9 FRONT ANTI-ROLL AND ROLL PRE-LOAD
You can use each of the Belleville stacks with or without pre-load. There are two types of
pre-load, described in detail here below. The limit of the system is the rocker touching the
magnesium support when moving laterally.
Double stiffness pre-load
•
Within the pre-load range, the stiffness is double the stiffness of one stack, both stacks are
working
•
Passed the pre-load, the stiffness gets back to the nominal stiffness of one stack
Infinite stiffness pre-load is accomplished with an additional nut and a counter nut
•
Within the pre-load range, the rocker doesn’t move at all
•
Passed the pre-load, the stiffness gets back to the nominal stiffness of one stack
•
The choice of a pre-load setting, or the non pre-loaded setting might be based on the car’s
balance exigencies, tyre wear, drivers’ preference etc…. Pre-load settings generally help for
sharper turn-in characteristic.
•
Clearance between the platform and the rocker (B) shall not be more than 6.5mm when
platform just touches the Belleville stack, with no pre-load.
•
The amount of pre-load is the difference between the current and the free length of the
Belleville stack.
•
For any Belleville stack, in running condition, rocker lateral motion and the chosen pre-load
must never reach the "Maximum Deflection" (see Table 6), to avoid a sudden lateral locking
of the rocker.
•
Once the rocker overcomes the pre-load, the total stiffness reduces to the nominal stiffness
of one Belleville stack. You may like to work within the roll pre-load range under certain
conditions (turn-in…) and wish to pass over the pre-load range in some others (mid-corner,
curbs…). Set accurately the transition point (pre-load level) between the two conditions, since
the stiffness change is sudden and affects transient car behaviour.
You can achieve a progressive load / displacement characteristic by combining in series two different
stacks or a regressive load / displacement ratio by fitting an appropriate pre-load. Total length of
any stack should be maximum 34 mm.
BELLEVILLE STACK CONFIGURATIONS (Belleville thickness 2.0mm)
Stack configuration Max deflection
mm
Stack width
mm
Nominal stack stiffness
Kg/mm (no pre-load)
Maximum
notches
<<<<>>>>
1.12
17.50
2504
8
<<<>>>
1.12
13.50
1796
8
<<<>>><<<
1.69
20.25
1197
12
<<>><<
1.69
14.25
761
12
<<>><<>>
2.25
19.00
571
17
<<>><<>><<
2.81
23.75
457
22
<><
1.69
8.25
362
14
<><>
2.25
11.00
272
17
<><><
2.81
13.75
218
22
<><><>
3.37
16.50
181
26
<><><><
3.93
19.25
155
28
<><><><>
4.50
22.00
136
34
<><><><><>
5.62
27.50
109
44
Note: the front rocker lateral movement has been increased from the previous (F399-301) maximum
6mm to about 10mm on the F302/3/4 car.
