Cawthray's Roadster Build

[davidimurray]

Originally Posted by flyerncle

The daft thing is,so long as your seat belt mounts comply with the regs there is nothing mandatory for a roll bar so its probably out of the remit of the tester to say yes or no to how it is fitted.

But if your seatbelts are mounted onto any part of the roll bar, then the roll bar structure becomes a structural part of the safety system. hence you may need to show that it is adequate to take the load of the seatbelts in an accident + that any fixings are adequate + that any fixings are secured against vibration - e.g. lock nuts / spring washers.

In particular taken from the manual :-

In a severe accident, the seated occupant can exert huge loads upon their seatbelts (in the region of 1.5 tonnes for a 75kg person). Seatbelt anchorages together must withstand these large loads from the seatbelts. These loads in turn must be dissipated by the vehicle structure.
In assessing the strength of the anchorages, it is essential to consider

the vehicle structure in the immediate vicinity of the anchorage, and

the parts of the vehicle structure into which the loads from the anchorages will be dissipated.
These large loads will act in several directions as shown in Figure 1.
All Vehicles
What to look for:

Evidence that anchorages in a vehicle of the same or a very similar type have been subjected to a seatbelt anchorage strength test to “European Standards” by a recognised authority. This may be acceptable where there is clear evidence that the structure is identical to the vehicle originally tested.

Welding should appear neat and of good quality; whilst it is impossible to judge the quality of a weld just by looking at it, messy welding is rarely strong welding.

Bolts used in structural areas should be of grade 8.8 or better. Such bolts will be marked 8.8 or 12.9 on the hexagonal head, however, cap-head bolts or 7/16" ( 11mm ) UNF seat belt anchorage bolts (with an anodised finish) not marked in this way may normally be considered to be of equivalent strength. Bolts should be M8 or larger.

Threaded bushes should be welded (at both ends) through the tube, and not end mounted on the surface. (A threaded bush may be attached by its side surface to a structural component).
Cause for Concern:

Welds of poor appearance, gaps or visible lack of penetration.

Anchorages in thin and/or flat panels with little stiffness or reinforcing structure or in thin walled tube.

Low grade bolts (less than grade 8.8).

Insufficient bolt capacity, e.g. number of bolts and/or diameter of bolts


and


Steel Chassis with Anchorages on Roll Cage (See Figure 3)
What to look for:

Triangulation and bracing which will provide strength and spread the loads effectively into the chassis.

The joint where the roll cage joins the chassis and the chassis itself must be sufficiently strong to withstand the loads from the anchorages.

Upper anchorage must be adequately braced from near the anchorage to strong areas of the chassis.

Threaded seatbelt anchorage fastening should be welded into tubes or onto plates of sufficient thickness.

Bolted joints joining the cage to the chassis and parts of the cage to each other should be of sufficient strength.