Electric Bicycle Road Racing Theory
Electric Bicycle Road Racing Theory
The idea of this thread is to start with some basic principles and realities and build the sport of EBRR up from the roots. Along the way I will attempt to recreate existing arguments about electric bicycles that seem to recur regularly. This is to be made as a sort of college course... even though it's not really going to be taught anywhere. (well, you never know, I can remember some college courses at about this same level)
We begin with a review of bicycle physics.
An ordinary human being can (at best) produce 400 watts of power over a sustained period by pedaling. For short durations it's possible for peak athletes to achieve 750 watts of power going out the rear wheel. At about 30 mph the primary losses are due to air resistance, so it's very difficult to go faster than 30 mph by pedal power alone in an upright bicycle.
The electric bicycle was created as a "bicycle" replacement or enhancement. In order to retain a definition of "bicycle" we need to accept that motor power cannot significantly exceed human power. This sets a realistic upper limit of 750 watts (1 hp) as the boundry.
The first major point is that even BEFORE we look at the laws pertaining to electric bicycles we are already more or less bound to a limit of 750 watts simply because it what makes us within the definition of a "bicycle". Going significantly above this level and you are into motorcycle or moped territory.
Europe - 250 watts output
Canada - 500 watts output
USA - 750 watts output
The USA is allowing the logical maximum for a "bicycle" while the other nations seem to cut the limit down to something less than is within the accepted understanding of a "bicycle". This is unfortunate, but what we have to work with.
Since we are discussing "pure forms" in the abstract and we see that in the most pure sense 750 watts is the logical limit for an ebike we simply state that 750 watts is the "proper" level to establish as a worldwide standard for Electric Bicycle Road Racing. Since racing would be done on Go Kart tracks and these are not regulated by street laws there is no reason not to set the level worldwide as 750 watts. (that way in the future if you have the World Cup equivalent of EBRR then everyone is using the same limits)
So the "bottom line" is that laws exist and some are compatible with racing while others are not. In the USA it should be easier to produce machines that can be used on the street as well as the track, but in much of the world these machines would be sold as "off road only".
Motor Input verses Output
We know that at tax time we report our income and then deduct certain things before we actually calculate our taxes. Motor Input verses Output works the same way. Laws are written to limit the "Output" of a motor, but make no reference to what "Input" was required to get there.
A typical motor is about 75% efficient. This means that if you start with 1000 watts of Input power that you will get approximately 750 watts of real Output at the rear wheel.
Given the physics involved and also that fact that it's nearly impossible to limit Output directly (it's always something that is arrived at "after losses") the logical way to organize racing is around an Input side restriction.
So if we want approximately 750 watts Output, then we limit the Input to 1000 watts and we simply allow that through the process of motor losses we arrive at the desired result.
This is a critical insight, because if it's possible to electronically calibrate the precise amount of power going INTO the motor we can have a class of racing that is fair. With a simple meter on the Input it's possible to define a class of racing very tightly.
1000 watts of Input is the logical definition of EBRR.
It's always important to review each and every other argument for how to organize racing classes.
The most natural urge is to want to allow Electric Bicycle Road Racing to use as much power in the motors as the designer can achieve. On the surface this even seems like a good idea until you start to anticipate where the designs will naturally progress. If you can increase motor power on an unlimited basis you will also need to increase battery capacity to feed this higher power level. More battery means more weight and that means a stronger frame and possibly suspension to make it usable. At some point the machine resembles a motorcycle only it retains "faux pedals" to satisfy the bicycle definition. An acronym PINO (Pedals In Name Only - "Pee No") describes this type of machine.
The next logical step is to limit the overall weight of such an overpowered machine so that a limited battery weight places a self induced restriction on effective power usage. Let's say the bike is limited to 100 lbs overall. You now have a situation where a 150 lb racer has a 50 lb advantage over a 200 lb racer because the bikes are limited to a fixed amount of weight.
In order to still try to salvage this approach you have to figure out some sort of indexed relationship of power, body weight, and bike weight to equalize things. It simply gets too complicated and no one will perceive it as being fair.
