More cage, I've run out of cute titles
Posted by Adax , 06-08-2013 · 1,482 views
Triangulation is the key to construct stiffness. You can see several triangles forming and there are more to come. A top-bar is not required but it provides a means of triangulating the main cage so I feel it is important. I went through a couple of iterations before deciding on this one. My only regret is not making it out of the thin-wall tubing as it would have saved about 1.5 pounds on the highest point of the car. This was a very time consuming fitment (see previous bog entry) and cannot be done if the main hoop is already welded to the side bars. Well, at least not like I did it.
Forward attachment points: The rules limit us to 8 attachment points. Most put the forward ones at the lateral firewall frame braces. This seems like the best point to me as well. If we were allowed 9 one at the transmission tunnel would be ideal. I think this point doesn't get the attention it deserves. This is the closest you can get to the main parts of the front subframe, which like the rear one, is important. Most cages just have a single bar running to this point. I believe a lot of torsional rigidity can be gained by triangulating his point to the rest of the cage. So that's what I did. My triangle is not as broad on the driver's side. This is because a tube from the mounting pillar will interfere with your left foot as you try to find the dead pedal.
Door bars: NASCAR style are clearly preferred, and in my opinion, two bend bars are better than the four bend, S-style bars. This required a little tub trimming to get the angles right but I'm happy with how they ended up. I forgot to mention that I cut out all the OEM dash bar support metal at the front of the door openings and welded brackets to the cage for the dash bar. Another excellent application for a plasma cutter. I took some creative license with the bracing. I may add two more diagonals to the passenger side, I'm just a little worried about weight.
As seen above, I also welded in tubes from the side bars to the door bars on both sides. I went with a pseudo Petty bar; it runs from the rail mount to the center of the main hoop bracing rather than to the top. It is triangulated to the passenger's side as well and will be the mounting point of the cut-off switch and one of the fire system pulls.
BTW, this is not the OEM dash bar I'll be installing, it is just a mock-up one which allows the steering wheel to mount to something.
This only leaves the rear down-tubes and diagonal brace. I planned to use one off the package tray covers sold by several SM vendors so I was pretty liberal with the OEM package tray cuts (made mount plate welding easier). Unfortunately the covers have been back-ordered since early Feb. I can't weld in the down tubes until the package tray is here so cage work is at a stand-still for now. Plenty of other stuff to work on though.