3-Point Y-Harness Lap Belt Mounting Location?

[Stretch32]

I posted this on the other sight as well:

I'm building a '71 911E LWT hotrod and I bought a set of reproduction Repa ST style Y-harness to use in the build. I welded in the parcel tray shoulder harness mounting plates (under the back window) like the ST's used but I'm having trouble deciding where / how to mount the lap belts in conjunction with my reproduction Recaro RS seats.

My issue is: the harness lap belts are designed to use the factory Repa seatbelt L-brackets / bolts that are normally attached to the seat bases / frames of the factory comfort and sport seats. I'm 6'4" so I have the seat slid all the way back and this places the lap belt L-brackets forward of my hips (at about 10 degrees forward of straight down). Looking at lap belt mounting info, the lap belts need to be at about a 45-60 degree angle aft of my hips so this forward location won't safely work.

I've been looking at various weld in / bolt in harness lap belt arrangements but I'm not sure if they will work for me. The obvious solution (I think) is to mount the lap belt harness mounts on the floor pan behind the seat at the proper 45-60 degree aft angle but this will make the lap belts wrap around the back of the seat to some extent instead of coming straight down parallel to the side of the sport seats. I can't find any documentation to confirm whether or not this is an acceptable / safe mounting arrangement or not.

The car is being built for street driving (not track) so I need to find an arrangement that will meet those safety requirements. Any insight or suggestions on this or an alternative method of mounting these lap belts would be appreciated.

Stretch

[911MRP]

My 73 ( 72 built) Carrera RS has factory seatbelt threaded locations in the centre tunnel and the inner sill (inner rocker). Cees once posted a picture of his RS with same showing location which should come up on a search. I think British market cars in the day had this to comply with seatbelt anchorage regulation BS AU 48. A British 73 T I know has same.

Edit: Post # 5 show an example in Mike’s British market 73 T and Cees lhd RS is post #8.
https://www.early911sregistry.org/fo...SAU48+seatbelt
Some other cars have it behind U.K. and RS

Standard thread on the factory seatbelt anchorage . Kangol were the seatbelt brand typically used by importer in U.K.
this is the kangol harness.


The original three point statics on early RS here in U.K. were typically Kangol.

Other brands used on other markets and the factory.

Works with regular kangol mounting hardware for the original static three point using the B pillar or with a three point harness clipped into kangol original eye bolts in conjunction with the original seatbelt mount on the rear parcel shell my (and all?) the RS had as factory fitted anchorage location for harness.

I don’t know if these factory threaded seatbelt anchorages still meet current regulations in your region and of course any anchorage depends on the integrity of positions in fifty year old car but in principle the threaded mounts on tunnel/sills seems better than relying on someting that relies on the seat mechanism remaining locked even with do called double lockers.

I’m not an expert. Since your seatbelt and mounting is a safety critical item I’d recommend getting advice and have all the work done by a suitably qualified specialist.

I’m not recommending this as a solution, the information being shared for historical reference interest only!

Steve

[Stretch32]

Steve,

Thanks for the reply.

My US model '71 doesn't have these anchor points although I am familiar with them. I looked at adding this mounting arrangement to my car but it would be more difficult (in my opinion) and probably not as secure as a dedicated bolt in / weld in harness mount arrangement.

Stretch

[911MRP]

Understood. Since you’ve modified rear you're not constrained by originality so can go for whatever qualified experts deem the safest solution that complies with prevailing seatbelt anchorage regulations

Steve

[stretch]

Stretch32: i assume these are not the harnesses i supply because we don't make them to be mounted to the seat runner location. In my opinion that is not a safe location. Can you not weld in a couple of bolt receiver plates to your inner rocker and transmission tunnel.? Here's my recommendation as seen on my ST build.

[Stretch32]

Stretch,

They actually are your harnesses. I'm looking for suggestions on where to mount the plates or what sort of mount options (plates) / locations will work.

I was thinking about buying harness lap belt mounting assemblies that bolt in and attach those to the floor boards behind the seat. My big issue is, based on the width of the seat, the lap belts will wrap slightly around the seat and not actually mount (fall) parallel the the side of the seat. I'm trying to find documentation to confirm whether or not this is an acceptable mounting arrangement.

Other Stretch

[blue72s]

we don't make them to be mounted to the seat runner location. In my opinion that is not a safe location.

Why do you believe that?
In many modern cars, the seat belts are mounted to the seat runners.

[stretch]

The seat runners in our cars are over 50 years old, as are most of the bolts. These are "race" type harnesses and the recommendation for race car harnesses is to fix them to the chassis with spreader plates. New car mountings are stringently tested unlike an old classic Porsche. The choice is yours.

[Bobs 67S]

If the vertical surfaces are blind to one side you may have to weld the receiving nut to a rectangle 3/16" plate. Drill into that vertical surface with hole just larger than the nut, insert nut into the hole - then surface edge weld the plates.

Just be sure what is inside the tunnel is not electrical wires or fuel lines prior to drilling or welding.

If that is not a working solution for you, floor mount the anchor bolts.

Here is the locations for seat belts that were floor mounted. Note the oversized washers used both top and bottom.
The bottoms were edge welded to the floors. For your height - mount further back. I'm only 6' and the seat is full
back on the rails for this seat.

Note that the belts do not cross any metal edges - so no opportunity of belt sheering.

Hope this helps

[911MRP]

Why do you believe that?
In many modern cars, the seat belts are mounted to the seat runners.

In mid June 1975 the seat rail were found to bend and open on crash test ! Stronger material was used from this date.

I don’t know the details and if it is relevant to the mount on seats for belts.


Maybe this fact is a reason to give pause to some anchorage solutions when even the factory seat rails were found wanting after the G series facelift!?

As said previously I recommend getting specialist qualified advice for any new safety critical seatbelt equipment ans mounting.

Steve