MSuper 22" with 1600 Wh/ 2400 Wh

[Hunka Hunka Burning Love]

I'm no physicsologist, but I would think that once the motor starts rolling it just needs to overcome frictional forces to keep things going.  If we were in the vacuum of space with no gravity on a frictionless flat surface, the same motor with a small wheel versus a large wheel would expend a little more energy to start spinning the bigger one, but once rotating it would expend the same amount of energy per rotation.  With a larger circumference the wheel travels further per rotation.

I could be wrong, but then I would have to cut you.

Or think of it this way - some people like to put 24's on their Cadillacs.  If they put 15" wheels on, the car given a specific wheel rpm wouldn't go as fast nor as far.  The engine would have to spin a lot faster to travel the same distance.

[Cloud]

14 minutes ago, HunkaHunkaBurningLove said:

I'm no physicsologist, but I would think that once the motor starts rolling it just needs to overcome frictional forces to keep things going.  If we were in the vacuum of space with no gravity on a frictionless flat surface, the same motor with a small wheel versus a large wheel would expend a little more energy to start spinning the bigger one, but once rotating it would expend the same amount of energy per rotation.  With a larger circumference the wheel travels further per rotation.

I could be wrong, but then I would have to cut you.

If we were in the vacuum, with no gravity, on a frictionless surface, you wouldnt need ANY energy to go for a thousand miles ( except the slight initial push) as the inertia of the moving wheel ( large or small) would just keep it going forever and ever and ever....so this example is irrelevant

[Hunka Hunka Burning Love]

  But the battery would die at about the same time, yet the larger wheel would have traveled further in that time span.  Don't make me cut you, @Cloud  I will.  I guess though on a frictionless surface there is no traction so both wheels would not move.  Factoring it down to the linear distance spun in reference to point  A on each wheel, the larger one would have a greater net distance.  So we're technically both right.  I can live with that.  But I'm still gonna cut you.

[Mono]

1 hour ago, OliverH said:

I saw pictures form Kingsong and 1RadWerkstatt. No option. Do you've a small size 4A charger? Any link?

No, sorry. I also didn't need any yet, but would still be interested where to get one.

[Mono]

That would be cool if range and speed would grow linearly with wheel diameter 

[SuperSport]

26 minutes ago, HunkaHunkaBurningLove said:

  But the battery would die at about the same time, yet the larger wheel would have traveled further in that time span.  Don't make me cut you, @Cloud  I will.  I guess though on a frictionless surface there is no traction so both wheels would not move.  Factoring it down to the linear distance spun in reference to point  A on each wheel, the larger one would have a greater net distance.  So we're technically both right.  I can live with that.  But I'm still gonna cut you.

At some point, the larger wheel needs more power to travel the same distance, thus would be less efficient.  I'm not sure what that point is, as it's also regulated by the internal gearing and power of the motor itself.  That's why gearing is so important on cars and bikes, etc...

I've put large tires on my trucks, and it gets considerably less mileage.

[Mono]

A larger wheel has a (slightly) smaller rolling resistance. Given motor, controller, etc. are adapted to the wheel size, respectively, then rolling resistance is AFAIK the parameter with the most prominent systematic effect of the wheel size on range. Having said that, a different tire can have a much more pronounced effect on rolling resistance than changing the wheel size from 18" to 26".

[YaocH]

1 hour ago, HunkaHunkaBurningLove said:

I'm no physicsologist, but I would think that once the motor starts rolling it just needs to overcome frictional forces to keep things going.  If we were in the vacuum of space with no gravity on a frictionless flat surface, the same motor with a small wheel versus a large wheel would expend a little more energy to start spinning the bigger one, but once rotating it would expend the same amount of energy per rotation.  With a larger circumference the wheel travels further per rotation.

I could be wrong, but then I would have to cut you.

