Accepted front-hoop configurations for roll cages (Page 4 of 5)

Pics are small and only show half the cage, but right off the bat, your harness bar is too low.  The shoulder belts need to be at a 0-15 degrees below the seat holes.  Your bar is about 8" too low.  Also, the bar that goes from the upper left to lower right behind the seats needs to be a single bar, not two bars joined in the middle.  Beyond that, I can't see any of the front structure.

Jeff, that's pretty funny that we answered the same question at the same time using almost identical language. But I think that the diagonals can be split at the harness bar -- they don't have to be 1-piece diagonals. I think the problem with these is that they change angle at the split, so any force down on the hoop in a rollover would tend to splay those bottom bars further rather than transmitting it around the outside of the cage to the car frame.

Pat, I figured I'd be in a posting race with somebody. 

Bjorn,  Looking closer, it appears that the diagonal is not only two pieces, but doesn't even connect to the main hoop.  I can't imagine it passing tech connected to the backstays.  Can you post more, larger pics?

Yeah, you're going to need a diagonal that goes from the node where the halo bar meets the main hoop, bisects the new harness bar, and then continues in a straight line to the foot of the main hoop on the other side, assuming that the harness bar is planar with both of those points on the main hoop. Otherwise, it can run diagonally unbroken between the 2 main hoop nodes.

The driver's door bars will pass and the height actually really helps with the safety, but it's going to make it difficult to enter and exit the car. You might want to think about getting a steering wheel quick disconnect to make that easier. It's not a must-do, just a makes-life-a-lot-easier thing. Cheers.

I seem to recall some time ago in some "other" sanctioning body that in lieu of a main hoop diagonal one could have a dog leg diagonal or X. It probably is not accepted any longer, but might be where the cage builder was coming from.

if you had a printed copy of the rules that you left with this guy prior to starting the cage I'd go back and Pitch a fit and demand he rip it out at least all those diagonals/harness bar and fix it at his cost. It's pretty clearly outlined what's acceptable for a diagonal and for harness bar positioning and he followed practically none of it. One other thing I should point out, is why is it necessary for him to put the main hoop far enough forward that it puts the seats UNDER the main hoop?

Just sends pics to nick pon .
  Its funny because one diagonal from drivers upper to passenger side then notching others to that is a lot easier than that notching he went thru.

Correct it will be fine in accident as long as the welds are good.

Nick & Jeff - Lemons HQ .... our Team Owner sent you a question re #555 but, Nick, your email bounced.

would this configuration be legal on an open cockpit car?

Erik, the Lemons rules are silent on this point, but BMWCCA and NASC CCR's are virtually identical, so if you follow those, you should be safe. The key stats are as follows:

-no plate smaller than 9 square inches;
-no plate larger than 100 square inches;
-no side of any plate may be less than 2 inches on one side;
-no side of any plate may exceed 12 inches on one side
-plates must be at least .080 thick.

Here's the BMWCCA reg, which is slightly more anal than the NASA one (is that a cliche? ):
Each mounting plate shall be no greater than 100 square inches and no
greater than 12 inches or less than two inches on a side. Welded
mounting plates shall be at least 0.080-inch thick, and must contain an
inspection hole of .325-inch diameter. Plates may extend onto vertical
sections of the structure. Any mounting plate may be multi-angled, but
shall not exceed 100 square inches total including vertical sections.
Each mounting plate must have an area of not less than nine square
inches. Each mounting plate must be welded around a minimum of 50%
of each edge, and with a minimum stitch weld length of 1.5 inches.

Lemons doesn't require an inspection hole, either, although I've heard rumor somewhere that that may be in the cards in the future. Oy.

In that case, it is possible to reinforce the 2x2 square with spreader plates along the top and sides of the tube - i.e. make a C-channel where the tube will meet the frame. 

I'm in the process of designing a LoCost (with leftover Lemons parts) and that is how I plan on mounting the cage to the frame.

Don't spreaders refer to unibody cars? I thought direct to frame is OK for full frame chassis...