Formula 1 Chassis & Suspension
Formula 1 chassis design centers around 2 ideas,
rigidity and safety. The chassis of a formula 1 car is
designed to have minimal flex and high safety. The
design of the chassis does allow for movement but only
within the suspension design, such that the
characteristics of the movement will be predictable and
therefore tunable.
The chassis can be subdivided into two parts, the
monocoque which consists of everything in front of the
engine, and the rear drivetrain, which is the engine,
gearbox, differential, and rear wing. It must be noted
that the engine block and gearbox case make up the
structural elements of the rear of the car. There is no
frame or other structure holding the back of the car
together. The rear wheels of the car are attached to
the differential and the gearbox as are all suspension
components. This design saves weight by eliminating
any unnecessary structure. The front of the engine is
bolted directly to the rearmost bulkhead of the
monocoque with as few as 4 to 6 bolts.
Monocoque
The monocoque is designed to encapsulate the driver,
fuel cell, electronic controls and provide a structural
point to mount the front suspension, wheels, and front
wing. Construction is of carbon fiber composite. The
carbon fiber is a cloth woven from strands of pure
carbon embedded in a hardened epoxy resin. It is
basically a reinforced plastic, extremely strong and
lightweight compared to steel or aluminum. However,
the structure of the carbon fiber cloth and how it is laid
is vital to achieving maximum strength. The carbon
fiber cloth is impregnated with resin and is kept at a
temperature below freezing, until it is laid in a vacuum
mold and heated in an autoclave (a pressurized oven)
for several hours to harden the resin. Once hardened
the bare monocoque, essentially a tub surrounding the
driver, is light enough to be lifted by one man.
Suspension
Formula 1 cars universally utilize a double A-Arm design
on all four suspension corners. The rest however,
differs greatly by team. For example some teams use
coil springs, some use torsion bar springs. The springs
and shock absorbers or dampers are all mounted within
the chassis and actuated by either pushrods or pullrods
through rocker arms.
The pushrod suspension is favored by teams for the
front because the springs and dampers are most easily
packaged in the upper part of the cockpit above the
drivers legs. The downside of this setup is that the
weight of the bulk of the suspension components is
high up in the chassis adversely affecting handling.
The rear suspension is currently divided between
pushrod and pullrod for the 2011 season. The more
aggressive and advanced design favored by some of
the leading teams is for a pullrod suspension in the
rear. The benefit of a pullrod is it allows packaging of
the springs and dampers lower in the chassis, freeing
the space above the gearbox for straighter airflow into
the lower section of the rear wing. This increases the
downforce produced by the rear wing. This is critical as
beginning in 2011 the design of the rear diffuser is
severely restricted, reducing its contribution to overall
downforce. This lost downforce must be made up
where permitted in the rules and this has manifested
itself in the performance of the lower wing plane.
Floor
One of the purposes of the suspension is to keep the car
at ride height. This measurement is defined by the FIA
and is strictly enforced. The cars are kept honest by the
FIA through the placement of a wooden plank in the
center of the floor. The thickness of this plank is
stipulated by rule, and after a session or the race it can be
measured to see if the bottom of the car has scraped on
the ground.
The floor of the chassis itself is a flat carbon fiber piece
that essentially covers to bulk of the chassis. The floor
begins underneath the driver with a splitter and proceeds
back all the way to the diffuser. The purpose of the floor
panel is to aerodynamically seal the bottom of the chassis
and direct all underneath airflow to the rear diffuser.
Brakes
Brakes are critical in a road race where cars have to slow
from high speeds to make turns in slow corners. Disc
brakes use friction between the brake pad and the discs to
slow the wheels; the side effect of this friction is heat.
Excessive heat causes disc brakes to fail. To overcome
this Formula 1 cars use carbon ceramic brake discs and
pads which work best in a high heat environment, in fact
they almost don't work at low temperatures. That being
said slowing a Formula 1 car down from 200 mph to 45
mph in a hairpin turn generates more heat than even
carbon ceramic brakes can handle. Engineers direct airflow
through ducts and shrouding on the inside of the wheels
through the wheel rim to cool the brakes. The harder a
track is on brakes the bigger the air ducts are, and of
course the greater the aerodynamic drag effect slowing the
car down. Therefore getting the optimal size of brake
ducts is critical to achieving maximum performance.
Gearbox
The gearbox of a Formula 1 car is unique to the sport in
that it must perform several functions at the same time.
First, it must change gear ratios so that the engine may be
kept in its ideal rpm range while accelerating and
decelerating. The gearbox mechanism is a semi automatic
sequential shift design, where the driver doesn't need to
operate the clutch for each shift the driver simply selects a
gear using the up or down button, or as is more often the
case a paddle on the rear of the steering wheel. The
actual clutch operation and the changing of the physical
gears is actuated hydraulically, and controlled by
computer. Shifts are nearly seamless occurring in fractions
of a second.
Second, the case of the gearbox must provide a mounting
location for the rear suspension and the rear wing
assembly. This secondary role cannot be underestimated,
the forces acting on the suspension are substantial, as is
the force produced by the rear wing assembly. These
forces must all be accommodated by the structure of the
gearbox casing, typically constructed of cast aluminum or
in some rarer instances carbon fiber.
Differential
The driving of the rear wheels is accomplished by the
differential through a pair of axle shafts. Each wheel is
independently sprung and therefore the axle shafts have
flexible joints. All of these components must be made
robustly in order to withstand the extreme torque being
transmitted through them. In addition to being sprung
independently, the wheels rotate at different speeds when
going around a corner. In order to maintain maximum
traction going around a corner, the speed differential
between the two wheels can be adjusted electronically at
multiple points during the corner. It is however against
the rules to use computer control to make on the fly
adjustments to traction (through the differential or any
other way) while the car is running. Any adjustments
must be made by the driver through knobs on the steering
wheel.