Or think of it this way - some people like to put 24's on their Cadillacs.  If they put 15" wheels on, the car given a specific wheel rpm wouldn't go as fast nor as far.  The engine would have to spin a lot faster to travel the same distance.

Simply: Work done (Energy) = Force X Displacement = Mass X Acceleration X Displacement. (ignoring rotational kinetic energy)

Power = Torque X Wheel RPM

With a larger wheel, the motor has to exert a larger torque as the frictional torque from the surface will be larger (moment arm larger). This is countered by the slower wheel RPM. Thus it is right so say that a larger wheel will travel further with each rotation, but it will have to exert more torque to do so. Thus there are no energy gains / losses. Energy cannot be created or destroyed.

Back to the first equation: a larger wheel diameter will give a larger displacement but will require a larger force to do so.

If we do decide to consider rotational KE:

KE(Rotational) = (1/2) moment of inertia X wheel RPM

A larger diameter wheel will have a much larger moment of inertia (tires especially, doubling the diameter of the wheel results in almost 16X (simplified) the moment of inertia). This will absorb a large amount of the energy that is output by the motor and will increase exponentially with increasing diameter of the wheel. This will limit the top end speed of the EU.

32 minutes ago, MoNo said:

A larger wheel has a (slightly) smaller rolling resistance. Given motor, controller, etc. are adapted to the wheel size, respectively, then rolling resistance is AFAIK the parameter with the most prominent systematic effect of the wheel size on range. Having said that, a different tire can have a much more pronounced effect on rolling resistance than changing the wheel size from 18" to 26".

This gentleman here has put it exactly if we consider rolling resistance. Rolling resistance is a whole topic on its own with much more variables to consider.

[Hunka Hunka Burning Love]

I wonder how much more range @Mistagear gets with the larger tire than a regular 18" KingSong with the same battery pack.  I would think the larger wheel does take more power to get rolling, but once going it wouldn't consume a lot more energy.  The rotational mass would be slightly larger but probably not by much.  I wonder what the ideal size for maximum distance would be then with these hub motors.

On those solar racers that people have designed (electric recumbent bike with shell and solar panels), they use pretty large, thin tires.  I wonder if there's a way to determine the ideal tire/motor size for EUCs to maximize their range.

[Marty Backe]

31 minutes ago, MoNo said:

A larger wheel has a (slightly) smaller rolling resistance. Given motor, controller, etc. are adapted to the wheel size, respectively, then rolling resistance is AFAIK the parameter with the most prominent systematic effect of the wheel size on range. Having said that, a different tire can have a much more pronounced effect on rolling resistance than changing the wheel size from 18" to 26".

The ACM 16 and MSuper V3 both appear to have the same battery capacity (820wh in my case). The MSuper is certaily heavier then my ACM, and of course the wheel is larger and thicker. I expected the MSuper would have less range than my ACM, but it turns out that my MSuper has the same range as my ACM, and my sense is that the MSuper actually has more range than my ACM.

[Mono]

1 hour ago, YaocH said:

This gentleman here has put it exactly if we consider rolling resistance. Rolling resistance is a whole topic on its own with much more variables to consider.

The question brought up in several posts of this thread was how wheel size influences range. I tried to explain that rolling resistance is the most relevant factor to answer this question. Sorry, if this wasn't clear.

[YaocH]

1 minute ago, MoNo said:

The question brought up in several posts of this thread was how wheel size influences range. I tried to explain that rolling resistance is the most relevant factor to answer this question. Sorry, if this wasn't clear.

That's what I meant as well.

[Mono]

9 hours ago, Marty Backe said:

The ACM 16 and MSuper V3 both appear to have the same battery capacity (820wh in my case). The MSuper is certaily heavier then my ACM, and of course the wheel is larger and thicker. I expected the MSuper would have less range than my ACM, but it turns out that my MSuper has the same range as my ACM, and my sense is that the MSuper actually has more range than my ACM.

Right, neither the (small) difference in wheel size nor in weight should be relevant for the range you can actually get.