With a 1000 watt power restriction the rider's pedal strength will tend to match their weight (if they are athletes) so the heavier rider can compensate by being stronger. This nullifies weight differences during accelleration. (though when it comes to top speed aerodynamics the smaller rider probably glides better)
Battery Capacity Limits
Another approach to equalizing the racing is to set a limit on the battery capacity without regard to it's physical weight. This allows all the bikes an equal overall quantity of power but alters the way people will operate their machines in a race. Rather than an all out sprint where the racer applies full throttle whenever they can the Battery Capacity Limited racing will favor those with a smoother riding approach so that less energy is wasted getting around the track. While we can applaud the ideal of increased efficiency, if the effect is to take the passion from the racing experience the psychological negatives tend to make this less attractive. However, there are special cases where this could make sense. (fragile streamliner recumbents for instance)
To date these are the main alternative approaches to ebike racing.
There are several broad categories of people that have fairly clearly defined perceptions and opinions about ebikes.
The pure cyclist simply will not allow a single thought towards electric bikes because it's a violation of everything that the cyclist holds dear.
The Senior Citizen
Many Senior Citizens view the electric bike as a "mobility device" for those who are by now too frail to get around under their own power. In this view the electric bike is a sort of wheelchair. This person will guard the low speed image of ebikes and oppose anything that gives a racing perception.
The outlaw is someone that knows the laws on the street, but just completely disregards them in favor of whatever power they can achieve by their own bike modifications. When presented complicated issues about how high powered ebikes fit into the larger scheme of things their response is "I do whatever I can get away with." This person might race, but possibly in some other racing category. To the outlaw having a 1 hp power limit seems confining.
If you are shopping at WalMart for childrens toys you will come to realize that within the store bicycles are classified as "toys". They sell some electric "toys" such as scooters, pocket bikes and even ebikes. The parental perspective is that ebikes are more or less silly toys that you get your child for xmas, but that they will grow out of them quickly so you shouldn't pay too much or worry too much about quality. The parent will be a little worried about something that appears too fast, so the 1 hp power limitation will provide some comfort to help them decide to purchase an EBRR bike for their child.
...the target demographic for Electric Bicycle Road Racing begins at about the age of twelve and fades out at about thirty much the same as in BMX. (this isn't to say that some older folks might not like it too)
What will make Electric Bicycle Road Racing unique?
Cycling already provides numerous excellent racing styles that demand athletic performance of their racers. Motorcycle road racing already gives the rider skill thrills of riding at the edge of traction.
Part of the reason that newer sports like Mixed Martial Arts have taken hold is that they took the best of several other sports and blended them into something that brings out the best of all of them. That same mindset needs to be used in EBRR in that the top level racers need to have mastered all elements of the sport to succeed. There can be no room for the out of shape racer if EBRR is to be considered a real sport.
Walk Through A Race
Let's walk through a typical race...
At the start riders are lined up in rows of two (ideally) based on heat races or best lap times which were decided in advance. The faster riders are placed at the front. To get a fast start the rider needs to stand up and pedal explosively off the line because below 30 mph aerodynamic effects are small. Once the rider gets up to about 25-30 mph it makes sense to drop down onto the seat and tuck behind the fairing to increase top speed to near 40 mph. This is taking place on a Go Kart track that isn't going to allow top speeds for very long, so just as you are hitting your top speed you quickly need to brake for the upcoming corner. In the corner you ride the very edge of traction and both tires may drift a little. Depending on how much speed you lost in the corner you would either stay in the tuck and use all motor power or you might stand up again and get another burst of pedal power.
Different Go Kart tracks are going to stress different racing styles as the tighter tracks will reward more frequent bursts of acceleration coming out of the turns while other faster tracks will reward more time in a tuck for faster top end speed.
Drafting will be a big factor in this sport as it is in Cycling because at 40 mph the aerodynamic wake is much larger than at the 30 mph level that most Cyclists are used to. This means that the rider in second place on a straight away will almost always have passing power coming into the next turn. This means that the racing will be very intense with a lot of chances for passing.
At this point it's important to bring up the notion of "fair play".
You simply cannot allow dirty tactics into a sport like this because it's simply too easy to disrupt another rider and cause a crash. While in many cases the dirty rider goes down with the innocent anyway the sport suffers if there is no authority to penalize foul play. Riders should be stripped of any win if they intentionally cause another rider to crash and if they repeat that behavior that rider should be banned from the sport.
What about doping?
I don't think that doping would be a big issue in this sport. Even if some guy is using steroids it will only benefit in the acceleration portion of the sport and that is not so dominant as to make for instant success. While there might be problems down the road with doping it doesn't seem important for now.
