The technological top speed limits of EUC’s

[andrew900nyc]

As a new member, I apologize if this topic has already been discussed. If that is the case, I would be most appreciative if someone could direct me to the relevant thread. Thanks!

If the topic hasn’t been discussed, my specific interest is in knowing the limits of the electronics with regard to the top speed of a self-balancing vehicle. In other words, forget about (1) the limitations of the power of the motor (2) the limitations of the size of the battery that could be utilized, and (3) the ability of a rider to safely operate the vehicle at high speeds. All I’m interested in is the ability of the electronics to keep the vehicle longitudinally stable throughout the speed range capability of the vehicle.

So imagine that you find yourself in a society that has developed an electric motor capable of propelling a EUC to a maximum speed of 100mph. They also developed a small, super powerful battery that can be utilized to power the motor for three hours (of average usage on mostly flat ground).

So my question is:

Given the current state of technology, would it be possible to build the self-balancing system needed for such a hypothetical vehicle to maintain longitudinal stability at a speed of 100mph? If the answer is no, why not and what do you think is the fastest achievable speed for a self-balancing vehicle?

Of course, I am most interested in hearing from people who have the technological knowledge/expertise to answer these questions based on the relevant math/computer science/electronics. Thanks! Can’t wait to hear your answers!

[null]

Not a science guy here, but I’d bet any smartphone CPU could balance a wheel at any speed the motor might follow. AFAIK the calculations aren’t that complex. Anyone with hard facts?

[tenofnine]

Currently I think it's possible to make a 100 mph EUC, the hub motor tech exists already. The main issue is that it would be quite large and heavy. You'd need very thick gauge wires to transport the amount of power needed to and fro the motor. and you'd need a very robust battery pack to absorb and deal out massive amounts of energy quickly. The worst problem is air resistance, it makes EUCs require much higher energy demands to reach the same speeds that electric motorcycles can easily (220mph current top). I think there would be some kind of terminal velocity effect horizontally on an EUC. Free falling a human can only reach 122 mph under the constant accelerating force of gravity....the only thing stopping higher speeds being the air around us. If you put a bubble encasing or fairings then maybe you can reach higher speeds on an EUC.

The balancing part I don't think is really a bottleneck at all given your lenient parameters. That just boils down to CPU speed, sensor quality, and power delivery/dissipation.

But I think the better question is how fast should these be able to go?

Frankly I think anything over 35 mph is insane. For me the discussion ends there. I think anything over 50 mph is dumb even on a motorcycle let alone a scooter. Not sure why everyone wants to go faster than needed.

[Sidewalk Enforcer]

I'll take the pessimistic approach that it's not technically possible. 

A wheel capable of that speed cannot exist in the EUC form-factor we've become accustomed to. The analogy with an electric motorcycle is not entirely accurate as that vehicle does not need reserve torque to sustain the upright vehicle and rider. Whether such a vehicle could be operated safely on public roads? I'll go with a solid no. Closed circuit racing with sufficient training and practice ... maybe.

http://lancet.mit.edu/motors/motors3.html

The page above describes the torque-speed characteristic of a constant voltage DC electric motor. Notice that maximum torque is produced at 0 rpm (when the wheel is stationary). As speed increases, electro-magnetic resistances build and build within the motor until there is no longer any more power in the wheel and you arrive at 0 torque. The maximum power for a DC electric motor develops at 50% max motor velocity, there-after your're heading towards face-plant city if you're riding a self-balancing vehicle. So if one were to design an EUC that could safely sustain a self-balancing profile @ 100 mph, you would need to design a wheel motor that has a max velocity of 200 mph!!!!

Even if you had an imaginary power source that could deliver enough power to the motor by increasing the amount of voltage available, the current draw would require massively larger gauge wires. Larger wire gauge means less windings for the rotors. Less windings means lower efficiency. So maybe you increase the size of the motor to increase the space between the rotors and achieve the same number of windings - but now you have more mass, an impractically large wheel and need even more power to drive the motor.

Then we need to consider the material science and the forces at play at those types of speeds. For example, a 16 in wheel operating at 100 mph is experiencing ~ 28 revolutions per second and ~ 800 G in centrifugal forces. I doubt the bicycle tire that could handle those types of loads would make for a very comfortable ride!

[meepmeepmayer]

I don't agree with that, 100mph should be technically possible.

But apart from the fact that EUCs are just not high speed devices and simply are the wrong vehicle for that speed, you have a good point with the motor characteristics.

As I understood it, the more you design a motor for speed, the less torque it has. There will be a point where you can go very fast, but in return the torque when starting or riding at low speed will be so low, it will be impractical and unsafe (and no fun) to ride such a wheel. Sluggish behavior, bad braking, etc. Also the extra torque to deal with a bump at any speed might get too low then. The bigger tire diameter required for a 100mph wheel will also reduce torque. I can see torque being a problem for such a theoretical EUC.