[Cloud]

4 hours ago, YaocH said:

Simply: Work done (Energy) = Force X Displacement = Mass X Acceleration X Displacement. (ignoring rotational kinetic energy)

Power = Torque X Wheel RPM

With a larger wheel, the motor has to exert a larger torque as the frictional torque from the surface will be larger (moment arm larger). This is countered by the slower wheel RPM. Thus it is right so say that a larger wheel will travel further with each rotation, but it will have to exert more torque to do so. Thus there are no energy gains / losses. Energy cannot be created or destroyed.

Back to the first equation: a larger wheel diameter will give a larger displacement but will require a larger force to do so.

 

Well put. This is what i was trying to say, there is no farther distance because of larger circumference at same angular speed.

[Cloud]

4 hours ago, Marty Backe said:

The ACM 16 and MSuper V3 both appear to have the same battery capacity (820wh in my case). The MSuper is certaily heavier then my ACM, and of course the wheel is larger and thicker. I expected the MSuper would have less range than my ACM, but it turns out that my MSuper has the same range as my ACM, and my sense is that the MSuper actually has more range than my ACM.

In real life examples, the difference between 18 -and 16 is not great enough to make this conclusion based on this difference alone. So many more factors that can affect the range with different wheels. One of the i portant ones is acceleratikns and braking. I feel that one reason a larger wheel ( that otherwise would travel less than the smaller) can reach the same distance is because of a smoother ride. On my nimble 14" ks, i accelerate and brake often. When i was riding the msuper i ride in a calmer manner as it wasnt feasible to constantly rush forward and brake on a bigger mass wheel. This must use uo the battery far less.

[Marty Backe]

40 minutes ago, Cloud said:

<snip>

On my nimble 14" ks, i accelerate and brake often. When i was riding the msuper i ride in a calmer manner as it wasnt feasible to constantly rush forward and brake on a bigger mass wheel. This must use uo the battery far less.

Good point. I had a 20 mile ride on my KS14C today and I did feel like I was accelerating and breaking a lot more then on my MSuper. Fortunately the 14C with 840wh battery has an amazing range even with the larger battery drain --  40% remaining after 20 miles :-)

[Hunka Hunka Burning Love]

  While we're on the subject, I'd like to bring up some religious arguments that I have been pondering for quite some time... ooooor not.     Best to leave that to another forum...

[Smoother]

Yeah your right I shouldn't have started.  My apologies. Moderator please feel free to remove my rant

[Smoother]

Never mind I did it myself.

[Chriull]

8 minutes ago, Smoother said:

Yeah your right I shouldn't have started.  My apologies. Moderator please feel free to remove my rant

You can whenever you want edit your own post (delete the original content and replace by something like ... removed my rant...) or hide the whole post.

[Cerbera]

I wonder if 22 inches and 2400 wh doesn't make for a rather impractical, somewhat unportable device... you're gonna have to lift it some time... 

[Peter Brierley]

All the physics theorising is very amusing, here's the reality.

my 26" wheel and my 18" wheel both have same motor and battery combo ( 1200W x 680wh ). The 26" has a 40% greater tyre circumference, hence travels 40% further for each revolution. (and faster )

The 26" can travel much further on one battery charge. Depending on where I ride, but I think it possible to travel greater than 40% further under certain circumstances..

eg, off-road where I'm forced to slow down for ruts and bumps then re-accelerate, more with the 18", because the 26" rolls much better and maintains speed in this terrain, it rolls along easily.    Alternately

If I were to use constant, near top speed on both wheels, the additional wind resistance travelling in excess of 40kph (26" does 56kph) consumes battery charge fast, I'm not sure which would go further distance, although the 26" will arrive there first

[Mono]

1 hour ago, Peter Brierley said:

All the physics theorising is very amusing, here's the reality.

I was in the believe physics "was" reality, or rather the only way we know how to describe this aspect of reality in an adequate way and make accurate predictions. As always, I might be mistaken. 

