Chassis Design Details
Chassis Structure
Description:
The chassis is a semi-Monocoque structure
fabricated from thin wall (.109 and .060) square steel (1018) tube and stress bearing panels of
mild steel (1018) .050 in thickness.
In Figure 1, the tubular structure is shown
without the installation of the stress bearing panels.
Figure 1
As can be seen, this structure
alone would be considered a fairly substantial structure when compared
to the standard "ladder" type frames as are currently in predominant
usage as COBRA chassis. This tubular structure is in reality a space frame,
which alone would have a torsional stiffness of only 1800-1900 lbs per
degree. This is due to inadequate triangulation of the various box sections.
The total weight of these tubes is 288.41 lbs.
In Figure 2. below, the various .050 mild steel
(1015) panels are shown before installation on the tubing in their relative positions.
These panels also serve as the footbox, firewall, and tunnel skins.
The total weight of these panels is 129.59 lbs.
Figure 2
All of the panels shown above
are welded to the tubular subframe. (Please note: a bottom tunnel panel
is recommended for competition usage. This is attached with .250 bolts
directly into the inserts in the lower 2X2 tubes after engine and gearbox
installation.)
In figure 3, the tubular structure is shown with
the installation of the stress bearing panels in place. The stress bearing panels are
welded to the underlying tubular structure to make up the complete chassis. The
application of these panels completes the semi-Monocoque structure.
The total weight of the chassis structure is
418 lbs.
Finished car weight with 351 alloy head motor
is 2350 lbs.

Figure 3
The resulting chassis structure has
an torsional stiffness of over 4800 lbs per degree. In its racing configuration (Engine
and Gearbox stressed) the torsional stiffness will exceed 5500 lbs per degree. This
compares quite favorably to current WINSTON cup and TransAm race vehicles. The inclusion
of a full roll cage would further raise the rigidity to the area of 7500 lbs per degree.
The importance of chassis torsional rigidity is very simply the ability to maintain a
stable platform for the suspension to operate from and relate to the road surface.
Suspension Type And Geometry Description
This chassis utilizes fully independent
suspension on all four corners.
Front:
Rocker arm type, unequal length, non parallel,
with inboard coil-over dampers and inboard attachment of anti-roll bar. Adjustable for
caster, camber, and toe.
Description of various components:
- Upper Rocker Arm. CNC 6061-t6 alloy with Aurora PTFE
lined rod ends and center pivot Garlock composite bearings. Also includes
camber adjustment on outboard pickup point.
- Lower Control Arm. Fabricated tubular steel with Aurora PTFE lined
rodends at inboard chassis and outboard pickup points.
- Upright (spindle) CNC machined 6061-t6 billet with
ford cartridge bearing, with 12 inch by 1.38 inch thick
vented rotor. The caliper is a Wilwood NASCAR Ultralight 4 pot unit.
- Anti-Roll Bar & Dampers. The anti-roll bar is a dual rotary
blade adjustable unit, the rate is adjustable from 85-1200 lbs per inch. Damper and
springs are conventional alloy coil-over type with spherical ball joint ends.

Figure 4 Upper Rocker Arms

Figure 5 Front Suspension - General Layout
Rocker Arm - Aluminum, 2. Coil-Over Dampers, 3.
Filament Wound Composite Bearing,
4. Lower A-Arm, 5. Anti-Roll Bar, Rotary Blade Type, Adjustable
Rear:
Conventional unequal length, non-parallel,
A-arms with outboard brakes and pull rod actuated coil over dampers and
anti roll bar. Adjustable for caster, camber, and toe.
Description of various components:
- Upper Control Arm. Fabricated tubular steel
with urethane outboard pivot and FK PTFE lined rodends at the inboard
pickup points. Attachment of the anti-roll bar is on the upper surface.
- Lower Control Arm. Fabricated tubular steel
with urethane outboard pivots and FK PTFE lined rodends at the inboard
pickup points and toe adjustment location. Attachment of the damper
and spring is to the pullrod actuated inboard rocker.
- Upright (hub carrier) And Halfshaft. Ford Alloy
unit with 12 inch by 1.25 inch vented rotor and Wilwood 4 piston caliper.
Halfshaft is standard Ford large diameter unit with CV joint and inner
tripod joints.
- Anti-Roll Bar & Dampers. The anti-roll bar is a dual rotary
blade adjustable unit, the rate is adjustable from 85-650 lbs per inch. Damper and springs
are conventional alloy coil-over type with spherical ball joint ends.
- Differential. Standard Ford 8.8 Alloy center section
unit with
Traction-Lok limited slip. Ratios are customer selectable.

Figure 6 Rear Suspension
Figure 7. shows the general layout of the rear suspension components.
Figure 7
Upper A-Arm, 2. Anti-Roll Bar, Rotary Blade Type,
Adjustable, 3. Coil-Over Dampers,
4. Lower A-Arm W/Toe adjustment, 5. Half Shaft, 6. Constant Velocity Joints
Geometry |
Front: |
Rear: |
1. |
static camber |
.5 deg neg. |
.2 deg. neg. |
2. |
castor |
1.5 -3 deg. |
-5 deg. to + 5 deg. |
3. |
scrub radius |
3.408 in. |
0 |
4. |
king pin angle |
9.27 deg. |
15.84 deg |
5. |
roll center altitude |
0 in. |
.635 in. positive |
6. |
ride height |
5.00 in. |
5.00 in. |
 |
 |
Index |
Cont'd. |
|