Maris Raisch - Bike Rack Lights

Bike Rack Light Bar

So here was the problem: our four-bike Saris bike rack all loaded up completely blocked the brake lights.

Materials Specific to this Project

Aluminum C-channel (the one I bought was 4 ft long and 0.3 inches wide, about $14.47)
12V Led Tape ($25.99 for 16.4 ft, but only 4 ft used, coming in at $3.94)
4-flat Trailer Side Towing Connector ($5.49)
Trailer Cabling (four cables 16/18-gauge, I bought an entire roll for $22.99, but only used about 4 ft, coming in at about $7.66)

Total cost for these materials used is $31.56, but I spent $68.94, and now have an extra 12 feet of led tape and a bunch of trailer cable.

Expendables and other things I already had

Electrical Solder ($17.99 for the entire spool)
Electrical Tape (I already had some but a roll is around $2)
Metric screws and washers ($14.99 for the set)
- M4(count number and size of screws)
- M4(number of washers)
- M4(number of nuts)
PLA Filament (65.05 grams for all the pieces, about $1.65 worth of PLA, a roll like this goes for $12.74)

Total cost for buying all of these outright is $47.72.

Equipment

drill (I have a regular DeWalt drill, worked great)
1/8" drill bit (I used wood drill bits for this, it worked, but probably wouldn't recommend, just buy some metal ones)
3D Printer (I used my Prusa Mini)

Goals

Keep it cheap, light, and have it visible both when the rack is down and loaded with bikes, as well as when it is folded up, not in use.

Research

I was able to find the solution to my problem available pre-made online, but at crazy prices. Often these products were lights that mounted temporarily to the bike or other item you were carrying, rather than a permanent fixture on your bike rack. They were also small, usually only 12-16 inches wide. See Beacon and Kody brand lights. I did find someone diy-ing the same thing, but on a hanging bike rack. He used two ready-made lights, and made a pvc mount system for them. You can find his project on ReRack here. All of these wired the lights into the trailer plug in. This video, however, for a ready made truck's led strip, showed them wired directly into one of the brake lights.

Going into this I had used leds and led strips in projects before, but I had no clue on car wiring or trailer hookups. The car that carries the bike rack in question is a Subaru Outback, and has a four-way flat trailer hookup. I read through this article by etrailer.com. My priority was brake lights. I knew I was going to keep it simple, only one line of leds, so I didn't end up using the tail lights capability. Because of the wiring, I split the leds in half: a left and right, corresponding to the yellow and green wires. The hookup is 12 volts, so I made sure to buy a 12 v led strip. More on on the final wiring later.

Prototyping

Over a year ago, when I first thought up this project, I printed a mount. A very simple two-sided clamp, bolts on the top and bottom. The thickness throughout the plastic is 3mm, and I printed it with 100% infill, in the same orientation shown here. When placed around the rack, a spacer (in orange) goes on the top, and the arm (tan) on the bottom. For the arm, I took inspiration from GoPro mounts, the friction fit prongs and bolt. There is a space for a large nut on the one side but since I ended up using M2 bolts, it went unused. Ideally I would reprint the parts, but these work just fine so I didn't waste the plastic.

At the time I was scavenging junk drawers and spare parts bins for bolts and washers, so I mounted it and crossed my fingers. My biggest concern was bolts loosening over time from the vibrations and movement of the car. I left it on there for about a year, and kind of forgot about it. It held strong, other than a little bit of rust and some fading from sun damage, the mount and bolts were just fine. Now there was nothing attached to this part, it was simply the mount and the one arm, no weight attached.

Initially I had printed these attachments (in pink) as well, but did not end up using them. I thought the multiple slots and holes made for lots of options for zip ties and bolts, but the holes were too small.

Mounting the bar

I found this aluminum C-channel at Home Depot for $15, and this became the base for the bar. It was thin enough to drill through easily, and didn't weigh much. The led strip (red) was able to fit nicely inside the channel.

I scrapped the original mounts I printed (above in pink), and redesigned them (grey).

Because of the tire trays and asymmetry of the rack, I had to be strategic about where I mounted the supports to the aluminum channel. One is mounted about 11 in from the end, and the other is only 7 in from the end of the channel.

Arm difficulties

By this point I had the mounts around the rack itself, as well as the mounts bolted onto the aluminum channel. I had initially printed thin arms to attach the two (in green), only 3mm thick. I tested these, and they bent quite a bit when trying to rotate and reposition the bar.

The redesign (teal), use the 'gopro' style mount on both sides, allowing for more range of motion. I also made it much thicker, 6mm at the thinnest part in the center.

I also made the new arms longer after realizing the rack's mechanism would hit it.

Wiring

When it came to wiring, I had planned to buy only the cable I needed, and run the four separate wires from the end of the rack to the car, but I ended up buying a spool of cable specifically for car wiring, color coded and labeled. This way the four cables were connected, making mounting easier. See the circuit diagram below. I used heat shrink in an attempt to keep it water tight, we'll see how that works.

I temporarily taped the cable to the rack, estimating the length needed, and how the cable would run. I ended up zip tying the cable to the rack.

Circuit diagram

Aluminum channel end caps

Assembly, Fusion 360

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