3 & 4 Link Calculators - JeepForum.com

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post #1 of 27 Old 12-15-2011, 11:09 AM Thread Starter
jkl
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3 & 4 Link Calculators

I'm sure these will come in handy for those using this forum. You will need Excel to use them.

3 Link Calculator
4 Link Calculator

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post #2 of 27 Old 12-15-2011, 11:22 AM
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Quote:
Originally Posted by jkl
I'm sure these will come in handy for those using this forum. You will need Excel to use them.

3 Link Calculator
4 Link Calculator
I can't open these on my phone but I've seen the ones on pirate... The ones on pirate aren't so user friendly. Do these need "how-to's"?

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post #3 of 27 Old 12-15-2011, 11:27 AM
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There's a text file (in the ZIP) that looks like a brief "how-to".
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post #4 of 27 Old 12-15-2011, 11:48 AM
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What is "vehicle CG Height"

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post #5 of 27 Old 12-15-2011, 11:49 AM
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What is "vehicle CG Height"
Center of gravity height? Maybe it should have been GC (Ground Clearance).

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post #6 of 27 Old 12-15-2011, 12:12 PM Thread Starter
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What is "vehicle CG Height"
Center of gravity height. IIRC the basic cheat method is the center of your engine. This goes into extensive detail. http://www.jeepaholics.com/tech/cog/#_Toc535118705
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post #7 of 27 Old 12-15-2011, 12:33 PM Thread Starter
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Here's a link to a dumbed down version on Pirate http://www.pirate4x4.com/forum/showt...center+gravity
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post #8 of 27 Old 12-15-2011, 01:51 PM
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If you're going to use these calculators, you need to fully understand that the outputs will only be as accurate as the inputs, referring mainly to the CG height. You can estimate it pretty closely (I use approx location of the throwout bearing or center of bell housing) but going through the entire process to determine exactly where it is is lengthy and complex. If you're wanting to design and build a suspension, don't focus so much on the calculator but instead focus on the set of conventions, or "general rules". A link suspension is just a geometric system. Break it down into the X, Y, and Z planes and look at the mounting points and distances between them. That's what determines the behavior of the suspension.

There are hundreds of good link resources out there. Here's a good one to get the gears turning.
http://pirate4x4.com/forum/showthread.php?t=168577

Once you've got a very solid fundamental understanding of the terminology used, what it all means, and how all of the numbers are derived THEN play with the calculator to use as a verification tool.

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post #9 of 27 Old 12-15-2011, 05:47 PM
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Originally Posted by Imped View Post
If you're going to use these calculators, you need to fully understand that the outputs will only be as accurate as the inputs, referring mainly to the CG height. You can estimate it pretty closely (I use approx location of the throwout bearing or center of bell housing) but going through the entire process to determine exactly where it is is lengthy and complex. If you're wanting to design and build a suspension, don't focus so much on the calculator but instead focus on the set of conventions, or "general rules". A link suspension is just a geometry system. Break it down into the X, Y, and Z planes and look at the mounting points and distances between them. That's what determines the behavior of the suspension.

There are hundreds of good link resources out there. Here's a good one to get the gears turning.
http://pirate4x4.com/forum/showthread.php?t=168577

Once you've got a very solid fundamental understanding of the terminology used, what it all means, and how all of the numbers are derived THEN play with the calculator to use as a verification tool.
The center of gravity measurement is important, but for the heck of it I started changing it in my calculations to see how badly it would affect the other measurements and truthfully changing it up or down a few inches does not seem to make a lot of difference on the the numbers. So going with the center of the engine or the upper bellhousing bolt as other writeups suggest. Seems to be fine. Overall the whole process looks a lot harder than it actually is. Once you stick the wheel base and tire diameter in and then all the link measurements it becomes a lot less intimidating and gives a lot better insight of where to place link mounts.
Once that is done start playing with link locations to see how it affects antisquat and roll center. Just got done repositioning my upper rear link frame mounts to make the numbers look better. Haven't taken it on some big ledges and steep climbs yet though to see if the rear tires hook better.

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post #10 of 27 Old 12-15-2011, 08:35 PM
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The center of gravity measurement is important, but for the heck of it I started changing it in my calculations to see how badly it would affect the other measurements and truthfully changing it up or down a few inches does not seem to make a lot of difference on the the numbers.
Yep, thanks for mentioning that. I was surprised at how inelastic that relationship was as well. So, you can almost say that estimating it is 'good enough' AS LONG AS you have some adjustment built into the uppers and have a very good understanding of the rest of the parameters.

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post #11 of 27 Old 12-16-2011, 05:28 AM
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I know how to find the COG horizontally, thats easy. But how do you locate the point vertically? Just out of curiosity. Using the top bell housing bolt is good enough for me.
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post #12 of 27 Old 12-16-2011, 06:08 AM
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I know how to find the COG horizontally, thats easy. But how do you locate the point vertically? Just out of curiosity. Using the top bell housing bolt is good enough for me.
There is a link in the text file that comes with the download that sends you to the Jeepaholics forum, where they give you a in depth description of how to figure that out. Is pretty involved, but an interesting read

My Tinkering and wheeling thread http://tinyurl.com/pbwdm5u
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post #13 of 27 Old 12-16-2011, 07:41 AM
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Quote:
Originally Posted by aw12345

There is a link in the text file that comes with the download that sends you to the Jeepaholics forum, where they give you a in depth description of how to figure that out. Is pretty involved, but an interesting read
I must have skimmed over that post.

Very interesting indeed. Maybe its just his abbreviations, but that seems overly complicated. I just had a Statics class and learned all about CoG, it didn't seem nearly as involved. Of course breaking things down to linear components for calculation simplicity ends up taking more calculations.

*edit*
Just took a look at the spreadsheet. Wow that's easy. Now I need a place with a scale willing to deal with these shinanigans.
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post #14 of 27 Old 12-17-2011, 05:56 PM
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So does "forward from rear axle centerline" mean from the center of the axle and axle tube (near pumkin) or straight forward from the center of the axle tube?
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post #15 of 27 Old 12-17-2011, 06:21 PM
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Quote:
Originally Posted by MurdaJs
So does "forward from rear axle centerline" mean from the center of the axle and axle tube (near pumkin) or straight forward from the center of the axle tube?
Looking at it from the side, like its a 2D object.
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