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Dienstag, 3. Dezember 2013

Broken Aluminum Frame repair with fiberglass and resin.

I bought a used bike to repair and resell and noticed, that the frame had a crack. I decided to build up a rigid mountain bike for myself and repair the frame. 

The bike was a Pinarello Treviso Mountainbike, a very rare bike from 1990 or 1991. Aluminium frames were pretty rare at that time, however the weight of the frame is only 1.6 kg.  Quite obvious that it broke.

If you look at the dropout, you notice, that it is welded the rear tube, which got squashed. An obvious design flaw. Since I can't weld aluminum, and always wanted to repair a cracked frame with fiberglass and resin, I repaired the frame this way:
 At first, I brazed a steel base layer, which distributes the force from the dropout better to the brittle aluminum frame.

 With a lot of good glue and some fibres, I glued the steelframe to the aluminium frame.
 I covered everything with resin and added fiberglass. I used an old bicycle tube to apply pressure to the fiberglass. With this technique you can use a lot more fibers and less resin which makes the frame stronger.
 After a few layers, I finished it.

 As a test ride, I took the bike to the most difficult trail in my area and rode it hard. It is interesting what you can do with a rigid bike, if you have tires with a lot of grip. I always thought before, that I would need my Enduro to ride that trail.

 I know I mixed up the components from two decades. I can already feel the retro bike enthusiasts cringing.
 The repaired part of the frame: