Rice Lake Intercomp SW™ Deluxe Portable Vehicle Scale - Manual (Page 27)

SW Users
REV G, February, 2000
27
Appendix C: C.G. / Vertical C.G. notes
Center of Gravity
This appendix deals with the use of scales to determine static tire loading and center of
balance. For detailed instructions on using this weight and balance information for
performance tuning of a racing chassis, please refer to a book like "Chassis
Engineering" by Herb Adams. This note is intended for use by racers, chassis setup
personnel, and any other interested persons.
Q: What is the "Center of Gravity?"
A: CENTER OF GRAVITY (CG) - That point about which the car would balance if
suspended. This point has a longitudinal (front to back) part , a lateral (side to side)
and vertical (up and down) part.
Q: Why do I care about the C.G.?
A: The C.G. has many impacts on how a car handles. The better a car handles, the
faster you can go!
With certain qualifications:
a) The higher the center of gravity the more the body will roll in a turn, accelerating
or braking.
b) The closer the C.G. is to the front or rear end the more weight that end will carry.
c) Moving components can change the C.G., as can adding or subtracting weight.
A good rule of thumb is the lower and more centrally located the C.G. under the most
demanding traction conditions, the better. For circle track racers this is in a turn, for
dragsters this is in a straight line.
Q: How do I find the longitudinal and lateral C.G. points?
A (part 1): Using an Intercomp SW scale you can find the horizontal C.G. this way:
Measure the wheel base and track. Center of gravity will be measured from the
center of the tire contact patch; use the center of the tire for the track, and the center
of the hub for the wheel base. The scale will use the left front pad as the reference
point for all calculations. Use inches to the nearest tenth of an inch.
Scale the car normally. When you have all four wheel weights on the display press
the ENTER key. This pulls up the features menu. Press 1 for C.G. calculation.
Enter the track width measurement taken above and press enter. Next enter the
wheel base measured above.
The display shows you side to side and front to back C.G. The first and third lines
display the C.G. in inches from the left front tire. The second and fourth line show
this value as percentage of wheel base and track, starting from the left front wheel.
A (part 2): If you are using other scales, this involves a little work with a calculator.