Going from a 14in to 18in wheel, suggestions?

[NylahTay]

So I've only ridden a 14in EUC, as I've been exclusively riding the Ninebot S1 for the past 2 years. I'll be getting a KS18XL in the mail next week. What should I expect with the upgrade? Any tips with making such a change? Should I expect it to be more difficult to learn to ride? 

[Dzlchef]

Take your time learning the new wheel, watch your speed.  It'll be a lot heavier so keep that in mind when turning/carving as it won't be nearly as nimble and top heavy. 

You'll have the biggest grin on your face after the first ride!

[NylahTay]

Thanks @Dzlchef, I didn't think about curves. I'm so used to easily making small turns on this. Does the larger wheel make it easier to balance, or more difficult? 

[Dzlchef]

Balance won't be an issue, just get used to the wheel.  I stepped on an 18XL and rode it 30+ miles with only being stupid once, hence my counsel on weight. Very easy wheel to ride imo. 

[houseofjob]

Bigger diameter wheel means the same turns you did from the knees down on a typical 14" wheel, will now need to come more from your hips & torso due to the higher center of gravity of you on wheel with the bigger diameter wheel.

The wider tire of the 18 x 2.5 KS-18XL tire when compared to the thinner S1's 14 x 2.125" tire, means balancing should be easier, as a thicker width of the tire means it's slower to fall over, as it has more distance it needs to travel to fall over.

Edited April 22, 2019 by houseofjob

[Jerome]

I am probably twice your age and went from a Ninebot E+ (16 in) to a KS18L seamlessly. What you will notice most is how much heavier it is and although you can handle it well, you're not going to be able to flick it around with out some hips/upper torso effort like you can with the S1. I found it easier to balance as it is more planted with the wider tire and heavier weight. It rides so much smoother than smaller wheels because it soaks up bumps and road irregularities much better. You will feel you can ride it anywhere to anywhere  and .. you probably can with that large battery and more than sufficient power and speed. Enjoy!

[UniVehje]

I started with the Ninebot S2 1,5 years ago and also have the 18XL arriving in a few days. Meanwhile I’ve been riding the V10F, which is pretty similar. 

Everything said above is true. Also remember that the tire size is basically the same as gears in normal bikes. The S1 is on permanent first gear and the 18XL will be on permanent 3rd gear, so to speak. 

You will feel like it doesn’t react at first. It will accelerate slower from standstill. And be very carefull with first breakings, it will be slower.

Generally speaking you will have to adjust your riding style to be more physical. Use your whole body to lean and turn. You will enjoy it more at higher speeds. 

Edited April 22, 2019 by UniVehje

[LanghamP]

No one ever on the existence of this forum has had problems going from a 14 incher to an 18 incher, because an 18 incher isn't a wheel people crash on unless there's a mechanical failure.

However...

100% of people who own both a 14 and an 18 incher crash on their 14 incher after being on their 18 incher.

Correlation is not causality, but in this case it is. The 18 incher makes you crash your 14 incher.

Everyone raise your hand (the one with roadrash), if you've crashed your 14 incher within minutes of stepping off your 18 incher.

It's gonna happen...

[eddiemoy]

20 minutes ago, LanghamP said:

No one ever on the existence of this forum has had problems going from a 14 incher to an 18 incher, because an 18 incher isn't a wheel people crash on unless there's a mechanical failure.

However...

100% of people who own both a 14 and an 18 incher crash on their 14 incher after being on their 18 incher.

Correlation is not causality, but in this case it is. The 18 incher makes you crash your 14 incher.

Everyone raise your hand (the one with roadrash), if you've crashed your 14 incher within minutes of stepping off your 18 incher.

It's gonna happen...

actually, folks who come from 14" tend to overlean and face plant.  They are used to the instant reaction from a 14" and take that for granted.  At least one in the NYC group have faceplanted because of that.  Overleaning going form 14 to 18.

[eddiemoy]

3 hours ago, NylahTay said:

So I've only ridden a 14in EUC, as I've been exclusively riding the Ninebot S1 for the past 2 years. I'll be getting a KS18XL in the mail next week. What should I expect with the upgrade? Any tips with making such a change? Should I expect it to be more difficult to learn to ride? 

will feel a hesitation from stop.  at least one person in our group have faceplanted coming from 14" because he overleaned.  The wheel didn't catch up to him and he faceplanted.  I've had a couple of near over leans.  scary.  you will need to get used to the less nimble feeling 18".  everything requires more effort.  although going faster will feel a lot more stable.  

[Planemo]

Although I know this issue occurs, I dont understand why. I am clearly missing something.

