acceleration over uneven road surface while braking

Discussion in 'Gen 3 Prius Main Forum' started by Laird Banks, Aug 24, 2010.

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  1. teeasal

    teeasal New Member

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    I was not talking about when your car was temporarily IN the pot-hole. I was talking about when your cars was REBOUNDING back up from the pot-hole.

    If you keep discarding sincere helps I think we are running out of them here.

    Goodbye and good luck.
     
    #41 teeasal, Aug 24, 2010
  2. mwok86

    mwok86 New Member

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    Ford just released a new car....you can go 300mph full speed and come to a full stop in half a nanosecond.

    I don't expect my Prius or ANY car to go 50mph and be able to come to a complete stop in half a second at full speed. You might want to read the NHTSA stopping distance standards. There are over a million Prius drivers, none of them have actual braking problems or sudden acceleration. It's the driver, not the car.
     
    #42 mwok86, Aug 24, 2010
  3. Joe166

    Joe166 New Member

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    Is Portugal in South America in your version of the world?
     
    #43 Joe166, Aug 24, 2010
  4. dr_d12

    dr_d12 Member

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    Not this again.
     
    #44 dr_d12, Aug 24, 2010
  5. Rae Vynn

    Rae Vynn Artist In Residence

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    Then why don't you return to your "path" and take your documented data elsewhere?

    You don't come onto a car forum, post a complaint about the car, then refuse to answer the questions of the forum's experienced denizens, without getting exactly what you are asking for - complete disregard of your issue.

    You, sir, are a troll. Be gone. :troll:
     
    #45 Rae Vynn, Aug 24, 2010
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  6. qbee42

    qbee42 My other car is a boat

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    This situation is well documented and well understood, despite the OP's insistence otherwise. It is triggered from a loss of traction during ABS braking, where the ABS modulates braking action to reduce the chance of wheel lockup. All ABS braking systems are susceptible to this, but it is exacerbated by the regenerative braking system on the Prius.

    During regenerative braking, only the front wheels brake, and they do so through the transaxle. This means that a loss of traction with either front wheel causes a complete loss of braking action. The system compensates for this by quickly transitioning to ABS friction braking. You still have a loss of traction, but now four wheels are working through ABS to slow the car.

    The momentary loss of braking action produces what physicists and engineers call "jerk". Jerk is the rate of change in acceleration; in other words, how fast is your acceleration changing. During a constant G braking maneuver the jerk is zero. The driver would experience a constant force appearing to pull him forward (it's actually the other way around, but humans see things from the perspective of self.) When you briefly lose braking action, the acceleration (deceleration if you will) briefly drops. Your speed does not change, you don't shoot forward, or anything of the like. It feels that way because of the short change in apparent force.

    The only case where a loss of braking will cause forward acceleration is when braking downhill. However, in this case the acceleration can be no more than that which would occur naturally when coasting down the same hill. Generally this is a very modest amount of acceleration, and not something I would relate to a slingshot.

    Unfortunately for the OP, this is not a defect in his car. His Prius is working as designed, and it's not considered a safety defect. That eliminates the lemon law. His only options are to learn to live with it, or sell it.

    Tom
     
    #46 qbee42, Aug 24, 2010
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  7. teeasal

    teeasal New Member

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    Thank you. Your definitive answer is what's need here to clarify the question.

    And may I add to your "Unfortunately for the OP, this is not a defect in his car." with "It is actually a defect in his opinion, his approach and his personality."
     
    #47 teeasal, Aug 24, 2010
  8. Codyroo

    Codyroo Senior Member

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    Tom,

    Thanks for the detailed explanation of what happens and why.
     
    #48 Codyroo, Aug 24, 2010
  9. Laird Banks

    Laird Banks Junior Member

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    Thank you for your explanation. Will mention what you wrote should it be accepted into the program. Should it not be accepted into the program, I will likely sell the vehicle. Should I have known about this querk prior to the purchase, would have likely not purchased. Thank you for not getting caught up in others politics and providing a very cogent response. Appreciated.
     
    #49 Laird Banks, Aug 24, 2010
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  10. Laird Banks

    Laird Banks Junior Member

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    Look like you do and call me a troll? You must be kidding. I have a purpose in posing the question and have already commited to pursuing a particular path. I had not asked you for your help. I just posed a question....period. Even with all the technical response, all people can say is "live with it", "it's part of the design" and "it's the driver". All very substantial in proving my point. Politics aside, it exists and had you known about it prior to your purchase, you too Hobbit Head would probably not have bought the car and likely, neither would 50% of the others involved with this forum.
     
