It's critical to that you have the correct lap belt mounts for these new double shear brac
Loose lap belts also reduce the ability of the shoulder belts to remain in their respective position to control the upper body motion properly in a wreck. Wraparound belts also have a tendency to slide on the seat rail, sometimes under a load, unless they are secured in place to prevent lateral movement. Serious injuries to the abdomen, groin, and upper thigh area are all a result of improper belt placement and anchoring of the lap belts. The resulting load angle pulls either too low on the hips and thighs or too high on the abdomen.
In addition, certain head-and-neck restraint systems (HNS) depend upon the shoulder belts doing their job and holding the HNS in place. If the belts move, the HNS moves out of its design parameters and consequently, needless injuries occur.
Military tests on fighter pilots have proven that in order to best protect the pilot in an impact or through their g rolls and maneuvers, the aviator's pelvis had to stay put in the seat. Race car drivers are no different.
Keith Grant of RSI Safety stands next to the 2010 Safer Chassis.
Sled tests performed at several top research universities in the areas of motorsports restraint performance, HNS, and full-containment seats delivered the same results as the military tests; the only way to properly keep the driver in the seat is to make sure the pelvis stays put in that seat.
When the pelvis stays locked in the seat, the body is then able to absorb more of the impact load, then control and dissipate that energy. Less bodily injury occurs with the properly mounted full-containment seat, HNS, and driver safety equipment working together as a comprehensive system.
During the construction of the new Shaw Safer Design coilover chassis, Shaw and Grant decided to use double shear brackets instead of wrapping the lap belt anchor point. Double shear brackets utilize a U-shaped steel bracket with two equal legs, through which the belt anchor is bolted. These brackets utilize a Grade 8 bolt and locknut with a sleeve spacer separating each leg of the bracket. This design allows the bracket legs to be tightened against the sleeve, allowing the belt anchor to pivot and self adjust to the load as needed with no restriction. A double shear-style bracket can also prevent belt dumping from occurring. However, they must be properly located to do so.
With the help of A&A Manufacturing, Shaw and Grant designed a new double shear bracket to reflect a 30-degree offset pin location to compensate for the load path the new lap belts and ratchet tensioner would take in their proper mounting place on the chassis.
This picture shows how Shaw used A&A Manufacturing's double shear weld-on brackets to moun
Shaw's new design puts the lap belts at the proper angle to secure the pelvis in the right points as indicated in crash sled testing. With the pelvis secured, it was now onto the upper body.
For years, shoulder belts have been mounted on the rear lower chassis cross rail for strength and ease of mounting.
Most belt and seat manufacturers suggest that the shoulder belts' anchors should be approximately 10 degrees below the plane of the top of the shoulder or clavicle area. That horizontal anchor point translates to approximately 1 inch below the top of the shoulder or clavicle area where the shoulder belt contacts that area.
In a Sprint Car application, the lateral A-frame bar provides a directional change equivalent to the 1-inch lower anchor mounting point. Initially, Shaw and Grant attempted to mount the shoulder belts directly to the seat bar, but, because of the close proximity to the seat and the awkward mounting angle, the belts could not be wrapped properly to keep the three-bar adjuster from protruding through the shoulder belt holes. This problem could possibly injure the driver's neck or head in an accident or interfere with the HNS, so they chose to use the lower A-frame bar as the alternate anchor mount.
What they did find during their research was; that to lessen the chance of the A-frame becoming damaged in a bad wreck, they strengthened the A-frame and the belt mounts by continuing the middle A-frame lateral bar to the outer chassis upright to provide an increased level of safety. Shaw began implementing this new change in all his new Sprint Car chassis starting in 2010.
Shaw's new safer design has already won four races in Florida Top Gun Sprint Series, proving that a safer Sprint Car chassis can also be a stronger, faster Sprint Car chassis.
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Here you can see how the properly mounted belts pass over the middle A-frame lateral bar h
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The new 30-degree double shear bracket is shown next to the 2009 version on an older chass
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Shaw shimmed the bottom of the seat to prevent any abrasion problems from damaging the sub