Understanding the real world considerations and implications of Speed VS Torque models

[Rawnei]

12 minutes ago, on one said:

This is all very informative. It's refreshing to hear that the consensus seems to be gimmick, which is another thing I suspected and needed confirmation on. I suspected that wattage seemed gimmicky like ghz is gimmicky in computer lingo, when bus throughput is more informative.

Now I am curious about Voltage as relates to electric unicycles, is that gimmicky too? Maybe this question might be apropos as a new thread? Though it would be nice to get a consensus on that number here too.

Higher voltage opens up new potential for different things but also comes with new challenges and potential problems, voltage in itself doesn't mean much either it's what the manufacturer do with it, what their design goals are by raising the voltage and how well they design all the parts.

It's the whole that matters don't get lost on a number by itself.

[Rider1]

11 minutes ago, on one said:

Voltage

Well, higher voltage does enable higher motor speeds, but there is a "limit" where it's no longer sensible to keep upping the voltage, especially as you have to have all components working reliably at that higher voltage (properly isolated cables, capable MOSFETs, ...)

So I don't think any higher than the mid 100s we currently have makes a lot of sense, but I might be proven wrong soon

Another factor one needs to consider is the layout of the battery packs. As you can see with the ET Max, those high-voltage packs are quite tall, so they would either need to be longer (front and rear, which might cause them getting hung up on things more easily), thicker (will be uncomfortable) or you just reduce the number of packs in parallel in favor of more cells in series, but I don't think that makes a whole lot of sense either, since the speed the motors are capable of are already high enough, it's rather the overall power output of the pack or the board that's the limiting factor at 100kph+, which won't change with how you connect the batteries.

[on one]

Continuing the comparison of z10 to v14 that z10 has maximum charging voltage @ 59.5 volts compared to v14 @ 134 volts. Yet the Inmotion v14 isn't more than twice as fast at maximum speed as the Ninebot z10.

I also noticed that Ninebot Z10 publishes 1800 watts as motor output while Inmotion v14 doesn't declare the 4000-9000 watts as power output.

All the while, Inmotion v14 does report torque to be 85N Ninebot doesn't report torque as an N value.

This is all very confusing as I am forced to compare apples to oranges. So I am thankful for @meepmeepmayer comment to just ride it and decide, though test riding isn't really an option for me in my small rural community.

[xiiijojjo]

I'd like to know if we'll ever see standardized figures for "power" ... I remember someone making standardized testing of the pulling ability of different EUC models, with some contraption strapped to the back of his car.. But I doubt the manufacturers would care to do that.

[Whalesmash]

 

 

[on one]

oh , it's published as 200N.M, What does N.M even mean?

 

Edited July 24 by RagingGrandpa
(fix url)

[Rawnei]

2 minutes ago, on one said:

oh , it's published as 200N.M, What does N.M even mean?

Newton Meter.

Would be more interesting to know their test methodology, again just a number in a vacuum.

Community already have a comparative test by performing the pull force test, it's a real and tangible way to compare torque from a standstill.

[meepmeepmayer]

3 hours ago, on one said:

Now I am curious about Voltage as relates to electric unicycles, is that gimmicky too?

No! The general consensus is, higher voltage is great, with pretty much just one real downside (less battery size flexibility, and doesn't work for small batteries). Historically, it's been a real improvement, totally different to the pointless motor wattage numbers.

2 hours ago, on one said:

Continuing the comparison of z10 to v14 that z10 has maximum charging voltage @ 59.5 volts compared to v14 @ 134 volts. Yet the Inmotion v14 isn't more than twice as fast at maximum speed as the Ninebot z10.

Voltage directly scales with the max speed of any given motor. If you ran your Z10 at 134V instead of 58.8V, its motor would run 134.4/58.8 = 32/14 = 2.3 times faster. The V14's motor is built for more torque (done typically with more/stronger magnets and windings) instead of the higher max speed you could get from its higher voltage. That's why it isn't 2.3 times faster. It would rather have more oomph at low speed/better acceleration. That's a design choice.

High speed and good acceleration/zippyness is always a tradeoff with electric motors. Choose one to lose the other, so you have to find a balance. There used to be HT (high torque) and HS (high speed) motors and you could choose which variant you wanted on your wheel (goes back up till the V12). Higher voltages allow for wheels that are fast and have good acceleration. No more choice necessary. Higher voltages are great! They can solve a real problem.

The one downside is: a high voltage performance wheel, meaning good acceleration and speed, must have a big battery.

