A dummy's guide to electric motorcycles

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Electric_Motorcycles_Dummys_Guide.jpgConfused by all the new words we have to use when we talk about electric
motorcycles
? We are too, but luckily we noticed that one of our
commenters (Brett Vegas) was throwing around amps and volts in an
intelligent manner and managed to convince him to share his wisdom with
us in article form. So here you go, everything you ever wanted to know
about electric motorcycles, but were afraid to ask. >

Amps and volts: nuts and bolts
Some metaphors liken voltage to the size of a pipe and amperage to the flow through the pipe. Electricity does not flow like water, so that metaphor can only take you so far. In motorhead terms amperage = torque and voltage = revs. Even that is still a metaphor(and only true for DC), but it is closer to what a motorcyclist cares about. The really important thing is that amperage and voltage are multiplied together to get wattage (power) and, with a factor of time, gives you horsepower, which is really what  motorheads care about. 740 watts-per-hour = one horsepower, but, with motor and driveline losses, you can usually say that one kilowatt-per-hour = one horsepower.

Update: Wattage is equal to voltage multiplied by amperage, but those sneaky electrical guys hide time in amperage (A = coulombs-per-second). When you look watts = volts x amps, it appears there is no time factor, which would mean that it is not a measurement of power, but it is there, which is why you can freely convert kilowatts to horsepower (746w = 1hp). Mechanical power is defined by moving an object at a given rate in a given time (~550lbs, 1ft vertically in one second), electrical power is sorta counting how many friggin’ electrons are flying by, in a given amount of time. Electrical power is not  mechanical power, until you actually turn a shaft with it, its power but with a little different definition. My mistake.

Horsepower is a measurement of power over time, wattage is a pure power measurement, it has no time factor.

The first thing that anybody does when looking at pretty pictures of a new motorcycle is see how much power it makes. On Internal Combustion Engine (ICE) bikes thats easy, stick a dyno on the motor shaft or the rear wheel and you can see how much power it makes. In fact, there are rules that make all manufactures do that in the same manner, so the numbers are pretty trustworthy. Electrics haven’t gotten there yet, for some reason (Where the hell is SAE when you need them?). They are all rated by controller output, the power, in watts, going to the motor. Until a magazine sticks the bike on a dyno, it is sorta hard to compare the electric to the gas, the electric always ‘looks’ like it has more power than it makes.

So what difference does having greater or less values for voltage and amperage? I can answer that better by going into motors a bit.

Motors: the bit what turns or AC/DC rock and roll
Most of these silly little bikes use a DC motor, except the KTM Freeride, which is an AC motor, which nobody in the press seemed to pick up on, kinda like not noticing if a bike is twin or a single (no offense to the members of the press!). What’s the difference? Hmm, perhaps I should define some motor types and move from there.

Direct current,or what we got for now:

Permanent magnet brushed direct current
Permanent magnet brushed motors are what the Zero, Quantya, Ekrad and most other high-power bikes are running. They are rugged, simple and easy to do. Motor and controller are off-the-shelf. Cydric Lynch from Agni invented the motor everybody is using, which is now licensed to a number of motor producers. It is notable for being a ‘pancake’ type (as opposed to a ‘can’ type). In low voltage applications nothing comes close for power-to-weight. It’s limitations are mainly that it cannot be revved over about 4000-5000rpm (and power for a single motor is about 20kw peak), and it is not quite as efficient as a BLDC. It is a large diameter rotor and low resistance, so this isn’t a really big deal. The rotor consists of windings(with the lynch-type, bus-bars), and the magnets are stationary on the case. One disadvantage of DC motors is back-EMF (electromagnetic field). As the revs go up, the motor is less and less able to conduct current. The torque curve falls off as revs rise.

Brushed series wound direct current
Series wound motors don’t depend on magnets, instead they establish the magnetic field with an additional set of windings. There are no permanent magnets, but they still use brushes. The motors are sorta lossy, but since there are no magnets they have a great ability to pull current, though it makes them bad for lower power applications. Starter motors in engines are a common use of series wound motors (my beater DR400 has one attached to the magic button on the bars). The most notable bike using series wound motors is the Killacycle, which recently ran under 8 seconds in the 1/4 mile at 168mph.

