Inertial impact attenuating barrier

A sacrificial inertial barrier and an array thereof particularly useful on race circuits. The frangible barrier includes a thin walled plastic tub containing an energy absorbing dispersible mass such as water or sand, the tub being supported on a thin-walled plastic ring which elevates the dispersible mass to a height at which its CG is the same as the CG of a particular type racecar, e.g. a Formula I car.

BACKGROUND OF THE INVENTION 
This invention relates generally to inertial barriers and more particularly 
to a novel sacrificial inertial barrier and barrier system especially 
useful on race circuits to decelerate errant race cars heading towards 
obstructions such as a wall or a fixed guard rail. 
The inertial barrier of the invention is an adaptation of the well known 
life saving Fitch barrier used on America's highways to decelerate 
uncontrolled vehicles as they approach immovable obstructions such as 
bridge abutments. The Fitch barrier is generally illustrated in my earlier 
U.S. Pat. No. 3,606,258. The inertial barrier of this invention operates 
on the same exchange of momentum principles discussed in that patent and 
that discussion is incorporated herein by reference. 
Safety systems designed for race circuits must be able to accommodate a 
wide variety of racecar types, since most circuit operators have to 
schedule several different kinds of events in order to sustain their 
commercial operation. 
At the top levels, race cars capable of speeds in the region of 200 mph may 
include Winston Cup stock cars (weighing 3200 lbs), IMSA World Sports Cars 
(1500 lbs) or Formula I or Indy-car type single-seaters (1100-1550 lb). 
Those with a 150 mph capability might include Super Touring cars 
(2100-2300lb) and Formula 3 single-seaters (1000 lb). In amateur track 
racing where top speeds are substantially lower, the same circuit may also 
have to accommodate 100 mph vintage sports cars (weighing approximately 
2600 lbs) or H-modified sports racers from the 1950s (700 lbs). 
These race cars not only vary in size, speed and weight but also in the 
height of their center of gravity (CG), and any safety system used must be 
adjustable to accommodate these variables to safely bring an errant 
racecar under control. In addition, after an impact, a safety system must 
be quickly restorable to its original configuration by track personnel so 
that the race may continue without significant loss of time. 
SUMMARY OF THE INVENTION 
It is a primary object of the invention to provide a novel inertial barrier 
and an inertial barrier system capable of satisfying the requirements for 
race circuits as described above. The inertial barrier system includes a 
high angle impact, energy-absorbing array of inertial barrier modules 
capable of arresting a car, e.g. Formula I racecar, from any speed at any 
angle at a chosen G level without ramping or submarining, with a low risk 
of injury to the driver, and with minor damage to the car. Each of the 
modules includes a dispersible mass such as water or sand contained within 
a sacrificial vessel at a center of gravity corresponding to that of the 
car, the vessel being designed to disintegrate on impact with the car. 
Within the array the weight of the dispersible mass in successive modules 
increases with the direction of travel of the car in order to optimize the 
inertial forces that will maintain a chosen rate of deceleration or G 
level as the car progresses into the array. 
Another object of the invention is to provide, in a preferred form, a novel 
inertial barrier module which includes a generally frustoconical, hollow, 
ground engaging support ring and a separate dispersible mass containing 
tub resting on the support ring. In each different sized module containing 
different weights of dispersible mass, the ring and the tub are designed 
so that the CG of the mass is elevated to match that of the car. The ring 
and the tub are constructed of the thinnest possible brittle and frangible 
plastic material which breaks upon impact with a car but produces only 
little bulk of fragmented parts and thereby prevents a build up of debris 
under the front of the car and lifting or ramping of the car. 
Consequently, after impact the area may be quickly cleaned up, the damaged 
modules replaced, and the array promptly restored to its original design 
configuration without significant loss of race time. 
The novel barrier and barrier system of the invention, although of general 
utility, has primary application at the end of high speed straights on 
road racing courses, at pit wall ends on oval tracks, and at the ends of 
runouts on drag strips. 
Other objects and advantages of the invention will become apparent from 
reading the following detailed description of the invention wherein 
reference is made to the accompanying drawings.

