When will we see 3000 Watts?

[Mitch]

Hey gang

So I have just ticked over the first 500 Kilometres on my EUC journey and I frekin love it. I negotiate time with the wife to sneak out and ride whenever I possibly can. Like most I toyed with the first wheel conundrum for ages. Do I buy a learner wheel, or pad up a high performance wheel etc etc.. I ended up just buying an 1845 MSX 100V right off the bat and am SUPER glad I did. Best part is after 500km of learning I havent dropped it once. I used the Chooch Tech method of putting a strap through the handle and what can I say, frekin genius. I used it for my first `250km of riding just while I was new and nervous, but now it is gone and my mounting and dismounting is pretty solid. Anyway progress update over, I now find myself wondering...

I have been toying with the idea of buying a second wheel (KS-16X) so my brother in law can learn and come riding with me. But I am so properly impressed and in love with the MSX its hard to execute that purchase without wondering how far away the next big thing might be. So my question is (considering the 16X jumped a bit to 2200w), when will we see a 3000W motor on one of these things?? Or are we limited by the size of the hub and how many coils etc can physically fit? I'm not riding my MSX around at 70PKH by any means, I just think excess power limited by firmware is the best option for safety and performance. 

 

[Aneta]

1 hour ago, Mitch said:

Hey gang

So I have just ticked over the first 500 Kilometres on my EUC journey and I frekin love it. I negotiate time with the wife to sneak out and ride whenever I possibly can. Like most I toyed with the first wheel conundrum for ages. Do I buy a learner wheel, or pad up a high performance wheel etc etc.. I ended up just buying an 1845 MSX 100V right off the bat and am SUPER glad I did. Best part is after 500km of learning I havent dropped it once. I used the Chooch Tech method of putting a strap through the handle and what can I say, frekin genius. I used it for my first `250km of riding just while I was new and nervous, but now it is gone and my mounting and dismounting is pretty solid. Anyway progress update over, I now find myself wondering...

I have been toying with the idea of buying a second wheel (KS-16X) so my brother in law can learn and come riding with me. But I am so properly impressed and in love with the MSX its hard to execute that purchase without wondering how far away the next big thing might be. So my question is (considering the 16X jumped a bit to 2200w), when will we see a 3000W motor on one of these things?? Or are we limited by the size of the hub and how many coils etc can physically fit? I'm not riding my MSX around at 70PKH by any means, I just think excess power limited by firmware is the best option for safety and performance. 

 

If you raise the voltage by 50%, the 2000W motor becomes a 3000W motor, max unloaded speed also increases by 50%. As long as the controller has a phase current limit, there shouldn't be any increase in heat. The torque will be the same, but the max speed will be higher. We "just" need to increase battery voltage from 84V to 126V (20s to 30s). Controller should have components rated for something like 150V, not 100V as 84V controllers typically do.

If you want the same max speed, but more torque (so that 2000->3000 increase comes not from speed, but from torque), then the only option is to make the magnets and stator 50% (?) wider (and thus, the motor will be approx. 50% heavier). Which translates to about 45mm magnets. Such motors are long available from Quanshun and are typically used in electric scooters (the "real" scooters, not electrified kick scooters) or "hot rod" e-bikes.

Edited December 17, 2019 by Aneta

[Planemo]

I did have this thought some time back which I posted on the forum as part of a power discussion but I am not sure we got to the bottom of it.

There is only so much power we can use isn't there? I mean, how much power does it take to prevent an average human falling at 1g? The wheel will only need as much power as required to stop this. We can't lean any more (taking aside assists like power pads etc). So lets assume a wheel is constantly applying enough force to prevent a human leaning at an extreme angle (oooh shall we say 45 degrees?) from falling off the front. How much power is needed? I am sure it can be calculated but its all a bit much for me

 

[mrelwood]

One important thing about the motor power ratings is to learn what they actually mean. The ratings we are shown for each wheel is the motor’s sustained power rating. So it’s the amount of power the motor should be able to handle continuously without overheating or getting toasted, for example at @Marty Backe’s overheat hill. Short term power peaks, the actual max power handling, can be even three times more when the wheel for example tries to keep the balance when riding into a pothole.

The sustained power rating of the motor also doesn’t tell us how much power the controller is able to produce. Which might be the reason why the 2200W 16X has been a bit too easy to overlean north of 40km/h, while the 1500W MCM5 or other 2KW wheels show no signs of getting weaker at those speeds despite the smaller diameter tire having to spin faster. (That’s not to say that the 16X wouldn’t be able to provide more power at smaller speeds though.)

