New Version of the 4 Link Calculator

[Treefrog]

Figured I would post an update on 6.0. Finished link sizing earlier tonight, planning to get through driveshafts tonight as well. Link geometry is done, but I need to do the output portion of it still. Also have the unit conversion for the inputs. Figured I would share some pictures, so here some of what Link Sizing / Materials looks like in 5.5 and also in 6.0.

 

[vetteboy79]

What are you using for loading the panhard bar? Seems like that could be awfully indeterminate, depending on steering situation, cornering, sideload, etc...

 

[Treefrog]

What are you using for loading the panhard bar? Seems like that could be awfully indeterminate, depending on steering situation, cornering, sideload, etc...

It used and continues to use transverse acceleration. I am relying on the work of those who did the earlier versions for the equations. The only change that I have made to any of the force equations is to use the max force from throughout travel and not just the force at ride height. Some of the values in the 6.0 figure might look off. That's only because I didn't want to go through the effort of figuring out all of the inputted value conversions to metric for one photo.

But transverse acceleration should account for both cornering and being off camber. Only downside is that it doesn't account for axle or body roll.

 

[Treefrog]

Another update on 6.0. Watching the race is giving me plenty of time to grind away at it. Just got finished the link calc sheet. The plots have been nonstop 2 steps forward 1 step back. Between having to deal with metric and imperial, dealing with all the possible configurations and possible parallel conditions, and excel chart formatting resetting when editing them it took a long time to get through. That leaves driveshaft (should be quick and easy) and shocks (wish it was quick, but shouldn't be too hard) outputs to get the calc to the rest of the stuff from previous versions. And then it will be onto the new features.

As for the changes to the Link Calculator portions, switched over to plot outputs instead of tables, should show what is going on better. Still have it reporting full bump, ride, and full droop values. Simplified the output of the force on the links to just the maximum force on the link through travel. Also rearraigned it some in order to add some new features.

 

[Treefrog]

And its once again time for a new version. Except for possible bug fixes, this is the last one for a long time, as I have run out of features to add to a 2D calculator. The rest of the features that I can think of require having the ability to solve in 3D dimensions. Such features might/should be doable, but are quite complex, and would require developing the needed equations.

So, glossing over a lot of the backend changes, minor changes, and general refinement here's a list of the new features/improvements:

• Choose positive direction for front X values
• Added view toggles to link geometry views
• Switch from table output to plot output for values of interest
• Auto-scaling views, may appear stretched
• Added solid link options to Link Sizing (previously Materials)
• Account for portal height in finding anti CG heights
• Report minimum distance between coilovers and bypasses
• Added lever arm distance from coilovers/bypasses to body roll axis
• Changed slider stop from 50% up travel to user input
• General clean up and auto hiding of stuff on views
• More error checking on various tabs
• Added the ability to highlight a position on the sideview travel plot. Also highlights data points on the value output plots

And the big changes for this version.

Increased the number of travel heights for which data is calculated. This gives a much better picture of what is happening with the suspension.

Support for metric inputs and outputs. Setting up metric inputs wasn't too bad. Outputs was a pain. Pretty sure they are all accurate, but haven't really dug into testing all of them. All inputs are converted to imperial to make things simpler from a math perspective, and converted back. Shocks left me a bit perplexed as all of the shocks and shock sizes used to set up the sheet are in imperial units. I convert all of the shock values that I thought made sense to convert, pretty much everything that isn't the manufacturer specified travel and body size. Any feedback on metric is highly welcome, as I do not have much (any) experience working with that system or ordering shocks/springs outside the U.S.

Added a new sheet called Vehicle Pitch. This one shows a geometry snapshot at various levels of front and rear travel, moved to level ground. Also added predictions for suspension height for positive and negative acceleration at the provided g amount. It also predicts it for a user inputted acceleration. And it predicts travel for a being on a slope. It does not predict it for slope and acceleration at the same time. Personally I think this sheet is one of the more interesting, also one of the more fun ones to play around with and see what is going on.

Austin Sorry to bother you, but mind putting it up under the resources tab?

 

[Weasel]

nice, good job man! 🍺

 

[Austin]

nice, good job man! 🍺

x10


Updated the Resources Page

 

[Eric]

. . . Also added predictions for suspension height for positive and negative acceleration at the provided g amount.. . .

Great job with all the updates! I have not yet studied this latest revision but have a couple questions about the above calculation. If I am understanding correctly, this is an attempt to compute pitch arising from a given translational acceleration? 1.) What assumption is made regard to rotary inertia about the transverse axis? 2.) What assumption is made with regard to 2WD vs 4WD and distribution of tractive forces? Jacking forces, and resulting pitch, will probably be quite different depending on the scenario.

P.S. Excel reports that the latest version 6.0 is corrupt. The version 5.5 works fine.