A bigger wheel can have a bigger motor and bigger batteries. Surely that would level the playing field between diameters? Why, with all the tech we have, cant the manufacturers build an 18" wheel with the same torque as a 14"? We are up to silly watt motors and crazy wH/voltage batteries for chrissakes!

[eddiemoy]

2 minutes ago, Planemo said:

Although I know this issue occurs, I dont understand why. I am clearly missing something.

A bigger wheel can have a bigger motor and bigger batteries. Surely that would level the playing field between diameters? Why, with all the tech we have, cant the manufacturers build an 18" wheel with the same torque as a 14"? We are up to silly watt motors and crazy wH/voltage batteries for chrissakes!

they need a new motor without spokes and push the magnets out to the edge.  i think if they design a new motor like this we would have the ultimate wheel.  though they would also need to use some better materials so it would be 1/2 as heavy.

[LanghamP]

5 minutes ago, Planemo said:

Although I know this issue occurs, I dont understand why. I am clearly missing something.

A bigger wheel can have a bigger motor and bigger batteries. Surely that would level the playing field between diameters? Why, with all the tech we have, cant the manufacturers build an 18" wheel with the same torque as a 14"? We are up to silly watt motors and crazy wH/voltage batteries for chrissakes!

I think just moving the magnets out towards the rim of the wheel would make the torque equal to a 14 incher, however there might be a trade-off in torque at speed.

Maybe @meepmeepmayer can help more on this one, but from reading his torque versus speed faceplant graph, I think by having the magnets close to the center yields a higher top speed before the torque collapses to zero. I may be reading his graph wrong, and the top speed is independent of how close the magnets are to the rim of the wheel.

[mrelwood]

In addition to all that’s been said, I think turning at slow speeds on a 18” will benefit a lot more from purposefully tilting the wheel between your legs than on a 14”.

The third gear is a good analogy, it will feel lazy to accelerate and brake. But all the power is there, it will just take larger physical movements to command the wheel.

Start slowly and try different turnings and accelerations at slow speeds first. The differences will reveal themselves to you right away, and you should be able to adapt quite quickly.

26 minutes ago, Planemo said:

Why, with all the tech we have, cant the manufacturers build an 18" wheel with the same torque as a 14"?

Because it is up to the laws of physics, not advancement in tech. On a 14” wheel you can easily reach the front end of the wheel with your center of gravity. Imagine a 100” wheel. You would have to take an actual step forward to get your CoG to where the front end of the wheel is.

Moving the magnets to the edge of the rim will not affect the CoG in relation to the wheel diameter. 10”, 14” and 16” wheels each already have the magnets right next to the rim. The same behavior is still present, bigger wheels feel more lazy to accelerate/brake.

Edit: Moving the magnets would increase the maximum torque available from the motor. But the 18” isn’t lazy because reaching the maximum torque. It’s because you need to physically move more to get the same offset in CoG in relation to the wheel diameter.

Edited April 22, 2019 by mrelwood

[erk1024]

1 hour ago, eddiemoy said:

actually, folks who come from 14" tend to overlean and face plant.

Could you tell me more about "overleaning". Obviously you can lean forward too dramatically and no wheel in the world would be able to catch up. But what happens in this situation? I'm imagining the wheel trying to surge forward, which re-levels the pedals, but as the rider you fall off the front edge of the pedals because your CG is over-extended. Or does the wheel sense the situation and the motor cuts out?

[Planemo]

33 minutes ago, mrelwood said:

 

Because it is up to the laws of physics, not advancement in tech. On a 14” wheel you can easily reach the front end of the wheel with your center of gravity. Imagine a 100” wheel. You would have to take an actual step forward to get your CoG to where the front end of the wheel is.

I dont follow your physics. A CoG is just that. To be more specific, the axle of our euc's. The axle reads the riders input, not the outer edge of whatever diameter wheel you have.

You would not need to 'lean over' the outer diameter of a 100" wheel to get it to move, nor indeed step foward. As soon as you CoG shifts foward of the axle it should move.

[eddiemoy]

56 minutes ago, erk1024 said:

Could you tell me more about "overleaning". Obviously you can lean forward too dramatically and no wheel in the world would be able to catch up. But what happens in this situation? I'm imagining the wheel trying to surge forward, which re-levels the pedals, but as the rider you fall off the front edge of the pedals because your CG is over-extended. Or does the wheel sense the situation and the motor cuts out?

overlean is rider issue, you lean forward and fall.  wheel just can't catch up, it doesn't cut out.  that is different. it is a matter of getting used to how much you can lean in the 18" vs 14".  if you are used to the faster reacting 14" and expect for the 18" to react the same, you are in for a rude awakening.

