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Thread: Empulse RR not sure if this is a repost.. LOOKING GOOD!!

              
   
   
  1. #11
    Dir of Prod Dev @ Brammo BrammoBrian's Avatar
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    Quote Originally Posted by mechanic View Post
    Good point and I agree... racing a scooter would likely be a disaster but the article refers to their "performance bike" which could see and should be able to handle at least a few laps around a track! - seems logical.
    Dang... Harsh. Who said the bike can only do a few laps?

    For the record, I think alot of teams (full of some crazy smart guys I might add!) have struggled with either overheating motors or controllers, neither of which are simple issues to solve. The problem with these motors is that they cannot run as hot as your typical gasoline engine, so using motorcycle radiators and cooling methodology doesn't always get you there. There are other issues introduced as the motor starts spinning at 10,000 + RPM and the switching frequency required to maintain control at that rotor speed. I should also point out that if you don't push the limits from time to time, then you don't make progress. Let's see what happens in the race... I'm optimistic.
    Brian Wismann
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    www.brammo.com

    Personal Enertia Mileage: 5,482 miles
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  2. #12
    Senior Member Skeezmour's Avatar
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    Cooling is no small task. I am working on some cooling issues for a small EV in my conversion shop. The work teams like Brammo, Swigz, Zero, Lightning ect are going to pay dividends to all of us consumers of electric motors and controllers.

    I'm optimistic that this race season is going to see some HUGE advances over last year.

    See you there Brian

  3. #13
    Moderator Nuts & Volts's Avatar
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    Quote Originally Posted by BrammoBrian View Post
    ...I should also point out that if you don't push the limits from time to time, then you don't make progress. Let's see what happens in the race... I'm optimistic.
    Yep, how else do you know that you need or should make something better, faster, stronger, or whatever. The more you break the smarter you are! (well kinda)

    Push it too the limits Brammo and then sell us whatever doesnt fall over the edge
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  4. #14
    teddillard
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    Quote Originally Posted by Nuts & Volts View Post
    The more you break the smarter you are

    I must be WICKED smaaat.

    Thanks for chiming in, Brian, it's nice to hear it from the source.

  5. #15
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    Quote Originally Posted by BrammoBrian View Post
    The problem with these motors is that they cannot run as hot as your typical gasoline engine, so using motorcycle radiators and cooling methodology doesn't always get you there.
    Electric motors can successfully run up to 130C/250F, ICE around 130C/250F+ (though specific combustion and exhaust temps can be much higher++) However electric motors are 3x+ more efficient and typically produce far less kW so in the end there is LESS heat to remove. And that is exactly what "motorcycle radiators" and "cooling methodology" do... absorb heat then reject it, is Brammo working on another method?

    Quote Originally Posted by BrammoBrian View Post
    There are other issues introduced as the motor starts spinning at 10,000 + RPM and the switching frequency required to maintain control at that rotor speed.
    So you are having controller issue too? Now that is a big problem. But of course there is probably little/no reason for you to spin your motor to 10,000rpm. I would expect that 10K is outside of your motors efficiency curve and beyond its peak torque and power output but I guess that is pushing the envelope!?

  6. #16
    teddillard
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    For them that want to understand the issues of cooling a little bit better, there are a couple of things that happen. First, when a motor gets hot, the resistance in the motor windings increases, making it less efficient. Lemmee see... I have it here somewhere. Here it is, on this thread:
    http://www.elmoto.net/showthread.php....-redux.-again.

    "In a nutshell, losses due to resistance are equal to the motor current squared x resistance.
    Copper resistance increases about 40 percent per 100 degC (and hence do the losses!)
    A typical armature resistance is about 0.04 ohms at 20 degC

    So losses from 20 degC to 120 degC at ..
    10A go from 10A x 10A x 0.04R = 4 watts to 5.6 watts
    100A go from 100 x 100 x 0.04 = 400 watts to 560 watts
    200A go from 200 x 200 x 0.04 = 1600 watts to 2240 watts"


    Thanks Rob.

    Then, there's the fact that permanent magnet motors loose their magnetism after a certain temperature. Not a good thing.

    And, of course, the fact that motors tend to burn up if they are run too hot... pretty much everybody that can is running some sort of cooling and having problems with overheating stuff, as Brian said, didn't he just now?

    Anyway, contentious posters jumping to conclusions aside, yeah, cooling is a problem.
    Last edited by teddillard; 03 May 2011 at 1643.

  7. #17
    Dir of Prod Dev @ Brammo BrammoBrian's Avatar
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    Quote Originally Posted by mechanic View Post
    Electric motors can successfully run up to 130C/250F, ICE around 130C/250F+ (though specific combustion and exhaust temps can be much higher++) However electric motors are 3x+ more efficient and typically produce far less kW so in the end there is LESS heat to remove. And that is exactly what "motorcycle radiators" and "cooling methodology" do... absorb heat then reject it, is Brammo working on another method?
    Yes.

    Quote Originally Posted by mechanic View Post
    So you are having controller issue too? Now that is a big problem. But of course there is probably little/no reason for you to spin your motor to 10,000rpm. I would expect that 10K is outside of your motors efficiency curve and beyond its peak torque and power output but I guess that is pushing the envelope!?
    No, we are not having controller issues. Why would you assume that 10k is outside the motor's efficiency curve and beyond its peak torque and power output? Do you have particular experiences with this type of motor? Will we be seeing you on the grid at the race? You seem to have many strong opinions related to EV motorcycle racing is why I ask, so I assume that you're a member on one of the teams?
    Brian Wismann
    Director of Product Development
    Brammo, Inc

    www.brammo.com

    Personal Enertia Mileage: 5,482 miles
    Gallons of gas offset (vs. my car @ 21mpg): 261 gallons
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  8. #18
    Senior Member markcycle's Avatar
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    I can tell you first hand when you are pushing every component to the limit it doesn't take much to fall over the edge and things go bad fast. testing in the public eye is not the best environment for product development but at times can't be avoided, i just learned this the hard way as most of us on small budgets with limited time have learned.
    Trying to Change the old school ways of doing things
    But I never Never try to break the laws of Physics
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    http://www.youtube.com/watch?v=nEldNmBgIF0
    http://www.evalbum.com/2568

  9. #19
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    I think the critical issue with motor cooling centers around what part of the motor is overheating. Simply circulating liquid around the motor housing may keep the housing and stator cooled, but this doesn't do much for keeping the rotor cooled. Cooling the rotor is a much more complex affair which may require a specific motor design. Using either a hollow rotor shaft allowing coolant to carry away heat from the rotor, or perhaps internal spray jets that shower the rotor before draining into a sump to get recirculated through a radiator.
    The key is to accurately map heat buildup in the motor, then find the most effective way to cool it. This takes some time, but I'm sure they'll figure it out soon enough.
    Last edited by cycleguy; 03 May 2011 at 1812.

  10. #20
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    Does anyone find it odd that the most powerful, heaviest electric bikes like those of Yates, Czysz and Lightning don't seem to have thermal issues with the motor?

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