Brushless direct current (BLDC)
Brushless DC motors are a little strange. The magnets are mounted to the rotor and the windings are stationary. DC power is delivered via commutation (a timed reversal of polarity). They tend to have great efficiency, but a lesser ability to deliver current and a lower power-to-weight ratio than traditional brushed motors. R/C airplanes are a common use of brushless DC motors and most modern cars have started (no pun) using them for starters. They tend to have more expensive controllers. The Brammo Enertia and the Vectrix both use a permanent magnet brushless motor.

Alternating Current: or the real deal

Permanent magnet Synchronous AC
PMS-AC is a motor type very similar to a BLDC, it has magnets mounted to the rotor, with the windings stationary. The difference is that AC varies speed with frequency (usually 0-400hz) instead of voltage. This means full voltage and amperage can be applied at all speeds. The motor still suffers from some of the same problems that a BLDC does, they are current limited and overheating can demagnetize the magnets. Not as common as BLDC or series wound, PMS-AC are prized for the ability to control speed precisely. No back-EMF. Common use is in servo, and CNC applications. Not an ideal traction motor, but better power-to-weight than a BLDC. The KTM is using a permanent magnet synchronous AC motor.

Induction AC motors
Finally, the king of motors. Induction AC motors don’t use magnets, the magnetic field is created in the rotor by induction. If I said I knew what that means, I would not be entirely truthful (especially three-phase; totally hurts my brain). Suffice it to say that only a true madman like Nikola Tesla could have invented such a motor. Because there are no magnets and the more power you push into the motor, the more powerful the magnetic field, they have all the advantages of brush motor and brushless, without the drawbacks. No back-EMF.  Induction motors are used in everything from turning the screws on aircraft carriers to turning the drum on clothes dryers. That said, it is not the easiest motor to use for motorcycle applications. The controllers are fussy, they require really good software to run the motor right. The industrial motors do not have good power-to-weight. There are not many bikes with induction motors, Electric Motorsport offers a low voltage one and the overweight, overpriced Mission One is indusction too. The most notable example of an induction motor in motorsports is the Tesla car, the motor is made by Alan Cocconi of AC Propulsion. Very cool motor, pretty much flawless.

Back to Power
So, knowing a little more about motors, lets compare the Zero with the KTM. The Zero is a low voltage/high amperage drive system (58v@300a), the KTM is a high voltage/low amperage drive(300v@75a). Nearly perfectly inverted numbers, kinda funny.

On paper, the KTM should walk away from the Zero, it has 20% more peak power, and is running AC (no back-EMF to speak of). The reason I hesitate to say that is another spec that is considered when looking at motors: continuous power. The Agni DC motor is rated at 10kw continuous, the KTM is rated at 8kw continuous. This means that over time the Agni is better able to pull power without overheating. Very hard to judge which is better, the Zero will have a higher top speed, but perhaps less punch than the KTM.

The continuous power rating is why an electric has a low top speed despite having enough peak power to go faster, if you gear it up the motor won’t make more power past its continuous rate. A 10kw rated motor can make no more than 10kw in an hour, even if it can momentarily make twice that. An engine has no continuous rating, peak and constant are the same, sorta. If you run a high performance engine at full power all the time, they wear out much faster than if you ride like an old lady (which is how I ride).

A motor acts like an engine of its continuous rating as far as top speed goes, but the punch is the peak power and can be two or three times the continuous rate. Thats why they holeshot like mad, but fall back on a straightaway.

Personally, I am waiting for one of the big three to give Alan Cocconi a million bucks, and have him put together a scaled down induction motor for a dirt bike. Sure, you could get to 450′s power levels with two Agni motors or two of the motors that KTM is using, but a single larger induction motor is better. Sooner or later, someone will stick a high voltage AC induction motor on a bike, that could be what we’re all waiting for.