[meepmeepmayer]

(Offtopic)

2 hours ago, LanghamP said:

I think just moving the magnets out towards the rim of the wheel would make the torque equal to a 14 incher, however there might be a trade-off in torque at speed.

Maybe @meepmeepmayer can help more on this one, but from reading his torque versus speed faceplant graph, I think by having the magnets close to the center yields a higher top speed before the torque collapses to zero. I may be reading his graph wrong, and the top speed is independent of how close the magnets are to the rim of the wheel.

Sorry that graph stuff was by @Chriull, not me But torque (extra, available, free torque) just seems to drop linearly to zero as speed increases. Nothing complicated there.

As far as I can tell (might be completely BS), it's like this:

The more windings (= number of magnets, naturally there's one magnet in the rotor for each winding in the stator) you have, the more torque and less top speed (= zero torque speed) you get for a given wheel diameter. Moving the magnets out towards the rim does effectively give more windings (same size magnets assumed), so more torque. But you could as well just NOT move the magnets outward, but use more windings with more (= now smaller) magnets. Same effect.

So in the end, moving the magnets out is NO magical solution to building better EUC motors. You'd either have more magnets (less top speed, more torque) or the same number of (now bigger) magnets (same top speed, same torque). It might be better for cooling to have the motor as big as possible, though, but that is an unrelated issue.

A wheel is a black box where you put some given amount of power in and it rotates the tire for you against a given resistance. The problem of a bigger tire diameter is simply that it needs more torque to rotate it, which gives you less available extra torque which you feel as "torque" during riding. The only thing that counts here is the distance between the axis of rotation and the outer edge of the tire. How the motor is built in between doesn't matter. That problem doesn't go away by building the motor in one or the other specific way, it's always the same regardless of motor build, so it can't be solved by motor build, it's a physics problem.

You always have a trade-off between torque and top speed, and just like a bigger tire gives you a bigger speed for the same rpm, it gives you higher torque requirements (less feeling of "torque" riding the wheel because there's less leftover free torque). You could build a 14 incher with the higher top speed and "lower torque" of an 18 incher (simply use less motor windings or whatever), but you cannot get an 18 incher to "have higher torque" without simply increasing the power input (higher battery usage).

Otherwise, you could build arbitrarily fast and torque-y motors with arbitrarily small power input, I don't think you can cheat reality this way

TLDR: in simple Wikipedia formulas: power = torque * velocity, so if you don't want to increase power input, you gotta take from one to give to the other. Motor build doesn't matter. No cheating!

(There will be other, technical reasons to build good motors a certain way.)

Edited April 22, 2019 by meepmeepmayer

[erk1024]

Thanks for all the info guys! Makes sense.

I think this was mentioned someplace: the assumption is that when KS make the 18L and XL that they set the max speed to 50kph even though the wheel could probably do 56kph or more. They left some torque / speed in reserve to be able to achieve tilt-back in an attempt to keep riders from overleaning at max speed. (The only way to "tilt" the pedals is to add more torque to get the pedals into the new position along the axis of rotation.) And as the battery gets lower (e.g. 25% on the XL) they bring down the max speed further to maintain the safety margin.

[meepmeepmayer]

1 minute ago, erk1024 said:

I think this was mentioned someplace: the assumption is that when KS make the 18L and XL that they set the max speed to 50kph even though the wheel could probably do 56kph or more. They left some torque / speed in reserve to be able to achieve tilt-back in an attempt to keep riders from overleaning at max speed. (The only way to "tilt" the pedals is to add more torque to get the pedals into the new position along the axis of rotation.) And as the battery gets lower (e.g. 25% on the XL) they bring down the max speed further to maintain the safety margin.

Yes, exactly. There's no reason to believe that the 2000W motor and the 6p 120 cell battery of the 18XL are weaker than the 2000W motor and the 6p 120 cell battery of the MSX for some mysterious reason.

One thing to mention, actually in Gotway's favor in some way, is that Gotway batteries are considered empty at 3.3V of cell voltage, whereas the 18XL is empty at 3.0V. Or in other words, when the 18XL is (very roughly!) at "25% battery", the Gotway wheel will consider itself at 0% battery (same charge state of the battery!). Of course Gotway wheels can offer less reductions at the lower end if the lower end is really much higher than on the 18XL. That's why the 18XL also seems to get a higher range, they simply let you drain the batteries more and need to be more careful then.