There will be an absolute need for precise power limiting circuitry to ensure that no one exceeds the 1000 watt input limit. Anyone caught tampering with the circuit (which needs to be supplied by the racing organization) would get an instant penalty of some sort. For the early days of the sport there will be the need to accept less precise limiting techniques (like just using known 1000 watt controllers) but over time that will need to be made more strict to ensure fairness. (*see next posting)
Distance and Duration
The length of the race needs to be compatible with the amount of battery that is used. We calculate battery size:
Power input restricted to 1000 watts per second = 1000 watt / hour (Wh)
So if the race lasted a full hour at full throttle you would need a battery that was something like 48 volts and 21 Ah. In order to lower the battery requirement it would be preferred to shorten the race to about half an hour which would drop the battery required to:
1000Wh / 2 = 500Wh
...and this can be achieved with a 48 volt and 11 Ah battery.
Lead Acid (SLA) ~ 50 lbs (Peukert's Effect requires 20Ah)
NiCads ~ 30 lbs
NiMh ~ 20 lbs
LiFePO4 ~ 15 lbs
Rider ~ 175 lbs
Bike ~ 55 lbs
SLA = 50 / ( 55 + 175 ) = 22%
LiFePO4 = 15 / ( 55 + 175 ) = 7%
As long as the race duration is kept low the battery is reduced in it's influence on the race outcome. However, just like with being overweight the more athletic rider and the lower weight battery will have an advantage. As with Cycling the quest for lighter and lighter machines will guide technological progress in the sport, but the shorter distance will tend to place a cap on battery costs. The sport needs high technology, but should not only be about technology.
How far is half an hour?
We assume that the average speed is about 30 mph. Half of 30 miles is 15 miles so we calculate that the maximum distance should be LESS than 15 miles.
A realistic track length would be 10-15 miles.
A realistic race duration would be 20-30 minutes.
Could someone fix that last post? I'm new and didn't realize you can't edit the first posting. Looks like I missed a [/b]. You can then delete this posting after.
It sounds as if you're already having a vision of a specific race series...? Or is this "hey, wouldn't it be fun to race electric bicycles"?
I agree that high power electric bicycles make you scratch your head and think "Motorcycle" .. see: http://visforvoltage.org/blog/reikiman/9320 for a blog post about this.
But at the same time it's possible to draw some ideas from motorcycle racing.
a) multiple race classes
b) rule making authority
c) race promoter
d) bike & rider qualifications
In motorcycle racing they have multiple classes for some of the purposes you name. Each class is made of evenly matched machines, so that the given race is more of a competition of human skill than it is of technical capacity of the machines. For example there could be a European e-bike class made up of bikes which would be road legal in Europe.
I disagree that race officials should be in charge of supplying electronics and batteries. A very useful goal should be to incentivize R&D of electric bicycle drive train technology. See Electric motorcycle racing speeding up electric vehicle technology development for my take on the value that racing can have to speed up technology development. One way to put it is - while splitting bikes/riders into multiple classes is meant to have an evenly matched field, an aspect of the competition can/should/could be the technology each team develops.
This formula is (I think) true in all forms of racing. That teams are developing technology, seeing how far they can push the technology, and the competition is partly challenging the people and partly challenging the machines.
By the way - the history of V is for Voltage includes some races which were held in 2003 and 2004. These were organized by the guy who originated the "V is for Voltage" name, and who ran the forum which preceded this instantiation of V is for Voltage.
The format of those events weren't a speed race, but instead an uphill climb (for speed). Climbing uphill is an interesting challenge for electric vehicles.
It could be fun.
Modded XB-600's banging around a short pylon track in an empty parking lot.
I'd do it
I disagree that race officials should be in charge of supplying electronics and batteries.
Well, batteries would never be supplied, but a "meter" that precisely limits input to 1000 watts is the way to ensure that everyone is operating within the same power regime. This would be sort of like "restrictor plates" in NASCAR where everyone gets the same amount of power. People could supply their own, but there needs to be some way to verify that it's in place. The R&D becomes about increasing efficiency with the input you are allowed to have. Actually, most all forms of racing have some static limit (like CC) and then the builders find ways to get more out of that limit.
The real problem is PINO ("Pedals In Name Only" - "Pee No") if you allow power significantly above that a human could provide. Some of the ebikes already are producing over five horsepower and that's already a moped as far as the law is concerned. (so many have already gone PINO) So I think the first step is to get out of this sort of "make believe" land of unlimited power for ebikes.