So I guess then you need gears or a system with similar effect (maybe a motor with two different, parallel windings could work somehow?).

For now, the MSX 100V limits itself at 69kph max and still has massive torque for going up very steep, gnarly offroad tracks. So we're still a bit away from when too little torque becomes a problem. I don't think anyone would ever want to regularly ride a EUC at above 75kph on normal roads, so this tradeoff dilemma might not mean much in reality.

[andrew900nyc]

 

Thanks a lot for all your feedback. I appreciate it tremendously!

While I am very interested in this topic from a curiosity perspective alone, I also have a very practical reason for wanting to know the answer to this question. 

The practical reason for my interest in this topic is because I invented a new type of self-balancing vehicle that is meant to be operated on a racetrack. It is an entirely new class of vehicle and there is nothing like it currently on the market. Thanks to your feedback, I now know that the hub motor I sourced that can power an electric motorcycle to a top speed of 100MPH should hopefully be able to  provide the power needed to achieve a top speed of close to 50MPH on my self-balancing race vehicle. I'm shooting for the vehicle to have a top speed of 100MPH (for the version that would be ridden by professional racers only), but you gotta start somewhere!

 

[Ronko]

The main limitations to speed as with any vehicle is the drag force which you need to overcome.

So doing some basic calculations (ignoring rolling resistance), a rider of average height standing upright has a coefficient of drag of 1.2 (and a frontal/reference area of 0.72m).

Travelling at 100mph the drag force acting against the rider will be 106kg (and the EUC would require 46.5kW to push through this).

So 100mph seems very unfeasible...

 

Calculating for different speeds:

30mph, you would have a drag force of 10kg and require 1.3kW motor.

40mph - a drag force of 17kg and a 3kW motor

50mph - a drag force of 26kg and a 6kW motor

60mph - a drag force of 38kg and a 10kW motor

70mph - a drag force of 52kg and a 16kW motor

 

So I think speeds of up to 50-60mph are possible.

[Planemo]

Interesting. So, assuming you could reduce the drag by crouching down like a road cyclist, do you think you could say halve the drag, thus allowing, in theory, a 100mph EUC?

Would need kahunas like watermelons to ride the thing mind... 

[andrew900nyc]

Just to clarify, I only used EUC’s as the self-balancing vehicle for this question for illustrative purposes and for the sake of keeping the question simple. I had hoped to focus the discussion on the limitations of the electronics with regard to the top speed of any one-wheeled, self-balancing vehicle (assuming there is a top speed for practical purposes).

Regarding the very important issue of drag force that Ronko has brought up, I don’t think the vehicle I invented will have as much drag as a EUC, but I will defer to the professional opinion of those who are far more knowledgeable than I am to comment on this matter. I will be very interested to find out from experts if they think my vehicle has the potential to reach speeds of 100MPH (if a powerful enough motor were available). The motor I intend to use to power the prototype to a max speed of at least 45MPH is this one:

http://www.customevperformance.com/p/8535643/enertrac-hub-motor-20kw-cont-40kw-peak.html

It was used to power this 1993 Suzuki GSX-R 1100:

 http://www.evalbum.com/3931

 

[Smoother]

I look forward to your big reveal.  Good luck.

 

[andrew900nyc]

Thanks, Smoother, I really appreciate your good wishes! 

I’d like to provide some information about my thinking regarding this invention.

1)    Passion is what motivates me to bring this vehicle to market. While I am confident that there is plenty of money to be made, financial reward is not the driving factor for me. Rather, it is my tremendous desire to operate this vehicle that pushes me to develop it. I need to bring this vehicle to life because of my burning desire to ride it. Although I’m biased, I think this vehicle is one of the coolest racetrack vehicles ever invented!

2)    I have a very specific plan to promote this vehicle worldwide, along with certain other PEV’s. I believe that, if successful, this plan will help EUC’s and electric skateboards obtain far greater exposure, reach a much broader market and achieve significantly increased sales. This sounds like a bold claim, but once you understand my plan, I think you will consider my claim to be within the realm of possibility. If, having heard my plan, members of this forum think my claims are unreasonable or overly optimistic, I would like to know that information.

3)    I would like to just reveal my invention and plan to the entire forum, but I don’t think it would be in my best interests to do that right now. Rather, I am hoping the forum members can recommend some senior members who are likely to be trusted the most by the membership of this forum to hear about my invention and my marketing plan. Then these senior members can let the membership at large know if they think I invented something really cool or if they think it’s a dud or if they think it’s just not nearly as cool as I think it is. Of course, at the right time, the invention will be publicly revealed on this forum. 