    #50 Laird Banks, Aug 24, 2010
  11. Skoorbmax

    Skoorbmax Senior Member

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    You have been asked for a video of this. You've not produced it. Thus I am concluding your 'acceleration' is merely a well documented temporary respite in braking. Unfortunate, maybe unacceptable, but not acceleration. The onus is on you if you want to convince me (and most of us, evidently) otherwise.

    FWIW I'm at almost 10k and I MAY have experienced this for the first time on Sunday. I know exactly where it happened and will try and reproduce it for my own fun at some point. It was raining, though, so it would be harder to reproduce in dry.
     
    #51 Skoorbmax, Aug 24, 2010
  12. Laird Banks

    Laird Banks Junior Member

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    I mentioned my situation this morning. Said that I'm already pursuing a remedy. Have a busy professional 7:30am - 7pm practice. Please have some humility and understand I have nothing to prove to you or the others, nor have to spend time doing so by video taping while I'm driving in Manhattan.

    What was said is what I'll keep to. Once there's determination made by NYS-DOS attorney generals office, I'll let the forum know. I realize there's nothing that can be done to fix it. Thank you for all your helpful advise.
     
    #52 Laird Banks, Aug 24, 2010
  13. xs650

    xs650 Senior Member

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    Bwahahaha!

    Physician, heal thyself.
     
    #53 xs650, Aug 24, 2010
  14. Laird Banks

    Laird Banks Junior Member

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    Funny....thanks and enjoy your Prius.
     
    #54 Laird Banks, Aug 24, 2010
  15. Laird Banks

    Laird Banks Junior Member

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    I'd like to help you put together that information. Please send me a message on my email. Your help would be much appreciated. Thank you.
     
    #55 Laird Banks, Aug 24, 2010
  16. Laird Banks

    Laird Banks Junior Member

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    Thank you. I have asked Bob for his assistance. Laird
     
    #56 Laird Banks, Aug 24, 2010
  17. xs650

    xs650 Senior Member

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    Good luck with that guy:D
     
    #57 xs650, Aug 24, 2010
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  18. bwilson4web

    bwilson4web BMW i3 and Model 3

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    About Christmas time 2009, a stranger came to PriusChat and posted a note about the 'dangerous brakes'. At the time, there was a little buzz but about a week later, someone posted a URL to a news article where the original poster claimed 'PriusChat was discussing this dangerous brake problem.' It was a made-up story that tried to lend credibility by citing PriusChat 'chit chat' as made up evidence of a problem.

    Regardless, we did a survey to find out how frequent this problem was and discovered it was rare and except for a small minority, not considered dangerous. In fact many had noted that it was in the earlier, NHW20 model although not as pronounced. Still, it was an intermittent problem and enough folks had acknowledged it happened that even though I could not reproduce it, it needed investigation.

    WHERE DID IT HAPPEN?

    We asked members to post photos of where the problem occurred:
    http://hiwaay.net/~bzwilson/prius/Prius_bump_010.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_020.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_030.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_040.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_050.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_060.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_070.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_080.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_090.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_100.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_110.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_120.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_130.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_140.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_150.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_160.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_170.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_180.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_190.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_200.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_210.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_220.jpg
    http://hiwaay.net/~bzwilson/prius/Prius_bump_240.jpg

    ​
    WHAT IS GOING ON?

    Eventually I was able to reproduce the problem at will with instrumentation:This gave us insight just as the fix, SSC-A0B came out.

    THOSE WHO ARE NOT PART OF THE SOLUTION ARE PART OF THE PROBLEM

    I asked those claiming it was hazardous to document where it occurs so I could try to replicate the problem. Eventually I found the four pre-requisites and was able to reproduce the problem with instrumentation. That is why I asked my earlier questions.

    Now I'm not expecting a video but just some JPG photos of where the problem occurs. I've also offered an accelerometer to document what is going on. But I understand you believe you are already pursuing a successful approach that includes lawyers and the court system. Fine but I'm an engineer and deal with the natural world and the Natural Laws of physics and math are orders of magnitude more credible than Internet postings or legal proceedings.

    So my offer stands, I remain committed to investigating interesting physics, but that means offering what is missing . . . fact based observations, not just testimonials. Let me know when you want to be part of the solution.

    Bob Wilson
     
    #58 bwilson4web, Aug 24, 2010
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  19. Flaninacupboard

    Flaninacupboard Senior Member

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    Yes its real, no it's not acceleration (it's momentary reduction of deceleration), yes it feels a bit weird, no it's not dangerous, no you can't reject a car because of it, yes i bought the car while well aware of the issue.
     
    #59 Flaninacupboard, Aug 24, 2010
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  20. Laird Banks

    Laird Banks Junior Member

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    Thank you Bob. I will gather the photo's and information you asked for. Laird
     
    #60 Laird Banks, Aug 24, 2010
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