Go Racing - Index

Go Racing - goracing - Index

By Jeff Grist & Memo Gidley
Photos by Sean Buur
SOS for 4-Cycle Racing
SOS for 2-Cycle Racing
SOS for Shifter Kart Racing
Available through Go Racing Magazine.
$24.95 USD plus shipping.
Call 760.949.7447 to place
your order NOW!
Tilett 1/4 padded seat Tilett full padded seat
Tech Article 12 – Seat Dynamics 101
In this installment from Memo Gidley’s Secrets of Speed for Four-Cycle
Kart Racing we will begin a new series of articles focused on seat set-up
including an in depth look at how a kart seat works. Also, while we are going
over the seat, we will look closely at the base line set-up and some helpful
tuning tips. In this first segment we will look at how a kart seat works, the
features that make a kart unique and begin the installation process. We will
de-mystify the seat and make sure you get it right the first time.
The seat is one of the most critical components of a kart because it’s the
seat that connects the largest mass, you the driver, to the kart. Too often
the seat is improperly positioned or poorly installed, directly affecting the
handling performance of the chassis. The seat can control the weight transfer,
center of gravity, chassis flex and weight balance. A properly installed seat
will compliment these forces, while a poorly installed seat will work against
the chassis, causing a number of handling problems. A well-installed and
properly fitted seat means seconds a lap.
Like the geometry and flex built into the chassis, kart manufacturers
spend a lot of time on seat positioning. Most manufacturers will have
recommended settings for optimum performance. These are available from
your dealer or from the manufacturer’s website. You should always consult
your chassis manufacturer or your seat manufacturer for exact mounting
specifications. We will provide some seat set-up guidelines, which should be
compared to your manufacturer’s specifications.
When installing your seat you need to look at driver size, track conditions,
tire type and engine style. The position of the seat can be adjusted to ensure
maximum performance from each of these elements. Drivers must learn
that, like tires, the seat is a commodity that gets consumed. Top drivers will
change seats regularly to keep the handling performance consistent. This
is especially relevant to North American drivers who may run street races
during which the seat can hit the ground, sustaining significant damage.
How a Kart Seat Works
As we mentioned earlier, the seat will affect the transfer of weight, the
flex of the chassis, the weight balance of the kart and the center of gravity.
All of these help to pick up and set down the inside rear wheel, which is
required to help the kart handle properly through a corner.
As the geometry of the chassis transfers weight, the seat can affect this
by transferring more or less of the driver’s mass. The force applied by the
driver as the kart is changing direction enhances this weight transfer as the
driver’s body pushes outward on the seat when the kart turns through a
corner.
We can use the seat to control how much of this energy is transferred. A
loose or incorrectly fitted seat can create unnecessary transfer of weight and
throw off the balance of the kart. The weight of the driver can “slosh” if the
seat is not bolted properly or the seat is too big for the driver.
Much like torsion bars affect frame flex, the seat can add to the torsional
flex. Kart seats are manufactured using resin-based composites like fiberglass
and carbon fiber to create a shell that is shaped to hold a driver firmly in
place. Different materials are used to create a range of torsional stiffnesses
and weights. Varying the stiffness of the seat directly affects how much or
how quickly your body loads the frame and/or tires on your kart.
We know that ride height affects the center of gravity. The seat height
can be used to control how high the center of gravity is set. The center of
gravity of a kart starts off low to begin with. However, add in the driver and
now a large mass is positioned very high. The seat can be used to adjust this
critical point, which can amplify the weight transfer and inside rear wheel
pick up on the entry to the corner and tire loading on the exit.
Finally, we will use the seat to make major changes to the weight balance
of the kart. By moving the seat forward you can take weight from the back
to the front.
By moving the seat to the left of center you can offset the weight of the
engine.
Proper mounting hardware should
be used for seat installation
Key Components
The design of a kart seat is very basic and similar from manufacturer
to manufacturer. A kart seat needs to support the driver in cornering,
accelerating and decelerating. In a racecar, the driver is belted in, while in a
Page 44 Go Racing Magazine