Power in Flux
Likes Likes:  0
Page 1 of 3 123 LastLast
Results 1 to 10 of 26

Thread: Need help deciding motor parameters.

              
   
   
  1. #1
    Junior Member
    Join Date
    Dec 2013
    Posts
    20
    Post Thanks / Like

    Need help deciding motor parameters.

    Earlier this year I started messing around with the math to do an electric conversion for a car, but then a few weeks ago i decided why not try a bike? It would be a much simpler project, and if I ditch AC, I can make my own controls, save some money and have some fun. I also saw a 2000 Buell M2 with a titled frame, so I snagged it. The guy I bought it from has a bunch more parts, tools, and curiosity in the project, so finishing the bike won't be an issue.

    Now here's where I'm stuck. When I was planning the car, I looked at motors based on what torque I needed to move the mass of the thing. I gathered up all the equations I needed and plugged them into MATLAB. My intent was to do the same for this project, but I can't get a hold of a lot of variables, frontal area being one of them.

    Basically, I'm looking for motor advice at this point. The dry weight of the bike is ~400 lbs. and I'd like to be able to go at freeway speeds, 15 miles for range.
    Has anyone used golf cart motors? This one looks like it'll spin fast enough(4 HP, 4400 RPM, 36V, 102A), but I don't know if I'll overspin since I can't find a datasheet and I don't know if it has the torque anyways.

    Thanks in advance.

  2. #2
    Electric Warrior CaptainKlapton's Avatar
    Join Date
    May 2012
    Location
    Memphis TN
    Posts
    105
    Post Thanks / Like

    My Social Networking

    Add CaptainKlapton on Google+
    First of all, Welcome to Elmoto!
    I have most commonly come across frontal area figures between 0.55-0.65m^2 without rider. Which leads to a CdA of around 0.7m^2 with rider for a naked bike.
    As for using a golf cart motor, I would stray away from it unless you are planning on doing A LOT of modification to it. It will probably spin fast enough but they tend to be low power and heat will be a serious issue. For freeway speeds, I would look for something upwards of 20kw (26.8HP). That way you still have some grunt left if you need it.
    The 15mi range should be easy. Are you considering Lithium or Lead?
    Anyways, looks like you are off to a good start.

    Here are a couple links I have found useful:
    http://books.google.com/books?id=rJT...20area&f=false

    http://books.google.com/books?id=l2Z...20area&f=false
    "Never let schooling interfere with your education."
    -Mark Twain

  3. #3
    Junior Member
    Join Date
    Dec 2013
    Posts
    20
    Post Thanks / Like
    Quote Originally Posted by CaptainKlapton View Post
    First of all, Welcome to Elmoto!
    I have most commonly come across frontal area figures between 0.55-0.65m^2 without rider. Which leads to a CdA of around 0.7m^2 with rider for a naked bike.
    As for using a golf cart motor, I would stray away from it unless you are planning on doing A LOT of modification to it. It will probably spin fast enough but they tend to be low power and heat will be a serious issue. For freeway speeds, I would look for something upwards of 20kw (26.8HP). That way you still have some grunt left if you need it.
    The 15mi range should be easy. Are you considering Lithium or Lead?
    Anyways, looks like you are off to a good start.

    Here are a couple links I have found useful:
    http://books.google.com/books?id=rJT...20area&f=false

    http://books.google.com/books?id=l2Z...20area&f=false
    thanks for the reply! i'm going to go lithium for weight/space and it shouldn't run me that much considering the range i'm looking for is so slim. if I do my circuitry right, I can just add more later.

    is there any motor in the <$500 range that could be feasible for my project? if not that's fine, but being able to hit 70+ is definitely a priority. freeways around here are nuts.

  4. #4
    Electric Warrior CaptainKlapton's Avatar
    Join Date
    May 2012
    Location
    Memphis TN
    Posts
    105
    Post Thanks / Like

    My Social Networking

    Add CaptainKlapton on Google+
    I would look for something like a Motenergy ME1003 (23kw) or ME0913 (30kw). They can both be found for $550-$650 now. Do you know what voltage range you want to run? You will probably want around 72V to help keep the current down at high speeds.
    "Never let schooling interfere with your education."
    -Mark Twain

  5. #5
    Junior Member
    Join Date
    Dec 2013
    Posts
    20
    Post Thanks / Like
    Quote Originally Posted by CaptainKlapton View Post
    I would look for something like a Motenergy ME1003 (23kw) or ME0913 (30kw). They can both be found for $550-$650 now. Do you know what voltage range you want to run? You will probably want around 72V to help keep the current down at high speeds.
    Thanks again for the reply. I originally wanted to do 48V, but the way this math is stacking I think I'll do 72. Has anyone built a system that switched between the two? Shouldn't be hard to design, toggling a few switches of any type between battery connections to alternatively stack them in parallel/series is easy, the hard thing there would be getting good efficiency.
    EDIT: Forget efficiency, good battery balancing ain't easy either, and toggling from 72 to 48 is a wonky topology jump for sure.

    Those Motenergy might be fun, permanent magnet DC makes for easier regen etc. than series wound anyhow. I hear permanent magnet are really loud though, is this true?

