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Thread: Elmoto v2.0 Data sheet

              
   
   
  1. #21
    Senior Member Coninsan's Avatar
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    Quote Originally Posted by DaveAK View Post
    Good work! A couple of questions though. Here's the spec sheet for my motor: http://www.thunderstruck-ev.com/Manuals/D&DSepEx72.pdf I can't figure out the torque numbers to put in at a given RPM. It seems backwards to me. (The spec sheet, not your spreadsheet.)

    Also, is gravity different in Denmark, or are you just so far ahead of the game you thought we might like to use our bikes on Mars?
    Yea, it is backwards, but that's just because your sheet features RPM up the Y-axis and Torgue out of the X-axis, it should perform fine just as well.

    And no, I'm not figuring riding on mars, as far as I know gravity is still 9,807m/s^2
    The only problem I can spot is that the redition of gravity is a bit off in in/sec^2, I havn't bothered checking the values really..
    If you want more accurate results: Change in/sec^2 from 32*12 to 32.2*12 since gravity in Imperial is 32.2ft/sec^2
    "I reject your reality and substitute my own." Adam Savage

  2. #22
    Not to be taken seriously DaveAK's Avatar
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    Quote Originally Posted by Coninsan View Post
    Yea, it is backwards, but that's just because your sheet features RPM up the Y-axis and Torgue out of the X-axis, it should perform fine just as well.

    And no, I'm not figuring riding on mars, as far as I know gravity is still 9,807m/s^2
    The only problem I can spot is that the redition of gravity is a bit off in in/sec^2, I havn't bothered checking the values really..
    If you want more accurate results: Change in/sec^2 from 32*12 to 32.2*12 since gravity in Imperial is 32.2ft/sec^2
    I figured out what was wrong with the graph. I put in the torque figures and entered 45 for anything under 2500rpm, because that's where my graph ends. That sounds right, yes? It's going to pull at that torque for the first half of the rev range, and then decrease after that, right?

    I need to get home and get some more figures particular to my bike, but over all it's looking good.

    I was just kidding on the gravity thing. I just got a chuckle out of it being a user changeable figure. Just my poor sense of humour.

  3. #23
    Not to be taken seriously DaveAK's Avatar
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    Question about motor RPM as it applies to your spreadsheet.

    The specs I have say 4500rpm @ 72V. I'm assuming this to be no load. I was originally planning an 84V system and prorated the RPMs to 5250, then decided that under load I would be getting less RPMs to determine speed, so left my calcs at 4500. Following my convoluted logic so far? Anyway, now I'm only running 76V and for the sake of argument I put 4000RPM in the Motor Specifications area, which gives me a top speed with my gear ratio of 75mph. This is about where I had it before.

    Your Motor Output section basically takes whatever data we can find from spec sheets, which are typically no load, right? So here's my question, is there anything in your spreadsheet that takes the motor output numbers, applies a load (based on areodynamics, weight, etc.), and calculates an actual motor RPM? I can plug anything I want in to get a top speed calculation. It would be cool if you could make some kind of determination as to whether the 4000RPM I entered is reasonable or not. Does this all come down to dyno testing in the end? No theoretical calcs? Fudge factor? Rule of thumb we can apply?

  4. #24
    Moderator Nuts & Volts's Avatar
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    Quote Originally Posted by DaveAK View Post
    I figured out what was wrong with the graph. I put in the torque figures and entered 45 for anything under 2500rpm, because that's where my graph ends. That sounds right, yes? It's going to pull at that torque for the first half of the rev range, and then decrease after that, right?

    I need to get home and get some more figures particular to my bike, but over all it's looking good.

