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Thread: Rf wheel spacer

  1. #41

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    Quote Originally Posted by Kromulous View Post
    Matt49 i agree with you, but would some of the force get reduce by the leverage of the wheel location to the ball joint if if it was excessive? It would be small but you are introducing a moment there, correct?

    I think you talked about that before, some of the load getting transferred thru the upper ball joint, but just making sure.
    No, I'm pretty sure Matt49 stated that the force is "completely absorbed" by the upper ball joint/upper control arm.

  2. #42
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    Quote Originally Posted by collateralDamage View Post
    No, I'm pretty sure Matt49 stated that the force is "completely absorbed" by the upper ball joint/upper control arm.
    That's right. The wheel is pushing up on the spindle snout and the force that goes into the spring is not on a solid beam. It has a point of articulation (the lower ball joint) so some of the upward force on the spindle snout goes into stress on the upper control arm and ball joint. Just take the upper control arm off and see how that works. There is NO mechanical advantage gained by lifting up on the spindle further from the ball joint. Again...other than the VERY small amount of motion ratio gained by the affect that camber gain may have on the distance the end of the snout can travel without moving the spring the same amount. But on a setup without camber gain, if the end of the snout moves up one inch, the ball joint moves up one inch. Therefore the spring moved the exact same amount. Motion ratio the same means rate is the same. It doesn't get any simpler than that.
    Now I realize that we ALL have camber gain in our suspension geometry. But the point that I've been trying to make is that the distance between the wheel and the ball joint has no affect on motion ration OTHER than the camber gain factor of it. There is no leverage being gained by the distance but it isn't a solid "lever" like a beam axle. All of the upward motion is at the lower ball joint. So moving the wheel out two inches is not going to have any noticeable impact on wheel rate. Wheel load? Yes. Wheel rate? No.
    Last edited by Matt49; 04-27-2018 at 05:14 AM.

  3. #43
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    if the ball joint moves up 1 inch and the spring is mounted in board of the ball joint , how can the spring travel the exact same distance?

  4. #44
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    Quote Originally Posted by fastford View Post
    if the ball joint moves up 1 inch and the spring is mounted in board of the ball joint , how can the spring travel the exact same distance?
    That's not what I'm saying. I'm saying if the ball joint moves up one inch and the wheel moves up one inch, the spring will travel some distance (call it X) depending on it's location on the LCA and that will dictate wheel rate. Moving the location of the wheel away from the ball joint doesn't change the distance that the ball joint travels relative to the travel of the wheel therefore it does not change wheel rate.
    If there were no camber gain, the wheel could be 10 feet from the ball joint and it would take the same amount of force to move it up one inch because you still have to move the ball joint up one inch to compress the spring X amount. You don't have any leverage on the spring by moving the wheel out which is why moving it out doesn't change wheel rate. It is NOT a beam axle and people seem to be stuck in the mindset of treating it like one.
    Camber gain would generate a certain amount of motion ratio change but only a very minute amount at the distances we're talking about moving the wheel.

  5. #45
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    i guess im still confused , if the wheel travels 1 inch up , then you move it out 5 inches and it moves up 1 inch , the ball joint is not gone travel up as much as it did to begin with before you moved the wheel out , this is what i would consider a change of rate at that wheel....

  6. #46
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    Quote Originally Posted by fastford View Post
    i guess im still confused , if the wheel travels 1 inch up , then you move it out 5 inches and it moves up 1 inch , the ball joint is not gone travel up as much as it did to begin with before you moved the wheel out , this is what i would consider a change of rate at that wheel....



    If you raise the ball joint 1" the spring will compress 1/2 that distance, since that crappy drawing I did has basically no camber gain the tire (blue or green) will still only move up that 1" regardless of which one you choose.

    Now change the suspension so it has camber gain and you will see a difference.

  7. #47
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    Quote Originally Posted by billetbirdcage View Post



    If you raise the ball joint 1" the spring will compress 1/2 that distance, since that crappy drawing I did has basically no camber gain the tire (blue or green) will still only move up that 1" regardless of which one you choose.

    Now change the suspension so it has camber gain and you will see a difference.
    Billet is that Solidworks you are using for your 3d modeling?

  8. #48
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    So if I move my mounting points out one inch. What does that do?

  9. #49
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    Quote Originally Posted by billetbirdcage View Post



    If you raise the ball joint 1" the spring will compress 1/2 that distance, since that crappy drawing I did has basically no camber gain the tire (blue or green) will still only move up that 1" regardless of which one you choose.

    Now change the suspension so it has camber gain and you will see a difference.
    so in your drawing , your saying if the ball joint travels up 1 inch , the blue tire is going to travel the same as the green tire? how can that be with it out 6 inches more than the other?

  10. #50
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    Quote Originally Posted by fastford View Post
    so in your drawing , your saying if the ball joint travels up 1 inch , the blue tire is going to travel the same as the green tire? how can that be with it out 6 inches more than the other?
    The spindle never changes camber (snout will always be level as it is in the drawing), so it moves the same whether the tire is right at end of snout or 100 foot away from the snout.

