Friday, 25 November 2011

A brass headbadge

Here's a headbadge I knocked up from brass for my next frame.

The process was surprisingly simple. I started with an offcut of 1.6mm brass sheet. I polished the front surface with brasso, then cleaned it thoroughly and coated it in a thin layer of etch resist. I overlaid the black part of the little fish logo printed on clear transparency paper, and exposed the resist with ultraviolet light. Then I developed the resist to remove the unwanted stuff, put some tape across the back to protect the back, and bunged the whole thing in an etchant tank for about 30 minutes.

This setup is usually used to make circuit boards, and etch times are usually about 3-4 minutes.

Once I pulled it out of the etchant and washed the resist off, I had this:

I then rolled it to fit a headtube, cut it out, gave it a quick polish, and hey presto. The etching is remarkably deep. I confess I'm surprised at how well it turned out. It was done as a quick experiment during lunch, and I expected all the lettering to disappear.

All that remains is soldering it to the headtube and infilling the etched areas with colour.

Sunday, 20 November 2011

A better dropout fixture

Up until now my jig has made use of a piece of threaded 10mm rod as the "axle" supporting the dropouts. This has been okay, but has been the most annoying thing about the jig.

So I figured I'd improve it. I noticed Alex Meade was selling dummy axles at quite reasonable prices, so figured I'd buy a couple and adapt them to my jig.

First thing I did was to turn up a sleeve to slide over the dummy axle. This is simply a piece of brass tube 50mm long, turned 19.05mm on the inside and 25mm on the outside. I made sure it was a nice accurate slip fit over Alex's axle. I used brass because it doesn't rust, is easy to work with, and is easy to soft solder.

Then I drilled and tapped a hole for an M6 grubscrew in the middle. Now the dummy axle can be held accurately in my brass tube.

I made a pair of flange pieces with 25mm holes in the middle, and 9mm holes to suit my 8020 extrusion. I used 3mm copper sheet because there was some in the scrap bin. Brass would have been fine here as well.

Then I jigged one flange piece on the axle, so it was accurately perpendicular, and soft soldered the two together. This is much like brazing, except that you use lead/tin filler and soft-solder flux. The solder melts at 180 degrees, so the pieces don't distort. Be careful to orient the tube on the flange to ensure the grub screw hole is accessible once it's all assembled.

Finally I bored a 26mm hole through the 8020 extrusion where the original 10mm hole was, and slipped the tube through. I then put the other flange on the other side of the extrusion to provide a bit more support.

If you have a thumping big bit of brass to hand, you could turn flange and tube out of one piece. I didn't, so made it out of what was kicking around.