Alpine951

I am looking into hanrnesses for my car. How long do the shoulders straps have to be for an H style that goes around a harness bar and mounts to the rear seat mounting points. Is 60" long enough?

Skip

75" I believe is the minimum for that application. 60" would probably not reach - you could measure to be sure. Is this a C-pillar or B-pillar bar?

Alpine951

I don't have the bar yet. It will probably be the stable energies one though.

Edit:

Just looked at stable energies site. pparently it can go both B or C pillar. Do the belts mount to the same location for both B and C pillar bar location?

Skip

Yes, but the B-pillar is best. There are some other options you may not be aware of - Weltmeister and Brey Krause also make harness bars - the B-K unit is pricey, but the best.

Have you considered the Hajny (Redline) rollbar?

Skip

Alpine951

WHy is the B pillar best?

dave120

Because the B pillar is the strongest one so it can take the most force without having a problem.

Skip

It is closest to the driver. It looks like all of the bars except the BK are made to fit the C-pillar. That puts the belt very far away, and I'm not even sure you can loop 75" belts over the bar and down to the rear seat belt mounts, and still have enough to reach the locking area at your abdomen. The problem with mounting a straight bar to the B-pillar is that it will restrict movement of the seat for taller drivers, and would really be too high for safe and secure use (without debating the safety of harnesses without rollbars or proper pass-through seating). I ran for a few years in autocross with a Weltmeister C-pillar brace and the belts connected directly to it (Tom will be here shortly to scold me, again <img border="0" title="" alt="[Wink]" src="wink.gif" /> ) - it worked great for the intended purpose, which was to hold me into the seat much better than a 3-point could do.... however, I did not ever consider this a safety measure, and usually wore the 3-point over it.

Without bias (for obvious reasons), I think the BK brace or a Rollbar (with belt bar) are the only "safe" ways to do it. Other ways work to give you "cinched-in" feeling, for sure.

Skip

Skip

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by dave120:
<strong>Because the B pillar is the strongest one so it can take the most force without having a problem.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I would tend to disagree - the B-pillar is narrower and in harm's way (thinking of side-impact) more-so than the C-pillar

I have absolutely no engineering study to prove it - just a thought...

Skip

Alpine951

I would think the C pillar is the strongest. But i don't know what I am talking about.

<a href="http://www.stableenergies.com/stable/shoulder.html" target="_blank">http://www.stableenergies.com/stable/shoulder.html</a>

Thats a good point about restricting seat movement. I have to recline the stock seats a bunch because my helmet is wedged against the roof.

smokey

Looping the belt over the harness bar and then connecting it to the seat belt mounts increases the stress on the harness bar by about 40 to 50 % compared to simply attaching the belt to the harness bar.

dave120

In traditional engineering, a 90 degree angle is always the strongest. The A and C pillars are at much more extreme angle than the B which is nearly straight up, and angled a bit of course. If you notice no rollbars that I have seen mount to the C pillar (full cage might?) but the B pillar is one of the strongest points on the car, hence the front seatbelts mount to it. The rear seatbelts mount to the C pillar for the shoulder part only, the bottom ones mount to the panels on the side which is another major reinforced section of the car.

Side impact I guess the B pillar might not be as strong as the others but I'm talking rollover type stuff.

My dad did all the physics work on that stuff when he was designing the rollbar we built for my car. If someone else has any info to the contrary please correct me.

Skip

First, I'm not anything close to an authority on this... just logically guessing... is very good to talk this out.

I agree with the principle that the B-pillar may be stronger through incident angle alone. However, the rear C-pillar in larger (wider/thicker) and shorter (less standing area) and the connection point is lower relative to the B-pillar mount. It is not in what I would think to be a crush zone in a rollover. The reason no rollbars or cages are connected to the C-pillar is that there is no reason to protect that area of the interior.

Skip

smokey

In a fore and aft direction the C pillar is stronger because it is a triangle extending to the back of the trunk and is effectively in tension, whereas the B pillar acts as a simple beam. It's academic anyway, because the forces acting on a shoulder harness in a survivable collision are probably well within the limits of either pillar. I hope never to have to test this theory, however.

wjk_glynn

Hi folks,

I've seen 6-point fittings advertised. How do they differ from a 5-point harness?

Karl.

Skip

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by smokey:
<strong>Looping the belt over the harness bar and then connecting it to the seat belt mounts increases the stress on the harness bar by about 40 to 50 % compared to simply attaching the belt to the harness bar.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I need to see an engineering example of this - anyone? I don't know enough to disagree, it just doesn't feel right...

Another item to consider is the strength of the bar itself holding the harnesses compared to the strength of the rear seatbelt mounts holding the harnesses. While the harnesses would be far less usefull if the bar were to collapse, is the fear more that the bar may bend, allowing it to lose it's strength and snap free - allowing the harnesses to come free. I just can't picture the forces of looping the harness over the bar being as strong and direct as the forces if it were attached directly to the bar... I almost picture the load of looping over the bar being in more than one direction, thus reduces the load relative to that of it being in one point (as in tied to the bar)... I'm probably missing a lever theory in here somewhere?

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