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Thread: Adding a centrifugal clutch to the drag bike.

              
   
   
  1. #1
    Old EV Racer EVcycle's Avatar
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    Adding a centrifugal clutch to the drag bike.

    Hello all!

    We are looking to knock off some time on our drag runs.
    I have always felt the Toque at Zero RPM is not really translating to the wheels when the motor is stationary in a AC system.

    We have a motorcycle manufacturer that builds automatic clutches for various bikes and have chatted with him about this project.
    I have sent him our specs what we think we need to get the bike to launch harder.

    Please do not suggest more batteries, a bigger motor, etc. What we have on the bike is what we have. This project is for a SPECIFIC application.
    If i had a bigger bike I would add more batteries, a bigger motor, etc.

    We also have the Wife's electric Legends drag car that we might do the same to if this works well enough.

    Questions and constructive comments are always welcome.

    44590200_2053868754664955_2667284362805903360_o.jpg

    Ed
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  2. #2
    Senior Member Stevo's Avatar
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    Rekluse makes a slipper clutch for dirtbikes that really help when riding difficult and steep offroad trails. I dont know if something like that would help on an electric
    dirtbike. My bike is way too heavy to really be a competitive enduro bike, but I am curious and wonder if something like this would be an improvement.
    I look forward to seeing your experiment
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  4. #3
    Old EV Racer EVcycle's Avatar
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    Quote Originally Posted by Stevo View Post
    Rekluse makes a slipper clutch for dirtbikes that really help when riding difficult and steep offroad trails. I dont know if something like that would help on an electric
    dirtbike. My bike is way too heavy to really be a competitive enduro bike, but I am curious and wonder if something like this would be an improvement.
    I look forward to seeing your experiment
    Thanks for the info.

    I may reach out the them if the company I am working with does not pan out.

    Ed
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    Before upgrading to a larger controller on my drag bike a few years ago, one of the options I looked at was using a snowmobile clutch. You could keep a motor close to Max power with some sort of cvt.

    Sent from my SM-T380 using Tapatalk

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    Quote Originally Posted by EVcycle View Post
    the Toque at Zero RPM is not really translating to the wheels when the motor is stationary in a AC system.
    How sure are you that this isn't more to do with how your controller is programmed than anything else?
    If you're dealing with some sort of software limit on the ramping rate for current, then the flywheel dump may not help as much as you expect as the controller is still going to attempt to regulate the rate of change - granted if any such rate is RPM linked then it may not try quite so hard... but the point is that there are a substantial number of unknowns there.

    Once the magnetic fields are established (for which I would expect there will be a larger time constant in the case of induction than PM), then the torque should be pretty much instant in any practical terms. Only reason for this not to be the case is if something is the control stages is trying to be too clever.

  8. #6
    Old EV Racer EVcycle's Avatar
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    Quote Originally Posted by Spoonman View Post
    How sure are you that this isn't more to do with how your controller is programmed than anything else?
    If you're dealing with some sort of software limit on the ramping rate for current, then the flywheel dump may not help as much as you expect as the controller is still going to attempt to regulate the rate of change - granted if any such rate is RPM linked then it may not try quite so hard... but the point is that there are a substantial number of unknowns there.

    Once the magnetic fields are established (for which I would expect there will be a larger time constant in the case of induction than PM), then the torque should be pretty much instant in any practical terms. Only reason for this not to be the case is if something is the control stages is trying to be too clever.
    AC motors.....100% torque at zero RPM is still not moving HP. This is not always a bad thing as in Drag racing you do not want to "blow your tires off"

    I have everything running at 100% in the controller (2 different controllers and motors) The start seems soft until I get to about 100 RPM or so.

    I recently had an interesting chat with one of the leading AC motor manufacturers explaining my 100 RPM theory and was surprised to find out that the was the magic number to get things really rolling...100 RPM. The had proven it on a dyno.. (go figure)
    Depending on your gearing, you may get to 100 RPM very quickly so it may not be noticed, but I have two vehicles with no transmission and am drag racing them to 100+ MPH in a 1/4 mile.

    I still think a centrifugal clutch would help us with our ET.

    Ed
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    When you say AC you're referring to PMAC not squirrel cage I expect yes?

    You've answered my question in any case - it sounds like there's a necessary lag until sufficient angular velocity is developed to really launch the thing (which makes perfect sense of course), so having something in there which permits you to have it spun up before you try and move certainly makes sense alright.

  11. #8
    Old EV Racer EVcycle's Avatar
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    Quote Originally Posted by Spoonman View Post
    When you say AC you're referring to PMAC not squirrel cage I expect yes?
    Yes, A Motenergy 1507.
    EV Ed
    Never let being a responsible adult get in the way of passion and curiosity.
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    oh my goodness that's pretty!

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    Senior Member Stevo's Avatar
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    16008826318728076174625456194715.jpg


    Is Acceleration exponential at the start?
    When you drop an object from a tall building, it takes an acceleration constant to reach max velocity, then the speed varies by wind drag, but the initial acceleration from a dead stop isn't linear. If you dropped a heavy Pb ball and a really light ball same size, they should still fall at the same velocity. But that is gravity, not emf.
    Maybe your feeling that initial exponential acceleration in the seat of your pants!
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
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