My "vision" of this (and I've been at it since 2007) is to advocate / participate in the creation of a new sport that produces viable products that real people can by. I want to see street legal and EBRR legal road racers in every garage across the country and around the world. Without the 1000 watt limit the entire "vision" collapses into something for "Do It Yourself" garage projects and I don't want to see that happen.
1000 watt input limit - Legal, mass production, mass appeal. (potential for huge growth in the millions of ebikes sold)
No power limits - Not legal, not mass produced, no mass appeal. (no real future)
1000 Watt EBRR Power Chip
In order for EBRR to become a reality it had been missing an essential piece of technology. Since ebikes vary in their power output it's necessary in order to achieve fairness to have some means to limit the power of the ebike to 1000 watts of input.
In the earliest days of circuit design people used analog circuits cobbled together so that voltage and current were combined to produce an approximate power result. I say "approximate" because analog circuits tend to be inaccurate. This earliest design has fallen completely out of favor.
The next step was to switch to a digital conversion process which also lost precision due to the conversion of analog to digital signals. While the digital technique was an improvement over the original analog approach it still was combersome and inaccurate.
The most recent concept is to use modern chip fabrication techniques to precisely control the creation of a dedicated chip using analog techniques to arrive at a power figure. Since chips can be produced to very high precision they can actually minimize the inaccuracies at the source.
4V to 80V High Side Sense, 100V Max
The LT®2940 measures a high side current and a differential voltage, multiplies them and outputs a current proportional to instantaneous power. Bidirectional high side currents and bipolar voltage differences are correctly handled by the four-quadrant multiplier and push-pull output stage, which allows the LT2940 to indicate forward and reverse power flow.
An integrated comparator with inverting and noninverting open-collector outputs makes the LT2940 a complete power level monitor. In addition, an output current proportional to the sensed high side current allows current monitoring. The current mode outputs make scaling, filtering and time integration as simple as selecting external resistors and/or capacitors.
12/15/2009 9:33 PM EST
Milpitas, Calif. Linear Technology Corp. has introduced the LT2940, a power and current monitor for 4V to 80V systems.
According to Linear, the LT2940 provides the necessary circuits to accurately measure, monitor, and control power in situations in which both the current and voltage may vary due to supply voltage uncertainty, component parametric changes, transient conditions or time-varying signals.
Unlike traditional power monitors that rely on data converters and multiplying registers to calculate power, the LT2940 uses a true four-quadrant analog multiplier that results in what the company says is a 5% power measurement accuracy and 3% current measurement accuracy, ensuring that boards and systems achieve optimum power efficiency and reliability.
The LT2940 is suitable for use in line cards and servers, power-sense circuit breakers, power control loops and a wide variety of metering applications.
Pricing: Starts at $2.05 each in 1,000 piece quantities.
Notice that the chip came into existence not long ago in Dec 2009.
The first idea I have from reading this is "Spec Series." Everyone would have the same bike, the same firmware, etc. This becomes a rider's series, theoretically noone would have a technical advantage. The problem in trying for an unlimited series is they can already build a bigger and better bike than you're describing, no need for engineering/R&D.
Pedal assist can offer many interesting events; A streetbike LA to SF/Tour de PCH., sunup to sundown. A mountain bike for the Baker to Vegas run. And of course a boardtrack racer. Not much demand for classes beyond that to start, as there won't be all so many people showing up. Besides, you have what? The 500 watt class, the 750 watt class, etc. Not much difference really.
Autoracing tries to stick with what they consider to be relevant to street car transportation, although the cars can be far too esoteric to seem as though there's a correlation. In the late 60's Indycar racing banned the gas turbine and 4 wheel drive under the claim that they wuold never catch on in commercial vehicles. Next thing you know, there's all wheel drive. They don't always get it right.
So racing an electric bicycle is not going to capture the imagination of the fans right off. Doesn't conjure the romantic images of the AHa music video for 'Take on Me.' Naybe the site of some desert hillclimbing on the mountain bikes will change that thinking. But I think the popularity itself would be an uphill climb.
The first idea I have from reading this is "Spec Series." Everyone would have the same bike, the same firmware, etc.
Let's think of recent history...
NEDRA (National Electric Drag Racing Association) was the first to introduce the idea of Voltage Limited racing.
ePower (Portland International Raceway) introduced the idea of ebike racing (mostly recumbents) using Battery Capacity Limiting.