 

[Treefrog]

Great job with all the updates! I have not yet studied this latest revision but have a couple questions about the above calculation. If I am understanding correctly, this is an attempt to compute pitch arising from a given translational acceleration? 1.) What assumption is made regard to rotary inertia about the transverse axis? 2.) What assumption is made with regard to 2WD vs 4WD and distribution of tractive forces? Jacking forces, and resulting pitch, will probably be quite different depending on the scenario.

P.S. Excel reports that the latest version 6.0 is corrupt. The version 5.5 works fine.

Your understanding is correct. It uses the g value labeled acceleration that has historically been used to determine loading on the links.

To answer 1 and 2: Only steady state acceleration is looked at, so stuff like rotatory inertia and shock damping is not influencing it. The process for getting an estimate is: determin weight transfer->determine change of force at each end of vehicle-> determine change in force on the shocks = force change*(1-anti)->look up that travel for said amount of force and the second closest amount of force.

As such, it uses the drive bias inputted by the user.

Is it 100% accurate, no. But its an estimate.

Thanks for the heads up about the excel saying it is corrupt, looking into that now.

 

[Treefrog]

Great job with all the updates! I have not yet studied this latest revision but have a couple questions about the above calculation. If I am understanding correctly, this is an attempt to compute pitch arising from a given translational acceleration? 1.) What assumption is made regard to rotary inertia about the transverse axis? 2.) What assumption is made with regard to 2WD vs 4WD and distribution of tractive forces? Jacking forces, and resulting pitch, will probably be quite different depending on the scenario.

P.S. Excel reports that the latest version 6.0 is corrupt. The version 5.5 works fine.

Looked into the corrupt file issue. The link to the file in my google drive in post #1 is good. It seems that the version in Resources is being hosted as the wrong file type. Version 6.0 is a .xlsm since it has macros. I've reached out to Austin about it.

Edit: Its been fixed.

 

[Yellow4r4]

Are the calculations different from version 5.5? Because when I enter the exact same numbers in the new version the light blue lines for the 100 percent values at ride height and the dash red lines for the front link projections don't match the 5.5 version or line up with the solid red lines. And I liked the grid on the old top and side view, it made for a quick assessment when trying multiple changes. And forgive my ignorance if it's something that I should already know, but the only time I have used excel is this calculator. Thank you for all your hard work and those that contributed before!

 

[Treefrog]

Are the calculations different from version 5.5? Because when I enter the exact same numbers in the new version the light blue lines for the 100 percent values at ride height and the dash red lines for the front link projections don't match the 5.5 version or line up with the solid red lines. And I liked the grid on the old top and side view, it made for a quick assessment when trying multiple changes. And forgive my ignorance if it's something that I should already know, but the only time I have used excel is this calculator. Thank you for all your hard work and those that contributed before!

Thanks for the feedback. I've readded the gridlines and values for 6.1, as well as one or 2 small things that I found. Looking into the calculations, I put the wrong equation in for 100% anti-dive, forgot to reference it from the front, so that's been fixed. I've changed the end point for the lower convergence lines. And it seems I reference the rear frame Y not the fronts for front roll. That is a big enough issue that I am putting out 6.1 in a few moments. Sorry for the inconvenience of having to put numbers in again.

 

[Treefrog]

New version is up. Restored some graph features that were removed. Fixed an incorrect cell link, and some bad equations.
Austin Mind uploading a new one?

Edit, hold off for a moment. Checking all of the other antidive equations

Edit 2: good to go now. They were all wrong. Messed up trying to keep track of where the measurement point is in relation to the convention for the biases.

 

[Treefrog]

Version 6.2. Haven't been messing with the calculator much, which results in less quirks and bugs being patched. Still managed to find one. Messed up a copy paste again, this time in the vehicle pitch section, so that's fixed. Other than that, updated all of the links between threads in post 1 across all 3 of the 4-link threads.

The other big change is in regards to the changes to the Resources page. Loving the new way of doing things. No more host on Google Drive and asking to have them added. Thank you Austin .

Well, onto 6.3. I've got a few features in mind.

 

[FJ73]

Hi Treefrog,

I have used the 6.2 version in metric and its thrown out the percentages in the anti graphs seems to only happen when switched so i guess this only applies to a small portion of us. Thanks heaps for all the hard work.!

 

[Treefrog]

Hi Treefrog,

I have used the 6.2 version in metric and its thrown out the percentages in the anti graphs seems to only happen when switched so i guess this only applies to a small portion of us. Thanks heaps for all the hard work.!

Odd, mind sharing some images of all the input values so I can dig into it?

 

[FJ73]

Odd, mind sharing some images of all the input values so I can dig into it?

No worries its not the best numbers but im working around some chassis and rules that hamper the mounting. Happy for some constructive suggestions.!

 

[Treefrog]

I'll look into the issue as soon as I can. The metric side of things did not get much in the way of error checking as I don't often use that system in it's entirety. Any feedback on improvements and issues regarding that side of things is greatly appreciated.

 

[Treefrog]

No worries its not the best numbers but im working around some chassis and rules that hamper the mounting. Happy for some constructive suggestions.!

