Quote:
Originally Posted by BR3W CITY
The version I was reading (a bit out of date, but shouldn't matter for this particular part), says that the "rear bars must support the main hoop in a way that prevents it from collapsing or buckling".... but also that "the rear bars must be welded or bolted to the frame, subframe, or oem driveshaft tunnel"
I'm not sure where your down/rear bars would be connecting in that image. Trailing arm/suspension xmember?
|
That should be the design criteria, and for just a hoop 'bar' then something going backwards would employ that support per 4.10. BUT wouldn't the door bars going forward employ that same criteria? From a purely structural engineering standpont it would, because it makes it into a cage at that point. Lateral and shear forces would be taken care of by windshield and dash bars, cross bracing and gussets at the welded corners. In my drawing the middle bars would mount to a frame crossmember directly under the cab. It could all be bolt in so the cab can separate from the chassis.
Quote:
Originally Posted by vin63
4-10 is the description for a "Roll Bar" not a "Roll Cage" just so that we're all on the same page. For a "Roll Bar" the rearward bars must be welded to the main hoop. If your track tech inspectors will allow for the rearward bars to not pass outside the cab in an extended cab truck configuration, then go for it. Check with your track to see if they have a minimum length of the rearward bars...some do.
|
Yea they (NHRA Tech) never called me back, must be too much to think about in the "off-season".... But my explanation above makes structural sense to you?
Whether its called a 'bar' or a 'cage', the MAIN hoop is supported one direction or the other by welded attachment by 2 other points minimum, to 'keep from collapsing'. That is the intent of the rule I would think. If its 4 points forward or 4 points rearward, why should it matter if the MAIN hoop is supported over the drivers head?