So what would a 3000W MSX feel like? Likely the same as the 2000W version, since it already has enough power to keep the pedals rock solid. ”Wouldn’t 3KW accelerate faster?” It can be accelerated faster, but the amount of acceleration is determined by the rider’s lean. Just like a 3000W stereo system still has a volume control that needs to be cranked to take use of the power. And a powerful sports car will still be a slouch unless the driver commands the car to accelerate faster. With the EUC the rider’s lean is the volume control / gas pedal.

https://forum.electricunicycle.org/topic/14032-what-determines-wheel-zippiness/

I have only been able to overpower the 84V MSX under very extreme conditions, like trying to accelerate hard from standstill while quickly pushing my 100kg weight up for a 2m long incline with zero runway. A 3KW MSX just might have made it, but perhaps the 100V MSX would’ve as well.

[Planemo]

So I think you are confirming what I thought

Theres only so much power we can actually use, as a human can only lean X amount , and only weighs X amount.

[Aneta]

2 hours ago, Planemo said:

I did have this thought some time back which I posted on the forum as part of a power discussion but I am not sure we got to the bottom of it.

There is only so much power we can use isn't there? I mean, how much power does it take to prevent an average human falling at 1g? The wheel will only need as much power as required to stop this. We can't lean any more (taking aside assists like power pads etc). So lets assume a wheel is constantly applying enough force to prevent a human leaning at an extreme angle (oooh shall we say 45 degrees?) from falling off the front. How much power is needed? I am sure it can be calculated but its all a bit much for me

 

Maximum thrust possible is limited by total weight times maximum coefficient of friction, thrust any higher than that will result in drifting and the rider will fall in a spectacular cloud of smoke. Assuming max coeff. of friction 0.75 for tire on asphalt and total weight 135kg (very powerful wheel will be also much heavier than what we have now), we estimate max thrust possible as F=1000N. If you are moving at V=20m/s (72km/h), the mechanical power required will be P = F*V = 20kW. Taking ~80% efficiency of BLDC motors at optimum RPM, electric power then can be about 25kW.

Of course, there won't be 100kg of aerodynamic drag at 72kph (only maybe 20kg), so the rider will also need to accelerate at about (100-20)/135 = 0.6g = 21kph/s rate at the moment.

So, rephrasing Bill Gates, "25kW is more power than anyone will ever need on a segwheel".

Edited December 17, 2019 by Aneta

[Planemo]

So you're saying it needs 25Kw to stop a human falling forwards under gravity? Sounds like an awful lot...

We are not talking about how much power is needed to accelerate 135Kg without breaking traction, we only want enough to keep the rider from falling flat on their face under the maximum lean possible for a human being.

As an aside, I suspect the max a human can lean forwards (with both feet still flat on the pedals to maintain full traction) is maybe 45 degrees, if that helps with the calcs.

[EOneFun]

Hey,

I'm Just getting into EUC so don't know much about the motors used, but thought this might be of interest. It illustrates (no advert) an e-bike manufacturer that gives you a choice for the winding (T3 - T6) in the motor when building individual units. I guess this is not an option that EUC manufacturers are going to offer anytime soon, but the info might be of interest to opensource EUC builders.

Basically, higher T (turn) value gives you greater acceleration and hill climbing ability + heat. Lower T value provides lower acceleration but higher top end speed. Same controller is used in both examples in the vid. 

I'm sure the EUC manufacturers use optimised motor/battery/controller combos for each wheel size/design, which is why we see individual character in all models. 

 

 

[MexicanBatman]

DarknessBot tells me my MSX has over 8000w and over 100a peak at times LOL

 

anyone know the actual peak output of an 84v MSX?

[Seba]

28 minutes ago, Trevor Phillips said:

DarknessBot tells me my MSX has over 8000w and over 100a peak at times LOL

Gotway wheels doesn't report real power. This value should be divided by three to get very, very rough approximate.

[Chriull]

1 hour ago, Trevor Phillips said:

DarknessBot tells me my MSX has over 8000w and over 100a peak at times LOL

 

anyone know the actual peak output of an 84v MSX?

 

33 minutes ago, Seba said:

Gotway wheels doesn't report real power. This value should be divided by three to get very, very rough approximate.

Especially it's speed dependent - the lower the speed, the higher the deviation - the higher the speed the more valid the power numbers get.

