The roll
cage in the Project Sidewinder is a multi-purpose structure.
It provides crash protection for the occupants of the
truck while simultaneously adding structural rigidity
to the chassis, providing suspension attachment points,
and accommodation for the special 9-inch and quick-change
rearends that will be used in this vehicle.
Any
well-designed roll cage actually serves a number of
purposes. First and foremost, it must provide protection
for the driver and any passengers. It does this by
preventing either partial or total collapse of the
passenger compartment structure in the event of a crash.
It should also prevent the incursion of outside objects
into the passenger compartment. Perhaps this is best
exemplified by the roll cages in NASCAR Winston Cup
stock cars where the benefits of such protection are
often demonstrated during racing incidents. The safety
importance of such a cage cannot be overstated for
any high performance vehicle that will be operated
at high speed or in competition.
Another
important function of a well-designed roll cage is
to add structural strength and rigidity to the chassis
of the vehicle. It should reduce any flexing or twisting
of the chassis under dynamic conditions, thus providing
a stable platform for the vehicle’s suspension
system. Equally important, the roll cage provides solid
mounting points for suspension components, pedal assemblies,
shoulder harness attachments, etc.
All
of the above considerations went into the design and
construction of the chassis/roll cage for Project Sidewinder.
Sheldon Tackett, the crew chief for the Sidewinder,
designed the roll cage and handled its fabrication
and installation. The cage was installed before the
firewall and floorpan were cut to accept the Cummins® 5.9L
diesel engine and the New Venture Gear® 6-speed
manual transmission. By installing the cage first,
additional strength was added to support the body when
the cutting began. All joints were TIG welded for maximum
strength.
Like
most stock vehicle chassis, the Dakota chassis exhibited
measurable flex when the truck was jacked up. For example,
before the cage was added, jacking the rear of the
frame to lift the rear wheels off the ground would
result in the frame deflecting, or sagging, in the
middle 1/4-inch. Similarly lifting the front of the
truck allowed the lateral distance between the front
suspension upper mounting points to spread nearly 1/2-inch.
After the cage was installed, both the front and mid-truck
deflection was reduced to zero.
Another
modification that was made to the chassis was to replace
the rear frame from the back of the cab to the rear
of the vehicle. This was done to make room for the
large rear tires that would be used, to accommodate
the Speedway Engineering® Track 9™ Grand National,
and Quality Machine® quick-change rearend assemblies
and their associated four-link suspension with Watts
linage to control lateral movement, to add structural
strength, and to provide support for the trailer hitch.
Yes, that’s right, a trailer hitch. One of the
objectives of this project is to be able to tow a trailer
to Bonneville carrying the needed parts, tools, pit
equipment, and tires required for the Land Speed Record
attempt. The new custom rear frame rails were made
from mandrel-bent 2 x 4-inch rectangular steel tubing
with a .090-inch wall thickness. The rear frame laterals
are a mix of 2x 4-inch rectangular tubing and 1-3/4-inch
.095-inch wall tubing. Two of the laterals at the rear
of the cab serve as a driveshaft containment loop,
and a second forward containment loop fabricated from
1-inch round steel tubing is located just behind the
transmission.
The
passenger compartment cage is constructed of .134 x
1-3/4-inch DOM (drawn over mandrel) mild steel tubing
with diagonal and triangulating bars of .120- or .095-inch
wall thickness. Careful attention was given to locating
the bars as close as possible to the roof, A-pillars,
and the back of the cab to provide maximum interior
space. A lateral bar was positioned behind the dash
to give structural integrity to the front of the cage.
This lateral bar also supports the steering column
and brackets for the Wilwood® clutch/brake pedal
assembly. Diagonal door bars add strength to the long
cab expanse while providing some side impact protection.
The driver-side window net also attaches to the side
diagonal bar and the top cage hoop. Two bars run diagonally
down from the rear of the top cage hoop to the rear
frame rails, securely triangulating the passenger compartment
cage and the rear frame. The rear “down bars” prevent
any mid-truck frame flexing. A unique feature of these
bars is that they can be unbolted to allow removal
of the pickup bed. The bars are capped and sleeved
at each bolt-together slip-joint for maximum strength,
and the four bolts securing each joint are special
aircraft bolts with shanks that extend fully through
the bars to eliminate possible shearing stress risers
in the threaded area. Very neat.
Ahead
of the firewall, the front frame remains relatively
stock. Two bars run diagonally down from the front
of the passenger compartment cage to the front frame
rails, attaching just ahead of the front suspension
mounts. The upper coil-over shock mounts also attach
to these diagonal bars. A short vertical bar runs down
from the middle of each of these diagonal bars to the
frame just behind the front suspension where the engine
mounts are also attached. The result is a very strong
front frame that doesn’t flex or spread when the
vehicle is jacked up.
Structural
strength, chassis rigidity, and driver/passenger safety
are all in one structure – not a bad combination. |
