sjanes

That's what I figured until I saw this post by gbaker (the Isaac guy).

The problem is that most of us really don't understand the forces involved.

joseph mitro

Redlineman, sorry, no offense intended. Just commenting on your frequent posts regarding safety.

I better understand the difference between sheer forces and traction forces in relation to mounting harness bolts. Also, the floorboard mount you built makes sense. In fact, I may try to get a crossframe built in my M3 to mimic what you have shown and then mount the harness in sheer instead. It's not ideal from a convenience standpoint (it's not snap-in/snap-out), but I guess safety should be a priority over convenience.

My outer lap belt is mounted in what I consider to be a safe fashion - to the stock seatbelt anchor along the sidesill, and the inner is mounted to the central tunnel, which is two layers of sheetmetal thick separated by some sort of high density foam. I will consider switching over from the eyebolt anchor to the sheer mount, but it just means the harnesses will be a permanent fixture in the car. Oh well, I don't have to use it for the prom, so I guess it's ok

Thanks for all the info.

RedlineMan

Hey;

The 996 setup is totally custom. Kirkey seats with JAZ double locking sliders, mounted to fabricated brackets to interface with the OE floor mounts in the car.

To expand on what Stacy offered, Schroth measures nominal readings of 2800lbs at the lap belt mounts, and 1500ea. on the shoulder straps in an "average" crash.

gbaker's comments should be read to mean that video visuals can be quite apart from actual numbers, and vice-versa. Earnhardt's crash looked like nothing, but it killed him. The Delts V (change in velocity from forward to lateral) was not even that big. I have a "nothing" clip from the stands of a stock car hitting a wall, but the driver cam of the same crash is horifying.

Coming up with belt systems that gbaker mentioned to keep bodies restrained - based on visual dismay alone - may appear to be succcessful in a physical sense, and yet enter physiological loads into the body that it cannot withstand. Only crashing proves validity, and crashing enough times to create a scientifically significant database. What looks safe can be not, and what is safe can look terrible... and everything in between.

We are presented with huge variety when it comes to angles, forces, and such, but we have no such ambiguity where mounting POINTS are concerned. Making them Sherman Tank tough will never decrease safety. Only in what flows from these points do we begin to color or outcomes in various shades of gray.

RedlineMan

Joe;

Your lap belt mounts sound fine. Everything in shear. I would not hesitate to use eye bolts and clips in this sort of mount. I would also not hesitate to use eye bolts in the type of beam I fabricated, even in straight tension. At some point, the deficiency of any "improper" mount style can be overcome through outright strength, as in the angle iron I used. I probably could pick the entire car up with that beam. It is just not going to fail.

My bottom line is... well, someone said The Enemy of Great is Good, or something to that effect. I like to always shoot for great!

Kool

After 4 pages I have a much better idea of what a good harness really means. Which incidentally was completely opposite of what I thought when I initially posted here.

Thanks for everyones help.

joseph mitro

in medicine we say "the enemy of good is better." i find that philosophy frequently trickles down to my mechanical adventures, which i guess is a good thing.

gbaker

BTW, the load distribution between lap and shoulder belts is 80%/20% in the military. In auto racing it's about 60/40.

The military spent close to a million $ researching this decades ago, but the racing industry ignores it.

VaSteve

I have talked to a bunch of people and a couple of dealers. There is some confusion of how to use/mount a 6pt harness.

It is my understanding that if you have seats (with shoulder holes) that don't have a sub hole, you can wrap the sub straps around the sides with the lap belts. You then sit on the sub straps and encircle your legs. Am I right?

Since I can't find a photo of this in action, anyone have a photo of the proper use of these...or could take a photo (pants on ) of the proper use of 6pt harnesses with no sub hole?

Thanks!

RedlineMan

Hey Steve;

You are correct. The only way to really get a sub to function properly without a sub hole is to create a cradle of it as you describe.



In this configuration, the sub will not take up slack quickly because it is not running a straight path over body "hard points." As such, it needs to be worn quite snug to one's inner thighs so that it is essentially pre-tensioned. Here are the sub angles for various configs.



Blue is a single, Green is a "T" or Schroth Hybrid, and Red is a Cradle type. You probably want to find a "T" to use in a cradle, as the "V" gets a bit, ummm... familiar with The Boys.

VaSteve

John

Where do the bolts for the green one go? Or is there some kind of stand-off from the lap belt bolt. I'm trying to minimize drilling, cutting, etc. No due to the value of the car, due to the potiential to do it wrong.

This will be a DE car for me. Not a racer.

RedlineMan

As mentioned;

The Green is a Schroth Hybrid or "T" location - 20 degrees for the former and 40 for the latter - behind the "spine line." This only works with a race shell, obviously.

For DE use, I think it is perfectly acceptable to mount the sub to the seat underneath (I do this on alloy seats). In the strictest sense, this is not "proper", as it relies on an assembly (the seat) that might come adrift in extreme circumstances. However, it has the distinct advantage of keeping the sub in proper adjustment regardless of where the seat is placed, if it is on sliders. This suits our multiple driver DE purposes very nicely, and since the subs never see the high loads the other belts do, I feel it is a reasonable compromise.

CHEERS944

Hello! Back from the holiday madness!

Kool: My car is dual use...mostly street & as many DEs as I can afford! On the street I use the stock 3-pt belts which we left in for that purpose. The lap belts of the harness tuck right along the seat & aren't in the way at all. The sub strap slips between the seat bottom & seat back - gone, basically. The shoulder straps do hang down from the bar behind the front seats, and between them & the bar itself, the back seats are pretty much useless, but it's not like people could really fit in there before!
Again, I think my original intention was along the same lines as yours: safe & convenient. However, practically speaking, safety won out as it's not just a one-bolt or one-clip install/removal.
Yeah, I love my Acura, but not as much as the 944, of course! Great, reliable cars.

shiners780

I see it arrived in one piece
Looks good, I'm glad it found a good home.

Owain

Thanks again. I'm looking forward to trying it out Now I just gotta get a camera mount for it.

shiners780

I hope you never do!

Actually, I know what you meant, it just sounded funny.