Figured it out. For some reason I have it converting the antis from imperial to metric like the rest of the values. A fixed version should be out in a day or two. But in the mean time, the correct values are at the top of the calculations page under "Link Calculations".

On a different note, what are you building? Those are some tall portals. And you have rather heavy and large axles.

 

[Treefrog]

Version 6.3 is out over on the resources page. A quality of life improvement for those using panhards. Improvements to vehicle pitch page and some fixes to metric and some stuff on the vehicle pitch page.


Fixed the issue with anti graphs when using metric. I have no idea why I thought I needed to convert percentages from imperial to metric.

Added a gradient to the panhard displays. The dark end is the frame end. Hopefully this makes it easier to see which end is which.

Added two more data points to the vehicle pitch plots: both ends at bump and at droop. Mostly cause I got tired of having to hand enter these to jump between them.

Added combined acceleration and slope prediction to vehicle pitch sheet. Should have had this originally, it is just adding two numbers that were already found.

Added bias prediction to vehicle pitch sheet. Not sure how accurate this is, its based on load split, not which wheels have traction.

Caught and fixed an issue with the front axle plotting on Vehicle Pitch sheet. Forgot to account for wheelbase changes.

Vehicle Pitch sheet now has local drive and brake biases instead of using the same ones as the Link Calculator sheet. Easy enough to change, so might as well.

 

[93blackxj]

Not getting values for suspension travel predictions.

Numbers are there with your base parameters in V6.1 and 6.2

After I add my parameters it goes to this. Not sure if its just a situational case that creates some weird programming issue with my parameters but I can change numbers individually to see what actually causes it if it would help any.

On Version 6.3 this is what is shown as soon as I open it with your base parameters.

 

[Treefrog]

Not getting values for suspension travel predictions.

Numbers are there with your base parameters in V6.1 and 6.2

After I add my parameters it goes to this. Not sure if its just a situational case that creates some weird programming issue with my parameters but I can change numbers individually to see what actually causes it if it would help any.

On Version 6.3 this is what is shown as soon as I open it with your base parameters.

Odd. I can't replicate the issue in 6.3. Would you be willing to share your parameters for 6.1 and 6.2? I've run across a few situational cases that are a pain.

Interesting that it affects the travel predictions but not the bias prediction. Can you also share an image from the calculations tab? In particular, the box at the bottom titled "Dynamics", highlighted below?

 

[93blackxj]

Odd. I can't replicate the issue in 6.3. Would you be willing to share your parameters for 6.1 and 6.2? I've run across a few situational cases that are a pain.

Interesting that it affects the travel predictions but not the bias prediction. Can you also share an image from the calculations tab? In particular, the box at the bottom titled "Dynamics", highlighted below?

I will just post it all in hows my numbers page so you can see all the parameters and maybe give me some input on what could be improved.

 

[93blackxj]

Odd. I can't replicate the issue in 6.3. Would you be willing to share your parameters for 6.1 and 6.2? I've run across a few situational cases that are a pain.

Interesting that it affects the travel predictions but not the bias prediction. Can you also share an image from the calculations tab? In particular, the box at the bottom titled "Dynamics", highlighted below?

But here are parameters from V6.1 so i dont clutter up the heres my number thread. This is one that had values in the prediction chart before i entered my parameters.

 

[Treefrog]

But here are parameters from V6.1 so i dont clutter up the heres my number thread. This is one that had values in the prediction chart before i entered my parameters.

Is there any issues on the shocks page? The travel predictions uses the force at the wheels from that. It seems that there is some issue in referencing those values.

 

[93blackxj]

Is there any issues on the shocks page? The travel predictions uses the force at the wheels from that. It seems that there is some issue in referencing those values.

I have not gotten to the shock parameters yet but I will let you know if I do find anything when I get there.

 

[Treefrog]

I have not gotten to the shock parameters yet but I will let you know if I do find anything when I get there.

A screen shot of the page and/ or Calculations section for coilovers would be enough for me to figure some stuff out I think. I think that it may have something to do with the spring force and the travel distance.

Thanks for your help in figuring this out.

 

[93blackxj]

A screen shot of the page and/ or Calculations section for coilovers would be enough for me to figure some stuff out I think. I think that it may have something to do with the spring force and the travel distance.

Thanks for your help in figuring this out.

No problem, hope it helps you figure it out.

Edit: had the bypass info in here at first but realized you said the coilover calcs. Let me know if you need me to post anything else.

 

[Treefrog]

No problem, hope it helps you figure it out.

Edit: had the bypass info in here at first but realized you said the coilover calcs. Let me know if you need me to post anything else.

Thank you. Seems that I will need one more image from you, and hopefully the last. Cells B280:AC305 on the plot page. Its the rear shock travel and position sections.

 

[93blackxj]

Thank you. Seems that I will need one more image from you, and hopefully the last. Cells B280:AC305 on the plot page. Its the rear shock travel and position sections.

Yepp this is where its coming from it seems.