From: Christopher
J. Root
I did it once, on a finished frame, by drilling a hole in
the top tube at either end. the holes have to be drilled
at an angle so that the hole ends up being elliptically
shaped instead of round. then i inserted a stainless
steel tube through the front hole and pulled it out the
back hole. then, i silver brazed it in place, filed it
flush with the top tube, and brazed a little reinforcing
plate over the joint. i think i used brake bridge
reinforcing plates that you can buy already made, they're
nice oval shaped and have a hole already in them. anyway,
using a stainless tube brazed in place keeps your top
tube sealed off from the rain. however, like matt houle
said, it would be WAY easier to do it before brazing the
entire frame together; it was a real bear for me to get
the stainless tube into a completed frame. but when it's
done it looks really nice, well worth the trouble i think
From: Dave Wilkins
I use brass tubing from the hobby shop, sized for
generous fit for the NEXT larger size cable housing that
will be used. That way, if the thin (also lightweight)
brass tubing gets a dent in it, the housing will still
pass.
If it doesn't dent, maybe somebody later can put some
larger cable thru there.
Like Matt Houle mentioned, it's better to install the
internal routing before building the frame. So after
laying out the in/out locations for the internal, I'll
chuck up a drill bit that is slightly smaller than the
O.D., then drill a hole into the tube. To keep from
drilling thru both sides of the tube, I'll put a stop on
the drill bit. (just slide a short length of steel tubing
over the drill bit, leaving only a 1/4" showing)
Then with a pneumatic die grinder with a carbide bit, cut
the drilled holes to a long horizontal oval. Make these
oval shaped holes the same shape as the brass tubing as
it enters/exits the tube at a very shallow angle.
Next file the oval holes until you can pass the tubing
into the frame tube. As you slide it in, because the
tubing is very thin walled and soft, it will hit the far
side of the top tube and will take on a curve. This curve
is what will help to guide the brass tubing out of the
exit point. When you get the brass tube to where you can
grab it with a pair of needle-nose pliers, just grab it
and pull it on out.
Next, clean up and silverbraze; cut the excess brass
tubing off and file.
Look thru the frame tube from the end, and see if the
internal tube is touching the far wall of the frame tube.
If it is close, when you hit a bump, it will rattle. I
learned this on my pride and joy first frame which I
still ride. But it is a bitch to fix later if you don't
reach up in there with something like a piece of wood
like 1/4x3/4 trim and bend the internal
till it's centered.
Be sure and silver braze (low temp) because these can end
outside of a butted portion of a tube. That's some thin
stuff...
Now you guys who work in framebuilding shops day in and
day out may chuckle, knowing of some better way to do
this, but I have no mill, lathe, etc. I just use basic
tools in my garage. My daddy used to say that if I
inherited a cathouse, I'd try to run it by hand...
From: Bob
Brown
Dave Wilkins Wrote:
'Be sure and silver braze (low temp) because these can
end outside of a butted portion of a tube. That's some
thin stuff...'
This is the main reason I will not use this method of
cable routing. If done correctly, the inlet and outlet
should be in the butt of the tube, otherwise, they can be
prone to cracking at the holes. Miyata had an enormous
problem with this on thier team, 916, 912, and 712 frames
for a couple years. I worked at a shop that had about
thirty of these frames with cracked top tubes left from
warranty replacements.
So be careful where you're drilling those holes, and how
thin your top tube is.
Monday, 10 July 2000