– Brett Gober

Who is Brett Gober?
Brett did the design work  on the Electricmoto Blade in the fall of 2000. He can take the credit (or the blame) for being one of the first people to think that electric power and knobbies are a good mix. The bikes never sold all that great, but he likes to think that he had an influence on the motorcycle industry in general. After building bikes, he built cars at Brammo; the Ariel Atom in Jay Leno’s  garage was welded up by none other. Brett currently work for Ravensclaw Inc., building high end film camera heads. Brett says he doesn’t know a lot about anything, but he does know a little about electric vehicles

  • Lombardo Joe

    Hmmmm…. I don’t know how I’d feel about having a quiet ride…

  • Woody

    Good write-up Brett, It was very informative. Now I know to get a little stoked if I hear a new AC induction bike is coming out, even though I can probably never afford it.

  • s0crates82

    stellar article.

  • smokin88lx

    I did test ride a Vectrix at the Long Beach Motorcycle show and have to say I could get use to the lack vibration and noise from an ICE really fast.

  • Ray

    It’s been a while since I read an article on a blog and felt like I learned something my wife would be impressed to hear (even if it went over her head). Thank you.

  • Sean Smith

    Neat! A real deal gearhead who knows what he’s talking about s’plaining electricity to us.

  • http://www.motorsportretro.com rich

    Thanks for a great story. The whole electric bike deal does need some explanation!

  • Kevin White

    Posting on Facebook!

  • Darth Lefty

    Could you please go over the “watts-per-hour” part again? Because… well, the rest of your article is good enough that you shouldn’t have a mistake like that starting it off.

    • DoctorNine

      Give Brett a break, Darth. You know he meant watts applied for an hour, or watt hours. The problem with English, is that the word ‘per’ is used in physics specifically to mean a division, but general usage can mean an amount applied for a given time. And anyway, I much prefer use of the term kilowatt hours instead of the technically preferred megajoules, just because that’s what I’m used to reading on my electricity bill…

    • steve781

      2nd the motion to revise the Watts, Watts per hour, and Hp description. Otherwise very nice. Oh, and 3 phase isn’t hard. Once you get your head into it 3 phase is the easiest to work with. In heavy industrial applications speed regulated single phase AC is never an option.

  • jules

    Thanks for this article!!!! even though it’s in english, i have understand how electric motor work better than all french blog i ever see!! :)

  • Richard Gray

    The metaphor should compare voltage to pressure and current to flow rate. Both watts and horsepower are units of power which when multiplied by time give the work done (e.g. kilowatt-hours).

  • noone1569

    Great article. Pieces together a lot of the information out there on e-bikes and lays it out there so one can understand.

    Forwarding to my bueller buddies.

  • HerbL

    Nikola Tesla? Induction AC motors? Yup, if Tesla was involved in the invention, my guess it would be the way to go. All hail the future!

  • Random

    Would gas or ethanol powered, electric motor bikes be more efficient than current ICE powered bikes? That seems the direction cars are taking (even if they say it’s an intermediate step while battery technology improves).

    Given the current limitations in energy density in battery technology I wonder if it’s best to go directly to battery and (AC please!) motors or to adopt that step with combustion or fuel-cell energy providing energy to the electric motor.

  • Brettvegas

    Well, pretty sure horsepower=power/time, and watts doesn’t have any time component. It is just power, which is weird, it is just volts*amps, nothing else. watt hours is an energy measurement, watts/time=horsepower, If that makes sense. Energy/time=power
    And, yes, I am just a dumb redneck, thats know JUST enough to be dangerous…
    You can freely convert horsepower to KW, but it pays to realize that KW does NOT have a time component, and so is a little less of a true measurement of power.
    I hope that makes it a bit more clear, yeah that bit was confusing in the article.

    Oh, I sorta get induction motors, but DC is damn easy, and other than having it flawlessly turn the spindle on my HAAS at work, I have never worked with one.

