Page 536 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Standard sedan (saloon) – baseline load paths C HAPTER 16.2

16.2.2.4 Free body diagrams and Resolving forces horizontally:
equilibrium equations for each SSS
P 10 ¼ P 9 (16.2.12)
16.2.2.4.1 Transverse floor beam (front) (1) Similar equations apply for the right-hand panel.
Resolving forces vertically and by symmetry (loads are
assumed to be applied symmetrically about the vehicle 16.2.2.4.7 Panel behind the rear seats (9)
longitudinal centreline): Resolving forces vertically and by symmetry:

P 1 ¼ F =2 (16.2.3) P 11 ¼ P 8 (16.2.13)
pf

16.2.2.4.2 Transverse floor beam (rear) (2) 16.2.2.4.8 Rear parcel shelf (10)
Resolving forces vertically and by symmetry: Resolving forces horizontally and by symmetry:
P 2 ¼ F pr =2 (16.2.4) P 12 ¼ P 9 (16.2.14)

16.2.2.4.3 Left and right front inner wing panel 16.2.2.4.9 Floor panel (11)
(3) and (4) Reaction forces P 5 from the inner front wing panels and
Resolving forces vertically for the left-hand panel: forces P 10 from the rear quarter panel are applied to this
SSS. These will not necessarily be equal so additional
P 3 ¼ R FL F pt =2 (16.2.5) forces P 13 are required acting at the sides which react on
A similar equation is obtained for the right-hand the sideframes. It will be assumed these forces act in the
panel. direction shown in Fig. 16.2-4 although when numerically
Taking moments about the rear lower corner: evaluated, these may be negative (i.e. in the opposite
directions). Resolving forces horizontally:
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P ¼fR FL l 1 F pt ðl 1 þ l pt Þ=2g=h 1 (16.2.6) 2P 13 ¼ 2ðP 10 P 5 Þ (16.2.15)
Resolving forces horizontally:
16.2.2.4.10 Left-hand and right-hand
P 5 ¼ P 4 (16.2.7) sideframes (12) and (13)

Bothsideframesareloadedidentically. Examining theforces
16.2.2.4.4 Dash panel (5) acting on the sideframes shows that these have already been
Equal and opposite reaction forces P 3 to those on the obtained from equations (16.2.3), (16.2.4), (16.2.8),
wing panels act on this SSS. (16.2.9), (16.2.13), (16.2.14) and (16.2.15). However, it is
Resolving forces vertically and by symmetry: necessary to check that equilibrium conditions are satisfied
by applying the equations of statics. Experience has shown
(16.2.8)
P 6 ¼ P 3 thatitisessentialtomakethisequilibriumcheckaserrorsdo
occur with the use of the many equations.
16.2.2.4.5 Front parcel shelf (6) Resolving forces vertically:
Equal and opposite reaction forces P 4 to those on the P 6 P 1 P 2 þ P 11 ¼ 0 (16.2.16)
inner wing panels act on this SSS. Resolving forces horizontally:
Resolving forces horizontally and by symmetry:
P 7 þ P 13 P 12 ¼ 0 (16.2.17)
P 7 ¼ P 4 (16.2.9)
Moments may be taken about any point but in order to
16.2.2.4.6 Rear quarter panels (7) and (8) reduce the algebra it is better to take moments about
a point where two forces act. For example, take moments
Resolving vertically for the left-hand panel:
about the lower corner of the windscreen pillar where
P 8 ¼ R RL F =2 (16.2.10) P 6 and P 7 act. This simplifies the equation by eliminating
l
two terms.
Taking moments about the front lower corner: Moments about the lower corner of the windscreen:

P 9 ¼fR RL l 2 F ðl 1 þ l 2 Þ=2gh (16.2.11) P 1 l 3 þ P 2 l P 11 l 5 P 12 ðh 2 h 1 Þ¼ 0 (16.2.18)
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l
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