There is a Go Kart track in Arizona that allows races for both Cyclists and also Motorized Bikes, but on different days because the groups hate each other. They will likely allow Unlimited Power ebikes on the Motorized Bike days.
We have seen a multitude of electric motorcycle road racing with Unlimited Power.
What we have been missing is the concept of a Limited Power class much like you might ride in the 125cc class or the 250cc class in motocross. Most of the classes so far have not attempted to set any limit on the peak power consumption, however, ePower does require that all motors be rated as 1000 watts or less.
The "new breakthrough" from the electronic perspective is that this new chip opens the door to practically doing a Limited Power racing class.
A major misconception is that you need a special bike for any of this. With the Limited Power chip attached to ANY EBIKE it would perform as desired... so the openess of this concept is actually one of it's strongest arguments.
Any ebike could race... as long as they insert the chip between the battery and controller and connect it to the throttle it will even things out.
It just makes no sense to have 10hp ebikes because at that point they really are motorcycles in disguise. Better to simply limit the power to 1hp (1000 watt input / ~750 watts output) so that the "bicycle" aspect is recognized.
Is an ebike a "bicycle" or a "motorcycle" seems to be the point of confusion... I'm saying that it's still a "bicycle" while others want to sneak into the "motorcycle" definition.
Above and beyond all this is the aspect of practicality. If an ebike racing league is designed so that the bike can only be ridden on the Go Kart track, then you have a very small group of potential customers if you want to sell products into that market. On the other hand, if the Electric Bicycle Road Racers are designed to be still legal on the street then you can sell millions to anyone and they can ride the bikes around their neighborhoods.
So the biggest argument is really about mass production and wider mass appeal.
"An EBRR bike in every garage." ...might be the motto.
The Mental Checklist
The mental checklist for EBRR might go something like this:
Q: Do you expect to get a license to use an EBRR bike on the street?
A: If "No" then EBRR with power limiting will allow you to ride on the street as well as on the track. It's illegal in most states to have more than 1hp ebikes and they cannot be sold as being more than 1hp without legal problems.
Q: Do you want to go 100 mph?
A: If "Yes" then you are in the wrong sport and need to look into motorcycles. If "No" then EBRR is just fine. Top speed for EBRR should be about 40 mph on the flat based on 1hp and good aerodynamics. This compares to about 30 mph for Cycling.
Q: Do you hate Cycling?
A: If "Yes" then you aren't EBRR material. EBRR is still an athletic sport and does require that you pedal with authority at times.
Q: Do you live near a Go Kart track?
A: Since there are Go Kart tracks in every state in the US and in just about every country in the world there are plenty of places to hold EBRR races. So if "Yes" you are in luck and that's most everyone.
...I could go on, but the point is that EBRR is not attempting to compare itself with anything already in existence.
Sad Demographic Realities
America is obese... and it's not just adults, but even the children are obese. In the Southern states it's worse because of the weather, but across all the states people have gotten fatter recently.
Ebike riders tend to follow the national trends and are often even worse off as many take up the hobby because of advancing age or poor health. Overall the base demographic to draw from for a sport like EBRR is pretty grim.
Cyclists are abnormal because they buck the obesity trends and so they are actually the ones who best represent the future of any kind of athletic sport. Cyclists who would consider electric assisted racing might be rare though.
The core "problem" as I see it now is that if you expect any type of racing to emerge "organically" from out of shape Americans that it will tend to mirror the trends of those that are into ebikes now.
Unhealthy people will want sports that unheathly people can do.
So I'm aware of the disconnect between present reality and "ideal" future reality. The present unhealthy demographic is not very good raw material to get anything started.
Business is always Conservative By Nature
When Shimano made the corporate decision to get into the electric bike motor market they did so in the most conservative way possible. Their Steps 250 watt motor is the lowest common denominator across the worlds legal standards. In the US you are allowed three times as much power, but if Shimano chose to build a 750 watt electric bike motor they would be limited to sales in the US.
This should make us think...
If EBRR is to be a success you can't expect major corporations to fund the mass production if they perceive the investment as "risky". Any EBRR racing class that goes above 750 watts (1000 watt input) is going to alienate the world of mass production and the real people that lose out is the general public.
Business is conservative, it will never support racing that can't be sold anywhere.
P. I. N. O.
"Pedals In Name Only" - "Pee No"
...this has a top speed of 50 mph, but is it really a bicycle?