    • steve781

      I think I see the point where we differ. As was beaten into my head long ago, it is easy to mix up “power” and “work.” “Work,” as defined by people smarter than me, is the same as energy, be it Joules, Btu, calories, etc. For example, it takes a given amount of “work” to move a boulder up a hill. “Power” is the rate at which work is done, or how fast you rolled the boulder up the hill. If you can roll the boulder up the hill very quickly then you have more power than someone who rolls the same boulder up the hill more slowly. But either way the same amount of work was done. If you multiply power by the time you exerted the power then you get work again.

      Watts are a measure of Power, just the same as horsepower. That is why your lightbulbs, microwave oven, and stereo amp are all rated in watts. A watt is a Joule per second. Just to make it easy on the rest of us, somebody smart defined amps and volts such that 1 amp times 1 volt equals 1 watt.

      Simplified example: A motorcycle with a 5 KWatt motor, running continuously at max power, runs up a mountain in 1 hour. Total energy expended (work) is 5 KWatt-hours. A different motorcycle with a puny little 1 KWatt motor runs up the same mountain in 5 hours. Total work done by the little bike that could is again 5 KWatt-hours.

      Prof Steve mode off.

    • Mike

      Glad to see the units thing didn’t turn into a fistfight; it is, as Brett said, critical to understand how the various numbers relate to each other as well as understanding the limitations of the measurement process.

      Many thanks also for the rundown on the state of the art re: motor design.

      A comment on alt-fuel bikes for the folks asking. Fuel is just a way of moving energy around; you have to ask about the cost of capturing the energy in the first place, as well as the byproducts of extracting it again.

      My understanding of volume ethanol production in the USA is that it’s tied to the corn industry, and the energy efficiency of the process is very low (vs. eg. the Brazilian example where it’s obtained relatively cheaply via fermented sugar cane). The overall math for corn ethanol is bad due to the large amount of heat input in the drying phase.

      The ‘fix’ here of course is to give up on corn and move to a more suitable fuel crop, but that gets political…

      • s0crates82

        It’s only political if you’re talking about using food crops to make fuel. If folks used non-food crops like hydroponic algae or something, it wouldn’t be an issue.

        • Mike

          @socrates: Actually, I was referring to the fact that anything related to corn in the USA comes back to Monsanto and government subsidies for the corn industry, at which point the conversation turns particularly ugly.

          Hemp is a bad ethanol source too; ignore the hopeful stoners. Sugar beet/cane isn’t bad. Miscanthus or switchgrass seems to be a pretty solid bet though, eg.

          http://www.swivel.com/charts/2758-US-Gallons-of-Ethanol-acre-of-crop

          Miscanthus is a killer on the biomass per unit area front, but switchgrass is a US native and so there’s an ecological argument to be made for using it as a lower-impact species. Both of these are dependent on improving the cellulose->ethanol process; if you pass on that, then the sweet crops (sweet potato, sugar beet/cane) are the best option currently.

          Also, another vote for anything you might care to write on the battery issue, and if you know anything about the state of the art in terms of controllers (even just who is doing what and why) that’d be fascinating as well.

          Thanks!

  • brettvegas

    Random,
    I dunno, most of the problem with hybrids is packaging, make it a light motorcycle, it becomes a packaging nightmare. I could see doing a very small engine,with an electric system. It would have to be done very well to actually be better than a pure ICE.

    Fuel cells are mostly an investor scam(imho), at this point. We won’t solve anything having everybody require a chunk of platinum to get around. Huge technical obstacles, farther off than more energy dense batts…

    Oh, thanks for the thumbs up(those of you with your thumbs up!), I had fun writing the thing, and with a few more people yelling, maybe we will get that induction motor…

    • Random

      Thanks, Brett! Nice article.
      Electric do seem to be the way to go (and I even like the tie-fighter-like sound on high performance electric bikes) but range still seems a great problem. Not a fault of the motors, of course, but still a limiting factor.

      Here in Brazil the mean travelled distance by bikes is big, lots of couriers in towns too (and they ride the whole day), so low range would’t sell very well – meaning factories may not bring these nice bikes here. Ethanol, however, is in every corner and a (possibly more efficient) hybrid may be a good alternative (if someone develops them at all).

