Update: Just uploaded V1.5. Greg has helped me get it looking alot better with everything layed out in a more fluent manner. He also added some pull down menues for the link materials. If you click on the cell a little down arrow will pop up next to it. Just click on the down arrow and you will be able to pick from a list of choices. http://home.earthlink.net/~triaged/Files/4LinkCalculatorV1.5.xls V2.0 is being worked on (by Greg) that will draw a picture of your suspension geometry automatically. He has already drawn up one for the 2D anti-squat excel program he made and is trying to update it for the new 3D spreadsheet (which doesn't sound easy to me!). I am working on making it cycle your suspension so you can see how some of these values change as your suspension compresses or droops (articulation would be nice as well but I have no idea even where to start on that). I am also looking for some other people to help out. I need someone who knows all this math stuff (most likely another mechanical engineer) to check my work and see if my assumptions are valid. I would also like to have someone acutally use it to analyze their suspension with it and give any notes on how it works in real life. ------------------------------------------- Disclamer: I think this info is correct. If you use it and die (or injure yourself in any way) it is your own fault that you were stupid enough to listen to me. I finally finished my 4-link calculator. To the best of my knowlage it is correct. It should not be used as a substitute for common sence but as a guide. It also might be fun to play with. It isn't too pollished up but it is there. It requires that you use my "coordinate system" which is based on the ground right under your rear diff...so when you measure stuff start from there. "X" lengths are from the rear axle centerline forward "Y" lengths are half (1/2) of the horisontal sepperation. "Z" lengths are all measured from the ground. You can end up wiht negative (-) values for "X"...that would just mean behind the axle. If you do a Wishbone type link you will end up with a "Y" of zero (0) length. If you put in a negative (-) value for "Y" you are stupid because you won't be able to build it (the right link would connect to the left side of the chassis /forums/images/graemlins/rolleyes.gif). If when looking from the top your links are parallel make them "not" by some small # (even as small as .001") or it won't calculate your roll center or roll axis. If you put in negative (-) "Z" values you just designed a plow...not a 4x4. BTW: The cells are protected just to keep you from accidentally screwing it up. If you really want to change the formulas there is no password for the protection. For those of you that care... Assumptions: 1) Loads are calculated with 100% weight transfer. 2) Tire coeff. of friction of 1. 3) That you have 4 non-parallel links (if you use a wishbone don't forget to double the load to the center rod end) 4) For the F.S. (factor of safety) in bending you have half of the weight of the truck acting on the center of the link. 5) Your links are made of steel with a yield of 63,250 psi (normalized 4130)...if you want to use a different material you will have to find the spec's and plug them in on the 2nd page Keep this pic handy to help you figure it out As you can tell from this pic I have a 14B in the rear and a D44 up front /forums/images/graemlins/rotfl.gif Drumm roll please... http://home.earthlink.net/~triaged/Files/4LinkCalculatorV1.1.xls The rest of the list is below: http://home.earthlink.net/~triaged/Files/LeafSprings.xls This one has some guessed info, some measured stuff, and some BS...measure up your springs and plug in the #'s. http://home.earthlink.net/~triaged/Files/PartNumbers.xls This is some of the part #'s for parts I have used on my truck. http://home.earthlink.net/~triaged/Files/Swaybars_02.xls This file will calculate the stiffness of your swaybar in G's per degree. It is made for "fabricated" sway bars...not bent tubes. This is the "Really hard math" stuff and won't be much fun for anybody but...what the hell /forums/images/graemlins/thinking.gif Edit: This is an email I sent Greg answering some of his questions ------------------------------------------------------------ The F.S. stands for Factor of Safety. It is how much stronger than failure it it. The lowest F.S. is what will fail first (except for the bending). Ideally you would want to mess with the rod end rating, tube OD, wall thickness, and material (on the 2nd page in blue) to get them all around the same value (no use having a solid 3" diameter link and 3/4" rod end!). In this case a F.S. of 10 might be just a bit overkill...but you sure don't want a number as small as 1 or 2. It is also sometimes called a "Fudge Factor" by engineers because it is tossed in to account for all the stuff they didn't (or couldn't) include in the calculations (like dynamic shock loading in this case). There are also some more general guides for F.S. like "If this fails will someone die, just get hurt, or just property damage?" In this case "Someone might die" so try and keep the F.S. high...esp. for a street driven truck. The bending doesn't have as much of a "someone might die" factor because it will be (I hope!) at slow rockcrawling speeds. In the case of bending you can see that the link is much weaker than in compression (this is the same reason that cages need triangulation). I think your best bet would be to shoot for something just over 1 and then try not to slam the links all over every rock you see. The nice thing about a F.S. is that they have no units. At least not normal ones...they are in fact lbf/lbf (which cancles out to just 1). This way you can compair them with any other truck directly (just like AS values in % which is also unitless). For views I don't see the need for a front view (but it might be cool to see). A top view and side view should be able to show everything. For the vector algebra: I took the link length and sepperated it into it's components (how much it went forward, how much it went up...etc.). I then devided each component by the overall link length to get a "unit vector". This is like a arrow pointing in the same direction as the link but it has a length of "1". From that I know in what direction the force in the link is and I just have to find the "magnitude" of it. To do this is I added up all the moments (another word for torques) and set them equal to 0 (zero). This is one of the statics equations that will tell you why something doesn't move (in this case the pinion doesn't point to the sky on acceleration...we just want to know why/how). From there I devide the total link force back into the components (don't know that it is needed for the rest of the equations but it didn't really take any more work...the equation I gave you before calculated only the force in the "x" direction...you can see how it is an OK estimate if the links don't converge too much but it will always be too small...hence giving you a F.S. of 10 to work with...using the more exact forces the F.S. can be reduced some). Finding the buckling and bending loads was just a matter of "plug and chug" with some equations from an engineering book. I guess that's about it in writting. You already know how to find the intersections of the lines you'll just have to go back through and figure out how I went about finding them (I actually used alot of your ideas to do this...they were alot cleaner than my origional work).