Not a brilliant day today, thought it was time I dropped a seat in the car and bolt it in, seeing as I had welded the harness top mount bosses in place, then cut the ally bulkhead to let the harness clips - clip on.

Cut a 20mm hole in the lower door bar to weld in the threaded boss on both sides. The issue I have is with the inner lower harness threaded bosses.

The nearest floor frame is 25mm square tube, which I fell is a bit scant once Ive cut a 20mm hole in it, have made up some plates to reinforce the tubes. Will I be ok cutting a hole in the 25mm tube, or do I need to weld in another square tube (as per the yellow line)

Do I cut 20mm holes in the square tube then reinforce the box with extra sections, or span the tubes (as per yellow line) and create the mounts that way?

The Schroth harness I bought is a clip in type (4 point) and the lower sections arent long enough to fit round my kite.

The IVA manual has really good info and diagrams in what is needed for this.

For SVA my top mounts were threaded bosses welded top and bottom through the 25mmSST.
Your cross brace would certainly add strength but I'd be inclined to weld it between the bosses.
No doubt someone will be along shortly to give you the MechEng chapter and verse.
HTH.
Cheers, Pewe10

Thanks Pewe, i cannot find the harness mount diagrams in the manual ?

The inner pair will share this 25x25x3mm square tube, with welded vertical bosses. Once welded in place the mounting will get some plate welded over where it joins the thinner 25x25x2mm floor sections.

whats the verdict people ? Im very aware Im expecting this piece of metal to take the weight of 2 people in an impact.

I think that looks fine, particularly with the additional forward facing triangulation pieces.
Were it mine I would be confident it was up to the job.
If you look at the average tin-top lower seatbelt mounts they appear to be mounted in tissue thin metal with a small, equally thin metal reinforcing plate.
Go for it....
Cheers, Pewe10

quote:

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Originally posted by pewe
I think that looks fine, particularly with the additional forward facing triangulation pieces.
Were it mine I would be confident it was up to the job.
If you look at the average tin-top lower seatbelt mounts they appear to be mounted in tissue thin metal with a small, equally thin metal reinforcing plate.
Go for it....
Cheers, Pewe10

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Oh yes, see what you mean about the clamps (note to self - must book Specsavers appt!).
However cross braces at that point would certainly be belt and braces.
Cheers, Pewe10