18. Guidance on Welding
18.1. All welding should be of the highest possible quality with full penetration and preferably using a gas shielded arc.
18.2. Although good external appearance of a weld does not necessarily guarantee its quality, poor looking welds are never a sign of good workmanship.
18.3. When using heat-treated steel the instructions of the manufacturer must be followed( special electrodes, gas protected welding).
18.4. It is to be emphasised that the use of heat-treated or medium carbon steels may cause problems and that bad fabrication may result in a decrease in strength( caused by brittle heat-affected zones) or inadequate ductility.
19. Harness Bars
19.1. Minimum dimensions 38mm x 2.5mm or 40mm x 2.0mm. Cold Drawn Seamless Carbon Steel with minimum tensile strength of 350N / mm2. Harness straps may be attached by looping around the tube or by threaded fixings using inserts as drawing No. 44 welded into the tubes( s).
20. Material Specifications 20.1. Specifications of the tubes used:
a.
Material Cold Drawn Seamless Unalloyed Carbon Steel, containing a maximum of 0.3 % of carbon.
Note: For an unalloyed carbon steel the maximum content of additives is 1.7 % for manganese and 0.6 % for other elements. b.
Minimum Yield Strength 350 N / mm2 c. Minimum Dimensions( Ø in mm) i.
ii.
Mandatory tubular members 45 x 2.5( 1.75” x 0.095”) or 50 x 2.0( 2.0” x 0.083”) 38 x 2.5( 1.5” x 0.095”) or 40 x 2.0( 1.6” x 0.083”).( For roll cages / bars approved prior to 1.1.95). Optional tubular members 38 x 2.5( 1.5” x 0.095”) or 40 x 2.0( 1.6” x 0.083”).
20.2. In selecting the steel, attention must be paid to obtaining good elongation properties and adequate weldability.
20.3. The tubing must be bent by a cold working process and the centreline bend radius must be at least three times the tube diameter. If the tubing is ovalised during bending, the ratio of minor to major diameter must be 0.9 or greater.
21. Exceptions
21.1. The only exceptions to the foregoing requirements for Saloon, Single Seater and Sports Cars are as follows:
21.2. ROPS manufacturers may make application to the ASN for a Roll Over Protection System( ROPS) Certificate to be issued.
21.3. Note: ROPS manufacturers wishing to make application for such a certificate should contact the ASN Technical Department in order to obtain details of the requirements to be met and the fees payable. Subject to these requirements being met a ROPS Certificate will be raised and issued. Duly authorised
Motorsport UK 2025 National Competition Rules Version 11
Chapter 7 Appendix 3- Roll Over Protection Systems( ROPS) 256