Roll Center
I was curious where my front roll center was now. The car has just a tad too much steering. Only took a few minutes to take some measurements and calculate the roll center. The roll center is at -.12 inch. This is below the ground. I can raise it a bit. This will kill a little steering traction. The ground is a nice place for the roll center on asphalt. Here is the input and output of a program that I wrote that will calculate the roll center for a twin A-arm or A-arm plus camber link car. If you would like a copy send me an E-mail to
[email protected] It is a Microsoft Excel file so you would need that program for it to work. A private message will not work. I will see if I can make it downloadable later. The graph is also part of the output to visualize the instant center and the roll center. The roll center is where the line from the tire crosses the center vertical line in the center of the car.
Yes this will work on that RallyX car too unless it has struts.
John
OK here is a link where you can dowload it directly from the Web
When I dowloaded it it went into quick view plus but I could go from there and save the file for editing by hitting the excel logo at top left of quick view plus. Note that the quick view plus is not able to display it quite right.
Roll Center Calculator
Measurements (inch) Car on blocks wheels off
0.79 Center of gravity height. This value is not used in the roll center calculations, but for roll moment.
0.256 Chassis height on tires ready to race
0.268 Chassis height axles on blocks tires off
6.875 Width of car outer surface of hex adapter to outer surface of hex adaptor
0.332 Camber Link outer hinge pivot center of ball stud horizontal distance from block
1.672 Camber Link outer hinge pivot center of pivot, height above floor
1.8 Camber Link inner pivot horizontal distance to center of ballstud
1.429 Camber Link inner pivot height of center of ballstud to floor
0.222 Outer A-arm hinge pivot horizontal distance from block
0.554 Outer A-arm hinge pivot height of center of pin from floor
2.315 InnerA-arm hinge pivot horizontal distance from block
0.39 Inner A-arm height of center of pin from floor
CALCULATED VALUES
ROLL CENTER -0.12 inch
Roll Moment Arm 0.91 inch
Roll Moment @1.5 g 4.63 pound-inch