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  1. SusTestEng

    Remedying understeer

    "We have low speed compression damping adjustment on the rear shocks to increase rear roll stiffness and eliminate the need for a sway bar. " That sounds like a bad idea! I am going to take a wild shot at this and say that you are trying to control the rear too much initially. I bet when you...
  2. SusTestEng

    new guy needing suspension help

    The biggest challenge right from the start will be axle plunge. You can't use rear wheel drive caster amounts on a front driven axle. The caster sweep will try to pull the axles out of the diff. Most AWD cars have very little caster when compared to RWD cars. The caster amount in a FWD/AWD...
  3. SusTestEng

    Grip - what influences grip

    Proper Compliance Body and Suspension link rigidity Tire construction These are the biggest 3 I deal with. Yes, suspension geometry also play a big factor, but as a development engineer, this is what I deal with on a daily basis. You would be surprised at the gain in grip and response by...
  4. SusTestEng

    Designing a suspension with basically no constraints!

    Here are some good photo's of what I am talking about: http://randomnothingness.com/albums/userpics/silverstone/Dsc02267.jpg http://www.photof1.com/s6-toyotaf1-1.jpg Old (2003) way: http://photo.gotodon.net/albums/userpics/10003/normal_img_7758_std.jpg
  5. SusTestEng

    Designing a suspension with basically no constraints!

    I saw something the other day that got my attention. On a typical new era F1 car, the inboard mounting point of the front lower A-arm touches underneath the front nose. I am not sure if this joint is a common pivot or if it is fixed and uses the flex of the carbon fiber to make up the travel...
  6. SusTestEng

    Optimal damping

    Hutch: Here is a thread that gets into the "Black Art" portion of damper tuning. http://www.eng-tips.com/viewthread.cfm?qid=107747
  7. SusTestEng

    Optimal damping

    Norm, When a damping force machine takes data, it usually runs 3 or 4 strokes at each specific rod/piston velocity(0.02, 0.05, 0.1, 0.3, 0.6, and 1.0 m/s). It takes it's data point at the specific velocity at the peak of the force. The problem with that is that it doesn't show how it gets to...
  8. SusTestEng

    Optimal damping

    Hutch325: The BEST way is to spend some time with your damper builder! Ask him to show you every part and how the damper goes together. Or, if you have a boken shock laying around, open it up and check it out...as an engineer, I'm sure you have taken things apart to see how the work. :) It is...
  9. SusTestEng

    Optimal damping

    It seems that some of you in this thread are not directly related to shock tuning, so I will offer some insight that might completly confuse you, or it may shed some better light on the subject. Shock tuning is a "black majic", you CAN NOT look at a force/velocity curve and make a judgement of...
  10. SusTestEng

    Optimal damping

    "On our ride and handling circuit shock velocities max out at +1500 mm/s and -1300 mm/s, and on our durability events the same ratio applies." You must have some pretty smooth roads :) We have a section or 2 that we can get the piston speeds up to 2.5 m/s. It is a section of very rough/broken...
  11. SusTestEng

    Optimal damping

    1) The main reason you see twice as much rebound damping is due to the fact that during rebound, you are trying to control the spring force AND the body mass, while in compresson, you are sort of only controling the body mass as the spring force is building and helping to slow down the motion...
  12. SusTestEng

    Modern Spindle Geometry Design Practices

    I just started laughing when I read this thread, because it just hit me that maybe Ford spent way too much time designing the front geometry that when they got to the rear they ran out of time and said.."ahhh, just throw a 3 link suspension on there and call it a day!" As for the original...
  13. SusTestEng

    Designing a suspension with basically no constraints!

    "Basically judicious use of wishbone.bas and carsim and spreadsheets based on milliken would probably get you there." One of the guys that wants to help on the car actually works for Carsim now, so he can use it as a training for himself as well. This should be really fun! I started some...
  14. SusTestEng

    Designing a suspension with basically no constraints!

    Thanks Greg, I know you have much more experience in this area than I do. There is alot of work on this sort of project that may bring some more restraints to the table, like width of the powertrain, but I want to start playing and learning something new. I basically do all the development...
  15. SusTestEng

    Designing a suspension with basically no constraints!

    Background: A couple of my friends in the automotive industry want to design a car in our free time. The main drive behind this is to learn and get our brains working again. Most of us are in development or evaluation type jobs where the real hardcore engineering is not used on a regular...
  16. SusTestEng

    Delay - yaw velocity to lateral acceleration

    OK, I went back and read the original post and I think you are very close. I would have to think that Coriolis acceleration plays a factor. It must, because the radius is either increasing or decreasing during a slalom, therefor the center of the radius is moving and not constant like it would...
  17. SusTestEng

    Delay - yaw velocity to lateral acceleration

    "Incidentally I'm a bit disappointed by statements like " it doesn't act as math would suggest" I didn't make those equations up. Mr Newton did. If you measure the properties at a point, whether it is in the middle of a bowl of jelly, or a block of steel, they still apply." I am saying that...
  18. SusTestEng

    Delay - yaw velocity to lateral acceleration

    Then you have to ask, what is the result of 4-wheel steering in a similar situation? If the lateral acceleration response is much better, then shanba's assumption also holds some merit.
  19. SusTestEng

    Delay - yaw velocity to lateral acceleration

    "I would think its due to the elasticity of the system. If it were rigid, the delay would be much less." Shanba gets a star for that! Greg, the reason for the delay is compliance related. In a steady-state corner the compliance of the suspension is already near it's designed elastic...
  20. SusTestEng

    Ridiculous interview questions

    The question I hate to answer is: What are your weaknesses?" How the heck are supposed to honestly answer: I'm late for work most days, I surf the net a lot, and some days I just don't feel like working!

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