Cargo Rack, Part 4

In this series: Part 1, Part 2, Part 3, Part 4.

Wood

I wanted a bit of a retro look for my bike-rack, since I think it'll compliment the lugged frame well.  That being said, I don't think that anything TOO retro will work.  After all, it's a lugged frame with an 1 1/8" headset and compact geometry.

You can already see that the rack has a bit more "shaped" look than a lot of older racks.  To offset that, I'm adding a wooden deck to the top.

Frickin' 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, which is usually set to cut all of the way through.

Since the cutter I was using could only go through thinner pieces of wood, I cut it out as two pieces: a top and a bottom.  I also divided the file up into a bunch of layers, so that I could do all of the surface etching before cutting the piece away from the plywood sheet, which can shift things around a bit. 

If you look carefully, you can see that I've cut my face into it next to the "if found, return to" bit in case I ever have to prove that I own the damned thing.  The miracle of the laser cutter is that it's incredibly easy to do that kind of thing.  

Woodworking: An Inevitable Learning Experience

I had considered using the laser cutter to bore the screw holes in the deck for me, but decided to use the rack itself to line things up, since there were going to be some inevitable imperfections.

Once the holes were drilled in the bottom piece, I countersunk them a bit and then ground out a dimple on the top to make room for the head of the bolt.  The idea is that the heads of the bolts are sandwiched between the two pieces, with the threaded ends sticking out.  That way there are no holes in the top, but I can still secure the deck.  I also cleaned the bolts with acetone in a glass bottle, to make sure that the glue would really stick to them.  Don't be tempted to do this in the paper or plastic cup that you have sitting around your shop.  It will melt and it'll smell horrible. 

I assembled the whole thing with a nice layer of heavy duty wood glue in the middle and tacked down the corners.  Then, I clamped it in a vice with some scrap wood over it to prevent dents.  If I were to do it again, I'd use much thicker wood scraps and drill it out so that the bolts wouldn't get in the way.  As it was, I had to slip extra glue into a few areas using a business card and then re-clamp a couple of times.

Finish

After a heroic sanding to round the edges and remove excess glue, I stained the deck (and some scraps) a bunch of times to find the right look.  Lots of sanding and re-staining, and re-staining again with different stain on top...  

Eventually, I ended up coloring in the letters with a black pen for contrast, then staining with a light red and a dark brown stain.  On top of that, I added three coats of a marine sealant designed for use on the railings of boats.  It smells a lot like peppermint and probably kills you if you taste it out of curiosity.

I think it turned out pretty well.  There are a few spots where I sanded too much near the edges.  I think others will see them and think that they're intentional "weathering".  They'll annoy me, but I'm going to wait until the bike is done to even think about re-doing anything on this.

Next time: hopefully I'll have some brazing (mostly practice) done for the next post.  I planned on doing that today, but the tinted glasses that I'd been using for eye protection wandered off.  I tried briefly to use darker shades designed for gas welding, and found that I couldn't tell the difference between a bit of red glow and bright screaming orange.  

In this series: Part 1, Part 2, Part 3, Part 4.

Cargo Rack, Part 3

In this series: Part 1, Part 2, Part 3, Part 4.

Fillets!

I finally got around to doing the fillets on the rack.  I like doing fillets.  You can see what you're doing a lot more easily than you can when you're trying to flow bronze under a lug.  Something about there not being a sheet of metal between you and what you're working on.

Here's one that I started to clean up.  You can see that the fillet forms a nice smooth transition between the tubes.  There were a few spots where I didn't build up quite enough filler for that, but they're inconspicuous.  Considering how thick I made the fillets overall, I'm not worried about it  being structurally unsound.  

If I'm feeling especially neurotic I'll fill the little gaps in with J.B. Weld.  Since that particular epoxy has a bunch of powdered metal in it, the powder coat will stick to it.

Sneak Peak

In our next episode, I'll get into how I'm making the wooden deck for this rack.  It's all lasers and power tools!

In this series: Part 1, Part 2, Part 3, Part 4.

Cargo Rack, Part 2

In this series: Part 1, Part 2, Part 3, Part 4.

Yesterday I started brazing the rack, which was pretty exciting.  In this step, I just laid down a bit of bronze to hold things in place.  Later, I'll build up fillets.  A fillet is a meniscus of metal that joins pieces together.  When done properly, the metal creates a nice smooth transition between the two.  

Tabs

I cut the tabs out of some sample sheets of chromoly steel that I had lying around.  They're basically little metal guitar picks.  When the bike is done and all of the attachment points are installed, I'll drill them.  That'll let me level it out if something weird happens.  

I'm pretty sure, but not positive, that the sheets will be thick enough to resist bending when I'm carrying things.  If I was using it for loaded touring, I'd double them up.  I still may add a bit of reinforcement.  

Once the tabs were done, I slotted the vertical tubes of the rack, lined them up with the tabs on my basic sketch, and then squeezed them with a pair of pliers just enough to keep them from shifting (much).  

Brazing

I started brazing by securing the tabs.  I did each of the four connections one at a time.  The hard part was dealing with the last joint.  It kept wanting to spring free, as the rack widens slightly near the rear (for aerodynamic effect, or something).   I solved that with the sheet-metal vice grips that appear in one of the pictures below. 

Next, I attached the rails, where a bag will hang.  I clamped the first on one end, rotated it level, then tacked it on the other.  Then I was able to remove the clamp and tack the remaining end.  

The second rail was about 100 times harder, since it had to line up exactly with the first.  At one point I probably would have hurled it across the room if there weren't other folks around working.  Thankfully, after quite a bit of trial and error, it fell into place and I was able to tack it down before it slipped and hit me in the eye or something.

Here we go!  I need to finish the fillets and grind the ends a bit, but the look and geometry work.  

Next time: finishing fillets, adding tabs for the wooden deck, and making the strut to connect it to the seat cluster.

In this series: Part 1, Part 2, Part 3, Part 4.

Cargo Rack, Part 1

In this series: Part 1, Part 2, Part 3, Part 4.

I started making a cargo rack yesterday.  My theory is that fillet brazing the rack will give me some much needed practice with my heat control.  Additionally, a lot of builders at NAHBS used custom racks to highlight aspects of their frame, and I think I may have caught a bit of inspiration.  

I'm using 5/16" diameter tubing, with .035" thick walls.  I have some 1/4" tubing in the mail, which I'll use for the struts that run to the seat cluster, since it's a lower stress area.  

I used a cheap, $10 tube bender.  On the up side, it works.  On the down side, the guide marks aren't really lined up with anything useful.  I had to bend it little bit by little bit until it matched my blueprints. 

The pieces already bent here will form the sides of the rack.  They'll connect in front, and hang down a bit in back.  

Here are the finished struts.  Each U will cross over the wheel.  

When I'm done I should have a light, narrow rack, slightly flared at the back.  I'm planning to bolt a piece of finished wood to the top.  Since I have a laser cutter handy, I'll probably engrave "Cedite E Campo", the  motto of my fake bike company, into it in ridiculous flowery script.  

In this series: Part 1, Part 2, Part 3, Part 4.