    I was just kidding on the gravity thing. I just got a chuckle out of it being a user changeable figure. Just my poor sense of humour.
    Gravity will change from place to place due to altitude, so your not totally joking

    Also any torque data that you have must be loaded with something for it to be measured, so no need to recalculate RPM. If the spec sheet says the motor can deliver 25 lbft at 4000RPM and that is enough HP to overcome aero/rolling then the motor can maintain that speed.
    Last edited by Nuts & Volts; 02 March 2011 at 1236.
    Whats under my tank may shock you!!! R6 Build, Blog/, [/URL] OSU Current webpage

  5. #25
    Not to be taken seriously DaveAK's Avatar
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    Quote Originally Posted by Nuts & Volts View Post
    Gravity will change from place to place due to altitude, so your not totally joking
    I wasn't aware that it changed due to altitude. It crossed my mind, but I can't remember ever hearing about it. (Not that I would expect to!)

  6. #26
    Senior Member Coninsan's Avatar
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    Quote Originally Posted by DaveAK View Post
    Your Motor Output section basically takes whatever data we can find from spec sheets, which are typically no load, right? So here's my question, is there anything in your spreadsheet that takes the motor output numbers, applies a load (based on areodynamics, weight, etc.), and calculates an actual motor RPM? I can plug anything I want in to get a top speed calculation. It would be cool if you could make some kind of determination as to whether the 4000RPM I entered is reasonable or not. Does this all come down to dyno testing in the end? No theoretical calcs? Fudge factor? Rule of thumb we can apply?
    I'm following you and understand your concern.
    I don't think that the data one your motor is under no load, since it should be based on dynomometer testing which simulates load on the motor.
    Ultimately, RPM limited topspeed is only a guideline, look at the intersection between Motor KW and Required Kw or Motor ft-lbs and Required ft-lbs for a more accurate view of your top speed.

    Yes you can basicly type in whatever you want to achieve your desired topspeed on paper, but I trust that you want realistic results
    "I reject your reality and substitute my own." Adam Savage

  7. #27
    Senior Member Coninsan's Avatar
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    Quote Originally Posted by DaveAK View Post
    I wasn't aware that it changed due to altitude. It crossed my mind, but I can't remember ever hearing about it. (Not that I would expect to!)
    Guys, I see the joke now, I guess my European mind doens't go well with Americano humor

    And based on the theroy off differing gravity at different levels, this is only changes by a few thousands, so small units that it wouldn't make much difference in the results, but you never know..
    Last edited by Coninsan; 02 March 2011 at 1255.
    "I reject your reality and substitute my own." Adam Savage

  8. #28
    Seņor Member podolefsky's Avatar
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    Quote Originally Posted by DaveAK View Post
    I wasn't aware that it changed due to altitude. It crossed my mind, but I can't remember ever hearing about it. (Not that I would expect to!)
    Gravity varies as 1/r^2 as you move away from the center of the earth. But...that's if you don't account for the extra mass that is underneath you (i.e., a mountain). That extra mass adds back to gravity, so it shouldn't change much as you get higher.

    ...but, mountains are actually less dense than the rest of the earth, so gravity is lower over mountains because there is less mass below you. Don't worry about it - at the very top of Everest, the difference is about 0.05%.

    But air resistance DOES change considerably with altitude. Difference between sea level and Denver can be 5-10% depending on your speed.
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  9. #29
    Moderator Nuts & Volts's Avatar
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    I have used the sheet some. zero to top speed seems high and I dont know why the 0-60 time is a user input? Otherwise looks awesome. Oh maybe bold all of the headings like Driver, Rolling Chassis, Batteries, etc. just to distinguish (sp?) the different fields.

    ill let you know if i see anything else!
    Whats under my tank may shock you!!! R6 Build, Blog/, [/URL] OSU Current webpage

  10. #30
    Seņor Member podolefsky's Avatar
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    Couple things I found that could be bugs, or could be something I'm not understanding:

    - In the torque and power vs RPM graph, I get a bump right at the knee. Makes it look like a little torque increase right before the knee, but I can't figure out where it's coming from.

    - In the top speed graph, seems like the value's should start at 0 mph, but they start at the first mph tick (around 8 mph on my graph). (But I like this because it makes it look like I have a higher top speed )
    - Noah Podolefsky -
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