We also took the initiative...
We also took the initiative to remove all the sound deadening material from the floor of the Subie. No need for all that dead weight. For the task at hand we brought out the dry ice to freeze the material thus allowing us to scrap it off with ease.
The thickness of the body...
The thickness of the body shell alone cannot take the pressure of the end of a 1.5-inch tube with all of the vehicle's weight on it, so there are plates installed to spread the load should a car get upside down.
Once the body shell has been...
Once the body shell has been cleaned in the necessary areas, a few holes must be drilled in the body shell for later steps. First, 2-3-inch holes must be drilled under the plate locations for the B-pillar. Then 1.5-inch holes are drilled in the far outside of the firewall on both sides. This makes a provision for the tubes that will secure the front suspension to the interior roll cage.
There are many reasons to install a roll cage in a vehicle. The most obvious is for safety, the less obvious is the chassis strengthening that goes hand in hand with the installation of a proper race-legal cage. One point that needs to be addressed immediately: a roll cage in a street driven vehicle can do more harm than good. Although some might think the look of having a cage adds eye candy to his/her ride, most compact cars leave very little space for the cage tubes to coexist with the vehicle's occupants -- making the occupants quite vulnerable without a helmet. The bottom line: if you choose to do a full race cage, do it in a full race car. I've smacked my head pretty hard against the roll cage at track events, and that's with a helmet on -- I can't imagine the world of pain, and spilled brains, without one.
In this article we wanted to illustrate the fabrication and installation of a properly built roll cage. Since the employees at Turbo were fresh out of race cars in need of roll cages, we had to look elsewhere for a donor. In our search we found Steve Sawitz of Laguna Beach, California. Sawitz decided it was time to retire his '03 Subaru WRX from being his daily driver, and instead convert it into his weekend play toy/rally car. All good rally cars need a roll cage, of course, to prevent chassis flex during hard turns. A strengthened chassis allows the driver to get more feedback from the road -- key when every millisecond counts on a timed course.
Up for the task of installing a proper roll cage was L-Con Race Car Fabrication and Engineering in Placentia, California. Weighing the pros and cons of different roll cages we settled upon the Gravel Crew cage kit that was designed with rally racing in mind. The kit includes a 1.5-inch-OD (outer diameter) with a .120-wall thickness DOM seamless tubing B-Pillar, 2 A-pillars, and a windshield bar. From the available options, we chose the following: a complete water-jetted floor plate kit with attachment points of no less than 14 places for the '02 to current unibody shell. The kit was designed to work for many race applications and features only four main points -- leaving the decision to install additional tubes up to the customer and their racing organization's rules. This particular car was built to run in California Rally Series events. One of the main things that the owner stressed to L-Con was the importance of strengthening the vehicle -- as he wants to jump, and jump big.
The project gets underway with the complete disassembly of the interior of the car, trunk, and a good portion of the engine compartment. After the car's interior has been gutted, the car is prepared and further stripped of paint, primer, and body sealant in all the places where tubes will eventually make contact. Now we're ready to begin the installation. We felt the next set of steps is best shown visually, so photos accompany each part of the process.
For the final step in the process, L-Con fabricated custom sheet metal plates; drilled and dimple died them for weight and strength; and then installed them everywhere the cage comes into contact with the shell. The plates are imperative to tie all major points of the cage to major points of the car's chassis. Without plates attaching the upper half of the cage to the chassis, the cage would flex as much as a scary 3/8 of an inch under hard driving.
The end result of installing a high quality roll cage is a whole new car -- a car that will perform and last with some proper and effective suspension tuning. Look for this WRX flying down a dirt road or launching off in random industrial parks.
L-Con tack welded plates on...
L-Con tack welded plates on the frame rail in front of the strut towers; on the front, top, and rear of the front towers; at the base of the Subaru's A-pillars; base of the B-pillar; and front, top, and inside of the rear strut towers.
The next step was to fit and...
The next step was to fit and tack weld the four main points of the cage in place.
Two 1.5-inch .120 tube gussets...
Two 1.5-inch .120 tube gussets are installed from the front of the windshield bar to the middle bend on the A-pillar.
Next an "X" formed with two...
Next an "X" formed with two tubes is fitted on the roof plane.
The front of the X is fitted...
The front of the X is fitted to the back of the windshield bar, tubes aligning with the A-pillar gussets.
Finally two tubes are slightly...
Finally two tubes are slightly bent and installed from the lower bends of the A-pillar through the firewall and are fitted to the plate on the back of the front strut towers.
Once the whole structure is...
Once the whole structure is tacked and in place, the entire structure is welded as much as possible where it sits. Then the tack welds at the bottom of the B-pillar and its plates are cut with a die grinder.
The plates are then removed,...
The plates are then removed, exposing the 3-inch holes that were drilled earlier in the process.
This makes it possible to...
This makes it possible to drop the rear of the cage through the floor of the car at least 12 inches.
This gives L-Con access to...
This gives L-Con access to the top and outside edges of the roll cage structure for welding.
The remaining un-welded joints...
The remaining un-welded joints are welded while it is through the floor. The cage is then raised up through the floor and tack welded back in place with the floor plates.
Approximately 30 feet of 1.5-inch...
Approximately 30 feet of 1.5-inch .120 and 24 feet of 1.5-inch .095 DOM tubing is on hand complete the structure. An X is installed on the B-pillar, with two lateral connecting tubes for the shoulder harnesses.
Two more tubes are installed...
Two more tubes are installed to join the B-pillar to the plates fixed to the front face of the rear strut towers. A single tube joins the two strut towers via plates welded down the inside.
An "X" is installed on the...
An "X" is installed on the B-pillar to strut tower plane, offering a tremendous amount of strength to the entire chassis.
One of the major things to...
One of the major things to consider when installing a roll cage is the effect it can have on the handling and overall structural integrity of the chassis. For instance, when the front and rear suspension pick up points are tied together by the cage structure, the cage acts as a sway bar which dramatically cuts chassis twist and body roll.
The potential problem occurs...
The potential problem occurs over time as the car is driven to its limit and twists to the point where the mounting surfaces of the cage are compromised -- making it useless in a hard accident. The best way to avoid this problem (especially for rally cars) is to connect the cage structure to the body shell in as many places as possible.