Harness shoulder belt mounts

#1

Finally getting the roll cage installed and the main hoop cross bar is about 2 inches below the magic horizontal plane from my shoulders with the seat mounted. My cage builder and I were experimenting yesterday with ways to mount the harness that conformed to the +/- 20 degree range called out in the spec. He has access to a number of preformed tabs which could be welded to the top of the bar with a sleeved 12mm bolt between them to wrap the harness around. A picture of the bar/seat/tab location is attached. Would this be legal? I’d like to have some flexibility in moving the harness mounts vertically up and down because the seat is currently mounted about sedan height and everything I’ve read seems to indicate I might like to lower it in the future.
[attachment=1813]IMG00149-20120401-1825_2012-04-02.jpg[/attachment]

[attachment=1814]IMG00151-20120401-1825.jpg[/attachment]

#2

If you can mount it around the cage tubing that is better (larger area to spread forces). Being 2" down from the seat opening would not bother me. Chuck

#3

I don’t think that the cage specs in the NASA CCR get into this kind of detail so IMO there is nothing expressly prohibiting your mod. The greater issue is whether the chief of tech is ok with it. No matter what the rules say, the tech chief, and by extension the Regional Director have the final say.

Be sure to wrap the end of the harness around the cage bar, not your 12mm bolt. Then run the harness over your bolt. That turns the bolt into a harness “guide bar” instead of a harness “bar”, the difference between the two being the former “guides” and the latter “anchors”. Also, the larger you make that bolt the more likely the chief of tech will like it. No matter what the resistance to bending a long 12mm bolt might really be, it’s going to look kinda wimpy for someone’s life to depend on.

Like you, I raise the shoulder harness anchor points above the cross bar. There is a pic of that in my build thread.

#4

I like the guide bar option. I’m pretty sure the shear and bending strength of a 12mm bolt is vastly superior to the shear and bending strength of the human skeleton but to your point I have to convince the Scrutineer. Anyone know who that is for the GL region?

#5

See this thru the eyes of the tech guy. Even a little bit of bending is bad. The belt is already going to stretch in a crash, you don’t want to do anything that adds to the total amount of stretch. So the tech guy isn’t thinking about the bolt’s shear strength, he’s thinking “I wonder if that long bolt might bend 1cm if this guy hits a cement wall at 100mph.” Just the fact that the result of that thought experiment is not a slam dunk should be cause for concern when you’re still in the design phase.

#6

FYI, Lots of good info!

http://www.schrothracing.com/sdocs/2009_Competition_Instructions.pdf

#7

Great stuff! Thanks!

#8

[quote=“poppy” post=64606]FYI, Lots of good info!

http://www.schrothracing.com/sdocs/2009_Competition_Instructions.pdf[/quote]
Looking at this guide, and being on my 2nd pair of Schroth’s I’d read it a couple times previous, I see that my set up is still not right. My shoulder straps don’t cross like I guess they should and I don’t have the straps going thru my M buckles correctly. Thanks for posting this. Everyone else…take note.

#9

[quote=“Ranger” post=64613][quote=“poppy” post=64606]FYI, Lots of good info!

http://www.schrothracing.com/sdocs/2009_Competition_Instructions.pdf[/quote]
Looking at this guide, and being on my 2nd pair of Schroth’s I’d read it a couple times previous, I see that my set up is still not right. My shoulder straps don’t cross like I guess they should and I don’t have the straps going thru my M buckles correctly. Thanks for posting this. Everyone else…take note.[/quote]

The way I read it, the shoulder straps only need to cross if “Shoulder belts should be crossed when the anchor points are more than 500mm [20“] behind the seatback”. The non-crossed distance between the inside of the belts at the bar is determined by the length of the belts from the HANS collar and the bar.

#10

[quote=“poppy” post=64635][quote=“Ranger” post=64613][quote=“poppy” post=64606]FYI, Lots of good info!

http://www.schrothracing.com/sdocs/2009_Competition_Instructions.pdf[/quote]
Looking at this guide, and being on my 2nd pair of Schroth’s I’d read it a couple times previous, I see that my set up is still not right. My shoulder straps don’t cross like I guess they should and I don’t have the straps going thru my M buckles correctly. Thanks for posting this. Everyone else…take note.[/quote]

The way I read it, the shoulder straps only need to cross if “Shoulder belts should be crossed when the anchor points are more than 500mm [20“] behind the seatback”. The non-crossed distance between the inside of the belts at the bar is determined by the length of the belts from the HANS collar and the bar.[/quote]
Good correction, thx.

#11

I am working on a budget for my cage. It does not look like I will have one until the summer of 2013. Does anyone know if there is a way I could run HPDE days with a Sparco Evo race seat and the 5 point harness anchored in the car with out a cage?

#12

Google harness GUIDE bar.

#13

Im running into the same problem. My harness bar is too low and my seat is very close to the bar which will cause the belts to rub the seat and the angles are too great. What I’ve decided to do is add a parallel bar to get the height I need. The added weight is minimal.

Ray