I tried (once) a power/acceleration diagram within the current (torque) over speed limits diagram for the 84V MSX (from an overlean log i got):

The "hyperpole" lines show about motor output power (I_motor * U emf). They are every 500W. Multiples of 1000W are a bit thicker - the thickest line is 5000W.

As one sees at low speed with 100A (motor current) shown own can have just 500W motor output at around ~5 km/h. But depending on battery voltage (lets say 75V) the wheel would report 75*100=7500W!

To really reach this 7500W motor output with 100A one would need to the right (higher speeds) until one touches the 7500W hyperpole - but that's way beyond the wheels limit...

The grey lines (a little bit ascending from left to right) show lines for constant acceleration with friction and wind resistance. Starting from 0 m/s² increasing by 1 m/s¹. 0 and 5 m/s² are the thicker lines.

Accelerations above some 0.7g (~7m/s²) are not reachable (not enough friction between asphalt and tire) and this graph is some not validated first try / approximation, but something about 6-7000W could be the absolute peak shortly reachable. At around 45 km/h with full batteries with high accelerations/burdens.. But as one sees the 5000W line is continously above the one dotted line - that's the motor limit line for low batteries (20*3.3V=66V)

Edited December 17, 2019 by Chriull

[Aneta]

7 hours ago, EOneFun said:

Hey,

I'm Just getting into EUC so don't know much about the motors used, but thought this might be of interest. It illustrates (no advert) an e-bike manufacturer that gives you a choice for the winding (T3 - T6) in the motor when building individual units. I guess this is not an option that EUC manufacturers are going to offer anytime soon, but the info might be of interest to opensource EUC builders.

Basically, higher T (turn) value gives you greater acceleration and hill climbing ability + heat. Lower T value provides lower acceleration but higher top end speed. Same controller is used in both examples in the vid. 

I'm sure the EUC manufacturers use optimised motor/battery/controller combos for each wheel size/design, which is why we see individual character in all models. 

 

 

Turn number proportionally increases torque, but proportionally decreases speed, too. So if you were to rewind a 40kph wheel to double the turns to double the torque, you'll get a 20kph wheel (a vegetable).

[meepmeepmayer]

7 hours ago, EOneFun said:

Basically, higher T (turn) value gives you greater acceleration and hill climbing ability + heat. Lower T value provides lower acceleration but higher top end speed. Same controller is used in both examples in the vid. 

Completely correct, you can have more or less windings to tune the motor behavior. I don't know how that affects heat dissipation and the W rating of the motor.

The Gotway MCM4 actually came in different versions - high speed and high torque - with differently wound motors.

Problem with EUCs, more windings reduces the top speed, which is why we don't see this happening. Easier to sell 50+ kph wheels than explain a 40kph limit but increased acceleration/oomph. Also, you can brute-force better acceleration by allowing higher battery usage (wasting battery), but you cannot brute-force a higher top speed, because that limit depends on the motor build. Manufacturers also try to rationalize and use common parts and phase out (or never build) less popular wheel models. Different variations of a model are counter to that.

This is why we don't see wheel variations like this and manufacturers build on the side of speed. Maybe in the future, with better competition, manufacturers will have to branch out and offer more specialized wheels.

7 hours ago, EOneFun said:

I'm sure the EUC manufacturers use optimised motor/battery/controller combos for each wheel size/design, which is why we see individual character in all models. 

They try to re-use as many parts as possible. 16 and 18 inchers use the same motor, with the 18 inch realized by having a spacer between motor and tire rim (you can see by looking at the 18 inchers). Fundamentally, there's nothing wrong with that. Both Gotway and King Song do that. Gotway even uses their standard motor for the 22 inch Monster. Boards are the same anyways. I believe individual character is more due to the model-specific firmware and, most of all, due to different wheel shapes and geometry.

I'm just mentioning this because manufacturers are much much less professional than it may appear or one may expect from such a product. Even if everything works in the end - always prepare to be disappointed! Never trust they will do the obvious, right thing - because so often they do not. Welcome to the forum

[Aneta]

9 hours ago, Planemo said:

So you're saying it needs 25Kw to stop a human falling forwards under gravity? Sounds like an awful lot...

We are not talking about how much power is needed to accelerate 135Kg without breaking traction, we only want enough to keep the rider from falling flat on their face under the maximum lean possible for a human being.

As an aside, I suspect the max a human can lean forwards (with both feet still flat on the pedals to maintain full traction) is maybe 45 degrees, if that helps with the calcs.