  • JLove

    Probably a newbie question but I’ll ask anyway. Would there be any advantage to running 2 different types of motors with 2 different controllers? Kinda like a twin turbo set up on a car. One for the hole-shot, one for the top end. Obviously complexity and weight are the biggest hurdles I can think of.

    • Brett Vegas

      jlove,

      Nah, don’t think so. DC brush motors launch like mad, it is almost a problem(builders put in throttle ramps and such, I always liked it), but the mid-range and top-end are limitations. An AC motor might not have quite the 0-10mph launch, but it will still be pretty good, and the overall powerband is better.
      Two motors for more plain power is another question…

  • chili sv

    Great article. Pictures of the various configurations would help my visual brain understand the moving (and non-moving) parts, their orientation, and how they interact.

  • Brett Vegas

    Profsteve,

    Exactly, and I should have brought in ‘work’ to the equation. I explained it a little better in the ‘continuous vs peak’ part of the article. The continuous rating of a motor is the ‘true’ horsepower of a motor, IE how much ‘work’ the motor can do in an hour. Watts tells you how much ‘work’ a motor can do, but not over a period of time. Might be 3 seconds, might be an hour, there is no time component in watts.

    In your example, the bike with a 5kw continuous motor might be able to ‘peak’ 15kw. It cannot go up that hill any faster than ~5kw worth in an hour(total ‘work’ per hour) but it can accelerate a hell of a lot better than its nameplate rating. I am probably making a hash of explaining it, but when folks just convert KW to HP it raises my hackles.

    Random,
    The range thing is not easily solved, an EV only works well in certain circumstances. Batts are coming along, but we are still a long ways from being able to just toss internal combustion engines out the window. That said, china has been gobbling up little batt powered bikes like mad(10million units per year!), so things are changing.

  • Ian

    Great article!!

    …part 2 on battery technology perhaps?

  • Stefano

    Regarding the watt vs hosepower debate:
    Amperes is defined as Coulomb/second , so there IS a component of time in watts, just as there is horsepower.
    http://en.wikipedia.org/wiki/Ampere#Definition
    After all, watt and hp are both a measure of power, so they must have the same phisical dimensions. They both can be imagined as “force times speed”, since voltage can be seen as a force and amperes can be seen as a speed (of charge).

    I was nearly put off by this mistake at the beginning of the article, but it’s a good thing that I kept reading, because the rest of the article is just great. Thanks for the great reading, just fix that mistake so you don’t risk to put off other readers.

    • Brett Vegas

      Stefano,

      Well, I did NOT realize amps is coulombs per second, my f*ck up. Shit, learn something everyday(or at least today!). Kids, this is why you should go to collage!
      Ignore the bullshit about watts having no time factor.

      Sorry about that!

  • Brett Vegas

    Ian,

    I started writing about batts, but it was getting long, I might put something together.

    Re: ethanol,

    My understanding is like mikes, that it isn’t just the food crop thing, corn ethanol has a poor energy conversion rate, growing it and harvesting consumes more energy than it returns. Sugar cane is just above par, corn is a loss. If you use 1 gallon of fuel to produce 0.7 gallons of fuel, it isn’t all that sustainable…

  • Stefano

    I think I understand better what Brett means about the watt vs hp thing.
    The problem is just how electric motors are rated. They are rated by the power they can make “at steady state”, for a long time, without overheating, which is probably good for an industrial motor, but means little for a motorcycle motor. Peak power, which is what bikes are more interested in, is generally not officially stated and is significantly higher than the power on the motor label.
    ICEs don’t have this issue because their peak power and their steady state power are, is the cooling system is properly desiged, virtually the same.
    It’s not a units problem, it’s just a rating problem.

