used for balancing, which seems to be your claim. Still, it seems somewhat difficult to test any of these claims reliably. 

Take for example a quad (drone). on a quiet day, hovering uses a certain amount of power, not very high, because the brushless motors are operating at near constant output (not really, the PID loop still keeps changing speed, but relatively slow). The same exact quad on an even slightly windy day, hovers using 30% more power, at least.

That is, I am pretty sure, what we will observe with an EUC for going on a flat road vs going on a bumpy road. 

I'm intrigued by EUCs and will get one as soon as I find the right combination of weight and battery (for airplane travel). But I recognize that there are more efficient solutions, and I encourage experimenting outside of the current form factor (which is the reason I posted my initial comments)

I am all for experimenting on the current form factor. At the same time I want to see convincing data for the claim that huge amounts of power/energy are needed for balancing. I just haven't seen it (yet). 

Edited by Niko

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Is there much weight difference between two different rated motors of same sized wheel? I do get that 16" rim + motor + tire etc. is going to weight more than 14", but is there that much weight difference in coils of two same sized wheels, even if the rated power is different? Or does the motor contain other parts that need to be bigger / heavier for more power? Although I'm not sure, I'd expect that the weight difference between, say, 500W and 800W motors of same size isn't that much, probably just more/bigger gauge copper wire in coils?

In the example of King Song, the 800W motor is 2kg heavier than the same size diameter 500W motor. Was told by KS that this is to do with physical additional quantities of copper/iron/nickel needed to drive more current through the coils & stronger permanent magnets in the rotor.

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Saying that skateboards are not a a viable transportation option might be true for you, but clearly proven wrong every day by the many thousands of people commuting on a skateboard (I see many more skateboarders in London than EUC-er :) ).

I am seeing kick scooters (with pretty small wheels) all over the place since years, many more than skateboards, yet I believe they haven't got (and IMHO will not get) into the same popularity league as bicycles for day-to-day transport. EUCs are far from being anywhere near to any of these, including skateboards, but IMHO there is a good chance that they will end up in the bicycle league. That's how I can understand the focus of the Chinese manufacturers perfectly well. Just by 2 cents.

Edited by Niko

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In the example of King Song, the 800W motor is 2kg heavier than the same size diameter 500W motor. Was told by KS that this is to do with physical additional quantities of copper/iron/nickel needed to drive more current through the coils & stronger permanent magnets in the rotor.

One of the quickest way to estimate the power of a brushless motor for drones is weight. There is a direct relationship between the weight of the motor and its wattage. The stronger the magnets (which everything else being the same, means heavier) and the stronger the magnetic field (which requires more copper), the higher the power. Unless new magnetic materials are used, adding weight is just about the only way to increase power. In theory  you could increase current thru the windings without increasing the mass proportionally, but very soon you reach a thermal limit: less overloaded copper heats more, and above a certain temperature the magnets lose their properties, getting very quickly to a thermal runoff (i.e. motor burns). Above a certain temperature, magnets get permanently damaged and lose a big part of their magnetism, making the motor inefficient. Enamel insulation burns off above certain temperatures (depends on the enamel used), and that also ruins a motor.

So, unless materials dramatically change, an increase in power can only be achieved by an increase in weight

 

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Self balancing uses a lot of power, since the powerful motor must keep using lots and lots of torque to counteract any unbalance (and you keep losing momentum).

How does the power drain from balancing then depend on speed? Would it be different for cruising, say, at 5km/h versus cruising at 15km/h?

Edited by Niko

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I don't have exact numbers for electric skateboards, but even relatively low end units like the Yuneeq e-Go can do ~25 km range with a 240 Wh battery (and weighs only 6.3 Kg). Can also do 20 km/h, albeit not at max range.

I'd like to comment on your claim about the e-boards:  my friend has a Boosted Board (http://shop.boostedboards.com/collections/boosted-boards) and his realistic range is 10km (just under what the manufacturer claims).  He weighs about 160lbs.  His speed is much better than my NB1, but I'm all over him on range.  The problem with skateboards and range is that I think it is much easier to ride them harder and faster and thus chew up battery quicker.  I'm sure there are board models with bigger batteries and longer ranges, but I can't imagine that it would be such a big jump without a tradeoff somewhere else, like weight.

 

I'm not here on a EUC forum arguing for the superiority of skateboards :) they are not superior in absolute terms, and have their downsides... but electric skateboards are, unarguably, more energy efficient. Rider weight also has a smaller effect on the ride (no need to balance a heavier inverted pendulum).

Again, from talking with my Boosted friend (who participates on similar forums to this just for e-boards) rider weight has a dramatic effect on range for boards, just like it does for EUCs.  

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in the same category of not being an unicycle and not being a skateboard, but with 3 wheels (1 driving, 2 driven) :

http://www.autocar.co.uk/car-news/new-cars/volkswagen-last-mile-surfer-electric-scooter-revealed

 

vwlms-03.jpg?itok=LHwBu37Z

this one is announced for mid 2016 (£700 in the UK so roughly EUR 1000, 11kg). But what is really surprising, this is who is behind this project: Volkswagen !

When one of the largest car manufacturer starts to build electric powered and foldable tricycles (I don't have a better name for that), it sounds like the market for electric personal mobility starts to be taken seriously from the side of the industry.

