4-point seat belts / harness truss

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John Lindstrom
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4-point seat belts / harness truss

#1 Post by John Lindstrom »

I'm going to fabricate and weld up a bolt in truss that goes behind my seats at shoulder height so that I can mount some quality 4-point harnesses. Anyone else have any interest in installing one in their 356?
Last edited by John Lindstrom on Mon Nov 06, 2017 9:54 pm, edited 1 time in total.

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John Lindstrom
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Re: 4-point seat belts / harness truss

#2 Post by John Lindstrom »

This is what I'm referring to. No one currently makes one for the 356 that I know of.
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Obviously this is not a 356, but you get the idea.
Obviously this is not a 356, but you get the idea.

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Martin Benade
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Re: 4-point seat belts / harnesses

#3 Post by Martin Benade »

I would make sure part of it is low enough that in a rear end collision the seat back would be supported if the seat got bent backwards. Once the seat gives way the truss could break your neck..
Last edited by Martin Benade on Tue Nov 07, 2017 1:00 am, edited 1 time in total.
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Erik Thomas
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Re: 4-point seat belts / harness truss

#4 Post by Erik Thomas »

Re engineering this sort of thing is not as easy as it may appear. I have considered adding a GT roll bar and using it as a belt mounting opportunity, but the bar scares me in a street car (no helmet). A truss could solve this problem if you could figure out where to bolt it/weld it in. Are you planning racing seats?

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Jim Liberty
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Re: 4-point seat belts / harness truss

#5 Post by Jim Liberty »

I've fabricated roll bar with a full cross bar just above the seat backs. You can still bolt the belts to the floor. I installed GT seats in the car from Fiber Steel. No plug intended. It was a C - Coupe. Presently, I'm doing the same for a '57 Fiat Abarth 500.
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Patrick Doolittle
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Re: 4-point seat belts / harness truss

#6 Post by Patrick Doolittle »

Listen to what Martin said, if you have a stock low back seat, make sure not to put the truss higher than the seat. In a rear end crash, the seat could easily give way and if the bar is higher than the seat, your head or neck could very easily come in contact with the bar. Putting a roll cage/bar in a street car in my opinion is asking for trouble in a crash. They're meant to be used with helmets and without one in a crash, your head could easily come in contact with the bar. They've hurt people in street cars. It's like a steel pipe getting swung into your head. Think about what you're asking for either way.
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Jim Liberty
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Re: 4-point seat belts / harness truss

#7 Post by Jim Liberty »

Well said Patrick, and will be heeded.
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Re: 4-point seat belts / harness truss

#8 Post by Conrad Carter »

John,
Did you ever build a truss for your 356?
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Al Zim
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Re: 4-point seat belts / harness truss

#9 Post by Al Zim »

The B/C Factory shop manual outlines a satisfactory shoulder harness arrangement in section 0. Under no circumstances would I use the "C" style bolt for the hold down of the top of the shoulder harness. al zim
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John Lindstrom
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Re: 4-point seat belts / harness truss

#10 Post by John Lindstrom »

Conrad, I have not attempted to engineer a truss for the 356. Yet.

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Re: 4-point seat belts / harness truss

#11 Post by David Jones »

I put a long time T5B project back on the road for a friend some years ago. He had outlawed it and included a roll bar which I advised him not to do but he did it anyway. He regretted it. The back of his head hit it and he could not see out of the rear view mirror. If he had worn a helmet his chin would have been on his chest.
If I had known I would live this long I would have pushed the envelope a little harder.
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Re: 4-point seat belts / harness truss

#12 Post by Conrad Carter »

To John Lindstrum, did you ever design/build hArness bar for 356? Conrad

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Re: 4-point seat belts / harness truss

#13 Post by Glen Getchell »

I see this as a little bit of re-inventing the wheel. Why don't you just mount the harness to the rear firewall. I have seen this done in numerous 356's, and once even purchased a street legal C that had been vintage raced in the 80's (before the fuel cell, etc... were required). The harness went to the rear firewall.

As previously stated that last thing you want in a street car is a roll bar unless you want to drive around with a helmet all the time.

Why do you want four point harnesses in a street car? I literally just pulled out my Seat Belt Planet receipt from 10 years ago for the retractable three point belts I installed in my C coupe for another club member. I'll be happy to scan it. It provides all the info you need. Have you ever tried to let the parking brake off or get in the glove box with non-retractable harnesses? They are better left on the track.

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