4)    My goal is to assemble a team of cofounders with the enthusiasm, dedication, motivation and perseverance to help bring my vehicle and vision to fruition (assuming they agree with my assessment of the vehicle and my marketing plan). Because my main motivation is not financial, I am happy to partner up with the cofounders. Furthermore, the structure I have in mind is global and set up such that other individuals can participate in this new PEV business in their local areas. So basically nearly any forum member with the qualities mentioned at the top of this paragraph can have an opportunity to be involved, if they want to be.

 

Any recommendations for trusted forum members (who aren’t employees of any of the manufacturers) that you think would be interested in hearing about my invention and ideas would be most appreciated! I am quite eager to get some feedback.  

[Ronko]

13 hours ago, Planemo said:

Interesting. So, assuming you could reduce the drag by crouching down like a road cyclist, do you think you could say halve the drag, thus allowing, in theory, a 100mph EUC?

Would need kahunas like watermelons to ride the thing mind... 

Yes, if you reduce frontal are you will halve the drag force.  But you would still have 50kg acting against you while crouching down...  And if you suddenly stand up you will be blown away!

 

9 hours ago, andrew900nyc said:

I had hoped to focus the discussion on the limitations of the electronics with regard to the top speed of any one-wheeled, self-balancing vehicle (assuming there is a top speed for practical purposes).

From an electronics perspective, there is no maximum speed assuming you choose the right components.  The motor you linked will do 960rpm with a 96V supply and 20kW continuous, so the main factors affecting the top speed you can achieve are:

1. Tyre diameter (the bigger the diameter the faster you are travelling for a given rpm)
2. Drag and rolling resistance (at your desired top speed, 20kW needs to be enough to overcome the forces exerted by these)
3. Motor controller and battery pack (ensuring they can provide 20kW continuosly)

[Smoother]

19 hours ago, andrew900nyc said:

 

Any recommendations for trusted forum members (who aren’t employees of any of the manufacturers) that you think would be interested in hearing about my invention and ideas would be most appreciated! I am quite eager to get some feedback.

That's a tough one.  Possibly @mrelwood and @EUC GUY for their personal creativity, @meepmeepmayer for his ability to call a spade a spade, Someone from the San Francisco group because they have several different types of PLEVs to compare already. I'm sure I'm forgetting some people with obvious credentials (and I'm finding I can't speel many members names without quoting the via a click.  I'm not sure owning multiple EUCs counts, given your requirements.

[andrew900nyc]

 

Thanks for your suggestions, @Smoother. They all seem like excellent choices, but I am going to reach out to @meepmeepmayer because the most important thing to me right now is unbiased feedback and since meepmeepmayer is known for calling a spade a spade, he sounds like an ideal person from whom to (hopefully) obtain some feedback. If he's receptive to learning about my invention and marketing plan. I am hoping he can rate the vehicle on a scale of 1 - 10, with 10 being super cool and 1 being about the worst electric vehicle you can imagine. Please note that this vehicle is meant to be operated on a racetrack, so it should be evaluated with that context in mind.

I have already reached out to @Hsiang because after watching his videos I felt that he was knowledgeable about the industry, has good insights, and he is an enthusiastic promoter of EUC's with an excellent reputation in the community. And he's right here in New York! 

 

[meepmeepmayer]

57 minutes ago, Smoother said:

@meepmeepmayer for his ability to call a spade a spade

36 minutes ago, andrew900nyc said:

and since meepmeepmayer is known for calling a spade a spade

Good to know I guess

Don't forget the master of us all, @Marty Backe.

[andrew900nyc]

Thanks @meepmeepmayer... @Marty Backe is definitely someone who's opinions I will very much want to obtain, as well as some of the other members you recommended in your message to me.

I very much appreciate your taking the time to learn about my invention and marketing plan and offering to provide your honest opinion regarding this vehicle. 

I have sent you the information and look forward to hearing your initial reaction in the not too distant future! 

 

[andrew900nyc]

2 hours ago, meepmeepmayer said:

Good to know I guess

Don't forget the master of us all, @Marty Backe.

 

I tried to message @Marty Backe, but I'm only allowed two messages per day (because I'm a new member, I guess) and I already reached my maximum capacity for the day, so it looks like I'll have to wait until tomorrow to get in touch with him.

 

[eddiemoy]

This PEV sounds heavy.  I'm a little skeptical since you don't seem all that familiar with EUC's but you mention that your PEV will help EUC's and others?

100mph is terminal velocity.  I don't think anyone can go 100mph on an EUC.  Try going 100mph on a naked bike and you will understand what you are up against.  The wind really starts to hit you around 50mph.  100mph will be 4x the force or about your weight pushing you.  Have you seen what we stand on?  You have to be leaning pretty far forward to overcome those forces.

Good luck.

[meepmeepmayer]

2 hours ago, andrew900nyc said:

but I'm only allowed two messages per day

Gave you some upvotes, maybe that does something.

