This project was designed to fill a need I, as an Uber driver and Fire Alarm Installer, have. Constantly, I run into issues with running out of space in my vehicle due to my toolbox and roadside kit filling the interior. To solve this problem, first I looked into purchasing a commercial rack, however the options available for my specific vehicle (2011 Ford Explorer) were not only not cost effective, but not nearly strong enough to handle my heavy toolbox. Instead, I came up with this one, based on the shape and styling of a pickup-truck overhead rack.
My design also features 2 full toolboxes bolted onto the back, of the same modular type as my other toolboxes (As can be seen in my first Instructable, the Rigid Powerbox). This modular stacking ability allows me to simply lock my work toolbox onto the rack and go, taking advantage of the secure mounting bracket.
Step 1: Plans.
I measured my roof-rails and rooftop (back to the tailgate lid). These measurements are VERY IMPORTANT, as they will determine whether the rack will fit, as well as if you can still open the tailgate all the way. Mine had an internal width of 46.5", and a channel length of 59". This means all my mounting points have to be within that 59" range. My rack then extends out to the top of the windshield, just out of my line of sight, so as to avoid blocking my view of traffic lights. That gives me an extra 24" of forward length, while the back is able to extend another 15" without interfering with the tailgate. The rails themselves are 2" thick, which is only an important measurement if (like mine) you have to haul things wider than the span between your rails.
Step 2: Selecting the Parts
The material I chose to use is Schedule 80 PVC pipe, 1" ID. This gives me a pipe that is actually slightly more than an inch across (1.32" specifically). I chose it both for the durability and strength, as well as the cost and ease of obtaining.
Step 3: Plan
Draw a plan. Mine, for both stability and protection of my roof, has 5 main crossbars, and 5 riser bars running along the outside rails. This is where my rack became more complicated, as I cannot drill through the rails themselves, the outside and inside of the rack had to be self-supporting. They are connected at the front, however due to the design, the outer rails are unsuitable for supporting more than 70lbs.
At the back of my design, I made a crossbar that extends from the outer rail, connecting it to the inner rail over the top of the rails, creating slightly more stability. This crossbar pair also joins a sloped cavity (similar to the back of a roll-cage) for additional stability, and to protect my antenna from any cargo shifts. To either side of the antenna box is an H-frame that connects the outer and inner rails, as well as crossing the entire width. This H-frame is where the toolboxes attach.
Step 4: Cutting, Test-fitting, and Gluing
Cutting the pipe can be done with a hacksaw, a jigsaw, or a circular saw. I used a hacksaw and jigsaw for my cuts. Use a miter box and measure twice (or more) before cutting anything. Make sure to clean the ends of the cuts, and press-fit them fully into the couplers. After determining that the press-fit is solid, place it on top of the rack to verify that nothing else needs adjusted. Make your adjustments now.
At this stage I had to re-cut several of the long beams because the connections between the inner and outer rails were too short to encompass the entire rail. Ultimately, I used 50 feet of pipe, and 64 couplers of a variety of shapes.
Once the test-fit has been perfected it is time to glue. Any PVC glue should work, I used my dad's leftover Blue Glue (which stains. Don't do this step in anything you want to keep un-stained. Or over anything you don't want stained. Three hours with a disk-sander to get a splash off new concrete was NOT FUN). Clean the pipe and couplers and dry them. Lay everything out and apply the primer to the ends of all the pipe pieces and inside all the couplers. At this point, you may decide to glue it in segments. I glued mine in 5 parts, the center ladder-frame, the left outer, right outer, center stabilizer, and back. As this does not need to hold water, you may apply the glue to only the inside of the coupling before fitting the pieces together. Ensure that the piece is at the same exact depth and angle as it was on the test fit (if it helps to use a marker to line everything up, do so).
To glue the parts where multiple pipes have to be glued at the same time, get help. Attaching the five main parts of mine required myself and my brother and dad to get them to slide together neatly.
Step 5: Coating
Because PVC pipe does not like the sun, UV damages it and causes it to be brittle (Very bad for something that will be vibrating down the highway), mine is coated in a thick layer of UV-protect spray bedliner. I used 3 cans for my rack, and applied it before drilling any of the mounting holes, to ensure that it would have time to set before I attached it. (Really that only took a couple of hours, and I left it for a week).
Make sure to fully coat the entire rack, top, bottom, sides, front, and back in an even coat for maximum protection. Upon setting it should have a slightly grippy texture without being tacky.
Step 6: Attachment
Finally, it is time to start bolting things together. Place the rack on your rails, positioned along the measurements made earlier. This is where it pays to double-check your tailgate clearance. For the mounting bolts, I used 1/4-20 3" bolts and T-nuts (sunken into the side of the pipe facing the rails) along with lock-washers on the bolt side. These bolts were sufficient to snugly press against the inside of my channels and hold the rack firmly in place. Do not attach the rack yet if you decided to put on toolboxes, there's more drilling to do.
To attach the tooboxes, align them with the H-frame on the back and carefully drill 4 holes as near to the corners as your design allows. I again used 1/4-20 bolts, 2.5" length, with lock-washers and lock-nuts on opposite ends of the bolt to ensure that the toolbox would not come loose.
This is a point where you may decide to adjust the location of your mounting bolts, as the rear-most may be underneath the toolbox, making it difficult to access. In my design, I was able to leave enough clearance to get the lock-nuts onto the bolt from underneath the already mounted rack, however I would not be able to remove the rack without first removing the toolboxes.
MAKE SURE EVERY BOLT IS ALL THE WAY TIGHT. You don't want anything slipping off.
Step 7: Completion and Road-test
After securing all the bolts, I discovered that I actually had not accounted for anything to attach my tie-down straps to. This being a requirement of a functional rack, I immediately set out for Home Depot with my work toolbox secured to the rack, taking the highway. Beyond some faint whistling and the off-balanced rack (due to one side having a taller toolbox than the other), there were no issues. I will install the D-ring mounts later, to allow me to secure my tie-downs.
-Side note: The toolboxes I chose include padlock rings. Use them. The toolboxes (if you bolt them down properly) will be nearly impossible to remove intact without getting on the roof.