01: Here's our stock Mini Cooper S, the basis for our 2004 CES demo vehicle.
Many people that I talked to were pretty surprised when I told them we were building a Mini Cooper. After all, its small size makes it one of the more difficult vehicles to install a massive audio/video system into. However, BMW (the manufacturer of the Cooper) made us an offer we couldn't refuse, making our car choice easy. A few phone calls and faxed documents and we had a new, silver Mini Cooper S delivered to Alpine headquarters the last week of May.
Of course, it didn't stay stock for long. The first step, as always, was to completely strip the interior of the car to see what we had to work with. With the inside gone, we can see how easy or difficult it will be to build the system we want to build. In this case, the Mini didn't provide any particularly weird or difficult hurdles that we hadn't dealt with before.
Now that we knew what we were up against, it was time to start the fabrication. The first thing on the list was to make a box to hold the batteries and power supplies that would keep a constant 14 volts flowing to the power-hungry system. The best place for this box was in the rear of the car, behind the back wheels. The stock Mini has the battery in this area, as well as two HUGE mufflers on either side. The exhaust system was removed first, and the stock battery was taken out next. After that, the floor was cut out with a plasma cutter to make way for the custom-built steel box.
02: The dash area was completely removed, including the heater/AC unit.
After the floor was cut out, the edges were ground down and the paint was removed around the cut area. Next, box pieces were built from 16-gauge cold-rolled steel, and the pieces were welded together to form the enclosure. The steel box was placed in the car, and after some final fitting, it was tack welded in place. One-inch-tube steel braces were welded around the box to more firmly attach it to the car, and finally the seam was finished by applying 3M Panel Bonding Adhesive to both the inside and outside surfaces. A polished stainless steel bottom panel was also built for the box, and it was bolted to the main box using 10-24 hex bolts and nutserts.
Next on the list was the emergency brake. Since we were planning on a center-drive setup on this car, the brake would have to move from its normal location. Instead of simply moving it, we decided to motorize it using a 4-inch linear actuator. We built a steel bracket to bolt it to the car and an adapter to make the two brake cables pull evenly. A switch inside the car is all it takes to apply or release the brake, so it makes the brake invisible on the interior.
One problem that we always have with demo cars is dead batteries. Whenever you wire a demo system for constant operation, small current draws will eventually kill the battery if the circuit breaker is accidentally left engaged. Of course, this makes these cars difficult to move around from show to show. This time, we decided to have separate batteries for the car and the system to solve this problem. The system batteries were mounted in the steel box we built earlier, and we decided to mount the car's battery under the car in the center tunnel originally occupied by the exhaust system. This small battery is perfect for starting the Mini, and it is isolated from the sound system so we know we will always be able to move the car when we need to. To finish off the exhaust system, we simply built a "dump" tube, firing the exhaust out of the catalytic converter down to the ground underneath the car.
That's it for this month, so send your questions to sbrown@alpine-usa.com, and check out SteveBrownUniversity.com.
03: The stock floor area is stepped, and the center hump is fairly tall. In addition, the e-brake would have to be moved under the car. | 
04: The rear-mounted battery was removed in order to put a steel box under the car to house batteries and power supplies. The actual battery that starts the car was moved underneath the center hump. | 
05: The battery box from the bottom view, as well as the space taken up by the stock exhaust. |
06: Here, Mike is cutting out the stock rear floor with a plasma cutter. | 
07: The edges of the cut were ground smooth, and the paint was removed to allow proper welding of the new steel enclosure. | 
08: The under-car enclosure was constructed from 16-gauge steel, and here's me tack welding the pieces together to check the fit. |
09: From the bottom, we can see that the enclosure is flush with the lowest part of the car's suspension, creating the most possible space inside. It's lower than the bumper but the new body kit will fix that. | 
10: The steel box was welded in place and sealed with 3M Panel Bonding Adhesive, a super-strong epoxy that is used in automotive construction. | 
11: The emergency brake had to be removed, so we decided to make it operate electrically via a 4-inch linear actuator underneath the car. |
12: A steel mount was made to hold the e-brake actuator in place, and it was attached to the bottom of the car using two stock bolts. | 
13: This is the battery that starts the car, mounted under the center hump on a custom steel plate. It is isolated from the sound system by a breaker so it will never leave us stranded even if the system batteries are totally dead. | 
14: Here we can see the dump-style exhaust, making the most possible space under the car. |