Friday, May 30, 2014

Volvo 940 roof rack

Having a roof rack was something I'd wanted for moving bulky things like plywood and our homemade boat. I first bought a pair of crossbars that clipped onto the rain gutters which worked well, but couldn't really be left on all the time because they added road noise and reduced mileage.  Additionally, I replaced the leaking 20 year old donut with a full size spare tire, and it took up too much space so I needed somewhere else to put it. I decided to build my own that would be lower profile to help with aerodynamics, have a spot for the spare tire, and be more of an actual rack rather than just two crossbars.  It also would give a place to mount lights and antennas.

The construction was pretty simple, It's just welded steel. The main crossbars are I think 1 1/4" or 1 1/2" square tubing, and the tubing going around the edges is 3/4". Below is a closeup of the clamping mechanism, it's very similar to regular gutter mount racks. To prevent it from rubbing off the paint I put a small strip of rubber where the clamps attach. A piece of bicycle inner tube would work well. For security, the bolts are "security torx" head which is regular torx with a pin in the middle and a domed head. It just will keep someone from casually removing it with a wrench or pliers. The spare tire mounts using two 1/2" bolts that thread into nuts welded to the crossbar, and lock using a copy of a commercial spare tire lock. A tricky part of this mechanism is that you need the two bolts to be tight but also line up with each other. To do this I added a rubber donut (actually a rubber grommet) between each bolt and the tire. A spring would also work. The cover (which I really don't like the look of) is to prolong the lifespan of the tire by reducing UV exposure. The entire thing fits right on top of the roof (It has about 1/16" gap), so there's no added road noise even with the tire on. So far there's been no noticeable effect on mileage. There are also two plates with holes in the rear corners for NMO antenna mounts. To paint it I started by cleaning it with kerosene, primed it, and painted it with matte black enamel. I then covered the top with truck bed coating to provide a non-slip surface and reduce road noise and whistling by giving it an uneven surface.

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