I have a junker frame (1980 Carlton-made 531 db main tubes, Suntour GS dropouts, split seat lug) with a really thick sand-casted bottom bracket. I understood from asking a question on the bikelist version of this forum, about 4 years ago, that I could use a very long 400mm seatpost to solve the lug-splitting problem (tube has split for about 1cm below the seatlug, straight down, as if some idiot used a hacksaw to open the seat lug for a higher-diameter seatpost.)
Many vintage 1960's and 1970's have something like a 2.5mm BB shell, but this one has one that's at least 50% thicker, and is very plain in appearance, and is probably a significant percentage of the frame weight (Carlton XYZ in
http://www.ece.ubc.ca/~gillies/raleigh/weights.txt). Bike has Bocama Pro (teardrop cutout) lugs.
I would like to drill some holes in the bottom bracket. One possibility is to drill "CC" in it, which was used for some top-end Carlton Pro's a few years earlier. Another possibility is to just drill large holes, like an old Cinelli, to lighten it up. It would be nice to reduce the weight by 30-50 grams. If I cannot reduce it that much, I probably won't bother.
Has anybody done this after construction? Too much of a pain to be worthwhile? Too difficult to do? The CC cutout has square letters, so it probably involves just drilling 4 large holes per letter and then cutting & filing between the holes to get the proper effect. I might use this for practice, and do it for real with another frameset I have (1968 competition), which is unbelievably heavy in the frameset, about 150 grams heavier than a typical 24.5" frame, but has a very light 700 gram fork (see url above, 1968 competition is a 2370 gram frameset, 180 grams heavier.)
- Don Gillies
San Diego, CA, USA
P.S. I don't read this forum too often, please cc me (gillies@ece.ubc.ca) on any responses. I will put a reminder in my calendar to check this group again, periodically.