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Longitudinal slip exceeds the validity range

asheshshrestha
adam_error
Hi,
I had tried to model two-wheelers for a month, and I have made the model which is quite interesting, and Adams's view has no problems to simulate it and works fine. I have used tire model 'pac_mc_120_70R17_cross.tir' for both front and rear wheel where road profile is '3d_bump.rdf'. But the problem that I am currently facing is a warning message in the message window. It says, Long. slip exceeds validity range. And also the front wheel has no rotation motion at all. But If I remove the motorcycle chain, the front wheel will begin to rotate as the bike moves forward. Is there something that I missed because I don't have much experience in ADAMS.
  • 0
    The tire was tested to certain limits when it comes to normal load, camber, and lateral and longitudinal slip. These values are listed in the tire property file. So the fit is really only accurate inside these ranges. You can use a tire testrig or plotting tool to see what happens if you go outside these ranges. It is typically not recommended to do this, but the Magic Formula usually provide a smooth extrapolation, even if the values will be wrong.
    Depending on implementation, the values for these quantities that are sent to the tire model might either be capped at the min/max value or the actual value might be used. In either case a warning will be issued. As you can see from your warning messages above, the implementation in Adams does cap the value to the range {min,max}. (I don't agree with that implementation, but in one way it is a safe keeping to prevent your model to explode).
     
    The other problem is clearly something you have done wrong. How did you model the chain?
     
  • 0
    E1
    E5
    E4
    E3
    E2
    I had modeled the chain and sprocket using Adams machinery in which I have used 12 teeth sprocket as drive and 64 rear sprockets. The chain that I used here is a 2D chain with Non-linear compliance. Other parameters of the chain are defaults value except for chain pitch which I changed from default value 9 mm to 9.6 mm. It says total links in the chain will be 158 and chain tension is 72.565 N. I have attached several photos that I gave input to make chain sprocket
  • 0
    I am not familiar with the chain element (I always write my own GFOSUB unless I was really interested in the chain dynamics).
    But use the Graphical topology tool and make sure that the front wheel is not connected to anything it should not be connected to.
  • 0
    My front wheel tire has touched the front fork tube but I thought Adams view ignore unless we gave connection or any contact between them. I am curious that do we have control over tire geometry like width and radius of the tire by changing the moment of inertia of the tire for particular tire model. Thanks for the response!
  • 0
    Yes that is ignored. And will not show up in the graphical topology either.
     
    If you want to you can change the radius and width for the tire. There are parameters in the tire property file for this.
    Only changing mass properties will not be inherited by the geometry. But when changing the geometry properties you probably want to make sure that the mass and inertia are proper as well.
  • 0
    The parameters you are talking about here are the two highlighted portions in the below picture, right? We are given mass input that's why my understanding is two highlighted parameters must be Area Moment of Inertia of the wheel. Otherwise, it may be a mass moment of inertia. Is it correct or I have missed sth here?
    Thanks for your response!
    rr
  • 0
    Those are mass properties. The ONLY thing where ADAMS cares about area is for beam elements.
     
    Now open your tire property file "pac_mc_120_70R17_cross.tir" in a text editor (well, make a copy of it first to your working or private cdb). Then locate the [DIMENSION] block and look at the parameters in that block.
    [DIMENSION]
    UNLOADED_RADIUS     = 0.306        $Free tyre radius     
    WIDTH          = 0.120        $Nominal section width of the tyre  
    ASPECT_RATIO       = 0.70         $Nominal aspect ratio    
    RIM_RADIUS        = 0.216        $Nominal rim radius     
    RIM_WIDTH        = 0.15         $Rim width ??     
     
    Change those, sav the file and point the tire to it. As long as there is no imported geometry for the tire, it should update now.
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