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I'm putting 3-point non-retractor belts in my Lotus 7 replica, and need to anchor the shoulder belt to the roll bar. How do I put a 1/2" bolt through the 1 1/2" roll bar without kinking, crushing, or weakening the roll bar structure?

If it was me I would weld an anchor br@cket to the roll bar, not drill through it. But that's my opinion, I don't know the rules and regs regarding roll bars, maybe it's acceptable to drill through and weld in an anti crush sleeve so you can bolt through the roll bar

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Perry

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Yup, weld a bracket, tab, or bung to the roll bar. Make sure there's enough weld area that the tube won't rip in a collision.
Don't drill the bar unless you are welding a sleeve in the hole on both sides.

I would weld in a tube that just clears the bolt into a hole drilled through the roll bar. An alternative is welding on a boxed bracket.

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Or use belts that wrap around the tube instead of a tab and bolt termination.

You may be able to pull the belt out of the tab and wrap the tube if you have enough length in the belts.

Assuming you are using racing harnesses.

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Honey anyone?

Make sure the shoulder attachment point is at the correct height too. Compare the guide height relative to the seat bottom height to a production car in your driveway.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Make sure the bracket/attachment point doesn't become a hazard if you're thrown about in a side impact or rollover.

Often, it's best to put the bracket and/or fasteners on the back side of the tube and loop the belt over; that way there's nothing protruding that can hit you.