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Need help with Physics Project: Power-Over Drifting (Motorsport)

  1. Dec 7, 2006 #1
    Hi everyone, I am new to this forum, and I am in need of some help.

    I am currently in a General physics 1 course in an undergraduate college. We are doing individual projects that involve analyzing the cognitive and mathematical aspects of a motion. I have chosen to analyze drifting (motorsport) as my project. Specifically I have chosen a technical called Power-Over drifting. The reason I chose this topic is because it is something I am familiar with, (Familiar being... I do drifting as a hobby) and I am quite interested in the topic.

    Power-over drifting involves no handbrake (unlike 'conventional drifting') it is used for vehicles that are AWD or for people have alot of power (300HP+) and who want to do a drift at the fastest velocity and shortest time. What I understand is that through the entire time you don’t stop accelerating… You acceleration only slows down, but when you exit the turn you are at higher velocity then when you entered. How it is performed is as follows: You enter a turn as fast as you can on the outside. Right as you hit the turn, you continue to accelerate, at the same time, you would wrench the steering to the inside of the turn. This sudden change of direction combined with the continued acceleration causes the tires (all four) to slip, and the momentum of the car swings you around the turn. In order to do it successfully you need to continue to keep the wheels spinning and prevent them from gaining grip. The entire time you are to point your steering into the turn, and as you hit the Apex, you depress and then gradually step on the gas which causes your wheels to slow down, and then speed up giving you some traction. After this you exit the turn, and continue to accelerate.

    I am supposed to try to understand the forces at work during the drift around a turn, the before and after. We are supposed to use free body diagrams, drawings, verbal explanations, and graphs.

    I do not have to great of a physics background (almost none at all) and my professor has rushed the semester and in the last minute changed this product from being only 10% to being 40% and counted as a test. My understanding is quite limited and i really need some help.

    What I do understand that there is normal force, frictional force, both static, and kinetic, as well as centripetal force of both the car around the turn, as well as within the tires it self. I also know that there are torque forces that are involved, (created by both the drive train, and its opposing force - friction. My Problem is sorting through it, and since my understanding of physics isn’t that great I am quite lost when it comes to mathematical calculations. What should I be focusing on, and what do I neglect?

    Can someone point me in the right direction?
    Thanks
    Andrew
     
    Last edited: Dec 7, 2006
  2. jcsd
  3. Dec 7, 2006 #2

    berkeman

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    Cool project. I think it would be good for you to start by making a sketch of each different stage in the process of the turn, starting from driving normally as you enter the turn (no tire slipping yet) and ending after the exit of the turn with the tires hooked up again and the vehicle going straight. It sounds like you will end up with about a dozen sketches or more. Then on each one, start indicating what the tires are doing (mostly spinning with dynamic friction it sounds like), and then draw some vectors for the forces on the tires and the net force on the car (causing the overall acceleration of the car). The front tires and the back tires will be generating forces in slightly different directions sometimes, since you can steer the front tires. Remember that in the first couple of sketches, the tires still have static friction, and there will be a transition from static to dynamic as you throw the car sideways at the turn entrance.

    Let us know how many sketches you come up with, and how the force diagrams are sorting out for you. If you can do it with some simple CAD drawing software or something (maybe even Powerpoint?), then you could put them together into a little movie or something....
     
  4. Dec 7, 2006 #3
    thanks berkeman for the suggestion.

    Ive actually already made sketches (in adobe photoshop, and paint) i have about 10 pages of stuff. My problem is that there are somethings in physics that werent explained very well, and i really dont understand at all... ie... How torque works (esp when around the axel), how centripital force works (both within the tire, as well as the car relative to the turn) and how frictional force changes between kenetic and static.

    Thanks again
     
  5. Dec 7, 2006 #4
    Oh and what is Dynamic Friction?
     
  6. Dec 7, 2006 #5

    berkeman

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    Oh, maybe I used the wrong term. I was thinking of static and dynamic coefficients of friction, but maybe the more normal terminology is static and kinetic.

