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effect of lowered center of mass

Discussion in 'Technical' started by Doug_G, Mar 19, 2011.

  1. Doug_G

    Doug_G Lead Moderator

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    I suspect the car would lean in the opposite direction, which would be unnerving to say the least.
     
  2. AnOutsider

    AnOutsider S532 # XS27

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    Trying hard to picture that...
     
  3. Doug_G

    Doug_G Lead Moderator

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    Well picture the mass above the axles, which is where the force is applied to the car. As the car turns, the mass will try to continue going straight, which will tilt the car into the curve.

    Now picture the mass below the axles. As the car turns, the mass will try to continue going straight, which will tilt the BOTTOM of the car into the curve. So the top of the car will tilt in the other direction.
     
  4. JRod0802

    JRod0802 Member

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    Leaning into the curve..... hmm..... So from the inside of the car, it would kind of feel like a motorcycle! :)

    That would be cool!
     
  5. AnOutsider

    AnOutsider S532 # XS27

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    #5 AnOutsider, Mar 20, 2011
    Last edited: Mar 20, 2011
    I'm a tech guy, not a physics guy so bear with me. Using this photo for example this is typical cornering:

    [​IMG]

    So with purple being center of gravity and the axels being in blue:

    [​IMG]

    With the center of gravity lower, I'm still having problems imagining the outcome being any different:

    [​IMG]

    Unless you mean the arrows above would actually exert enough force out and up to push the opposite end down and in? Again, i'm no physics guy though

    [​IMG]
     
  6. JRod0802

    JRod0802 Member

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    #6 JRod0802, Mar 20, 2011
    Last edited: Mar 20, 2011
    I think it can be difficult to picture when looking at a traditional car, since when you look at a car it's pretty obvious that the majority of the mass is above the axle (just by human intuition).

    So picture this...

    You have a ridiculous looking car... a car with wheels that are ten feet in diameter. The axle of this ridi-car is at the roof of the passenger compartment, meaning the cargo / person portion of the vehicle hangs below the axle. In this vehicle, you can imagine that when cornering the people in that lower portion of the vehicle would kind of swing out to the side when cornering, kind of like a pendulum. If you looked at it from the outside, though, it would look like the car had leaned into the corner.

    Are you with me so far...

    So that would mean that if there was a person sitting on the roof of this ridi-car, s/he would actually be force to lean into the corner since all that weight below him/her cause the bottom of the vehicle to swing out.

    Does that make sense? I'm just trying to change the visual on this hard-to-visualize situation.

    ---

    As for the Model S, if the battery pack was actually low enough that the entire thing was below the axle, and the battery pack was heavy enough that when cornering, it would cause the pendulum-effect of having the bottom of the vehicle swing out, then as a passenger sitting atop the pendulum, you'd be forced to lean into the curve.

    This is, of course, just hypothetical. This was already confirmed to not be the case. The battery pack isn't that low / heavy.

    ---

    Also, the picture on the bottom of your post was hilarious :biggrin:
     
  7. AnOutsider

    AnOutsider S532 # XS27

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    #7 AnOutsider, Mar 20, 2011
    Last edited: Mar 20, 2011
    Yeah I somewhat get it, but it's still sorta hard to imagine, because I imagine it as a straight pole going through the axels. The part above would naturally tick out towards the outer edge of the curve, while the bottom half if the pole is rigid, would go towards the inside. But when I picture something hanging from the axel I still pcture it swinging OUT, like a ride I once saw at universal studios:

    15y8ymr.jpg

    See, so the piece on the track actually leans INTO the turn, while the compartment below it swings OUT. If there were a rigid pole through it, anything ABOVE the track would actually lean INTO the curve as well, unless it was loose like a pendulum, then I can still imagine it swinging out. Aye... I thinkw hat I'm missing is the concept of where the actual center of gravity is. In both the scenarios I outlined, the compartment would be the heaviest piece, but would it be the center of gravity or would the piece attached to the track always be it?

    Ironically, having a hard time imagining something like this actually inspires me. Ever hate how in alien movies or anything supernatural everything is so cliche? Probably because the creators always try to take what they CAN imagine and then make it scary, vs doing something that is just way out that it's a mind-eff to even imagine it. Random I know ;)
     
  8. JRod0802

    JRod0802 Member

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    #8 JRod0802, Mar 20, 2011
    Last edited: Mar 20, 2011
    Using the picture that you showed, imagine that the place where those two people is filled with like 1000 lbs of weights instead of people (making it very heavy). Then imagine there are two seats on top of the ride (above the main guidance pole), with two people on them. On a corner, both the top and the bottom would want to swing out, but the bottom portion would have more weight behind it (and the 4 vertical poles are made of metal, so they wouldn't bend very much), so the bottom would "win", and the top would be forced to lean into the curve.

    In a car, if the center of gravity were below the axle, the bottom would try to swing out a little, and it would partially succeed, but the springs above each wheel will only allow it to swing out a little, not so much that your car is leaning as much as that amusement park ride.
     
  9. dsm363

    dsm363 Roadster + Sig Model S

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    A few very good explanations. Think I understand it. Thanks.
    I'm excited Tesla decided to build what they wanted from the ground up. Think they have a unique opportunity to do something amazing so I hope they follow through.
     
  10. Doug_G

    Doug_G Lead Moderator

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    Wow, you guys explained that at lot better than I did! Thanks.
     
  11. doug

    doug Administrator / Head Moderator

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    This tilting stuff is getting off topic and I may eventually move it. At any rate, (though not a true example since it's done via an active suspension) the Nissan Land Glider concept might help you picture what it would look like.
    13-nissan-land-glider-press_610x406.jpg
     
  12. JRod0802

    JRod0802 Member

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    #12 JRod0802, Mar 20, 2011
    Last edited by a moderator: Mar 13, 2016
  13. AnOutsider

    AnOutsider S532 # XS27

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    #13 AnOutsider, Mar 20, 2011
    Last edited: Mar 20, 2011
    OK that sold it for me, I got it now :)

    *edit* I think you SHOULD break it out into a new thread like "Lower center of gravity = ???"
     
  14. ckessel

    ckessel Active Member

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    FWIW, I vaguely recall Rawlinson (I think) talking about this and saying that having the center of mass that low actually led to a driving sensation that didn't feel normal and so they intentionally didn't want that to happen. Not that it might not be good for handling, but that it'd be disconcerting to drive.
     
  15. TEG

    TEG TMC Moderator

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