Hidden Front Seat belt upper mounts

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Brett027
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Re: Hidden Front Seat belt upper mounts

Post by Brett027 »

I'm just trying to work through it all. I have made the call to leave my frank bolts rather than take the risk of mucking up two already compromised pillars that have required considerable repairs on their bases. I'm just trying to understand the reasoning behind cutting the tops open too.
Of course if the hourly rate is sufficient ($$$$)I would be happy to offer my unprofessional services to you.
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Errol62
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Re: Hidden Front Seat belt upper mounts

Post by Errol62 »

I think the bolts look ok on a 4 door car where the b pillar is quite narrow. On the commercials it is easy to fit without cutting open. Yes the frank bolts probably are stronger although maybe the monocoque integrity is somewhat compromised. These jiggers weren’t designed with seatbelts in mind of course.


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Blacky
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Re: Hidden Front Seat belt upper mounts

Post by Blacky »

I didn’t bother with engineering any of my cars seatbelt mounts - I figured commonsense would dictate what will and won’t work - and if a 50x100 plate is going to fail or pull through the floor the crash is that big you are dead anyway 🙄
When you're faced with an unpleasant task that you really don't want to do, sometimes you just have to dig deep down inside and somehow find the patience to wait for someone else to do it for you.


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Harv
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Re: Hidden Front Seat belt upper mounts

Post by Harv »

Brett027 wrote: Wed Jun 03, 2020 6:36 pm Hi Harv, this seat belt loading stuff has me a bit perplexed. In relation to the frankenstein nut, has anyone ever seen this nut fail- ie be pulled through the pillar? I thought this was the method used by holden and others for quite a few models but might be wrong. I have always assumed that the idea of seat belts was to keep the belted body tight so that when there was a collision, the person's inertia is reduced to the same as the car, minimising the force associated with an accelerating mass (loose body). As well, given the belt is pulling on the pillar forward in a collision isn't the force on the bolt actually pulling forward perpendicular to the pillar and not pulling outwards. Essentially twisting the pillar rather than trying to pull the bolt through?
The load on the B-pillar is complex. The sash guide (top bit) is loaded at an odd angle. Most of the force tries to pull the bolt out of the pillar, but part of it tries to bend the bolt, and a small part of it tries to shear the bolt horizontally. The bottom mount on the pillar is less complex. It mostly tries to shear the bolt out of the B-pillar, with some of the force trying to bend the bolt and a very little bit of the force trying to pull the bolt through the pillar. If this bottom mount is on the floor, this changes again (mostly pulling the bolt out of the floor, little bit of bending, very little shear).

I've never seen a seatbelt bolt pull through, or shear for that matter. The safety factor on them is enormous, and for good reason. If you load them up to the point of breaking, all that energy has to go somewhere when they fail. They will deform, but will snap suddenly. The poor bugger in the belt is slingshotted. A 7/16"UNF bolt head (a.k.a Frankenstein bolts) have a surface area of just 235mm2... around 6% of the minimum area the rego authorities reccomend for reinforcing plates. Plates behind the pillar will hold 16 times the load that the Frankenstein bolts will.

I'm not sure GMH ever used Frankenstein bolts, though NASCO almost certainly did. The bolts in my HR pillars and floors look like they were there from factory as captive nuts and plates.

Cheers,
Harv
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vmx-mxr
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Re: Hidden Front Seat belt upper mounts

Post by vmx-mxr »

This thread kicked me into an outer orbit of distraction...

Found this and halfway through there is an interesting relevance to Holden. https://www.carsales.com.au/editorial/d ... ory-21137/

Also, regarding HR, I have two HR sales brochures which are virtually identical with the difference being one is devoid of seat belts and the latter release has seat belts clearly shown.

Dave Mac
EK283
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Re: Hidden Front Seat belt upper mounts

Post by EK283 »

Harv is correct in what he says,

The things that shit me is one rego my belts were knocked back just old and faded, no worries.I put them in myself years before and before any real engineering was required but I needed a certified seat belt person to install them, ok.
I track someone down and he installs the belts and doesn't even look at the mounting points, he assumes they are ok and just installs and then gives me a bill !!!!

From that day on I read and research everything and don't trust any so called professionals (that's why I'm obsessed with doing everything myself).

Anyway rules must be adhered to unfortunately so it's good to know them before you embark on any modification.

Greg
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Errol62
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Re: Hidden Front Seat belt upper mounts

Post by Errol62 »

vmx-mxr wrote:This thread kicked me into an outer orbit of distraction...

Found this and halfway through there is an interesting relevance to Holden. https://www.carsales.com.au/editorial/d ... ory-21137/

Also, regarding HR, I have two HR sales brochures which are virtually identical with the difference being one is devoid of seat belts and the latter release has seat belts clearly shown.

Dave Mac
Thanks Dave, they do publish some quite good articles.


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Brett027
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Re: Hidden Front Seat belt upper mounts

Post by Brett027 »

I guess the question for me is still about the b pillar. If the bolt doesn't pull through in an accident, the effective area to dissipate the force is the pillar not the area of the bolt head. The other thing to note is that the belts are designed to stretch and dissipate force (by changing the acceleration of the mass(me) as well, so the force on the bolt is less? Anyway, as has rightly been said, it doesnt matter a hill of beans if the regs require a plate for the car to be compliant. I can feel the warmth of the mig already!
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ardiesse
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Re: Hidden Front Seat belt upper mounts

Post by ardiesse »

The incident that ended my HD's life (and nearly my own) was getting T-boned at an intersection by a Land-Cruiser towing a trailer with a fridge on it. That would have been about 3000 kg travelling at speed hitting 1190 kg. Being an HD, it had Frankenstein bolts in the B-pillar. The bolt head pulled the outer B-pillar skin inwards about 1.5 mm. That was a very visible indication of the forces generated in a collision. As a result, I am no fan of Frankenstein bolts.

All Holdens from EJ onwards had (front) seat belt anchor plates in the floor. Half-way through the HR, front seat belts were made standard equipment, thus no more Frankenstein bolts. External rearview mirror, shatterproof interior rearview mirror were also standard, and the internal sunvisors changed from Masonite to wire-frame.

Rob
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Re: Hidden Front Seat belt upper mounts

Post by Cliff Regan »

I believe this is the requirement in the West. 50 x 80 and spot welded in, 7/16 UNF Bolts
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