This is the cage that I recently installed in the car. The car
is fully legal for SCCA competition. It is a six-point design made
up of 61 feet of 1.75" OD, .130 wall DOM tubing. At a rate of 2 lbs
per foot of tubing, that weighs over 122 lbs!!!Chassis & Roll Cage
This is the cage that I recently installed in the car. The car
is fully legal for SCCA competition. It is a six-point design made
up of 61 feet of 1.75" OD, .130 wall DOM tubing. At a rate of 2 lbs
per foot of tubing, that weighs over 122 lbs!!!
But anyone who has driven in a car with a full cage on a challenging road course will tell you that the weight is well worth it, in chassis stiffness and in safety. Even with subframes, I now realize that the car was as soft as a wet noodle. Now, the car does not bend a bit. I'm sure the stiffness of the car has been increased several thousand percent.
The cage was based in part on the cages of Scott Bleiweiss and Chris Herzog. Both run Mustangs in SCCA competition, and if there is one thing I have learned in racing, there is a lot of blood and sweat that can be saved by listening to and learning from others. I listened, I learned, and now, hey, I can offer up what I learned to others.
The cage starts with a main hoop. The SCCA dictates that all the tubing in the cage be the same size, so the main hoop is no bigger than other part of the cage, unlike many NHRA cages. This is done to make it easy to control the tubing size used, as well as to discourage ultra-complex computer designed cages. The SCCA also requires that the main hoop have no more than four bends in it, and that they total no more than 180 degrees. Across the middle of the main hoop, and in the same plane is a single cross bar to which the harnesses attach. There is also a diagonal which gives the hoop a large part of it's rigidity, especially around the driver's head.
In the
back of the car, the primary bar is a shock tower bar. Each end of
the shock tower bar is welded to a plate on the shock tower. These
plates actually wrap around the shock tower and down onto the floor, so
that they reinforce the weak sheet metal shock towers nicely.
You'll notice that there are no bars going back beyond the shock towers. This was a decision that was made for several reasons. First of all, there are no loads going into the chassis beyond the shock towers, so there is nothing back there trying to "bend" the chassis (aside of the weight of the car). Second, running bars back further would have cost excess weight, and reduced the effectiveness of stiffening the shock towers. Finally, and maybe most importantly, running the rear bars this way preserves the rear crush zone, which Ford Motor Company spent so much time and money to develop. Hey, I can use all the safety I can get.
From the shock towers, five bars were used to positively locate it relative to the main hoop, and provide maximum torsional rigidity. The first two bars go to the main hoop were the harness cross-bar attaches to it. Then there are two more bars from the shock tower which lead to the upper corners of the main hoop. Together, these two pairs of bars keep the back of the chassis from bending, and keep the shock towers from moving. They also help hold up the main hoop in the event of a crash. The final shock tower bar goes diagonally back, and is used to provide torsional rigidity for the chassis.
Most of the bars above are required by the SCCA for IT-E competition. Additional optional bars can be added, such as additional side impact protection for the driver, but I have elected not do so at this time, primarily because of financial constraints. I also elected not to add a dash bar behind the dashboard, or extensions going forward from the front down-tubes to the firewall. These decisions were also made due to time and financial considerations.
This is a picture of the front sub-frame, and shows the attachment of the through-the-floor subframe tie that was used to further stiffen the chassis. Note how the subframe was cut open, and the frame tie was actually placed inside it. There is a full seam weld on both the top and the bottom of the frame tie, along the entire length. This did a terrific job of holding the subframes firmly, as well as stiffening up the floorpan and the seat mounting points. The seats are noticeably stiffer after this mod.
(Note the spare trailer tire w/ bracket still attached in the background. The guy who built the trailer, although doing a good job on most of it, did a TERRIBLE job on the spare tire. He welded the bracket to a ridiculous spot, and it fell off after just a few hundred miles on the trailer. What's worse, he REFUSES to do anything about it unless I haul it up 6 hours to Canada. Screw him. If you know who I'm talking about, DO NOT buy a trailer from him. He'll just stiff you.)
You can also clearly see the exhaust in this picture. Nothing fancy here. Long-tube MAC 1 5/8" headers, an offroad H-Pipe, and Dynomax SuperTurbo 2 1/2" mufflers feeding dumps in front of the axle. We don't need no stinkin' tailpipes. The turn-downs were done partially because I had no tailpipes available at the time, and partially because I was expecting a Grigg's HD panhard bar in the near future. Oh, and it sounds great and saves about 10lbs. or so.
