Roll centers & tire data

[c2s]

Greg has published a simple roll center calulator using Excel, but there seem to be enough questions that I generated a web based .NET application to calc RC's for SLA & MacPherson. Ya, it's static, simple but may be of use to someone.
Tire data seems to be limited. So, I generated a web based .NET program to provide cornering & camber coefficients, vertical rate & some tread patterns for ~50 tires / pressures.
These are provided free for personal, non-commercial use. Hope folks in the form find them useful. The web apps are at

http://www.arengineers.com

--> Other Calc's (Note: these are pop-up windows, so if you block pop-ups - no go).
Kevin

 

[Joest]

C2,
That's a very nice calculator. Does it work out the geometry kinematically or some sort of convergence routine? Do you think you might be able to add additional tire that are more performance oriented such as 16 & 17 inch wheel sizes and width in the 245-335mm range?

-Joest

 

[GregLocock]

Great stuff. I wish you'd talked to me about your roll centre app, I could have given you the wish list that has built up over the years!

In the tire model one, are these real data from the manufacturers?

I'm a bit surprised by the ratio of camber stiffness to cornering stiffness, I though 20% was nearer the mark than 5%

Alos, running Mozilla under HP UNIX the vertical rate box overwrites the rated load box.





Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[c2s]

Joest - I've given everything I have. If someone wants to shoot me data, I'll gen the coefficients.
Greg - I'm running Mozila and looks OK (marginal) ... I'll try to fix it - aaahhhh the benefits of .NOT
Kevin

 

[c2s]

Greg,
Sorry, the answer to question #1 is that it's real tire data from a flat bed tester.
As for a wish list on the roll center app - let me know and I'll see what I can put in the next version.
Kevin

 

[GregLocock]

Wish list - camber gain, roll centre height gain, track gain

Thinking about it they apply more to my program than yours since I was mostly interested in gains, rather than the static values.

Did you ever spend much time looking at Wishbone.bas (in the FAQ). So far as I can tell it is accurate, and it is a full 3d model. So the guts of it are very useful, just the user interface lets it down. I can't bear to use it for development, but do use it to check solutions.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[c2s]

Thanks for the suggestions - those can be incorporated ... knowing the gain is clearly helpful. However, there's no substitute for a curve (which I suspect you are alluding to). Having looked at the referenced program - it's doable. Do I have the time to do it ... ?
Kevin

 

[GregLocock]

A curve would be terrific, evil grin. A bigger extension is to go 3d and include a toe link, at which point you are duplicating existing programs, like Susprog3d.

Running it on Mozilla Firefox and NT4 the formatting is fine. Lazy question, what units are the arm slopes in?

Also, I like the idea of using the ground as a z datum, but for the congenitally lazy amongst us it would be nice to make the z datum for the geometry, arbitrary.










Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[c2s]

In order:
1) Generating a full 3D model with toe curves is something I have looked at. I do not have the time to generate it from scratch. However, I have an existing Fortran program that we use for this. I've been looking into front & back ending the batch Fortran program with .NET for web use.
2) The arm slope is rise/run in whatever units float your boat.
3) At first blush, giving an elevation to the ground Z coordinate doesn't sound that hard ... the devil may be in the details of the quadrant routine to determine sign conventions ... it's now on the list.

Greg, as an FYI, I've added an veicle inertia calulator to the site. This may also contain actual, measured data in the near future.
Kevin