New Version of the 4 Link Calculator

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    New Version of the 4 Link Calculator

    Current Version: 5.2
    It can be found here. https://drive.google.com/file/d/1auF...ew?usp=sharing
    Past, and possibly current, versions can be found on the Resources Page.



    With the changes to the board, a goal was set of generating more current and up to date technical information. To this end, it is time for another update to the 4 Link calculator, which had its last major update done in 2016. The goal of this update is to assist in coilover placement and the selection of springs. This is done by adding portions of BillaVista's Preliminary Spring Rate Calculator, which was made in 2004.

    Despite the discussion around the accuracy of some of his recommendations in The Coilover Bible, the equations he presented are correct, except for one which is partially correct. Both approaches towards determining the ideal spring rate present in Primary Spring Rate Calculator are accounted for, as is the approach presented by ZukIzzy.

    The partially accurate equation presented by BillaVista is the equation for the install ratio (ratio between spring rate and wheel rate), "IR = DR * ACF = (d1/d2) * cos(alpha)." This equation is good enough for most applications, but does not account for all factors., such as the true rotation point of the axle, and the angle between the tangent of the wheel travel arc and vertical. It also has limitations when trying to determine wheel rate during travel.

    As per usual, the numbers in the Current Version are for testing purposes.



    Going forward. I plan to add support for a second shock, and possibly driveshaft length and angles.

    Feedback, suggestions, and math/error checking are all appreciated.

    At the very least, can we keep this from becoming a check my numbers thread?

    Edit: 7/27/2020 Updated current version to 5.1.

    Edit: 8/9/2020 Updated current version to 5.2.
    Last edited by Treefrog; 08-09-2020, 05:16 PM.

    #2
    Excellent and thank you for sharing!

    Comment


      #3
      Yes, thanks for taking time and for sharing. Austin This needs to be added to the resources page.
      Kevin

      Comment


        #4
        Thanks for sharing.
        Is there a there a thread that gives examples of stock suspension values or a good explanation on how to map/measure values?

        Comment


          #5
          Originally posted by Rob50lx View Post
          Thanks for sharing.
          Is there a there a thread that gives examples of stock suspension values or a good explanation on how to map/measure values?
          I don't know of a thread for stock values. As for measuring, a plumb bob and chalk might be the easiest way. Mark the points and tire centers on the ground, record the heights, move vehicle, and measure.

          Comment


            #6
            Originally posted by gt1guy View Post
            Yes, thanks for taking time and for sharing. Austin This needs to be added to the resources page.

            I know, I'm on a boat i a lake .... 100% will add it when I can

            Ok, so I didn't type that part about being on a lake...................I assume that was Austin. Or this site has scary ghosts already
            Kevin

            Comment


              #7
              Just updated to 5.1. Updated the links in the first post.

              Caught a big error in the calculation of the wheel rate when using the suspension height approach. This effect of the error is more pronounced the less equal up and down travel are. Also caught some errors in the link sizing that should not effect the values much. I forgot to check the factor of safety equations from when I changed them from force at ride height to maximum force. And, since I was working on the link sizing page, added some presentation of data from both ends. Also changed how the lookups for the material and rod ends work to make them more user friendly.

              Austin Would you mind adding the newest version to the resource page?

              Comment


                #8
                Originally posted by Treefrog View Post
                Just updated to 5.1. Updated the links in the first post.

                Caught a big error in the calculation of the wheel rate when using the suspension height approach. This effect of the error is more pronounced the less equal up and down travel are. Also caught some errors in the link sizing that should not effect the values much. I forgot to check the factor of safety equations from when I changed them from force at ride height to maximum force. And, since I was working on the link sizing page, added some presentation of data from both ends. Also changed how the lookups for the material and rod ends work to make them more user friendly.

                Austin Would you mind adding the newest version to the resource page?
                Done
                America is all about speed, hot nasty bad ass speed.
                -Elenore Roosevelt

                Comment


                  #9
                  Awesome, thanks!! Any chance there would be 3 link possibility added to this in the future?

                  Comment


                    #10
                    Originally posted by ParadisePWoffrd View Post
                    Awesome, thanks!! Any chance there would be 3 link possibility added to this in the future?
                    I've used it to run numbers for my front 3-link. You just adjust the number of uppers to 1 and panhard to 1. This constrains the axle as a standard 3 link, with your numbers for the upper link y location determining the side (positive for left side and negative for right side upper).

                    Comment


                      #11
                      Originally posted by Treefrog View Post
                      Just updated to 5.1. Updated the links in the first post.

                      Caught a big error in the calculation of the wheel rate when using the suspension height approach. This effect of the error is more pronounced the less equal up and down travel are. Also caught some errors in the link sizing that should not effect the values much. I forgot to check the factor of safety equations from when I changed them from force at ride height to maximum force. And, since I was working on the link sizing page, added some presentation of data from both ends. Also changed how the lookups for the material and rod ends work to make them more user friendly.

                      Austin Would you mind adding the newest version to the resource page?
                      Just one thing of note that I found when putting my numbers in the new 5.1 version. The travel numbers under the Front Upper Links, Front Lower Links, Front Panhard Bar, Front Roll Center Height are linked the travel input from the rear suspension (Cells C9 and C10) rather than the front travel (Cells P9 and P10). This does not affect anything other than the displayed travel numbers but figured I would let you know.

                      Thanks for adding all the additional features to the calculator! This is a great resource tool.

                      Comment


                        #12
                        Originally posted by azdirt3.0 View Post

                        Just one thing of note that I found when putting my numbers in the new 5.1 version. The travel numbers under the Front Upper Links, Front Lower Links, Front Panhard Bar, Front Roll Center Height are linked the travel input from the rear suspension (Cells C9 and C10) rather than the front travel (Cells P9 and P10). This does not affect anything other than the displayed travel numbers but figured I would let you know.

                        Thanks for adding all the additional features to the calculator! This is a great resource tool.
                        Thanks for letting me know. I have updated them for the next version.

                        Comment


                          #13
                          What about adding the CG bias front to rear as discussed in the "ThinAir" thread?
                          ....Just Add Lightness...

                          Comment


                            #14
                            Originally posted by Weasel View Post
                            What about adding the CG bias front to rear as discussed in the "ThinAir" thread?
                            Adding it to the calculations for what?

                            Weight distribution is there, it is used for the springs. Correct me if I am wrong, but it is my understanding that front rear balance does not affect squat and anti squat.

                            Comment


                              #15
                              Just updated to 5.2. Updated the links in the first post.

                              Found some more errors in the front shock movement and install ratio calculations, should only change things if you did not have the front set to axle. Missed a few values when copy pasting it seems. Fixed the stuff azdirt pointed out. Also fixed the initial wheel rate not accounting for preload when using the shaft showing approach. Should have been paying a little closer attention when fixing that for 5.1.

                              Oh, and I added bypass shocks to it. Doesn't have the ability to help with valving, but at least it has install ratio and stuff regarding length and travel usage.

                              Looked over a lot of the Shock math while setting it up for copy pasting for the bypasses. All of the cell links should be fixed, so the math should be good now, unless it is inherently flawed.

                              With the removal of bypasses from the planned features list, I am adding sway bars to the list. No guarantee on when it or driveshaft lengths and angles are getting added.

                              Austin Mind throwing this one up on the Resources page?

                              Comment

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