I've been wanting to install an underfloor storage box since I got my van but have been a bit turned off on retail cost of these accessories. Sportsmobile asks around $1000, Quadvan maybe $600. I believe that Quadvan builds theirs out of steel and subsequently powdercoats them. What's SMB do?
After a bit of thought, I came up with the following requirements for my build:
*Aluminum construction for corrosion resistance and no need for finishing
*Sized large enough for bottle jack, tools, recovery straps, jumper cables, emergency kit
*Sized small enough that I can easily access everything and nothing gets lost in the clutter
*Simple shape to keep fabrication costs and welding time to a minimum
*Interior light for late night rummaging
OK then....lets get started......I've got an EB so after blasting the spare tire mechanism out and taking a few measurements, I found I had roughly 16"x34" of space to work with. The limiting factors being the frame rails on either side and the transverse subfloor body supports fore and aft. Using a string to check for departure angle I came up with a useable depth of around 16". To keep things easy and get the most yield out of 4x8' sheet stock, I finalized my dimensions to yield a simple rectangular box of 15.5"x15.5"x32".
Here's a miniature version that I welded up to test my machine.
When sourcing sheet stock for this project I had a few choices in thickness and alloy of aluminum. Most diamond plate and job boxes that you see are made out of 3003 alloy, an easy working and extremely bendable type. After a bit of research I decided to use 5052. I wasn't keen on the diamond plate finish (and extra cost over flat) so the 5052 was an option, and the extra strength while retaining the ability to take a good bend seemed like a bonus. It was bit of a tough decision to decide on thickness. Most truck boxes that I have seen are about .085 to .100" thick. Given that I might pound this thing into rocks or stumps periodically, I stepped up a bit and chose .125" sheet 5052.
Here are my box pieces in their sheared and bent form. Delivered this way I saved myself about 100" of tig welding which at $1 an inch retail can really add up. I have a fairly light duty Tig machine with an air cooled torch that is only rated to 150 amps. Welding the .125 took 140 amps and on the 32 inch long runs the limiting factor was my ability to hold onto the torch as it got wicked hot.
I got the box tacked in just a few minutes.
Another 15 minutes later I had the ends welded up.
And finally after waiting a few times for the duty cycle of the welder and the torch to catch up I ended up with this:
Next time I'll cover cutting the hole, installation of the flange on the box, and fabrication of the interior trim piece and hatch. Then I'll give a review of install............