The beauty of physics here is to explain the possible and exclude the impossible reasons for your observations of reality. Increasing the wheel size by 40% cannot invariably increase the range by 40%, it just cannot (the reason is conversation of energy).^1 You are perfectly right, on rough terrain a large wheel can have a huge effect. Even if you don't brake and accelerate constantly yourself, from simple geometry the larger wheel makes the effective path smoother in vertical direction, the motor needs to do less repeated liftings and less small accelerations to keep the constant speed. Changing the wheel size also means changing the operating point at which the motor works for a given speed. Efficiency of the motor depends to a comparatively great extend on the operating point and is absolutely critical for range.

 

^1 It turns out that electric skateboards operate with very similar efficiency as EUCs, roughly 100Wh per 10km under ideal circumstances. That would be rather difficult to explain if wheel size and range were directly linked.

[Cloud]

3 hours ago, MoNo said:

I was in the believe physics "was" reality, or rather the only way we know how to describe this aspect of reality in an adequate way and make accurate predictions. As always, I might be mistaken. 

The beauty of physics here is to explain the possible and exclude the impossible reasons for your observations of reality. Increasing the wheel size by 40% cannot invariably increase the range by 40%, it just cannot (the reason is conversation of energy).^1 You are perfectly right, on rough terrain a large wheel can have a huge effect. Even if you don't brake and accelerate constantly yourself, from simple geometry the larger wheel makes the effective path smoother in vertical direction, the motor needs to do less repeated liftings and less small accelerations to keep the constant speed. Changing the wheel size also means changing the operating point at which the motor works for a given speed. Efficiency of the motor depends to a comparatively great extend on the operating point and is absolutely critical for range.

 

^1 It turns out that electric skateboards operate with very similar efficiency as EUCs, roughly 100Wh per 10km under ideal circumstances. That would be rather difficult to explain if wheel size and range were directly linked.

Yes exactly

@Peter Brierley do you ride the rough terrain or smooth? On rough terrain no wonder the bigger size wheel will perform better and conserve energy

[Roll Model]

Funny conversation...
I'll add only two points.
Rolling resistance is about the same for all rolling speeds - So roll fast, roll slow and the wasted energy (of rolling) is pretty much "the same".
Wind resistance is not like that, if you go from 10 to 20 mph you have not simply doubled your wind resistance (it goes up exponentially). So the energy needed to go from 50mph to 51mph is MUCH, MUCH greater than the energy needed to go from 10mph to 11mph...)  Wind (ambient air movement) will almost always increase your wasted energy, as only wind coming directly from behind will boost you. Wind coming from a few degrees off your butt will add to the drag and not be of any help.
But all that wind, all that increase in speed doesn't affect 'rolling resistance' it is pretty stable.
Load becomes a factor primarily when you accelerate (or go up hill, which is the same as constant acceleration) or when the load has a larger frontal surface. If you put a 100 pound back pack on a 100 pound rider he'd get further than a 200 pound rider simply because of the smaller frontal surface. If you double the load, you don't double the rolling resistance (it remains almost unchanged) where as if you double the frontal surface you will MORE than double the wind resistance (assuming the aerodynamics are roughly equal).
A wider tire will present more wind resistance at every speed (above 0). Increase the speed and the (air) drag will go up at the square of the speed, which is NOT TRUE for the wheel's rolling resistance.
Tire construction would contribute more to rolling dynamics especially how the wider tire (or the tires "profile") deals with different loads (and inflation values). So unless you are comparing tires of the same width, with the same basic construction, there is no real way to simply compare "Tire Size" and get much valuable 'seat of the pants' data from it...
Perhaps some one will inflate the tires and roll through a puddle or two to compare the CONTACT PATCH size of the 18" wheel versus the 16" wheel...? Rolling resistance has more to do with internal friction in the tire and contact patch than it does with the tires outer diameter.