Alvin,
Harness anchor points will take a load of up to 5000 pounds instantaneous
load ( 25G peak acceleration at 35mph DeltaV x 200lbs driver mass=load).
This would be what could be seen in a 35MPH impact into a fixed barrier
(i.e. bridge abutment). More modern cars will transmit less total G's to
the occupant, due to the crush characteristics engineered into the vehicle
chassis, but the Roadster has a rigid frame which terminates at the front of
the vehicle.
The loops shown in your photo are most probably not good enough steel to
anchor a harness.
I threw a picture up on my server
http://home.neo.rr.com/mark2000/grant/Alvin1.jpg The two options depicted
are to replace one of the roll-bar mounting bolts with a longer, grade 8
bolt and nut, ensuring that there is a sufficient doubler under the body tub
to distribute the loads.
The other option is to have a certified welding shop weld a 3/16" mounting
tab to the down tube on both sides of the bar to anchor the shoulder belts
to, and again, make sure the bars mounting bolts have doublers underneath.
I'm going to be taking this aproach on our custom. Most race car fab. shops
will have both the certified welder and the tabs on the shelf.
It is preferred to have the shoulder belt anchors at or above the height of
the shoulders, and or not less than 1" below, in case the seat back
structure would fail. Picture tying a slipknot loop around an orange and
pulling it tight - if the seatback fails to support the shoulder belts that
are anchored well below the shoulders, your body becomes the orange -
compressive loading of the shoulder belts downward on your spine can ruin
your whole day.
Mark Sedlack
OROC
Cuyahoga Falls OH
66 1600 http://home.neo.rr.com/mark2000/images/datsun1600/
77 280Z http://home.neo.rr.com/mark2000/images/datsun1600/Z.htm
----- Original Message -----
From: "alvin gogineni" <alvingogi@hotmail.com>
To: <Ofarrell.Fergus@hitco.com>; <datsun-roadsters@autox.team.net>
Sent: Thursday, September 19, 2002 1:31 PM
Subject: Seatbelt update/solution
> I think I found a way to mount that shoulder harness, it will need to be
> reinforced too. There's a picture in www.picturetrail.com/alvin6 with
the
> setup in mind. Let me know what you guys think.
>
>
> >From: "O'Farrell, Fergus" <Ofarrell.Fergus@hitco.com>
> >To: "'alvin gogineni'" <alvingogi@hotmail.com>
> >Subject: RE: seat belt mount option
> >Date: Thu, 19 Sep 2002 09:57:52 -0700
> >
> >Hey Alvin,
> >I am not sure if it was on the SummitRacing website or in the
> >instructions/safety warnings for my 4-pt Diest harnesses, but they
> >specifically said that if you have 4 or 3 points like ours, don't take
the
> >center strap over the seatback and down to the floor. you have to go
back
> >,
> >not down.
> >this is because when the body gets thrown forward, depending on how far
> >from
> >the belt attachment to the seat pivot, the belt will slide around the
> >corner
> >at the top of the seat, letting the body and seat move forward. Kind of
> >like a rope going around a pulley.
> >
> >Ya know what would work well but might be kinda unsightly in your nice
> >clean
> >interior, is instead of using a metal tang which bolts under the rollbar
> >mount, you use a piece of wirerope and a carabiner swaged into the end.
> >this would allow the belt to move all around, and transmit the load well.
> >I
> >am just not sure how to make it look as cool as the rest of your
interior.
> >
> >still thinkin'
> >Fergus O
> >
> >-----Original Message-----
> >From: alvin gogineni [mailto:alvingogi@hotmail.com]
> >Sent: Wednesday, September 18, 2002 5:07 PM
> >To: Ofarrell.Fergus@hitco.com
> >Subject: Re: seat belt mount option
> >
> >
> >Yeah, I was upset when I put a pinhole in that area through the vinyl,
only
> >to find out I couldn't use it! My rollbar does mount in that area on the
> >shelf, the pic isn't resized. There are mounting holes further back on
the
> >shelf? WE just drilled some holes to mount it. I will probably mount the
> >the
> >
> >belt directly behind the seat on the shelf. Will have to use a metal
plate
> >to reinforce though. ARRGH!
>
>
>
>
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