Spring What if Workbook

This is for Technical;
I have created a Workbook in Excel (97-2003) Format to help find and Modify coil springs.

Here are some instructions;

Wheel Load/Motion Ratio

These can come from your car. The ones I have entered are from a FBody Clip on a Street Rod and are fairly typical. They can be used to compare springs.

Rear springs work similar,



MOTION RATIO
Motion Ratio = (Dimension A / Dimension B) * sin(Spring Angle)

Note if you have negative or positive wheel offset you should subtract or add that to Dimension B, it is the wheel center that counts.

The motion ratio is the mechanical advantage (lever ratio) that the wheel has over the spring in compressing it.

You can use the following calculator, just use 3 " as the Shock Ride Height.

Rear springs work similar, just use trailing arm pivot to axle centerline as Dimension B, Springs on the axle have a motion ratio of 1, no leverage.

You can use the drop down filters over each column to filter springs.

You could look for all springs from 4 - 4.2 Inches with Square and Tangential for example.

This could help you find springs that may fit.

The compare height difference of 2 springs tells you the ride height difference.

Spring Load is calculated from Wheel Load / Motion Ratio.

Installed Height takes the Spring Load / Spring Rate (Compression) and subtracts it from the Free Height.

There are two other sheets for now, CrossRef which references Moog to two other spring suppliers.

The cut spring sheet shows you the spring rate after you cut a spring.

Enter the Height, the New Height, and the Spring Rate and it will show you the new rate.

I just did this so if you find a mistake I will fix it.

We can also add other sheets of calculations if requested. I have used Excel as a tool in racing and have many calculations.

You can open the file from my Skydrive

It will open in a web browser and you can use it but the first one to open it locks it, so go to file and save it to your computer.

Here are some screen shots;

Here you can see that cutting 1 inch off the CC850 in this example lowers the car 1.4 inches and raises the wheel rates 16 LB/In



Comparing various springs for 51 Ford.



Let me know if you need help.

PS: The values have to be realistic, if you put a 2000 pound load on a 100 LB/In spring it will obviusly not work and you wil get negative numbers.

Springs are fairly elastic in normal ranges, be aware of coil bind or other issues so dont go too crazy.
Hoop

 

To illustrate the use of the Workbook I have searched for springs with similar ID, and the same Ends for a 5.0L Mustang II.

This gives someone with a MII front end some ideas for springs.