DESCRIPTION OF THE INVENTION 
Referring to FIGS. 1 and 2, the preferred form of the inertial barrier 20 
of the invention includes a hollow lightweight brittle plastic support 
ring 22 having a ground engaging circular horizontal flange 24 and a 
frustoconical vertical wall 26 joining flange 24 at a flared large radius 
section 28. Wall 26 has a circular upper edge 30 defining its upper open 
end 32. 
Barrier 20 also includes a separate brittle plastic tub 34 for containing 
an energy absorbing dispersible mass 36, such as water or sand. Tub 34 
includes a circular horizontal bottom wall 40 which joins an upwardly, 
outwardly tapering circular vertical wall 42 at a peripheral notch or step 
44. 
When tub 34 is placed on ring 22, edge 30 engages within notch 44 and 
bottom wall 40 fits down into open end 32 to retain the tub and ring 
together and center the dispersible mass with respect to the ring. 
As mentioned the inertial barriers are provided in different sizes 
containing different weights of dispersible mass, e.g. 30 lbs water up to 
700 lbs sand. When placed in an array the barriers increase in size from 
the front to the rear of the array in the direction of travel of an errant 
car. In designing a system for use with Formula I cars which have a CG of 
about 12 inches, in the smallest barrier 20, tub 34 may have a diameter A 
of 12 inches, a height B of 7.34 inches, and the mass 36 may be 30 pounds 
of water. The height C of ring 22 may be 8.3 inches to locate the CG of 
the mass 36 at 12 inches, the same as that of the car. 
The barrier 20a of FIG. 3 is of the same general construction as that of 
barrier 20, except it is larger to provide a dispersible mass 36a of 200 
pounds of water. In barrier 20a the tub has a diameter Aa of 24 inches and 
a height Ba of 12.25 inches. The height Ca of the support ring 22a is 5.9 
inches to locate the CG of the mass 36a at 12 inches, the same as that of 
the car. 
Similarly, the barrier 20b of FIG. 4 is of the same general construction as 
that of barriers 20 and 20a, except that it is larger to provide a 
dispersible mass 36b of 700 pounds of sand. In barrier 20b, the tub 34b 
has a diameter Ab of 36 inches and a height Bb of 11.8 inches. The height 
Cb of ring 22b is 6 inches to locate the CG of the sand 36b at 12 inches, 
the same as that of the car. 
The general configuration of plastic barriers 20, 20a, 20b provides a 
number of desirable characteristics and advantages. The brittle plastic 
tub and ring of the barriers are readily breakable when impacted by a car, 
and prevent build up of debris under the front of the car, thus avoiding 
ramping. Debris can be a potential problem because of the low CG of race 
cars and their minimal ground clearance. Also, the fragmented parts can be 
quickly cleaned up. Because of the tapers on the walls of the tubs and 
rings, for each size barrier a plurality of tubs can be nested together 
and a plurality of rings can be nested together to facilitate shipping and 
storage of the two components. Also, the tapers on the tub and the ring 
facilitate their removal from the molds in which they are produced. 
Further, even though the plastic tubs and rings are of thin wall 
construction, they are sufficiently strong to resist breakage during 
normal handling and installation. 
Barrier 20 (and similarly barriers 20a and 20b) is assembled and installed 
by placing flange 24 of ring 22 on level ground, placing tub 34 on ring 22 
with upper edge 30 nesting within notch 44, and then filling the tub with 
the dispersible mass such as water or sand. The flared flange 24 
distributes the weight of barrier 20 over the ground and prevents the ring 
22 from sinking into soft surfaces. Notch 44 cooperates with upper edge 30 
of ring 22 to hold tub 34 and mass 36 in place on ring 22. 
FIGS. 5 and 6 illustrate another embodiment of the invention. The frangible 
barrier 50 includes an outer thin plastic casing 52 attached to an inner 
thin plastic casing 54 forming an inflatable air chamber 56 there between. 
Casing 54 has a bottom wall 58 and a generally spherical sidewall 60 
defining an open pocket 62 for receiving a dispersible mass 64 of sand or 
water. 
Barrier 50 represents a 36 inch diameter 700 lb sand module. The overall 
height X of the module is 18 inches, and the height Y to bottom wall 58 is 
6 inches, with the CG of sand mass 64 being 12 inches, the same as that of 
a Formula 1 car. 
Barrier 50a represents a 24 inch diameter 50 lb sand module. The overall 
height Xa is 13 inches, the height Ya to bottom wall 58a is 11 inches and 
the CG of sand mass 64a is 12 inches, the same as that of the car. 
When impacted by a car, the pressure in chamber 56 and 56a increases, 
causing casings 52 and 54 to burst and sand 64 and 64a to disperse. 
FIG. 7 illustrates another embodiment of the invention. The frangible 
module 66 includes a bottom air inflatable support pillow 67 and a 
separate water fillable bladder or container 68 supported on pillow 67 
such that the CG of the water mass is at the same height as the CG of the 
car. As with the other embodiments, the size of the modules and the weight 
of water may be varied within an array to accommodate a desired rate of 
deceleration or G level for an errant car. 
Referring to FIG. 8, the modules of the invention are arranged between a 
race roadway 70 and a fixed wall 72 to arrest an errant car under 
acceptable G levels. The array includes a first group 76 of smaller 
modules arranged in progressively increasing values, e.g. 50 lb, 80 lb, 
100 lb, from roadway 70 and a second group 78 of larger modules, e.g. 200 
lb, 250 lb, 400 lb, and 700 lb masses in progressively increasing values. 
Modules up to about 250 lb may contain water as the dispersible mass, and 
modules above 250 lbs will contain sand. They may be arranged in a 
water-to-sand sequence in order to optimize the inertial values to 
maintain a desired G level as the car progresses into the array. Water is 
used in the smaller modules impacted by the car when travelling at its 
highest speed because water has no shear strength and will follow the 
aerodynamic contours of the car without lifting. Where the possibility 
exits of water running onto the racing surface, a shallow water drainage 
ditch may be provided. An open aisle 80 is left between groups 76 and 78 
and an aisle 82 is left between group 78 and a tire barrier 84 placed 
against wall 72. After impact by an errant car, aisles 80 and 82 provide 
quick access for rescue personnel and service vehicles. This facilitates 
clean up of the area and replacement of damaged modules. Thus, the array 
may be quickly restored to its original configuration without any 
significant loss of race time. 
The invention may be embodied in other specific forms without departing 
from the spirit or essential characteristics thereof. The present 
embodiments are therefore to be considered in all respects as illustrative 
and not restrictive, the scope of the invention being indicated by the 
appended claims rather than by the foregoing description, and all changes 
which come within the meaning and range of equivalency of the claims are 
therefore intended to be embraced therein.