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I'd like to comment on your claim about the e-boards:  my friend has a Boosted Board (http://shop.boostedboards.com/collections/boosted-boards) and his realistic range is 10km (just under what the manufacturer claims).  He weighs about 160lbs.  His speed is much better than my NB1, but I'm all over him on range.  The problem with skateboards and range is that I think it is much easier to ride them harder and faster and thus chew up battery quicker.  I'm sure there are board models with bigger batteries and longer ranges, but I can't imagine that it would be such a big jump without a tradeoff somewhere else, like weight.

 

Again, from talking with my Boosted friend (who participates on similar forums to this just for e-boards) rider weight has a dramatic effect on range for boards, just like it does for EUCs.  

The Boosted board has a 99 Wh battery (even their dual drive 2000W unit). What is the range of an EUC with 99 Wh battery? I honestly doubt it would get a couple of blocks without cutoff (smaller batteries exhibit voltage drop much faster than bigger batteries)

I rest my case :) e-skate are more energy efficient. 10 Km on a 99 Wh battery(at high speed) is amazingly efficient

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The Boosted board has a 99 Wh battery (even their dual drive 2000W unit). What is the range of an EUC with 99 Wh battery? I honestly doubt it would get a couple of blocks without cutoff (smaller batteries exhibit voltage drop much faster than bigger batteries)

I rest my case :) e-skate are more energy efficient. 10 Km on a 99 Wh battery(at high speed) is amazingly efficient

In this forum, members have reported ranges of 14km with 132Wh battery (70kg rider, Solowheel) and 26km with 260Wh battery (88kg rider, IPS). It's only a couple of blocks, but still surprisingly efficient, isn't it? About 10km / 100Wh is apparently where we end up in each case, e-skate and e-wheel, though I am pretty sure there is still room for improvements, probably for both. 

The records seem to suggest that generic wheels tend to achieve 20-40% smaller ranges only, maybe due to cheaper batteries or less sophisticated control software, or both. 

I agree, maybe you better rest your case :), still in it for the bet? 

Edited by Niko

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So, unless materials dramatically change, an increase in power can only be achieved by an increase in weight

I politely disagree B)  In general, it is true what you say: for current BLDC motors, we just need more weight to get more range and power, and we will not see much more improvement in weight barring some new material inventions.

However, we can certainly improve in other design aspects to reduce of weight. Not so much for energy efficiency because this is already super good (compared to say, a car) and rider weight already overwhelms any weight savings here. We want to save weight to increase portability -- that would make EUC's much more popular as a 'laptop-vehicle' :D

The most promising way to reduce weight to me seems to just get rid of a direct BLDC motor but use a smaller motor together with a gear, like the Solowheel Orbit for example: this can probably reduce weight to about 6kg (14lbs) -- a huge weight saving right there. Also, I have read somewhere that current direct BLDC wheels that are used could perhaps be designed differently with EUC's in mind and also become quite a bit lighter.  Lots of engineering challenges, but certainly all possible with todays technology. Looking forward to see some innovation coming -- come on manufacturers ! B)

solowheel-orbit-2014-06-17-4-1.jpg

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Daan, I completely agree, there is no reason to believe that, even with current standard technology, the currently predominant design is the end of the story.

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You are right: a complete change in design would achieve the same. After all, e-skates have 2000W motors that weigh less than a Kg. If the motor design stays the same (big rotors, lots and lots of poles to achieve very precise positioning), though, the only way to increase that motor type power is by increasing weight

In this forum, members have reported ranges of 14km with 132Wh battery (70kg rider, Solowheel) and 26km with 260Wh battery (88kg rider, IPS). It's only a couple of blocks, but still surprisingly efficient, isn't it? About 10km / 100Wh is apparently where we end up in each case, e-skate and e-wheel, though I am pretty sure there is still room for improvements, probably for both. 

The records seem to suggest that generic wheels tend to achieve 20-40% smaller ranges only, maybe due to cheaper batteries or less sophisticated control software, or both. 

I agree, maybe you better rest your case :), still in it for the bet? 

I haven't been here long enough to see those claims (but I have no reason to doubt what you say). That seems to contradict a lot of advice I have seen here, where bigger batteries seem to be suggested at every turn. I'll see if I can get some experimental data to show that continuously changing power to balance has an effect (Jason data on the KS going downhill and only marginally doing regenerative braking seems to support the argument for less efficiency, though). Until I have more data, I'll shut up, then :)

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I haven't been here long enough to see those claims (but I have no reason to doubt what you say). That seems to contradict a lot of advice I have seen here, where bigger batteries seem to be suggested at every turn.

AFAICS there is no contradiction: various members advocate invariably for larger batteries, because this increases the safety margin w.r.t. maximal torque and acceleration and thereby the management of any unexpected events (bumps, potholes) or possible cutouts (which should anyway never happen by design, never, ever, but what do we know). This advocacy is not related to efficiency, or efficiency of self-balancing, and often also not to range. The concern is safety at the power limits (though it seems that in principle a wheel can also be controlled safely with weak battery, it's much less fun though) and riding quality. Insofar it is related to self-balancing, as power limits exceeding demands are less dangerous with tandem-wheeled vehicles (though bumps and potholes remain to be a concern, depending on wheel size). Many people are also not at all concerned with the added extra 1-2 kg (I am though).

Another point you made remains also valid for a larger battery: with an EUC you never want to get stranded with empty battery in the middle of the road. With an e-skate that's not a big deal.

Edited by Niko

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and another one I haven't seen before

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