[andrew900nyc]

6 hours ago, eddiemoy said:

This PEV sounds heavy.  I'm a little skeptical since you don't seem all that familiar with EUC's but you mention that your PEV will help EUC's and others?

100mph is terminal velocity.  I don't think anyone can go 100mph on an EUC.  Try going 100mph on a naked bike and you will understand what you are up against.  The wind really starts to hit you around 50mph.  100mph will be 4x the force or about your weight pushing you.  Have you seen what we stand on?  You have to be leaning pretty far forward to overcome those forces.

Good luck.

This PEV is a bit on the heavy side, but it will have a motor with plenty of juice powering it. Not sure if you saw the motor I'm looking into in my previous post, but it produces 20kw continuous and 40kw peak!

I would be skeptical, too, if I had as little information to go on as I've provided to this forum so far. That's why I am attempting to assemble a team consisting of some of the most knowledgeable and trusted members of this community to offer their opinions on my invention and the marketing plan I have to promote it (and other categories of electric vehicles). 

100MPH is the aspirational speed I have in mind for the professional racing version of this vehicle. 100MPH may not be an achievable speed given the current technology, but it may not be too far off, so I think it is a reasonable speed to aspire to achieve. 45MPH is my targeted top speed for our prototype and initial production version. Keep in mind that the rider does not operate this vehicle in the same riding position as a EUC, so the concerns you raised about the force of the wind/drag are not the same with this vehicle as they would be when riding a EUC.

Thanks for the good wishes. I very much appreciate it!

[andrew900nyc]

5 hours ago, meepmeepmayer said:

Gave you some upvotes, maybe that does something.

 

Thanks @meepmeepmayer! 

[eddiemoy]

3 hours ago, andrew900nyc said:

This PEV is a bit on the heavy side, but it will have a motor with plenty of juice powering it. Not sure if you saw the motor I'm looking into in my previous post, but it produces 20kw continuous and 40kw peak!

I would be skeptical, too, if I had as little information to go on as I've provided to this forum so far. That's why I am attempting to assemble a team consisting of some of the most knowledgeable and trusted members of this community to offer their opinions on my invention and the marketing plan I have to promote it (and other categories of electric vehicles). 

100MPH is the aspirational speed I have in mind for the professional racing version of this vehicle. 100MPH may not be an achievable speed given the current technology, but it may not be too far off, so I think it is a reasonable speed to aspire to achieve. 45MPH is my targeted top speed for our prototype and initial production version. Keep in mind that the rider does not operate this vehicle in the same riding position as a EUC, so the concerns you raised about the force of the wind/drag are not the same with this vehicle as they would be when riding a EUC.

Thanks for the good wishes. I very much appreciate it!

I guess you are not aware that 2kw motor of the msx allow for 45mph today.  20kw motor?  There is a reason I’m skeptical as you’ve done zero research.  

[LanghamP]

Motorcycle riders do wheelies well above 100 mph, while Tesla (geared?) motors in their cars, so I guess it's technically trivial to do.

Is it really all that hard to hot-rod an electric bike if we really wanted to, especially if price wasn't a factor (nor should it if it is a prototype). Now, instead of a bike rider doing the wheelie, we'd replace him with a self-balancing control board.

[eddiemoy]

3 hours ago, LanghamP said:

Motorcycle riders do wheelies well above 100 mph, while Tesla (geared?) motors in their cars, so I guess it's technically trivial to do.

Is it really all that hard to hot-rod an electric bike if we really wanted to, especially if price wasn't a factor (nor should it if it is a prototype). Now, instead of a bike rider doing the wheelie, we'd replace him with a self-balancing control board.

Bikes are 300lbs.  You ever do a wheelie above 100mph?  Give it a shot and we can talk.  I've seen bikes fail at doing wheelies a lot less than 100mph.

[andrew900nyc]

6 hours ago, eddiemoy said:

I guess you are not aware that 2kw motor of the msx allow for 45mph today.  20kw motor?  There is a reason I’m skeptical as you’ve done zero research.  

You are correct that I was not aware that the msx can achieve speeds of 45mph within its recommended operating parameters. I was under the impression that the top speed of high-end EUCS’s were about 35mph or so.

Your claim that I have done zero research is inaccurate and seems a bit odd to me. I previously explained to you that the vehicle I invented (1) is heavier than a EUC, and (2) has a different riding position. If I understand you correctly, you seem to be implying that I’m considering the wrong motor for this vehicle. My question to you is: Since I’ve provided so few details about the vehicle, how on earth would you know whether or not I chose the proper motor?

Lastly, I am not concerned about having too much power for the prototype. We can always limit how fast it can go. However, since it will be operated on a racetrack, I am very interested in knowing the approximate top speed this type of vehicle will be capable of achieving and that’s the reason for the powerful motor.