Mechanical power is force times speed, so the answer greatly depends on speed at which you're at 45 degrees. If you're at standstill and leaning, mechanical power is zero. Electric power is not, of course. Typical battery power at hard acceleration of ~0.3g (that's 0-40kph in just under 4 seconds) is equivalent to going up tan(asin(0.3)) = 31% slope, so something like 3-4kW (depends on weight), so for full 1g it would be about 10kW.

(but as discussed above, catching 45 degree lean is only possible with coeff. of friction greater than 1)

[meepmeepmayer]

16 hours ago, Mitch said:

I just think excess power limited by firmware is the best option for safety and performance. 

That's how it is since we went beyond 500W motors back in the stone age of EUCs. It's always the battery/firmware that limits what the wheel can do. Current motors can do pretty much everything thrown at them.

Motor power ratings are surprisingly meaningless. In the end, only real life experience and reports can tell how a certain wheel behaves.

-

As far as to your question whether we will see a tech jump soon:

I believe KS will be happy with their current 16X/18XL lineup for some time. The 16X motor is brand new and they just updated the 18L/18XL with it. What else would they do new?

Gotway's next wheel is a lighter city-commuter Tesla-successor type of wheel. Unless they use a new and more powerful motor for it (not exactly needed for such a wheel) which would then move to all their other 16+ inch wheels, that means there also is no immediate tech jump expected from Gotway.

Inmotion will come out with an 18 incher some day (in 2020 I hope), but this might be far off and I don't expect them to take the performance crown.

This is all speculation, I don't know the manufacturers' plans. Maybe Gotway will surprise-show a crazy msuper V4 early next year. Probably not. I expect 2020 is not the year of a big performance jump. No guarantees though

Edited December 17, 2019 by meepmeepmayer

[Aneta]

36 minutes ago, meepmeepmayer said:

Motor power ratings are surprisingly meaningless.

True dat!

https://www.ebikes.ca/learn/power-ratings.html

[meepmeepmayer]

Good link!

[xorbe]

16 hours ago, Aneta said:

If you raise the voltage by 50%, the 2000W motor becomes a 3000W motor.

If you raise V by 50%, then A also increases by 50% with the same resistive load, and 1.5*1.5 is 225%, so 2000W becomes 4500W.  You want to raise voltage by 22.47% probably... and none of that turns a 2000W motor into anything but a burned out motor probably, unless it's overbuilt.

Edited December 17, 2019 by xorbe

[meepmeepmayer]

35 minutes ago, xorbe said:

If you raise V by 50%, then A also increases by 50% with the same resistive load, and 1.5*1.5 is 225%, so 2000W becomes 4500W.  You want to raise voltage by 22.47% probably... and none of that turns a 2000W motor into anything but a burned out motor probably, unless it's overbuilt.

It looks like heat is a function of current (not power), so the nominal W rating of a motor is valid only for a given fixed voltage. So I'm not sure you can compare different voltages like this.

[Planemo]

2 hours ago, Aneta said:

Mechanical power is force times speed, so the answer greatly depends on speed at which you're at 45 degrees. If you're at standstill and leaning, mechanical power is zero. Electric power is not, of course. Typical battery power at hard acceleration of ~0.3g (that's 0-40kph in just under 4 seconds) is equivalent to going up tan(asin(0.3)) = 31% slope, so something like 3-4kW (depends on weight), so for full 1g it would be about 10kW.

(but as discussed above, catching 45 degree lean is only possible with coeff. of friction greater than 1)

So we are getting there. 10Kw is a lot less than 25Kw. 10Kw still sounds like a fair bit. So lets try dragging it down a bit further. I appreciate that power requirement goes up exponentially with speed so lets cap it at your 40kmh, at which point our imaginary brave rider would really need to start going vertical.

So at just after standstill he hits a 45 deg lean. You mention a 1g force but we need to take on board he's not horizontal, he's at 45 deg. Maybe we can throw in an all up weight of say 125kg to keep figures a bit easier. I like your comparison to gradient, so maybe we just work on a vertical rider on a 45 deg gradient.

(Lets put aside that a rider would struggle to apply enough lean to ride a wheel up a 45 deg gradient but I suspect the math still stands).

With that in mind, we just need to know how much electrical power it would take to maintain a 185kg load up a 45 deg hill at 40kmh. Does that sound about right?

And to make it easier shall we discount your (albeit very valid) point re traction for the moment as I have yet to see anyone wheelspin an euc on hot smooth ashphalt.

I am thinking around 5Kw but thats just a stab in the dark...