Voltages are achieved by having a certain number of battery cells in groups. For higher voltages, that number increases (e.g. 14 for the Z10 and 32 for the V14). So your overall battery size must be a multiple of a big number, giving less flexibility with different battery sizes. Additionally, your peak acceleration/torque/zippyness is roughly determined by how many of these groups you have, and you need a certain number of them as a minimum if you want trustworthy performance. So you get a certain minimum battery size if you want a performance wheel.

For 134V, with the typical cells used, your battery will be a multiple of 600Wh (that's what 32 cells contain), and you typically need 4 of those groups, giving 2400Wh. Just like the V14. With 168V, you end up with 3000Wh. Bigger battery, bigger weight, bigger wheel, costs more money, etc. You couldn't have the same performance with any smaller battery. That's why all the shiny new top wheels are big and heavy and expensive. Not just for bragging rights, it has to be like this.

That's why small wheels like the mten or Falcon or even mid-range wheels like the V11 and S16 don't go for such high voltages. They limit their top speed to be cheaper, lighter, smaller, more reasonable.

A way out of this is by using higher discharge battery cells. They allow for fast and zippy and light/small wheels. We're not there yet.

-

The one objective number to look at is battery size (in Wh). That's just an objective measure of how much battery you have and how much range you get.

Everything else is very hard to use for comparisons. And luckily, everything else is good enough nowadays (including voltage), so in my opinion one can happily ignore any reasonable sounding specs and just listen to what people say about which wheel rides how in real life.

Edited July 3 by meepmeepmayer

[on one]

Thank you @meepmeepmayer. That was a nice reasonable and credible explanation. I cross referenced the information you provided with the voltage of a Tesla 3 (the automobile) just to get a ballpark feel for the concept and it checks out at 350 volts for the Tesla 3 which has a top speed of 145 mph.

[InfiniteWheelie]

Non linear wind resistance.

[Mono]

On 7/3/2024 at 5:25 PM, on one said:

This is all very informative. It's refreshing to hear that the consensus seems to be gimmick, which is another thing I suspected and needed confirmation on. I suspected that wattage seemed gimmicky like ghz is gimmicky in computer lingo, when bus throughput is more informative.

Wattage is not a gimmick but a central property of a motor or a motor+battery+controller system. However, wattage is

1. difficult to measure or verify, in particular, but not only, because it can depend on heat transport / overheating resistance. For this reason, sustained power is very different from "peak power" and the length of the peak is decisive too.
2. only useful together with the speed, ideally we know the wattage (power) plotted vs the speed like this or this
3. hence difficult to comprehensively communicate well.

Still, if you have a reliable maximal sustained wattage number of the motor+battery system and the spinout speed, you already have a lot of useful information and the most important single numbers to estimate the maximal speed.

EDIT: pull force vs speed is a directly related but probably more useful (easier to interpret) graph than wattage. The pull force also doesn't need to exceed the force needed to accelerate wheel and rider with somewhat above 1g (against mass inertia and wind resistance) or the force the rider can input (related to their bodyweight and the current acceleration) to create motor torque. To have more power is in essence useless.

On 7/3/2024 at 5:25 PM, on one said:

Now I am curious about Voltage as relates to electric unicycles, is that gimmicky too? Maybe this question might be apropos as a new thread? Though it would be nice to get a consensus on that number here too.

Beyond of picking the right charger (for which voltage is extraordinarily important), voltage in itself is a useless specification (for implying performance). For example and in particular, voltage is neither necessary nor sufficient (gives no pathway) to estimate the maximal speed. Hence, yes, voltage is a gimmick.

Edited July 23 by Mono

[on one]

It's going to take me some time to process the information you provided, @Mono

For my next wheel, I am particularly interested in the capability of an EUC to accelerate between 8mph to 35mph. The faster the better. So, I'd rather consider a wheel that can go 8mph to 35mph in 3 seconds time than a wheel that takes 9 seconds to make the same acceleration.  Which wheels do well according to that measurement?

[Mono]

38 minutes ago, on one said:

Which wheels do well according to that measurement?

[I corrected a link above] Short answer: I have no idea, it's not likely one of the wheels I would be interested in to own. Long answer: for a start, it probably depends on your weight and it also depends on your (preferred) riding style (e.g., are you willing and able to ride like this?). Then, I doubt that anyone in this world has enough information (about all wheels) to answer this question decisively.

When it comes to motorbikes or cars, how do we answer this question? We measure their acceleration time, plein and simple, because there is no way to decide such a number by spec sheets. I suspect it's only marginally different with EUCs.

Out of curiosity, why don't you care to quickly accelerate from 0 to 8mph?

Edited July 23 by Mono

[on one]

Ideally, I would be able to go 0 to 55 in 3 seconds like a Tesla (the automobile), but it seems premature to make that request.

[Rawnei]

5 minutes ago, on one said:

Ideally, I would be able to go 0 to 55 in 3 seconds like a Tesla (the automobile), but it seems premature to make that request.

