Race Harness Help

[Mark Ferrari]

I need help with working out minimum steel plate thickness and design to attach shoulder harnesses to. I have a 6 point Sabelt to install into my RF40, but the standard attachment points are too high for the shoulder straps. The first photo shows location of bolt holes in roll cage (10mm) and yellow dots (love hearts actually - thanks to my young daughter) where buckles will be bolted.
Second photo shows buckles. Third shows diagram with measurements in mm. (not to scale). Has anyone have physics knowledge to work this out? I assume approx. minimum force to resist deformation at strap point would be around 400KG??? I weigh 80KG. Thanks.

 

[Howard Jones]

Are those yellow hearts on the engine cover behind the seats? If so it isn't even close to strong enough to support mounting points for a harness. Even if you used a 6" diameter plate behind that thin engine cover it wouldn't be strong enough.

Best bet would be to weld another cross tube across the roll bar like the one with the holes in it. Or at least use the two holes you have and build a mounting system that ties vertically into the chassis at the lower edge of the engine access hole behind the seats.

 

[Mark Ferrari]

Howard, thanks for the reply but you misunderstand. I need to bolt a steel plate to the roll cage bolt holes which the harness buckles then bolt to. ie. a support bracket which does not attach at all to the engine cover. I need to know the minimum thickness the steel plate needs to be to provide enough strength to support the harness buckles.

 

[Mark Ferrari]

Just to add a bit more - I don't want to extend the mounting bracket down below the engine cover for extra support. I only want to use the two roll bar mounting holes that are already there.