As far as the top-end, 50kph speed limit of the 18XL is concerned, Kingsong just seems to be more cautious or simply limit themselves to a nice round number. The 100% full batteries of the 18XL and MSX are the same (4.2V per cell), and the 84V MSX starts the 3rd alarm at 58kph which reduces with battery charge. So an 18XL should also be able to do 58kph at full battery. So you got some extra margin up there.

[mrelwood]

4 hours ago, Planemo said:

I dont follow your physics. A CoG is just that. To be more specific, the axle of our euc's.

Only at a steady speed. The only way to give the input to the wheel is to press the front end of the pedals more than the rear = more weight at the front of the axle than rear = CoG is forward from the axle.

4 hours ago, Planemo said:

The axle reads the riders input, not the outer edge of whatever diameter wheel you have.

Take a canoe vs a boat for an example. Stand on a canoe, and the slightest step sideways tilts the whole system a whole lot. On a rowing boat the same tiny step barely tilts the boat. The bigger the boat, the more you have to step aside from the center line to achieve the same tilt. And it’s the amount of tilt that tells the wheel how fast to accelerate.

Or tire width: Take a wheel with a 2” and a 3” wide tires, and tilt them the same amount. The contact point on a wide tire moves further away from the center line than on the narrow one, so the wide one turns more. During riding this means that the wide tired wheel doesn’t need to tilt as much during the same turn.

RockyTop made a marvellous illustration and a video about why large wheels require more lean at an uphill. The same physics apply. 

4 hours ago, Planemo said:

You would not need to 'lean over' the outer diameter of a 100" wheel to get it to move, nor indeed step foward. As soon as you CoG shifts foward of the axle it should move.

And it does, of course. But how fast? That’s the reason why large wheels feel lazy, they don’t need to accelerate as fast to balance the system.

[Planemo]

Your boat analogy doesnt apply because you are bringing displacement of water into the equation, along with a host of other things like hull design and shape. Nor (crucially) have you got anything acting on your behalf (like a CoG sensor) to amplify your body weight into additional raw power.

I will try another one...imagine you have your 100" wheel. We will rule out power requirements (which you said yourself isnt the issue) and lets fit say a 30Kw motor in it, with the magnets/coils at the very edge of the wheel. Lets add oooh say enough power to run a tesla. Then to rule out contact patch size (which I agree can slightly vary between tyre sizes/pressures) we will use a hard, solid trye.

We will use the same size footplates as we do now.

Step on (only the brave need apply), lean foward and it is my belief that the wheel will rocket foward to maintain your CoG. In fact, in this scenario I doubt if you could ever overlean the wheel, I imagine you could literally fall foward and the wheel would have enough power (therefore acceleration) to prevent you falling. Eg, 30Kw in this application is probably enough to create over 1g of acceleration.

[mrelwood]

3 hours ago, Planemo said:

Your boat analogy doesnt apply

Of course not, I’m just trying to help you understand the causality of a bigger radius requiring more weight displacement. Science in English is a bit difficult to explain for me. I hope someone can explain it in a way that opens it up for you.

 

3 hours ago, Planemo said:

Step on (only the brave need apply), lean foward and it is my belief that the wheel will rocket foward to maintain your CoG.

And how is that behaviour different from the current wheels?

 

[Planemo]

2 minutes ago, mrelwood said:

And how is that behaviour different from the current wheels?

Its not! You are the one saying it is, and that the bigger the wheel the more the rider needs to be ahead of the axle line CoG.

We do not need more weight to make bigger EUCs move, nor do we need to move our weight any further foward. The wheels job is to simply read tilt and apply as much power as is required to zero it. As long as there is enough power available this concept should work on any size wheel, in exactly the same way.

[meepmeepmayer]

9 minutes ago, Planemo said:

We do not need more weight to make bigger EUCs move, nor do we need to move our weight any further foward. The wheels job is to simply read tilt and apply as much power as is required to zero it. As long as there is enough power available this concept should work on any size wheel, in exactly the same way.

Yep.

A wheel moves when it tilts. For a bigger tire diameter, you'd simply need more power input to get a wheel that behaves like a smaller tire (= has more torque). It would simply have to react more sensitively to input, so essentially a harder ride mode. A bigger radius does not require more weight displacement in itself.

But maybe the same weight displacement leads to a smaller pedal tilt for some geometric reason. Could be that the pedals have to travel further as they are not on axle height, but below, so they trace part of a circle which gets bigger the further the pedals are away from the axle (like on the usual bigger tire wheels). Maybe that makes a difference? The wheel could still compensate that by having a harder ride mode which means only a smaller part of the circle is traced.