That sounds quite easy on an EUC actually.

[Rawnei]

@on one here's an example of Kuji doing 0-50kmh in 2.91 seconds on a OG Sherman 4 years ago, I'm sure you can find better examples on newer wheels if you search around:

https://www.facebook.com/watch/?v=870152796813562

 

[EUCzero]

I think they refer to 55 as miles per hour as some Teslas can do 0-60 miles per hour in 2.3 sec. (And "No one" is from the the US  )

Edited July 23 by EUCzero

[Rawnei]

12 minutes ago, EUCzero said:

I think they refer to 55 as miles per hour as some Teslas can do 0-60 miles per hour in 2.3 sec. (And "No one" is from the the US  )

Ah quite possibly, helps being specific.

[on one]

1 hour ago, Rawnei said:

Kuji doing 0-50kmh in 2.91 seconds on a OG Sherman

Wow, that's amazing.

[on one]

Veteran Sherman Specifications

Motor Power: 2500 W

Battery Capacity: 3200 Wh 100.8V

Climbing Angle: ~ 30 degrees

Weight: 35 kg

Max Load Weight: 120kg

Charging Time: 8 hrs (4 hours with dual charger)

Charger Output: DC 100V* 5Amp 

Tyre: Kenda K262 20 inch knobby tire

So, assuming that Kuji was doing his best to make the fastest time, then that means a 2500 watt 100v is extremely powerful! Would it be cogent to speculate that Inmotion Adventure's 4000 watt 134v should be at least 1/3 faster? So Kuji should be able to do the 0 to 50km in like 2.10 seconds?

[Rawnei]

6 hours ago, on one said:

Veteran Sherman Specifications

Motor Power: 2500 W

Battery Capacity: 3200 Wh 100.8V

Climbing Angle: ~ 30 degrees

Weight: 35 kg

Max Load Weight: 120kg

Charging Time: 8 hrs (4 hours with dual charger)

Charger Output: DC 100V* 5Amp 

Tyre: Kenda K262 20 inch knobby tire

So, assuming that Kuji was doing his best to make the fastest time, then that means a 2500 watt 100v is extremely powerful! Would it be cogent to speculate that Inmotion Adventure's 4000 watt 134v should be at least 1/3 faster? So Kuji should be able to do the 0 to 50km in like 2.10 seconds?

It's about torque and lean, V14 has a lot of torque so if you can provide enough lean then it will take off quite fast, Inmotion also have acceleration assist features in the firmware (help you lean more) so quite possibly you can get some good times on it.

[rcgldr]

Watt is a unit of power = volts x amps = force x speed.

The issue with speed is friction and rolling resistance increase with speed, and aerodynamic drag increases with speed^2.  If the only resistance was aerodynamic drag, it would take 8 times as much power to go twice as fast.

My 18XL has twice the power of my V8F, and top speed of the 18XL is about 50% faster, from 19 mph GPS (V8F to 28 mph GPS (18XL).

Edited July 24 by rcgldr

[EUCzero]

12 hours ago, on one said:

Veteran Sherman Specifications

Motor Power: 2500 W

Battery Capacity: 3200 Wh 100.8V

Climbing Angle: ~ 30 degrees

Weight: 35 kg

Max Load Weight: 120kg

Charging Time: 8 hrs (4 hours with dual charger)

Charger Output: DC 100V* 5Amp 

Tyre: Kenda K262 20 inch knobby tire

So, assuming that Kuji was doing his best to make the fastest time, then that means a 2500 watt 100v is extremely powerful! Would it be cogent to speculate that Inmotion Adventure's 4000 watt 134v should be at least 1/3 faster? So Kuji should be able to do the 0 to 50km in like 2.10 seconds?

You are doing it again. Saying WATT = a certain speed. 
Everyboby more or less told you not to care about the announced wattage on the different EUC. And now you are doing it again.

Speed and tourqe (and output power) is so much more on an EUC than motor rated power. It is a full system. Batteries can cripple output power, controller board can cripple output power, firmware can cripple output power, BMS can cripple output power.
Soooo PLEASE stop putting so much focus on the motor wattage. Even a 3000Watt motor can be faster than a 4000Watt motor if wounded different . WATT do not equal  speed/RPM in any way.
 

Edited July 24 by EUCzero

[on one]

@EUCzero

7 minutes ago, EUCzero said:

Everyboby more or less told you not to care about the announced wattage on the different EUC.

Nope, I have received a lot of different viewpoints, all of which I am thankful and respect.

[on one]

@EUCzero is it sensible to formulate a ratio between volts/watts to derive a number that would correlate to a given wheel's 0-50km time?