Electric Bicycle Road Racing Theory (Original)

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I quote myself from the theory study guide:

Unlimited Power

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.

 

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Selling The Sport

I've been getting ideas from the Tour De France as it's becoming a major TV event these days. One of the controversies in the Tour De France is whether the use of onboard cameras, radio communication and other technologies are good or bad for the sport. In the discussions "on the tube" they arrived at the conclusion that more technology is better if it allows the audience a chance to get into the action.

In EBRR the best feature would be onboard video cameras for all the race bikes. If the sport was broadcast on ESPN or other major network you could make use of the onboard cameras to compliment the external cameras of the event. NASCAR has already taken this to an art form (as has INDY cars) and I would see no reason that all the technology couldn't just be transferred over.

The audience would be drawn into EBRR because the main race length is only 20 minutes long and that's enough for the attention span of a typical viewer.

Some accomodation to the TV format might be needed if you are trying to fill out a full hour time slot. Heat races could be used much like in Supercross racing to pad the time. Three heats, a last chance qualifier, and then the main is a nice format. (all edited with a cool soundtrack of course)

It's all about action... can EBRR produce video that people want to watch?

...and like in the Supercross or NASCAR series they build points at each race so the viewer gets to watch a sort of mini-series to see the overall champion selected.

Anyway... EBRR needs to be explosive and action oriented to get the ratings. This doesn't mean it needs to be like rollerball with bad rider behavior on the track, but a crash here and there does boost ratings. The viewer doesn't want to see people crash because of a foul, so the there is a vested interest in the profit motive to keep everyone playing fair.

 

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1000 Watt Limiting Issues

In the beginning as long as someone is in the ballpark of 1000 watts on the input side they would be allowed to race, but over time the need for greater precision will mean that some attention is given to this problem.

The first "issue" about a standard controller is that they limit current to some constant value. Let's do the math on that:

Battery Voltage 50 volts * Current Limit 20 amps = 1000 watts

...but our battery voltage is at the beginning of the ride when it's at it's highest and by the end of the ride let's assume the voltage has dropped to 45 volts. Now we have:

Battery Voltage 45 volts * Current Limit 20 amps = 900 watts

...so with any standard controller the power being allowed varies from beginning to end and it gets worse as the ride progresses.

What would be a better alternative is an "adaptive" circuit that could sense the active voltage and adjust the current limit to arrive at the desired overall power limit. So we would want:

50 volts ---> 20.0 amps
49 volts ---> 20.4 amps
48 volts ---> 20.8 amps
47 volts ---> 21.3 amps
46 volts ---> 21.7 amps
45 volts ---> 22.2 amps

...so racers will actually appreciate the adaptive circuit because as their battery drops in voltage they will get more amps to compensate. Hopefully the extra amps don't overheat their motor (a real problem) but at least having the extra power available would be nice.

The power input limit of 1000 watts should be non-changing from the beginning until the end of the race for all battery voltages.

Ideally the manufacturers would build controllers with this design. To my knowledge no one does this and all the controllers simply set a limit on the current that is constant.

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The effect of a changing voltage and current limit is to shorten the peak rpm of the motor and to lower the overall efficiency if it's designed to work best at peak voltage. However, the smart engineer will realize that he can "tune" his motor so that it works better later in the race so that the maximum performance exists over a wider spectrum.

 

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The Debate Rages On...

http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=20030&start=15

Over on ES they are still searching for good ideas for EBRR rules.

A weight limit is a natural performance limiter, and a natural way to force the choices in design that make racing and setting up a racing machine so exciting and fun.

The problem with weight limits can be quoted from the study guide:

Unlimited Power

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.

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Search back to the old days of 50cc motorcycle road racing. Over time all the racers were these little guys weighing 100 lbs. Unless you want a sport for genetically rare people (or children) going for a static weight limit is a very bad idea. "Indexing" body weight to bike weight might work, but then it's getting really complicated. The 1000 watt limit is so perfect because it allows for extra speed over pedaling alone, but does not overly spread out the acceleration potential of different riders because of their weight.

Face it guys... I've seriously thought this through...

 

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I say do it like F1 racing, use the tires as the limiting factor. Basically you can only go as fast as the tires allow.

This is the best "new to me" idea I've seen. This has a lot of potential because if everyone was forced onto the same tires then people could decide how they might make use of the traction they have available. Since EBRR is almost entirely about turning speed the most significant factor in the sport is how much traction you get on the road.

ES: Whiplash deserves recognition for good input.

But what size tire?

I run 24" x 3.0" road racing slicks and they give lot's of traction. Many people prefer 26" rims and thinner tires. It has potential as a rule, but it also constrains technological development early on.

Also, light riders will be able to turn faster because the relationship of weight to traction is what defines corner speeds. (so it still is favoring the lighter rider)

It still comes back to pedal power being the "Great Equalizer" when it comes to power. Heavy people tend to produce more power and so they equalize their weight.

The Tour De France on VERSUS has very deeply gone into into all the effects of body type to bicycle performance. Each body type tends to do better in different environments. For EBRR we want sprinters like Mark Cavendish because they are able to produce short bursts of power. (up to 2 hp just by pedaling) Lighter riders are better climbers. Heavier riders do better time trials. But overall the performance is more equal than different across rider body types. EBRR might give some benefits to the smaller rider if they can get a tighter tuck on the straight aways, while the heavier and stronger sprinter might gain coming out of a tight turn. It should even out.

The best way to look at it is:

"The 1000 watt rule primarily determines how much wind can be pushed by the motor alone."

...all other factors reduce back to normal Cycling conditions.

Respect "Cycling Wisdom"... they are a lot smarter than you think!

 

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Disconnecting From The Death Race

The "Death Race" was a blessing and a curse. On the positive side it was the first time that any type of functioning pedal machines got onto Go Kart tracks. On the negative side the gas powered machines are based on moped laws and so they are not in the same classification as bicycles.

In the early days of Harley Davidson the first motorcycles they produced were essentially bicycles with motors. They (Harley and Davidson) nearly failed until someone ELSE (forget who, but I saw a show on it) came in and redesigned the bicycles with stronger frames and components. At this point the motorcycle was born.

(note that this has "functioning pedals")

We are in effect "re-enacting history" only this time it's with electric power rather than gas power. Part of the reason that the board track "retro" look is popular is that the first incarnation of motorcycles came from bicycles. But we know the ending... over time with unlimited power the machines got bigger and faster and stronger until now the motorcycle road racer has almost nothing in common with the bicycle.

The "Death Race" helped to wake people up and get the dialogue flowing, but the next step is to discover where Cycling has gone for the last 100 years. The two philosophies diverged and the idea of EBRR is to reconnect them in a modern technological setting.

We need to remember we are to be racing BICYCLES and not motorcycles. We need to study Cyclists more and motorcycles less.

We don't want to be PINO.