Seat belt captive nut plates

[Mark Wilson]

I'm in the process of painting the underside of my Traveller, and as I've replaced all the floors and inner wings I need to fit new seat belt mountings. I thought I'd finished all the welding before starting painting, but it has occurred to me that the captive nut plates could need welding in. Obviously more convenient if secured to the floorpan, but is it essential to weld? I'd rather set the stalk mounting positions after I've fitted the non- standard seats, which will be some time yet.

[RobThomas]

Welding the nuts directly can affect the strength of the threads if you blast them with a bit too much heat. Better option would be to buy the nuts already welded to plates and then affix the plates to the floorpan so that they spread out the load over a large area although doing that to the outer ones on the Trav will be hard to do since you'd need to be welding inside of the chassis box section, wouldn't you? The manufacturer will have ensured the weld quality. BMC sold a similar kit to retrofit belts to earlier cars.

http://www.ebay.co.uk/sch/Vehicle-Parts ... elt+plates

These look to be zinc plated and have a hole for a rivet so I guess they aren't expected to be welded in. Phil will know the motorsport regs and the reasoning behind them.

[Mark Wilson]

Thanks. The nuts in the sill steps are already in place, and I will be obtaining purpose made nuts on spreader plates for the floor pan and arches (and tunnel). Good news if I can rivet these rather than weld - I've no problem welding them in, but I would prefer to choose exactly where they go a little bit later, by which time the floor will be painted and the car back the right way up.☺

[bmcecosse]

No need to fix them in place at all - as long as they spread the load, and make sure they (and the bolts) don't foul the propshaft.

[Mark Wilson]

Thanks Roy. Glad I don't need to disturb my paint - it's starting to look good as if I'm getting somewhere at last!

[les]

Welding with too much heat can weeken the threads? Tell me more as I don't get it.

[RobThomas]

For an example...

http://www.portlandbolt.com/technical/f ... ut-grades/

Basically, decent quality steel hardware is heat treated / hardened / tempered and reheating it to welding temperatures knackers them. If you enjoy experimenting, try to snap a bolt by over-tightening it and then do it again with an identical one after getting it red hot. Flywheel bolts are great for this!

[les]

Well that surprised me, I thought providing they cooled naturally the integrity would be maintained.

[Nourish]

Mmmmm - are flywheel bolts high tensile?

[RobThomas]

Yes. Have you cooked yours?

[BLOWNMM]

It is necessary to fix the captive nuts. If the seat belts need to be removed for whatever reason they are then not captive and can cause headaches especially the ones in the B pillar. I have made mine and spot TIG welded the HT nuts to plates and secured them with pan head 10-32 UNC screws because the head is very shallow and does not show up as bumps when fitted in carpeted areas.
Bob

[RobThomas]

Before Les asks, doing it the way Bob has done doesn't get a vast load of heat into the nut and is only there to locate it and keep it from turning. The plate is inside the sill and the nut would need to pull right through both for it to fail whereas welding it to the sill directly would cook the nut. Hope that makes sense.

Good book on nuts/bolts/pins etc is by Carrol Smith.

https://www.google.co.uk/imgres?imgurl= ... VXDS3Idgs=

[BLOWNMM]

Looking at the images in Rob Thomas' first post the 'professionally made plates' may not be so. Looking at the images close up they are all welded along the length of three flats of the nut. This is much more than needed and I would guess not exactly good for the strength of the nut. My three tack welds would add up to considerably less than the length of one flat, probably about 20% as much weld as the illustrated nut/plates.
Bob

[RobThomas]

I agree. Not a lot of choice available on Ebay but maybe some searching would throw up a better option.

[BLOWNMM]

Not hard to knock your own up as I did.
Bob