Monday, April 9, 2012

Cargo Rack, Part 2

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


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).  


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 1Part 2Part 3Part 4.

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