    I also decided to clean up my models and run them for some really bad conditions (600 lbs. curb weight). but I'll have to mess around with some other stuff (transmisison efficiency, desired peak accel, axle ratio) to get me closer to a selection.
    Last edited by s33dless; 30 December 2013 at 1351.

  6. #6
    Senior Member Athlon's Avatar
    Join Date
    Jul 2011
    Location
    Milan, Italy
    Posts
    381
    Post Thanks / Like

    My Social Networking


    Add Athlon on Linkedin
    switching series/parallel is useless , it was an option for train something like 100 years ago but for every other vehicles is useless because at the switching you have huge spikes of torque/power and you loose the control of the vehicles.

    All the electric motor are almost silent , the only noise come from the PWM modulation of the electronic controller and sometimes you get some more noise if you mismatch motor and controller , for example using a trapezioidal controller with a sine motor, it still working but get noisy.

    In the very early days of electtric motorbikes ( '70-'80) there was a loto of conversion made out from forklift motor and controller. Motor form forklift are very often series wound , this motor is simple and have both great starting torque and a very high rotatinal speed so it fit very well for a motorbike.

    So if you want to build something "vintage" you can do it again looking for an old forklift witha 10-15 Kw motor and his controller or use a commercial controller for brushed motor.

    The "best" solution using todays technology is for sure PMAC ( Permanent Magnet AC) , is a brushless motor with permanent magnent , but you have to use complex 3 phase controllers to move it Motenergy ME0913 and ME1012 are 2 old but still good PMAC motor that you can find at a good price today (sometime cheaper than an Agni).


    So in short word:

    ""vintage old days"" solution
    Forklift motor and brushed controller

    "easy and cheap"
    Used Agni or used ME1003 or used ME913 and brushed controller

    "today's technology"
    PMAC or induction motor and 3 phase Mosfet controller


    Today's tecnology also made possible to have a "motorized" wheel , where the motor is inside the wheel so you just have to put the battery/controler inside the frame and you have your bike ready.



    .

  7. #7
    Electric Warrior CaptainKlapton's Avatar
    Join Date
    May 2012
    Location
    Memphis TN
    Posts
    105
    Post Thanks / Like

    My Social Networking

    Add CaptainKlapton on Google+
    Agreed, running a well thought out 72V system should be better pretty much all the time.
    Motors that use permanent magnets are not loud enough to be an issue. Though the constant cogging torque does add some noise, it will be mostly drowned out by the chain.
    Here is a guy running a ME1003 off a single 12 Lead acid battery. Though it is not near full speed, it really isn't a loud motor.

    Have you thought about the final drive? The stock belt drive on that Buell looks like it is only about 2.7:1 which is pretty steep for a street bike to run as a single reduction.
    "Never let schooling interfere with your education."
    -Mark Twain

  8. #8
    Junior Member
    Join Date
    Dec 2013
    Posts
    20
    Post Thanks / Like
    Quote Originally Posted by Athlon View Post
    switching series/parallel is useless , it was an option for train something like 100 years ago but for every other vehicles is useless because at the switching you have huge spikes of torque/power and you loose the control of the vehicles.
    .
    Dear lord! I didn't mean with the thing actually running, though that would be very cool if you got it to work well! I still need to do some math to see if it's even worth it, but I was planning on picking a voltage level at boot or when the thing is completely stopped. It can definitely work given the right BMS. If you have 6 12V batteries, pop 2 of them out of the chain and just have you SoC management take care of it.

  9. #9
    Senior Member Athlon's Avatar
    Join Date
    Jul 2011
    Location
    Milan, Italy
    Posts
    381
    Post Thanks / Like

    My Social Networking


    Add Athlon on Linkedin
    one of the most important thing for the battery is balancing , unsing all the cells at the same deep.

    popping out some cell it will unbalance the whole battery ( 12V lead batteries are just a series of 6 cell)

    With electronic controller you don't need to change the voltage , if you have a 72V battery but you are at half throttle your motor will just "see" 36V,
    if you are at one quarter throttle it will "see" only 18V , at zero throttle there will no voltage on the motor.



    One thing that may come back from the old days of train it a star/triangle switch to simulate a 2 gear "transmission" but up to today everybody is either stayin with regular 3 phase or integrating the controller in the motor and have each coil controlled independently

  10. #10
    Junior Member
    Join Date
    Dec 2013
    Posts
    20
    Post Thanks / Like
    Quote Originally Posted by Athlon View Post
    one of the most important thing for the battery is balancing , unsing all the cells at the same deep.

    popping out some cell it will unbalance the whole battery ( 12V lead batteries are just a series of 6 cell)

    With electronic controller you don't need to change the voltage , if you have a 72V battery but you are at half throttle your motor will just "see" 36V,
    if you are at one quarter throttle it will "see" only 18V , at zero throttle there will no voltage on the motor.
    Correct on both points. I already addressed the battery thing: your state of charge management has to be very, very good for this to work. Cell balancing is tricky business.

    what you say about the controlled voltage is true, but it doesn't matter, the system voltage is still 72V so energy is spent to get to the level the motor sees. The DC/DC conversion from 72V --> whatever at the motor is always lossy.

    Now the question is this: is it more lossy to bust the voltage down or to try to drain the 2 batteries into the 4 evenly? Time for some more modelling...

Page 1 of 3 123 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •