Anyone care to shoare how they keep their shoulder harnesses on the roll bar from spreading too far apart when used w/ a Hans?

Schroth specs the centerlines to be ~4" apart when the attachment point is close to the seat back.

I have aluminum shaft collars but the concern is chafing, yes/no?

 

I was told by my shop to leave them alone to allow them to spread until they find equalibrium. I'm sure there's some physics involved in "why", but I didn't ask - I trust them that much (Dan Jacobs). As to the Hans, I have the 3/2" shoulders and they align perfectly on their own.

 

The 4" is not correct for all setups.

Schroth uses the formula: Y = Z - (X*.50)
Y is the spacing.
Z is the distance measured between center of shoulder and center of shoulder with hans in place.
X is the distance from the center of the shoulder with the hans in place to the bar.

I use their SFI approved formula to set my spacing and use SFI high density roll bar padding to fix belts in place.

 

Hmm, I have the 3/2 shoulders too, maybe I should let them float, Dan is pretty smart, it just seems that they want to go too far...

 

for a large Hans Z = 10"(per Schroth, x = ~10"
so using that formula Y looks to be ~ 5" OC, roughly what I'm shooting for, the belts seems to naturally want to spread to ~ 8 - 9"

I do have some SFI padding coming, so just zip tie to the cross bar instead of the collars? I wonder what the magnitude of the spreading force is?

 

I'm looking for my Schroth CD, but I could swear that Hans Harnesses should be crossed behind the driver when they are a certain distance behind the seat.

 

Hans states "Reduce Results if using the 2"/3" webbing by 1".

Yes, zip tie.

 

This is correct. They cross over at X = 24" for the 3" and 2" belts

 

I'm guessing when Dan set things up for me he took many factors into account. My seats (Porsche Sport Buckets), mounting position / distance, 3/2 Hans belts, etc.

 

Hmmm...

In a contest of smarts between Mr. Jacobs and Mr. Schroth, regarding safety equipment... uhhhh... I'll go with that Karl guy. Having said that, you would not want any setup that allowed any unusual infringement of the belt material or its path, so this may have bearing on that Dan guy's thinking.

The general idea is to have the belts no wider apart than your neck. In order to facilitate the belts staying where they are supposed to be, mounting them narrower than that will pull them toward the neck/sternum when they are tensioned, which is intended to counter the phenomenon where the torso will "shape change," the shoulders will pull back, and attempt to spread and slip between the straps.

As for keeping the belts in place, padding and zip ties will not do. This setup is fine if you are sitting still or not intending to hit anything when moving (doink!) but will do nothing to counter any truly dynamic situations where you're getting thousands-of-pounds of load. In other words... DUH! You need the solid shaft collars to keep things in place.

In reality, I think you need to factor in all of the parameters. I would not try to out think Schroth on this stuff for one second. However, you don't want any undue chafing or other stress on the belt material. You need to compromise just enough to make it workable for a longer term than the race team budget people are likely thinking, since they usually consider such things expendable.

This discussion has just given me a brilliant new idea for belt bars that work better for close mounting!!!!

 

Split shaft collars from McMaster Carr. Buy them.

 

To be fair to Dan, I've seen setups he's done where the shoulders have been restricted by rings or foam. It's just that in my case with my seats, Hans harnesses and Hans device, etc. no restrictor was needed. Nobody should interpret my comments to suggest the method on my car is for everyone.

 

That's the thing what little Schroth has to show about this, it is w/ hard FSI foam zip tied to the roll bar used as a stop.

I do have the split al. collars it's just that I am somewhat concerned about chafing.

Maybe a bit of foam at the mating faces....

 

Or...muffler clamps.

 

For the amount of usage you get from the belts before you are supposed to replace them, I would not think that being located by smooth shaft collars would do much chaffing.