Safety of seat belts attachment to seats

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IanM
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Safety of seat belts attachment to seats

Post by IanM »

Steve (911MRP) mentioned at the ESR forum a few weeks ago that Porsche did a crash test in circa 1976 and found that the seat runners open and bend in a crash. So, it made me wonder whether the seat belts attached to the seats in longhoods are safe?

See pics:
063.jpg
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Gary71
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Re: Safety of seat belts attachment to seats

Post by Gary71 »

First rule of early 911 crash performance is try really hard not to hit anything.

These belts should at best be considered as a token effort to stop you sliding off the seat under heavy braking.

I modified my car to fit the inners under the seat rails and welded a plate to the sill for the outer long ends. Still no more than a token effort if you look closely at the shoulder anchorage… :)
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Re: Safety of seat belts attachment to seats

Post by IanM »

Gary71 wrote: Thu May 11, 2023 4:04 pmStill no more than a token effort if you look closely at the shoulder anchorage… :)
Thanks for the heads up about the shoulder anchorage. Didn't Porsche ever reinforce the upper B-pillar?
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Re: Safety of seat belts attachment to seats

Post by Gary71 »

The anchorage moved down towards the waist rail on later cars, probably to improve belt comfort but also would reduce bending into the middle of that skinny pillar.

Not sure about the structure on those later cars, but there not much of it on our early cars, most of the thickness is the trim :)

Image
Image
This is the later centre mount for the belt to the tunnel. This goes inside tunnel and the anchorage’s pole through slots.

Image
IanM
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Re: Safety of seat belts attachment to seats

Post by IanM »

I never noticed the lower shoulder anchorage in later cars. Thanks. What year did Porsche make that change? Less leverage on the upper pillar therefore stronger.
I think I will replace my early pillar with the later one.

Will updated seat belt mounting points mean a Q-plate? :roll:
deano
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Re: Safety of seat belts attachment to seats

Post by deano »

This is another reason why Targa's are better than coop's :lol:

I cannot comment on the tests, and they might be true. However, the seat anchors/brackets look extremely robust to me, as are the seat buckles which attach to them, I think. I don't see any weak points there. The upper anchors don't look very robust on my Targa pillar either - I would say that is the weak point if anything. A hefty gentleman might cause it to give a little in an accident..
Dean
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Gary71
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Re: Safety of seat belts attachment to seats

Post by Gary71 »

IanM wrote:I never noticed the lower shoulder anchorage in later cars. Thanks. What year did Porsche make that change? Less leverage on the upper pillar therefore stronger.
I think I will replace my early pillar with the later one.

Will updated seat belt mounting points mean a Q-plate? :roll:
I wouldn’t bother, marginal gains for a whole load of work and potential misalignment.

If you are getting to the loads to make that pillar fold then you’ve probably got a fuel tank on your lap so have bigger things to worry about :)
IanM
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Re: Safety of seat belts attachment to seats

Post by IanM »

.

I'm sometimes of the opinion that 1974 is the best year ever for an air-cooled 911.

Much safer seat belt anchorages
Belt reel recessed into the panel out of the way (and hidden)
Stronger upper B-pillar
Far better seat runner supports pictured below:
35122266474_eda69d1b6b_b.jpg

Still without a 5-blade fan or thermal reactors (introduced in '75)
Same dash-top as pre'73
Easy to backdate front end using a SWB front bumper and single battery setup

.
Last edited by IanM on Mon May 15, 2023 1:23 am, edited 1 time in total.
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AndrewSlater
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Re: Safety of seat belts attachment to seats

Post by AndrewSlater »

IanM wrote: Sun May 14, 2023 4:27 pm .

I'm sometimes of the opinion that 1974 is the best year ever for an air-cooled 911.

.
I totally agree - early 74 cars are great!! ;)

PS I did take a double take when I saw the photo :)
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
911hillclimber
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Re: Safety of seat belts attachment to seats

Post by 911hillclimber »

Interesting thread.
I have personally 'crash-tested' the road seat belts on my '73T Coupe at 40 mph into a tree re-enforced bank at a hillclimb competition run. The shell was 1" shorter on the impact side than the other...and needed a good pull on a Cellette to get it straight.

However, the home fitted inertia Britax seat belts used (from an MGB GT) stood it all well (I'm about 12 stone) but my head/helmet hit the top of the screen.

The car has the road belts on the tunnel drilled through for the bolts with 3mm thick 'penny' washers under the tunnel pressing and to home made brackets to the base of the B pillar and the seat runner pressing (the static one bolted to the shell).

After that crunch, I installed a full roll cage, racing seat and 4 point harnesses with eye bolts connections.
Kept the road belt for comfort on the road.

Top mounting on the B pillar held fast. Just my experiences.
73T 911 Coupe, road/hillclimber 3.2L
Lola t 492 / 3.2 hillclimb racer
Boxster 987 Gen II 2.9
IanM
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Re: Safety of seat belts attachment to seats

Post by IanM »

AndrewSlater wrote: Sun May 14, 2023 4:50 pm PS I did take a double take when I saw the photo :)
OH, it's your photo? Sorry. I borrowed it from the restoration thread. :lol:
IanM
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Re: Safety of seat belts attachment to seats

Post by IanM »

911hillclimber wrote: Sun May 14, 2023 5:12 pmThe car has the road belts on the tunnel drilled through for the bolts with 3mm thick 'penny' washers under the tunnel pressing and to home made brackets to the base of the B pillar and the seat runner pressing (the static one bolted to the shell).
Any pics?
911hillclimber
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Re: Safety of seat belts attachment to seats

Post by 911hillclimber »

I'll take few tomorrow and post here.
73T 911 Coupe, road/hillclimber 3.2L
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Re: Safety of seat belts attachment to seats

Post by 911hillclimber »

Sorry for the delay, got ambushed into doing some gardening...

Here are a few shots of my 911 installation. Seats are non standard, and the car used to be a hillclimb car.

Simple 30 x 30 x 3mm angle bottom seat anchor brackets bolted to the seat runner. I used the standard belt fixing hardware to ensure all moves freely, driver's side shown:

Image

The MGB GT (but i think a universal fit) reel was attached at the base of the B pillar:

Image

Finally, the attachment to the 'transmission' tunnel. The one strap uses an eye bolt to allow the racing seat belts to be attached. The bolts pass through to the 5mm thick mounting plates underneath.

Image

Hope this helps!
Graham.
73T 911 Coupe, road/hillclimber 3.2L
Lola t 492 / 3.2 hillclimb racer
Boxster 987 Gen II 2.9
IanM
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Re: Safety of seat belts attachment to seats

Post by IanM »

Many thanks for the pictures.

It's interesting that you have the buckles (receivers) bolted directly to the top of the tunnel without a bracket. Will an MOT test pass that?


911hillclimber wrote: Sun May 14, 2023 5:12 pmbut my head/helmet hit the top of the screen.
Ouch!
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