Car Audio Advanced Techniques July 2005

Every year, Alpine builds an award-winning demo vehicle designed to turn heads and drop jaws. This year, the car of choice was a BMW X5, the Best of Show winner at the 2005 Consumer Electronics Show in Las Vegas. This demo car took Alpine's Application R&D Team of Steve Brown and Mike Vu over 4,500 hours and seven months to complete, and the results speak for themselves. As always, we will cover the step-by-step build-up of this wild creation so that you can see the techniques and materials it takes to build the best.

Our cars always start with a complete disassembly, mainly in order to see what surprises are under the panels. In this case, the "surprise" was the large transmission hump in the center of the car. After cutting this off with an air saw, we then cut out the top of the transmission tunnel to expose the transmission. A new sheet metal panel was built to cover the transmission while lowering the hump by several inches. This new piece was welded in place; then 3M Panel Bonding Adhesive was used to completely seal the edge around the welds.

From the beginning of this project, we planned to do a unique door arrangement, which we'll cover in a later installment. To do this, the B-pillar needed to be cut out of the car. Whenever major structural braces are removed from a vehicle, you must replace the structure in another way to keep the car from flexing or sagging later. In our case, we decided to fabricate a complete roll cage inside the car to stiffen and brace the body structure. Two-inch steel tubing was bent and welded from the floor, along the A-pillars and across the sides of the roof. Unlike a regular racing roll cage, ours was welded all along the distance of the car to make it as stiff as possible. One-eighth-inch steel plates were welded to the floorpan where the cage contacts the floor to further integrate the cage into the structure of the X5.

As a further structural support, we also welded some 2" x 4" rectangular steel tubing along the edge below the doors. The paint was ground off along the edges of the brace to make sure the welds were strong and durable.

That's it for this month. Send any questions to sbrown@alpine-usa.com and check out SteveBrownUniversity.com.

The center hump in the middle of the X5's floorpan is far too tall for our proposed seat concept so it has to be cut down. An air saw is the perfect tool for the job.	With the center hump cut out, the transmission is visible through the floor.	A new floor piece was fabricated using 16-gauge sheet metal and tack welded in place over the transmission.
The completed steel panel shows how much lower the center hump is than the factory arrangement. Notice the small bump in the middle of the piece to allow for transmission clearance.	3M Panel Bonding Adhesive was applied to the seam around the new transmission hump panel to seal it completely to the floorpan.	A roll cage was welded into the interior to provide much-needed chassis stiffness since the plan called for removal of the X5's B-pillars.
Unlike a normal roll cage installation, this one was welded along all the body lines of the car to maximize the stiffening effect.	The roll cage ends were welded to the floor using 1/8" steel plates, as specified in racing rulebooks, to maximize contact with the floorpan.	Much time was spent bending the roll cage tubes to fit the interior shape very closely so it could later be easily camouflaged by the interior.
The roll cage extends to the rear of the roof, where it was welded into the existing metal across the top of the C-pillars.