slugbath said:*Due to the added height of a new seat adapter, I have to shorten the
seat tube on my chrome Yuni frame. *
I just did this to a Yuni frame a weekend ago, for the same reasons.
It's pretty simple and you've already got the right tools.
Step 0) Take EVERYTHING off the frame.
Step 1) Mark the frame for the right cutoff point. If you like a nice
square cut then wrap a piece of paper around the tube and line it up
before you draw on the frame. I didn't bother, as I knew that later I
would have the chance to file it square, so I just scored the paint with
a knife all the way around.
Step 2) Measure the current slot height. Measure down from your line
and mark the bottom of the new slot. Make sure it isn't to the left or
right of center.
Step 3) Measure everything again. Last chance to get it right.
Step 4) If you have a drift punch, then lightly dent the frame at the
bottom of the new slot. DON'T put a real dent in the frame, just a
little poc mark so the drill bit won't wander.
Step 5) Select a SHARP drill bit that is as thick as the slot is wide.
Chuck it in your drill. Find some mineral oil or other cutting oil.
Vegetable or olive oil works just fine.
Step 6) Set the frame down horizontally on a soft surface, slot side up,
and secure it somehow. I laid it down on a pine deck and put my foot on
it.
Step 7) Brace yourself so the drill doesn't wander, put a few drops of
oil on the frame and SLOWLY drill a hole where you want the bottom of
the slot to go. SLOWER is better. Take your time; the frame isn't
going anywhere. If you go too fast the bit will heat up and get dull.
The oil is to keep it cool and flush out the debris. Oil frequently.
Step 8) Find some other way to brace the frame, oil the hacksaw blade,
and SLOWLY saw through the seat tube where you drew your line. Again,
take your time and use lots of oil. This part took me about 10 minutes.
Step 9) Now hacksaw the slot out. Use two cuts, on on either side of
the slot, and alternate between the two slots so that you are sawing
against relatively solid metal.
Step 10) Using the file, carefully clean off all the burrs. Take your
time and sculpt the frame a bit. Make the top nice and square, round
off all the sharp edges, etc. This part should take you about a 1/2
hour or more.
Step 11) Make sure the inside of the tube is smooth so it contacts the
seat post all the way around. Use your finger and feel for any trace of
a bump or burr on the inside of the frame tube. If you did everything
else wrong, get this part right. If you have a half round file then use
it to smooth the inside the tube. If not, then either find someone who
does, or get very creative. Wet/dry sandpaper works just fine but it
takes a while.
Step 12) Clean up. Make sure there are no shavings or grit inside the
tube. Put a thin layer of grease all over the inside of the tube and
the new cut edges to prevent corrosion.
Step 13) Put the unicycle back together.
Step 14) Have fun riding it.
--
cyberbellum - Level 1.0 rider!
I was standing in the park wondering why frisbees get bigger as they get
closer. Then it hit me.
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