Fitting 4-point harnesses

[cobaltcodd]

The time has eventually come to fit some 4 point harnesses to my 1988 de-dion Supersprint.  as you can see the originals are the very awkward to tighten type.

Anyway, I seem to have a choice of where to fit the new ones.  There is the original mount (#1 in the picture) and under the trim, there are 2 welded threaded mounts on the crossbracing, marked as #2 and #3.  (the actual position of these are marked with pound coins)  Looking at it, should I use 1 and 3 or 2 and 3?

The trouble is, 2 and 3 don't seem to be equidistant to the centreline of the seat.

Any thoughts?

many thanks

[MADMALC]

I have just checked the build manual from that era and it just states that there are suitable attachment points on the rear cross member for the upper fasteners and to use the same attachment points for the lower fasteners. I used 1 and 3 on my car.

[cobaltcodd]

Many thanks Madmalc, and also to Jonathan Kay, who sent through a section of a 1998 updated manual, which I include here for other peoples reference.  Obvious really, if you had a better roll-bar!

 

[cobaltcodd]

Oh, how can I re-size that?

 

[Jonathan Kay]

[cobaltcodd]

Many thanks Jonathan.

 

[elie boone]

I would use 2 and drill a new hole the other side of the popper that is close to 3 towards 2. just use a long bolt and nut for the new position of the shoulder strap.

[MADMALC]

The original mounts are STRONG and comply with strict regulations. If you just drill a hole and use a long bolt there is no guarantee of integrity, and when it comes to seat belts better safe than sorry.

Sorry Elie but for this purpose I think your advice is flawed.

[brianjhall31]

As MADMALC says the mounting points that are already available in the crossmember will have been tested and approved in accordance with the relevant regulations.  If you drill any extra holes in that crossmember you will weaken it and negate this approval.  Its just like drilling holes in Roll Cages, you negate the approval.

Remember the first priority is your safety.

As an interesting aside my 2003 R300 SV (factory build) only has 4 mounting points for the Full Harness in the crossmember. And I can confirm that the FIA Roll Cage diagonals do mean that the outer Harness mounting bolts don't have sufficient clearence to be removed.  This means that the simple "I'll just buy and fit a new Boot Cover" turns into a much bigger job! (jack up car, remove suspension units, remove all Roll Cage attaching bolts and extract from car, remove 2 outer seat harness attaching bolts, remove old boot cover, fit new and then rebuild car!)

But the best point is.....there is always someone on Blatchat who has done it before with good advice!

[7 wonders of the world]

Elie,

you would crush the tube andcause a stress riser with you idea, as a minimum you would need to weld a sleeve into the new hole, if your doing that then weld a 7/16 UNF threaded sleeve in as per the OE ones.

However although the holes look wrong, I remember having the same thoughts on my first car once a seat is in they do align.

[7 wonders of the world]

also look on CC parts and invest in the crutch straps to upgrade to 6 points for added security, comfort and greatly reduced change of submarining in a shunt.

https://caterhamparts.co.uk/seatbelts-harnesses/1195-crutch-strap-plug-into-4-point-black.html?search_query=harness&results=35

also available in red.

If your running lowered floors you need the spacers for theabove too in order to correctly anchor them behind the seat.

 

 

[elie boone]

If the bolt would brake out of the tube in an accident you be dead for sure, i never did say you have to do the bolt up so much that you crush the tube there is no need for that as the forces are more torsional. A incorrect placed shoulder strap can do much more harm the a new fixing point in a non std place without bush.

[SLR No.77]

IMO the issue is that with an additional sizeable hole drilled in the tube it reduces the integrity of the tube, the bolts themselves are not an issue. Welding/brazing in a suitable boss retains the integrity. I know a club member who had a serious frontal impact competing in a club sprint and he commented he was amazed at how far the upper bulkhead tube had bent during the impact, simply caused by his body weight applying forward force via the shoulder straps. If you're drilling safety critical holes, better to have it done properly.

Stu.