[Chriull]

23 minutes ago, Planemo said:

So at just after standstill he hits a 45 deg lean. You mention a 1g force but we need to take on board he's not horizontal, he's at 45 deg. 

45 degrees lean need 1g acceleration. An horizontal lean would need infinite acceleration....

[meepmeepmayer]

28 minutes ago, Chriull said:

45 degrees lean need 1g acceleration. An horizontal lean would need infinite acceleration....

Yep.

A more realistic limit would be: When would a given tire simply slip? Because there's no point in building wheels stronger than that.

Edited December 17, 2019 by meepmeepmayer

[Chriull]

9 hours ago, Planemo said:

So at just after standstill he hits a 45 deg lean. You mention a 1g force but we need to take on board he's not horizontal, he's at 45 deg. Maybe we can throw in an all up weight of say 125kg to keep figures a bit easier. I like your comparison to gradient, so maybe we just work on a vertical rider on a 45 deg gradient.

The 45° lean ==1g acceleration is (a bit) easier to compute. The needed mechanical motor output power is 125kg * 9.81 * 40 km/h / 3.6 ~ 13.6 kW.

In a 45° incline one should need an acceleration of g/1.4 ~ 7m/s^2, so about 10 kW.

9 hours ago, Planemo said:

how much electrical power

Depending on the coil resistance their could be some additional 1-3kW needed.

Edit: Should be much more... If 40 km/h is the speed with maximum power, no load speed would be 80 km/h. With 100V battery voltage at 40 km/h the motor would have 50 V back emf. So for 10 kW a motor current of 200A would be needed. With some coil resistance of 0.1-0.3 Ohm this would lead to additional 4-12kW needed from the battery...

For these powers higher voltages should be used...

8 hours ago, meepmeepmayer said:

A more realistic limit would be: When would a given tire simply slip? Because there's no point in building wheels stronger than that.

Havent found anything specific for bicycle tires. In most tables (car) tires on dry asphalt start from about 0.7. So 0.7 g acceleration could be about an "average maximum". Allowing something like a 33° lean...

Needing 13.6*0.7=9.5kW...

.... Still needing higher voltages or (and) much thicker wires...

Ps.: Besides the motor power the wheel and pedals would have to have the right geometry, too - a wheel build like the KS16S only allows about 4.5-5m/s^2 ~ 0.5g acceleration.

So no matter to how much motor power one would tune a KS16S a 33° lean would never be possible (without falling on the face...)

Edited December 18, 2019 by Chriull

[Aneta]

1 hour ago, Chriull said:

The 45° lean ==1g acceleration is (a bit) easier to compute. The needed mechanical motor output power is 125kg * 9.81 * 40 km/h / 3.6 ~ 13.6 kW.

In a 45° incline one should need an acceleration of g/1.4 ~ 7m/s^2, so about 10 kW.

Depending on the coil resistance their could be some additional 1-3kW needed.

For these powers higher voltages should be used...

Havent found anything specific for bicycle tires. In most tables (car) tires on dry asphalt start from about 0.7. So 0.7 g acceleration could be about an "average maximum". Allowing something like a 33° lean...

Needing 13.6*0.7=9.5kW...

.... Still needing higher voltages or (and) much thicker wires...

Ps.: Besides the motor power the wheel and pedals would have to have the right geometry, too - a wheel build like the KS16S only allows about 4.5-5m/s^2 ~ 0.5g acceleration.

So no matter to how much motor power one would tune a KS16S a 33° lean would never be possible (without falling on the face...)

To add to @Chriull's calculations: for decent efficiency in 80-90% range, the motor's RPM must be very close to no-load RPM, which means that the no-load speed should be something like 50kph max. If we assume linear falloff of the torque with speed, then at 40kph the thrust will be (50-40)/50 = 20% of the thrust at zero speed. So, if this motor is capable of producing 125*sin(45) = 88kg of thrust at 40kph, at standstill it will produce 88/0.2 = 440kg of thrust! Such monster motor will require magnets probably ~500mm wide and windings of 0AWG (?) copper wire and will weigh several hundred kilos. (So, we have to add it to total weight, recalculate power, recalculate weight, ...  and reiterate calculations until they asymptote). What we'll get is something like this from the future:

 

... or from the past:

[xorbe]

6 hours ago, Chriull said:

horizontal lean would need infinite acceleration

Technically, the Earth is curved, and the vector of gravity's acceleration is always changing with your movement ... you just need to go fast enough to achieve "orbit"