page Back one
|H = height of c.g. above
||SF = rollover safety factor,
|T = wheel track, in.
By itself, safety factor is a quantitative
measurement. The higher the SF, the more tip-resistant a vehicle is.
Theoretically, anything over 0% SF will not tip, but there is more too it. The
Stability Table below, Fig. 6, rates SF into categories which can be used to evaluate the
predicted performance of a vehicle.
SAFETY FACTOR, SF,
or equal to zero (<or=0)
test! Extraordinarily unsafe.
|0 to 21
|22 to 33
|34 to 50
than 75 (>75)
desirable but not attainable*
*State laws limit width of passenger cars to 80
inches. This places a limit on SF.
As you recall from the example of
Case 1, a
compact station wagon, the SF was 38%, which the chart indicates a rating of
"Acceptable". To get this car up to 50%, approaching "Very
safe", the track would have to be widened to 70 inches, an H to T ratio of
1:2.5. This ratio where T = 2.5 x H will hold true for any car. If T could be
widened ever farther, out to close to the legal
maximum for passenger cars, SF of 75% could be achieved. Fig. 7, below, will help the viewer visualize the Stability Table.
Fig. 7 represents Case 1, the
station wagon, with H fixed, but T variable. As the track is varied, SF will also vary, going through all the color codes, from red (unsafe) to
dark green (very safe). The actual wheel track of Case 1 would place the wheel
in the light green zone, which rates the car as acceptable.
one page Top of