Intro: Laser Etched Wooden Deck for a Bicycle Rack
I just finished making a laser etched wooden deck for my first attempt at a fillet brazed chromoly bike rack. It's shaped on a laser cutter in two pieces, assembled around some t-nuts, then clamped and glued together. It has a slot to carry a U-lock (the rack itself has a bar to prevent it from swinging into the wheel... that's important).
I made it at Techshop with their 65 watt laser cutters and my trusty Dremel. I've also been charting my progress on the rack (and the bike it's going to go on) at CurmudgeonBicycles.com.
A couple of sheets of plywood small enough for the laser cutter but big enough for your deck.
Lots of clamps.
400 grit sand paper.
00 grit artificial steel wool.
Step 1: LASERS
I'm no carpenter, and I've yet to take the woodshop safety course that would get me access to the tools I'd need here. I have taken the laser cutter course though, and can do pretty much everything I need with that.
Plus, you know... LASERS.
The laser cutter basically functions like a printer. The darker a color is, the more power the laser pumps out. You set it up for your materials, do some trial and error, and then burn the hell out of whatever you're etching. Specific line widths trigger a vector cut (I usually just use .0001), which is usually set to cut all of the way through.
I found that the techshop recommended power settings needed to be tweaked a bit. The plywood was a bit harder to punch through than normal wood... so I set up a bunch of test cuts at the bottom. Find something that makes it through the first ply for the images, you'll be glad to have the extra depth later when you're finishing and sanding.
Step 2: LASERS 2
Use a 1/8 thick piece of plywood, that will let you create a quarter inch thick plank... just thick enough to be sturdy without being super heavy.
Put your different elements on different layers in illustrator so that you can cut them in shifts. Print the images first, then the smaller cutouts, then the border. If you cut the border first, the piece will shift and things won't line up.
I've included my template file. Don't use my picture or people will be confused. It's a good idea to use photoshop's "rubber stamp" tool to turn your photo black and white so that it turns out looking crisp. I did it in two layers... one complex and one simple, so that I could cut out complexity where I wanted to by erasing that top layer.
Important: when designing, account for where the piece will bolt to the rack on the bottom. I had to revise after some of the images below to make sure it ended up looking good.
Step 3: Carpentry... Sort Of
Take the bottom piece for your deck and place the rack on top of it. Line everything up with whatever holes you're using to connect it and mark them on the piece.
Once It's marked, drill through each of the marks with a bit the same diameter as the barrel on your t-nuts. Use a dremel to carve away a shallow dent over each of these holes in the top sheet... test sandwich the two pieces before you place them, you want to make sure you're not forgetting how they should fit together.
These dents will let the heads of the t-nut fit in between the sheets without bulging.
Step 4: Nuts!
Now you need to grind down four t-nuts until the barrels will almost (but not quite) make it through the bottom half of the deck. You also need to grind down the little spikes so that they won't penetrate all the way.
Once they're cut to size, fit them into the holes and tighten them in place with the matching bolt. Use washers so that they don't make dents in the visible side. This will sink the spikes in and keep them in place.
Step 5: Lamination!
Take the washers off, but leave the bolts threaded in a screw or five. Just until they're flush with the back of the t-nut. This will protect the threads from getting all glue-clogged.
Get two larger boards and drill holes out of them to match the locations of these bolt heads. pour some heavy duty wood glue on the insides of each piece and sandwich them between the boards, then clamp them hard for an hour or two. Be sure to bring enough clamps... I had to disassemble a repair stand to get mine right.
Step 6: Finishing
Give the whole board a nice light sanding. It's a good idea to knock down the corners at this point, unless you want a kind of sharp rack.
Seal the board with either special magic pre-stain or a really light layer of polyurethane, let dry. Brush on stain, let dry.
Lay down a coat of polyurethane, let dry. Sand lightly with 400 grit. Repeat.
Paint in the letters and images with a paint pen, a marker, or really any kind of pigment that'll stick. Sand the piece with a sanding block to eliminate excess if necessary.
Lay down a coat of polyurethane, let dry. Sand lightly with 400 grit.
Lay down a coat of polyurethane, let dry.
For our purposes, let dry equals about 24 hours.
Sand it with some higher grit sandpaper, then with 00 synthetic steel wool. Apply finishing wax by folding a lump in some cheesecloth, let it sit for 20 minutes or so, then buff it with more cheesecloth.
Finishing takes the most time out of the process. A friend with more woodworking experience recommended trying to encase the whole thing in a coat of epoxy so that it'll wear better. Might be worth a try.
Step 7: BOLT IT DOWN!
You're done. Bolt it to your rack and gaze at it in wonder.