Bob P wrote:
“Shoulder harness mounts should be mounted high - close to shoulder level or higher. Otherwise you will be pushed down, not held back in the seat.” This is absolutely correct. But the angle up should not exceed 5 degrees for an upright driver position. (Reclining is a whole different design and dynamic issue-the upward angle becomes greater in this application.)
Wayne then wrote:
“Please folks, use caution when it comes to shoulder harnesses. I beg to differ with Bob on this topic. Five point harness assemblies (particularly the shoulder harness) absolutely must not be mounted higher than the shoulder. It’s an invitation for disaster or worse. I’ll be blunt: You can kill yourself with that approach.”
This is not correct as stated. Mounting above the shoulder line within proper design limits is acceptable and recommended by the FIA and practiced by all automobile manufacturers.
Wayne then includes the following excerpts from the NHRA rule book. “SECTION 10:5 DRIVER RESTRAINT SYSTEMS” and “SECTION 10:11 SEAT BELTS.” The only reference to position is in “SECTION 10:11 SEAT BELTS” and it says “All harness sections must be mounted to the frame, cross member, or reinforced mounting, and installed to limit driver's body travel both upward and forward.”
RDH Note: The forward vector is controlled by the combination of the two belts. However, upward motion should only be controlled by the lap belt and the shoulder harness should not apply any compressive force to the body.
Then Wayne posted the drawing showing the shoulder belt locations. Fine. This is what NHRA wishes and has been the standard in SCCA etc. for many years.
However, if one would read the SCCA rules you will also notice the statement “Shoulder harness should be installed 90 degrees to spine at shoulder line to minimize compression injuries under high “G” loading.”
The FIA mandates that shoulder belt mount height in F-1, F-3000, and Touring cars be at least 5 degrees above the shoulder line to eliminate compressive forces in a frontal impact.
In other words, Wayne’s statement of “absolutely must not be mounted higher than the shoulder” is certainly at odds with others and the statement “It’s an invitation for disaster or worse. I’ll be blunt: You can kill yourself with that approach” is patently incorrect.
The reason that shoulder belts in normal passenger cars are mounted high is to eliminate compressive forces being induced in a frontal impact. The reason that they are so high is to allow the systems to work within the 95th percentile that the design engineers have to deal with. (You know 5 foot 2 to 6 foot 4.)
If one would look at many of the current production cars such as Mercedes etc, One would notice that the upper mounts are adjustable for the height of the user. The owner’s manuals go into quite a bit of detail as to location of the belt and they state quite clearly that under no circumstances should the shoulder belt be below the shoulder line.
Now, it is not my intent here to make anyone wrong. Therefore, I wish both Bob P. and Wayne to accept my apologies in advance for using their respective posts to illustrate the points I have made. You are both to be commended for giving excellent guidance to the members on this very misunderstood subject. I have seen way too many extremely dangerous installations of belts and seats in all manner of vehicles and the Cobra typically is one of the worst.
As Wayne stated “I suggest you contact: Stroud Safety Equipment, Simpson Safety or Deist Safety and solicit their points of view” This is the very best advice of all. These folks have lived with driver safety for many years and certainly know what they are doing.
Best Regards,
Richard Hudgins
http://www.jblmotor.com