  • LASOVAN

    to socrates82 Maybe Mike was talking about the best(it will grow fast and virtually anywhere) plant, that can be eficiently “transformed” into ethanol? !!industrial CANNABIS!! Anyway, NIKOLA TESLA rules,the car industry is 1 century late,but General Electrics should have (all)his blueprints,and become the new GM or GEM he ,he

  • Brett Vegas

    Stefano,

    Yeah, I didn’t state the issue correctly(watts-per-hour is not a correct way to state horsepower,totally wrong about that).
    Wattage is a power measurement. It will tell you how much ‘oumph’ a bike has, but not how ‘fast’ it is. To be fair, most manufacturers do usually include the continuous and peak rating, but continuous is an output rating, and peak is not(its an input). It can be measured as an output, dyno it and any 20kw bike will make about 20hp. Make 20hp for about a half hour(or less), and you will see a molten wad of copper(or ‘letting out the magic smoke’). It might seem like you want a higher continuous rating, but the trade off is weight.
    Would like to see more of these bikes dyno’ed, the blade made ~19hp with a 20kw system(48v*400a, and if you were not careful you could burn up the motor), as the voltages climb the motors should be less lossy, but any HP comparison is silly without real data.

  • Stefano

    Hey Brett, glad I could help. Thanks again for the write-up, and let me join the crowd of those who wait for another one about batteries.

  • Random

    The “two electric motors together” thing surely conjures dreams of electric turbo Busas, Killacycle-like performance bikes. That said, it seems to be easier to engineer than a good induction AC motor for bike use – after all some bikes in TTXGP had put two electric motors together, am I wrong?

    Is the weight distribution/centralization for performance electric bikes easier right now with two engines, specially if there’s no lightweight induction AC available?

  • brettvegas

    To defend my ignorance, it is what happens when dumb rednecks get together and try to figure out what the hell is happening when a huge wad of current is tossed at a motor. Electrical power can be converted to mechanical(thats what a motor IS), but it can also be converted to light(20,000 watts! My EYES!), sound(20kw!, my EARS!), or heat(it BURNS!). It is weird.
    One of the puzzling things a motor can do is make torque without doing any mechanical work(a locked rotor@zero revs, but with power applied). Trying to pull time ‘out’ of watts is a half-assed attempt to explain above puzzle. Always made me slightly uncomfortable, you can’t call it power with out Time. That the sneaky bastards hid Time in amperage is just plain unsportsmanlike.

    Random,
    The agni bike ran two motors, motocycz ran three(but he blew them up). Same lynch-type brush-DC motors as zero is using. Motocycz is doing something different this year, pretty sure it is AC, don’t know if it is induction or synchronous.
    That race(isleofman) was silly(imho), you are putting an electric into the exact circumstance where they suck(WFO, long track). Neat to see them push the boundaries, but they should race them on a ten minute lap, and do a batt swap every lap. You might see some fast riding then.
    Weight distribution(center-of-gravity) is always sorta easy with an electric, the motor/batts are dense, and can ‘go’ anywhere. If you cut up a zero just bolt another motor on it, I’d guess that the CG would be too ‘low’(like a scooter), you would want to shift things around to get it centralized.

    • telekom

      “That race(isleofman) was silly(imho), you are putting an electric into the exact circumstance where they suck(WFO, long track). Neat to see them push the boundaries, but they should race them on a ten minute lap, and do a batt swap every lap. You might see some fast riding then.”

      That’s a cool idea Brett, instead of racing a long road circuit it would be good to see electric bikes doing short supermoto-type track racing. The cool thing would be developing different types of racing using new tech, not conventional racing which suits old tech. For example, lots of skiing enthusiasts look down on snowboarders. But in the winter olympics the best racing was in the snowboarding cross events.

      So yeah let’s all get electric bikes and invent a new sport which they suit, rather than trying to do what ICE bikes already do really well.

      Great article BTW, thanks to Brett and HFL for helping my brain understand a little better.

  • Brett Vegas

    That new motocycz is a synchronous AC, 75kw. He says that it is 75kw continuous, which is a lot like me saying wattage doesn’t have a time factor.
    Might be true, but I am highly skeptical. It is 75lbs, so it is sorta heavy enough, but permanent magnet AC motors are VERY heat sensitive, get those magnets over ~220 degrees and they ain’t magnets no more.