    *Note: This is with parallel and equal length control arms which a LM usually never has. I was only showing this because it shows what matt was saying with "no camber gain".

    Last edited by billetbirdcage; 05-02-2018 at 04:35 PM.

  11. #51
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    ok , i guess im not looking at it with both upper and lowers being identical in mounting points and length as with your drawing above.....

  12. #52
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    Thank you billet for explaining what I was trying to explain so unsuccessfully.
    As the old saying goes, a picture is worth a thousand words.

  13. #53
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    This tread got entertaining. More or less because it got heated in rhetoric. It is not good to be overly idealistic as the point can be lost and people mislead. I have been wrong many times because of simplifying the problem.

    Wheel rate is vertical spring rate at the wheel center. All our current used suspensions have resulting camber components so it is a waste of time to not consider that. You guys can point physics fingers all you want at that....

    A 1" wheel spacer on the RF of an XR1 will change the wheel rate ~10lbs/in. My example is with a linear 300lb/in primary spring. Wheel rate moves from ~103lb/in to ~94lb/in within the 3in of travel range. Tracking and steering influences will be easily noticed by the driver. I suggest you make this change only on a test track so you can back to back the resulting observation.
    Attached Images Attached Images

  14. #54
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    Quote Originally Posted by Ghopper View Post
    This tread got entertaining. More or less because it got heated in rhetoric. It is not good to be overly idealistic as the point can be lost and people mislead. I have been wrong many times because of simplifying the problem.

    Wheel rate is vertical spring rate at the wheel center. All our current used suspensions have resulting camber components so it is a waste of time to not consider that. You guys can point physics fingers all you want at that....

    A 1" wheel spacer on the RF of an XR1 will change the wheel rate ~10lbs/in. My example is with a linear 300lb/in primary spring. Wheel rate moves from ~103lb/in to ~94lb/in within the 3in of travel range. Tracking and steering influences will be easily noticed by the driver. I suggest you make this change only on a test track so you can back to back the resulting observation.
    Long time no see, nerd! (grins)

    Good to see you have a little time to race now and then, hope is all good.

  15. #55
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    Nice CAD work ghopper. I've been working on simulating some front end stuff in Fusion 360 but have been encountering some challenges that may simply be finding the limits of what it can do. What did you use for this?

  16. #56
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    dont know about the " heated rhetoric " thing , if you do not question things , then you may never know if your right or wrong. I have gained a lot of knowledge from you guy,s and I appreciate it......what Ghopper has explained is what I was trying to say concerning wheel rate , just did not know how....

  17. #57
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    Quote Originally Posted by Matt49 View Post
    Nice CAD work ghopper. I've been working on simulating some front end stuff in Fusion 360 but have been encountering some challenges that may simply be finding the limits of what it can do. What did you use for this?
    Siemens PLM Software's Simcenter 3D Motion. It is based on an NX CAD platform. I drew out some cars to get practice after being based in Dassault Catia V5 for a long time. Lots of holiday time with the wife sarcastically asking if I was drawing her pictures.

    https://www.plm.automation.siemens.c...center-3d.html

    Billet - It can be years between looking at this site. I should be at a race track a few times this year. Will probably be rusty as ever behind the wheel.

  18. #58
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    Quote Originally Posted by Ghopper View Post
    This tread got entertaining. More or less because it got heated in rhetoric. It is not good to be overly idealistic as the point can be lost and people mislead. I have been wrong many times because of simplifying the problem.Wheel rate is vertical spring rate at the wheel center. All our current used suspensions have resulting camber components so it is a waste of time to not consider that. You guys can point physics fingers all you want at that....A 1" wheel spacer on the RF of an XR1 will change the wheel rate ~10lbs/in. My example is with a linear 300lb/in primary spring. Wheel rate moves from ~103lb/in to ~94lb/in within the 3in of travel range. Tracking and steering influences will be easily noticed by the driver. I suggest you make this change only on a test track so you can back to back the resulting observation.
    That’s beautiful man. Lol. I’ve been using performance trends to map out the front, a little pre historic compared to that nice cad work, but it does tell a guy the same stuff. It’s nice they finally added a pitch setting and improved the four link aspect of their system a bit. Still do all the four bar and birdcage stuff on paper with separate drawings and then kinda mix it all together that way, so I’m always dealing with a certain amount of error based on scaling from iso paper to actual size. Need to invest in some new software lol.

  19. #59
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    dam , i may as well give up with my old school technology , i use strings and chalk and plum bobs , and a 4 ft by 8 ft white slick bathroom wall board to scale my front end out on , oh well........

  20. #60
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    I agree, fastford. Some of this stuff is very difficult to explain through words alone. I think we all just get frustrated trying to get technical thoughts out in plain English. There is a reason why all college-level physics classes typically have a lab class married to them. It takes really doing it to understand sometimes.
    Pretty much all of the regular posters on here have contributed quite a bit of valuable information over the years. Obviously not many of us are pros at this but this is FREE information and there a great many people out there that use it to help their racing program. And I learn stuff on here all the time.

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