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5.8 Frame Building Part 3




Description

This article is from the Misc Bicycles FAQs, by various authors.

5.8 Frame Building Part 3

In contrast to last week when Dave and Ron were extremely busy and we
did a lot of watching, we were very busy and Dave and Ron watched us.
This session involved a lot of small steps and the one major task of
cleaning around the lugs of the fork and front triangle from the brazing
done the second session. The other tasks were aligning the main
triangle, finishing the rear triangle of the frame, finishing the fork.

Cleanup
The main task for the day would be cleaning up around the lugs of the
front triangle of the frame and the crown lug of the fork.

Cleanup is probably the most tedious and time-consuming of the tasks to
be done with a frame, but also what makes the frame look the best. It
involves cleaning up around each area that was brazed. Brazing will
leave little bubbles of brass here and there that need to be sanded
down, and flux that has hardened onto the tube needs to be sanded off,
edges need to be cleaned and defined. Essentially it means making the
tubes smooth and the edges and points defined. Sounds easy enough until
you consider the space you're working in.

At each lug, the best way to work is starting on the tube, moving to the
edges, and finally onto the lug itself. On the tube, file backed
sandpaper is used to clean off the tube and to get into the lug edges.
For the most part this isn't too difficult, but takes time since none of
the lug edges are flat or smooth and obviously the tubes themselves
aren't square. You have to constantly be moving the file/sandpaper and
changing angles to get it all. Some are can be really hard to reach,
for example around the bottom bracket, where space is tight. Sometimes
different files are necessary or using your thumb. Because Dave had done
such a good job cleaning up with the torch, there were very few areas
which had blobs or bumps.

Most of the lug edges can be done with a smaller files. They had some
die-cutters files that worked well. Very small and narrow, but worked
very well. Again, because Dave had done such a good job cleaning up
with the torch, most of the edges remained well defined. Where there
was blobs of brass at the edges, larger files were used to start using
the edge of the file to cut into the blobs, without cutting into the
tube, and then working towards the smaller files. Very little of this
could be done with sandpaper. Again some areas were tougher and harder
to get to requiring for patience and some careful filing.

Cleaning the lug surface was generally pretty easy. For the most part
file backed sandpaper could be used since the lug surfaces were above
the rest of the tubing. For tighter areas, fingers were used as the
backing of the sandpaper and fingers provided good curvature to get into
tight spaces, such as the bottom bracket and the junction between the
down tube and head tube.

The sandpaper used was strips about 3/4" wide and fairly rough. I used
several yards of this sandpaper, backed up fingers or files to clean up
around the lugs.

The one exception to this was cleaning the junction of the steerer tube
and fork crown lug where lots of brass had been applied. Large half-
round files provided the cutting to get this shaved down and then on to
progressively smaller half-round files to get up onto the blades
themselves.



 

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