Fifth belt seat modification

[Jerry Scott[CO]]

After much thought about the problem with the 5th belt passing over the front of the seat cushion, as in the factory ACR set-up, I have come to the conclusion that the belt for my personal track car, should be modified for improved passenger-in-seat retention and improved safety.

I refer to a previous track accident whereby the occupants of a Viper that went off the track, hit a wall and rolled. They were wearing 5 point belts that had the 5th strap routed over the front of the seat and connected to the eyebolt designed for this attachment. As a result, both occupants were seriously bruised about the ribs, shoulders and hips, due to the amount of travel, caused by the lack of body containment from this belt arrangement. The excessive travel under the belts seems to be caused by the inability of the 5th strap to hold the lap belt low enough on the hips to prevent the body from sliding under the belt. The belt routed over the front of the seat crushes the foam pad within the seat, straightens the strap, which allows the torso load on the shoulder straps to raise the lap belt.

Most racecars that I have seen, have the 5th belt routed through the seat cushion with the load directed straight down. I have made this modification to my 97 GTS car seats and offer it to anyone interested in the same.

The hole in the seat was altered by an upholstery shop here in Denver, Auto Weave, Ron Nelson, 303-288-6222,and the cost for this part of the work was: $281 for the two seats. This shop has done several Corvettes in the past, but this was the first Viper. As you can see from the photos, the hole is about .75 in. wide by about 3.5 in. long, and located 4.75 in. from the front of the seat. This allows the attachment buckle of the Teamtech 5th strap to easily drop through the hole. The strap then passes through a fabricated steel guide bar that keeps the loading direction of this strap constant, no matter where the seat is positioned.

The guide bar is made of 3/4 x 3/4 in. 16 ga. steel square tubing with a stainless steel loop of 5/16 dia. rod welded to the bar, and weighs less than 1 pound. The bar has shims inserted in the ends of the mounting channels to prevent the channel from crushing when attached with the bolts. An acrylic clear coat was sprayed to the bar to prevent rusting, or you may want to consider powder coating. I looked for stainless in the 3/4 tubing but was not able to find it here in Denver. The bar attachment is made to the bottom of the seat, at the forward factory location of two of five bolts that hold the seat frame to the seat rails. Two slightly longer grade 8, 8 mm bolts are required to make this attachment. When tightening these five bolts, make sure to adjust the seat rail width to the 13 inch bolt width of the floor bolts, since some of the holes have some adjusting room. The 5th strap attachment is made at the factory location of the eyebolt between the two seat rail mounting holes on the floor. This modification does not interfere with the elastic mesh on the bottom of the seat, since it exits in front of this area. I have not track tested this set-up, but in a static garage test it feels very secure, with no side movement of the hips possible. When using the standard three point belt system, the fifth belt can be draped over the front of the seat, out of the way.

If you need a drawing of the bar, I can fax it to you, or I can tell you who will make it for you, if interested. I will also suggest that you have the bar in place before having the upholstery shop cut the hole. That way there is no question as to where the hole should come out on the bottom of the seat.
Jerry Scott
303-697-0662

 

[JimDavis MT 97GTS 650R]

Great job Jerry. Your attention to detail and illustration exemplifies your expertise in engineering. Every serious racer should consider this mod.

 

[MtHam ACR]

Jerry, great post. Its a pleasure to see guys take pride in their work and want to pass on the benefit of their experience.

Eric

 

[Tom F&L GoR]

Excellent work, Jerry. Clever idea to mount it to the seat. My feeble attempt (attached to rear seat mounts) convinced me that the stock tapped hole isn't healthy, you need the 5th belt closer to you to keep the lap and shoulder belts in the right place.

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[Jerry Scott[CO]]

Tom
The fifth belt does not attach to the seat, it only goes through the guide bar loop, then attaches to the normal factory floor eye bolt location that is provided on all Vipers. I didn't feel safe in attaching the belt to the seat. This allows the loading direction to remain in a constant direction with regard to the occupant, no matter where the seat is positioned in its adjustment.
Jerry

 

[Henry Cone]

I would like to suggest another alternative - 6 points instead of 5 points. The 6 point antisub strap attaches to the same eye bolts as the waist belts. The advantage is that there are no issues about the antisub strap not being able to hold the waist belts down in the correct position. The sntisub straps instead wrap around yout thigh bones.

We originally set up our cars with 5 point TeamTech hanresses. After prodding by Curt Tucker of TeamTech to try the 6 points we did. I will never bo back to 5 points. TeamTech redid our antisub straps to convert them from a single belt (for 5 points) to a V belt arrangement (for 6 points) at a nominal fee.

The biggest advantage of the 6 points in my mind is that you can belt yourself into the stock seat wll enough that the padding on it ie not an issue. Most race seats have little on no padding to prevent your body from moving too much in an accident. The stock Viper seats have enough padding that your body can move around quite a bit in an accident, particularly with 5 points using the antisub strap mounting location that Dodge provided for 5 points.

I applaud Jerry's efforts to make the 5 points work as they should. And his installation is a fantastically well done one. I just want to remind everyone that there is an alternative to this solution that is probably safer and more cost effective as well. This is particularly true for users of TeanTech harnesses.