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  1. #1
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    Sep 2017
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    Default Natural Frequency of DLM Tire

    Does anybody know the natural frequency of a DLM tire, roughly? I know this is probably dependent on compound but looking for a general idea/range.

  2. #2
    Join Date
    May 2007
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    Batavia, OH
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    Quote Originally Posted by smartguy13 View Post
    Does anybody know the natural frequency of a DLM tire, roughly? I know this is probably dependent on compound but looking for a general idea/range.
    I'd say it's really dependent on air pressure. Ghopper would know. Would he tell you?
    Droop isn't the problem.

    Arizona Speedway - 2 ........ Brushcreek -1
    Alltech -1 .................... Eldora - 8
    East Bay - 6 .................. Richmond -1
    Florence -1 ................. Lawrenceburg -1
    Atomic -6 .................. Circle City -1
    Tazewell -1 .................. Mudlick-1
    Moler -4
    Portsmouth -2. .....................Tyler Co. -1

  3. #3
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    May 2007
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    Kansas
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    3.5 hertz, well sort of maybe

  4. #4

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    [QUOTE=billetbirdcage;2390417]3.5 hertz, well sort of maybe[/QU Just wondering if heats effect on side wall flexability would have a bearing on frequency.

  5. #5
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    Quote Originally Posted by robbie35 View Post
    Just wondering if heats effect on side wall flexability would have a bearing on frequency.

    Sorry it probably wasn't clear that I said that in jest. 3.5hz is a Nascar cup tire (or was last time I knew where they resonated at). Dirt tire data is extremely rare and the tires vary a ton least as far as spring rates and probably frequency (I can't say with 100% certainty). I'm guessing here to a degree: while temp and compound most likely effect it to a degree but the carcass likely has the largest effect and there are several carcass's and I would say an open tire and economy/spec tire are likely quite different due to construction and what basic carcass they use on said tire.

    Like I said dirt tire data (Hoosier) is extremely rare and if someone has some, I doubt they are going to share much or any of it. I've talked to maybe 2 people that has any at all. It's been a couple years ago but talking to a couple of the Hoosier engineers and asked for whatever data they had. Reponse:" You know your only the 2nd person that has ever asked for that data and the other person was XXX (everyone would know the name here, I'm just not gonna say it). They didn't have the data on dirt tires and I'm not gonna go into what or why he said that was the case.

  6. #6
    Join Date
    May 2007
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    18

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    Looks like someone watched the video on F1 Inerters and specifically tire frequency.

    https://www.youtube.com/watch?v=t58qjcNwEbo

  7. #7
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    Sep 2017
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    Maybe Iím all wet but hear is what Iím thinking. Many guys are on a 225-275 right rear spring. Letís call it 250 for simplicity. Now letís say you replace that 250 with a stack of 500/500...a combined rate of 250. Instead of using a standard plastic divider what if you were to use a divider that has a mass that is specifically chosen to cancel out the frequency of the tire...something the shock doesnít do well. Essentially it would be a tuned mass damper which in theory would help mechanical grip. Might be something that works well on the 5th coil as well...sort of like the inerters guys were running a few year back. Certainly not as sophisticated, and may not be feasible, but itís a thought. Thoughts?

  8. #8
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    This is above my pay grade and I'm probably gonna make a fool of myself but here it goes:

    1. For starters a mass damper needs valving/dampening on the weight, so not sure how your gonna dampen the actual weight between the springs of a stacked coilover (in our rule set). Now granted you could make it rub on the shock body and do that but doubt it's very effective or tunable to get it right.

    2. I would think where you're trying to placing the mass damper is the wrong location. A better location would be on the axle itself or on the car, not the coilover.

    Again your talking something similar as what Renault F1 did in 2005/6, however it was dampened with oil around the weight thus the big problem per our rules and it was attached to the car not on the connection between the car and the suspension. IMO you need to have it fully on the car (unsprung weight of the car (axle) or fully on the sprung weight of the car (car).

    I could punch several holes in your idea or your way to do it, but it would take 4 pages of typing (again not my area of expertise and could be 100% WRONG). I know for a fact it has been tried on a LM and the results where not good but granted not enough time was spent on it but these where some pretty sharp minds and they couldn't get it right least without serious research and more testing. There where some pretty elaborate ideas using components already on the car as the weight, that is about as far as I can say.

    Not trying to discourage you, but it's not as simple as it sounds

  9. #9
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    May 2007
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    As thin and light as these rear clips are on these Race Cars are built, the rear clip its self could be a damper via flex.

    That or fill the tubes with some sort of polymer and use it that way.

    Just say no...

  10. #10
    Join Date
    May 2008
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    Iowa/Oregon
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    - First you need to be able to measure what you are trying to optimize. So reflect on your measurement system or limitations before getting too creative.

    - F1 was most concerned about aero ride height and that is why body control is so important. That is not the case for DLMs.

    - Tire vertical stiffness can vary 300lbs/in within 4psi, as well as loose significant carcass mass during a race. That means you need to have a wide tolerance for a frequency you are trying to cancel.

    You can move the order of these bullets around to fit what you think is the correct priority.

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