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F.5.12.1 When Roll Hoop Bracing is mechanically attached:
a. The threaded fasteners used to secure non permanent joints are Critical Fasteners, see T.8.2. Additional requirements apply in F.5.12.5 and F.5.12.7
b. No spherical rod ends are allowed.
c. The attachment holes in the lugs, the attached bracing and the sleeves and tubes must be a close fit with the pin or bolt.
F.5.12.2 Any non permanent joint at the end(s) must be a Double Lug Joint or a Sleeved Butt Joint
F.5.12.3 For Double Lug Joints, each lug must:
a. Be minimum 4.5 mm (0.177 in) thickness steel
b. Measure 25 mm minimum perpendicular to the axis of the bracing
c. Be as short as practical along the axis of the bracing.
F.5.12.4 All Double Lug Joints, whether fitted parallel or perpendicular to the axis of the tube, must include a capping arrangement
F.5.12.5 In a Double Lug Joint the pin or bolt must be 10 mm Metric Grade 9.8 or 3/8 in SAE Grade 8 minimum diameter and grade. See F.5.12.1 above
F.5.12.6 For Sleeved Butt Joints, the sleeve must:
a. Have a minimum length of 75 mm; 37.5 mm to each side of the joint
b. Be external to the base tubes, with a close fit around the base tubes.
c. Have a wall thickness equal to or greater than 2.0 mm
F.5.12.7 In a Sleeved Butt Joint, the bolts must be 6 mm Metric Grade 9.8 or 1/4 in SAE Grade 8 minimum diameter and grade. See F.5.12.1 above
Explanation
F.5.12.1 When Roll Hoop Bracing is mechanically attached:
a. The threaded fasteners used to secure non permanent joints are Critical Fasteners, see T.8.2. Additional requirements apply in F.5.12.5 and F.5.12.7
b. No spherical rod ends are allowed.
c. The attachment holes in the lugs, the attached bracing and the sleeves and tubes must be a close fit with the pin or bolt.
a. If you choose to mechanically attach your Roll Hoop Bracing (you use fasteners instead of welding it all together) to the Roll Hoop and Major Structure, the threaded fasteners (probably some version of nuts and bolts) you choose to use have to be Critical Fasteners. Critical Fasteners are fasteners that prevent accidental loosening of the fastener due to vibration from the vehicle. More information about Critical Fasteners is available in T.8.2.
b. No spherical rod ends are allowed to be used to fasten Roll Hoop Bracing to the rest of the chassis. Spherical rod ends are a type of fastener that have rotational degrees of freedom which can compensate for misalignment. Using spherical rod ends as fasteners would leave degrees of freedom for the Roll Hoop Bracing to move.
Spherical rod end
Short video that shows how a spherical rod end moves
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c. Regardless of the type of fastener used (whether it is a Double Lug Joint or a Sleeved Butt Joint), the holes and the pins/ bolts that go through the holes must be a close fit.
F.5.12.2 Any non permanent joint at the end(s) must be a Double Lug Joint or a Sleeved Butt Joint
If you choose to mechanically attach your Roll Hoop Bracing, the joints you use at the ends of the brace have to be Double Lug Joints or Sleeved Butt Joints.
A lug joint is a type of pin joint, with the Double Lug name being used because the example they provide is a lug pin joint in double shear. The Sleeved Butt Joint is a joint where a tube shaped bracket slides over other tubes and they all have holes that line up, which allows hardware to be used to connect them together.
F.5.12.3 For Double Lug Joints, each lug must:
a. Be minimum 4.5 mm (0.177 in) thickness steel
b. Measure 25 mm minimum perpendicular to the axis of the bracing
c. Be as short as practical along the axis of the bracing.
The lugs of the Double Lug joint are referring to the two tabs with holes for hardware on either side. These tabs have to be a minimum of 4.5 mm thick (pink), a minimum length of 25 mm (green), and be as close together as possible to minimize the bending moment generated by the pin or bolt (blue).
Diagram explaining the lug joint requirements
F.5.12.4 All Double Lug Joints, whether fitted parallel or perpendicular to the axis of the tube, must include a capping arrangement
Double Lug joints have to have a cap.
Why do they have to have a cap and what does this include?
This is the cap
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F.5.12.5 In a Double Lug Joint the pin or bolt must be 10 mm Metric Grade 9.8 or 3/8 in SAE Grade 8 minimum diameter and grade. See F.5.12.1 above
The pin or bolt used in the Double Lug Joint has to be 10 mm Metric Grade 9.8 or 3/8 in SAE Grade 8 minimum diameter and grade. See T.8.2 for more information about fastener grades.
F.5.12.6 For Sleeved Butt Joints, the sleeve must:
a. Have a minimum length of 75 mm; 37.5 mm to each side of the joint
b. Be external to the base tubes, with a close fit around the base tubes.
c. Have a wall thickness equal to or greater than 2.0 mm
If you decide to use Sleeved Butt Joints, the sleeve must:
a. Have a minimum length of 75 mm (with the physical butt joint of the two tubes having at least 37.5 mm of sleeve on each side)
b. Fit on the outside of the two tubes it is connecting (the tubes can not slide over the sleeve, the sleeve has to slide over the tubes) and the fit between the sleeve and the tubes must be close (almost snug).
c. Have a wall thickness of at least 2 mm
F.5.12.7 In a Sleeved Butt Joint, the bolts must be 6 mm Metric Grade 9.8 or 1/4 in SAE Grade 8 minimum diameter and grade. See F.5.12.1 above
The bolt used in the Double Lug Joint has to be 6 mm Metric Grade 9.8 or 1/4 in SAE Grade 8 minimum diameter and grade. See T.8.2 for more information about fastener grades.
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