    Heh, sooner or later somebody is going to slap one of the acpropulsion motors on a bike. It is around 110lbs, the controller is 70lbs, so a bike would be heavy(and packaging it would be a stone cold bitch). Makes 200kw(268hp)peak, ~60kw continuous.
    Way too much power, wait, did I just say that?

  • http://electrovelocity.com/ Ben @ EV

    Brilliant article! Bookmarked it to use as a reference.

  • Trav

    Duuude. This so makes me think of the “turbo encabulator”. Look it up on the ‘tube. I only read a litte bit, and I need a beer.

  • Brett Vegas

    Trav,

    Heh, ‘turbo encabulator’ is pretty funny. I tried to keep to technical jargon down, just to keep everybodys eyes from glazing over. Hard to avoid when they stick you with something like ‘axial flux permanent magnet synchronous alternating current motor’. Yikes!

    telecom,
    “So yeah let’s all get electric bikes and invent a new sport which they suit, rather than trying to do what ICE bikes already do really well.”
    Very well put. KTM tagging their bike ‘freeride’ indicates they ‘get it’. You cannot toss electrics head-to-head against gassers on a track that demands massive constant power. They fail. A tight track, with short straits, is damn fun, and electrics CAN develop fairly respectable power-to-weight. They get really good ‘drive’ coming out of turns(much better than a gasser of comparable power), you have to use them for what they are good for…

    I think wes is working on a correction I sent him, Wes, strike that third paragraph, starts ‘horsepower’ and insert that correction, please!. I am trying to clear things up, and made it a bit muddier, about the last thing I wanted. Sounds like wes is busy trying to get himself a ticket.

    Thanks, again, to Stefano(Mr.Smartypants) for correcting MY error. And, just to be utterly crystal clear, Watts(or kilowatts) DOES have a time factor(and IS therefore a ‘true’ measurement of power). I don’t want anybody to be running around as confused by this crap as I was, heh.

    If any of you guys learned something, I am happy. I learned something submitting it, and I thought I knew everything…

  • fazer6

    Thanks for the write-up. Looking forward to testing the KTM, and will keep my eyes peeled for an AC Induction bike.
    FWIW, while my BLDC powered bike isn’t terribly quick or fast, it is remarkably efficient.

  • http://www.emotorules.com Harry Mallin

    Great article, and the comments continue to help the evolution of my understanding of electricity, motors, and bikes. Now, you guys need to go to the technical rules wiki on the ttxgp site ( http://wiki.egrandprix.com ) and see if anything needs to be changed, corrected, added, etc. in any of the rules that talk about accumulators, emergency shutoffs, electrical safety…. I don’t know how long in distance the upcoming races will be, but your insights are welcome.

  • Brett Vegas

    fazer,

    BLDC motors ARE remarkably efficient, but it is almost like they HAVE to trade ‘power-density’ to get those good numbers. Pretty much ALL of the millions of electric-assist bicycles, all the scooters, in china, are running BLDC. One to five KW, mostly. I am usually not interested in a motor until it gets to 20KW, and a BLDC that can do that is 40-50lbs(twice the weight of a Lynch-type). Half the power to weight is, mmm, crappy. To be fair, Lynch-type motors are damn hard to beat in the power-to-weight arena, and some of the reason they are so powerful is they deliver lower efficiency than a BLDC. Don’t mistake ‘runtime’ for efficiency though. If you have a BLDC with a peak power of 3kw, and a brush-motor with a peak of 20kw, the bike with more power runs down quicker(duh!). The price you pay for wanting something that can accelerate 0-30mph in two eye-blinks…

    Henry,
    I’ll take a look over there.
    Electrical safety? Crap, we only JUST got to the point of making these stupid things dangerous, now we gotta make ‘em safe again? heh.

    I am working on a battery article, it is harder to talk about than motors, but I’ll grind through it.