No new exciting pictures today, just a catch up on bike school.

This week I started a frame building class, which covers everything from designing bicycles of different types to building them by hand.  Since this class has no requirement for previous knowledge or skill (thankfully), we are starting with the basics.

The technique we are using is brazing, which means that we are joining metal (in our case steel) with a dissimilar metal.  Depending on the joint that we are creating, our dissimilar metal is either a silver alloy or bronze.  Those require us to work at either just below or above 1500 degrees Fahrenheit, dependent on whether we are using silver or bronze.

Here is a fairly typical joining of the head tube of a bicycle and the top tube.  The head tube is where the fork runs through to connect to the handlebars and the top tube is the tallest tube on the bicycle, the one that you have to throw your leg over in order to get on the bicycle.  I’m using a lug, which helps hold the tubes in place and establish their relationship to each other, in this case 73 degrees.


Although it doesn’t look like it, that’s silver allow that is connecting the tubes to the lug.  It’s a bit of a messy job, but considering it’s the very first time I’ve ever done that, it really wouldn’t take but 20 minutes to clean it up to the point that you wouldn’t even realize it was there under the coat of pain that is required for steel.

But while it looks fine from the outside, we are concerned about the connections inside, beneath the lug and between the tubes.  And there’s only one way to check the quality of the connections.

Cut it apart.

Cut 73

You can see the discoloration of the steel from the heat and mostly the flux used to etch the steel during the process.  But the part that we were concerned about is where the tubes are joined.   And not a single gap to be found, so the silver is in contact with all of the lug and all of the tubes.  You won’t find that on most mass produced bicycles.

In other words, the tube would shear apart before this connection would tear apart.

Not too shabby for my first time.

A few more exercises like this and in just nine days, save for a paint job and component installation, I will have a rideable bicycle.  One that I built myself.

I think that’s pretty cool.


2 thoughts on “Brazing”

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