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Dual tire issue

PJ
Hi everyone,
 
I would like to know how to properly define dual wheels in acar. There is no problem when I create single wheels(left and right) and simulate them. The wheels remain stationary on the ground with the reaction force equal to the weight of the wheel. But whenever I create dual wheels either in a single template or by assembling single wheels from two individual templates and simulate them, the force on the wheels is shown as 1e6 N in the postprocessor and in the animation too, I can see the wheels flying off vertically upwards at tremendous speed. I am using PAC2002 tire property file for defining the wheels. In the simulation, I simply create a generic assembly using only the wheel subsystem that I created, There are no constraints (not even fixed joints between the two wheels) except the contact force with the ground that is created by default by acar (til and tir) ). Then I simply run a general actuation analysis for 2 seconds and 200 steps) and get the result as described earlier.
 
Can anybody give me any pointers as to what I might be doing wrong?
  • 0
    Have you loaded the A/Truck plugin? That *might* be necessary for dual wheels or at least there are good examples in the shared_truck.cdb.
  • 0
    Yes, I have loaded the atruck plugin and also viewed the shared truck database dual wheels template. Actually, now that it has been mentioned, I have a couple of doubts regarding that template too. See, it has a number of things that are different from my own wheel template that I cannot seem to incorporate. First off, there are no contact parameters in the shared truck wheels template, whereas those were cereated automatically in my template. Second, there is a perpendicular jprim called sse_jprim that I can't seem to delete in the shared template, nor am I able to figure out from where it was defined. (When I click Modify on those jprims, I can see that the I-Axis and J-Axis fields are empty, yet somehow the jprims existed).
     
    Any thoughts on this?
  • 0
    What contact parameters are you talking about? I have never seen contacts in a wheel template.
     
    The sse_jprim shoudl be there, and must be there for proper functioning. This one is controlled by the testrig and is used to lock the wheel for certain type of Steady-State Events (sse). This is why you NEVER build a template from scratch but always start from a supplied template and modify it.
    Unfortunate the sse elements are not described in the documentation.
     
  • 0
    Hi, you see I exactly did that...I made a wheel template myself . But what I don't understand is , what is the reason for specifically the dual tires to behave so oddly? , I made a single wheel template and it runs just fine, the problem occurs when I put two wheels on one side (ie four wheels on one axle). I am attaching the template I made, if you want to have a look at it (Its been made in Adams 2021.1 version) , also attaching a snip of the expanded view of the model tree where you can see the contact parameters I was talking about.
    PS :- I did not explicitly define those contact parameters, they were generated automatically once I made the wheel parts.
     
    Looking forward for some comments on this ,thanks for your time
     
    Regards.
    Attached Files (1)
  • 0
    The sse_jprim is responsible for locking the tire rotation (finding static equillibrium) and later being deactivated in order to give the tire the required initial rotation. It's used by the related consubs called in the acf.
    BTW: In the dark medieval times this was done by a static_lock rotational force in the suspension template.
     
    I wonder that someone labeld as "MSC Software" has to ask this in a public forum insted of asking the developers.
     
    My preferred method to create "own" templates is simple and leaves most of the maintenance and "you have to know" work to MSC:
    • Open the base template from the acar_shared (handling_tire in your case)
    • Use a command file / macro to modify the tire (things like deleting the original graphic, adding imbalance masses, force transducer or a second til_/tir_ tire UDE)
    • Save the modified template in your own database and use it
     
    Now imgine someone doing this with the existing dual tire template from the truck database to get rid of the few things not being required.
    How easy life could be ...
     
     
     
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