Nick; I have a question/concern about wording that I know you clarified in the first post, but;
3.1: Rollbar and Structure: Professionally made full roll cage required. A poorly built, improperly mounted, or badly engineered rollcage can keep you from racing: Don't show up with crap! At minimum, cage must include: Full front and rear hoop, appropriately braced to each other along the roofline; two drivers-side door bars (X-design is acceptable); appropriate main-hoop backstays with no bends, located as close to 45 degrees from horizontal as practical; one main-hoop diagonal; appropriate spreader plates and gussets; complete 360-degree welds at all joints. Each major load-bearing member must be formed from its own single, continuous tube. Shoulder-harness bars strongly encouraged, and virtually necessary for proper shoulder-harness mounting in some applications; dash bars very strongly encouraged.
this part; At minimum, cage must include: Full front and rear hoop, appropriately braced to each other along the roofline; makes it sound as if the first cage you posted,
Single-piece front hoop:
is the ONLY acceptable cage design, as this is the only design you posted a picture of that technically meets the requirement for "a full front hoop". the other designs aren't actually a "single, continuous tube" forming a complete hoop forward of the driver. Let me point out that:
a)Halo Hoop: you have a full main/rear hoop, with a top hoop directly attached to it. This is braced to the floor via the A-pillar/firewall, not via the roofline by attachments. We have this design currently on our 98 Crown Vic and there's been a bit of discussion on whether or not this is legal as my dad's a retired mechanical engineer and the car's owner.
b)Right and Left Bars: well, these aren't actually Hoops at all, and the ends attach perpendicular to one another, making these, at best, "arches" as defined in geometry. Other point about this configuration even if we state that by attachment to the main/rear hoop, each bar itself qualifies as a major load-bearing, continuous hoop as we've defined, It's still not a "FRONT HOOP".
They collectively would be "side hoops".
See what I'm getting at with the way the rules are worded? Some are very likely to still be concerned with it and they may not have the forethought to dig around these forums, or, still have reservations that weren't explicitly addressed in this thread.
One last Question; We have a custom-made Halo Hoop 10point cage almost exactly like Rudedog has posted, and were discussing ways to add a diagonal. My thought was to Weld in the bar at/near the same attachment point as the driver's side backstay, and run it down to the floor immediately behind the passenger-side main/rear hoop attachment point. The other would be attaching it to the same point at the top of the bar, and running it down forward of the hoop, and attaching it to the single passenger-side doorbar(even forward enough to meet the doorbar's floor brace or A-pillar bar). Are any of these acceptable? If so, which? Realistically, we are trying to accomplish the most simple way of modifying the cage to meet spec, by eliminating possibly unnecessary cutting of braces that are already present in the cage.