    Use wikipedia.org as a reasonable online resource of info for things like torque and horsepower as applied to cars, and probably for friction as well.

    In the simplest sense, when the car is sliding with the tires locked, then it's a matter of ballistic motion with the dynamic friction from all 4 tires directed opposite of the car's velocity vector. If the car is drifting under power with the tires rotating faster than they need to for the forward component of the velocity vector (remember my front/rear tire comment from my previous post), then there is a net force forward on the car due to the torque from the tires generating a force on the ground (through the kinetic friction mu), as well as a sideways-directed force from the tires (again kinetic mu I think) sliding sideways.

    If you start with that simple model, that will get you 80% of the way through the calcs, I think. Then if you really want full credit (and maybe even some extra credit), you can take into account some other 2nd order effects that come to mind:

    -- Side-to-side weight transfer won't change the total friction force or direction for the tires (because what is lost on one side is gained on the other). But forward-back weight transfer (like when you lift in the exit to re-gain traction) will change things when the front wheels are not pointed the same direction as the rear.

    -- You can spend some time more closely analyzing the transitions from one part of the drift to another, like the initial throw-in part where you are breaking the tires loose for the first time.

    -- You might look at what happens when the kinetic mu changes when you have cold tires at initial turn-in, and it's a long enough turn that you heat up your tires mid-corner.

    -- etc., etc. Have fun!
     
  7. Dec 7, 2006 #6

    berkeman

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    Oh, and I'd still suggest making the drawings with an eye to also making an animation or smooth slide show as part of your report and/or presentation. It would be very very cool to see the sequence with the different vectors growing and shrinking as the car rounds the turn. Keep the turn fixed in the slides, I think, so that the car moves around it with its vectors as the animation runs. You realize that you're going to have to post a link to your final report for us, right? That's a new PF rule that I just made up.
     
  8. Dec 7, 2006 #7
    Hey, wow thanks man, that really helps give me a good direction to move in. Ill Definatly post or link my final to this when its done!

    PS, do you know of any good free programs that i can use to make a decent animation or smoothslide? (smoothslide is what i though would be better, but im not a programmer or anything...i use to fix computer hardware)
     
  9. Dec 8, 2006 #8

    berkeman

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    I don't know about free programs, but PowerPoint is pretty common on most PCs.

    BTW, I thought of another thing you could incorporate in your project. You could compare the different techniques of cornering to show which is fastest and why. Compare just railing on good tires at the limit of traction to drifting optimally to drifting badly. I'd expect them to be in that order of fastest to slowest?
     
  10. Dec 8, 2006 #9

    berkeman

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    Sorry for continuing to blabber on, but this is a fun subject. Another thing you might do to spice up your presentation is start with a video of you drifting a corner to set up the context. I don't know if it would be better to show it from outside the car or inside the car or both. It would be really cool if you could hear the engine tone change on the audio when you use that lift trick at the corner exit to hook back up again. If you can voice-over the short video (just the one corner), you can say fast some of the stuff that you mentioned in your first post, to help set the stage for the technical analysis that will follow with your drawings.

    What's the name of that movie with all the drifting in it? Dang, my son had me watch it a few weeks ago, but I forget the name....
     
  11. Dec 8, 2006 #10
    Lol, the movie was Fast and the Furious: Tokyo Drift...
    Yea you know thats sounds like a good idea (with the movie and stuff). Problem is, this isnt the season to do drifting, and i need to do it on a track. (definatly not going to do it on the twisting road a few miles from my house). Unless it snows soon, i cant really take a decent vid. Maybe ill go on Youtube, and get some drifts. Power-over isnt that common, but there should be at least 1 vid.

    thanks again
    Andrew
     
  12. Dec 8, 2006 #11
    Couldn't you do it on a computer game such as Project Gotham Racing 3? Perhaps look at the modelling they use.
     
  13. Jan 30, 2008 #12
    Hey sorry to just kinda jump in here...but i have just kinda the same project wit the general physics of drifting and i was just kinda wondering where you found your information from and kinda how you put your presentation together

    any help would be wonderful
    thanks
    Wes
     
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