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Isaac® absorbes the shock of the
head moving forward during a crash. Without it, this shock is absorbed
by the upper neck and the base of the skull. It works by generating
a force which is opposite the crash force. It's not exactly "an
equal and opposite reaction," but pretty close.
Half the racing deaths in North America are caused by head and neck
injuries, which happen when the body stops but the head keeps moving.
Basilar skull fracture occurs at a load of 900 pounds (4.0kN) and happens
very fast: in about 30ms, or 3/100ths of a second. This is the same
injury caused by a hangman's noose.
In a severe racing crash that generates a 45G impact, the load on the
head is approximately 1,800 pounds (8.0kN), about twice the fatal limit.
In crash tests Isaac® reduced these loads nearly 90%, to 200 pounds
THE BASIC MECHANICS:
The secret to Isaac® is the shock absorber, sometimes called a damper
or dashpot. Shocks are easy to move if you move them slowly, but become
almost rigid at high velocities. This means that a driver using Isaac®
can move their head with little resistance, but in a high G crash the
shocks become very stiff, slowing the head velocity and reducing the
force on the head.