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  1. #1
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    Bottom bracket cutouts

    I have just purchased a hand made steel frame. I noticed that the bottom bracket casing/shell has several cutouts. Could someone enlighten me as to the purpose of those cutouts? My gut tells me that they may be there for better heat dissipation, but I am really just guessing.

    Thanks!

  2. #2
    Senior Member nick burns's Avatar
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    drainage.

  3. #3
    Forum Admin lotek's Avatar
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    lots of theories, not sure which is the real reason although I've
    seen all of these quoted.

    1) lets water drain out of BB shell, seat tube etc.
    2) Weight savings
    3) looks cool and is good Identifying mark (see a clover got a nago! see an M got a masi).
    Sono pi lento di quel che sembra.
    Odio la gente, tutti.

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  4. #4
    Senior Member nick burns's Avatar
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    Quote Originally Posted by lotek
    3) looks cool and is good Identifying mark.
    My favorite theory.



    AD Ultima Superleicht

  5. #5
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    Thank you both for your responses.

  6. #6
    Senior Member cyclotoine's Avatar
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    I have an M, but it's a Marinoni!
    1 Super Record bike, 1 Nuovo Record bike, 1 Pista, 1 Road, 1 Cyclocross/Allrounder, 1 MTB, 1 Touring, 1 Fixed gear

  7. #7
    ex frame builder
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    There was a craze in the mid 1970s for drilling holes in bike components to reduce weight. Chainrings, brake levers, and rear derailleurs were drilled full of holes, even seat posts and handlebars by a few people which was pretty stupid. Some bikes had so many holes in them they didnt have a shadow.

    The craze died out when components started failing and drilling out aluminum alloy parts saved only a small amount of weight anyway. The cut-out bottom bracket shell was a hang over from this and lasted through to the early 1980s. It did save a little weight as the BB shell is a pretty hefty chunk of steel.

    Doing this by hand was pretty laborious and Masi like most production framebuilders had a die made that would stamp out the M in seconds, using a fly-press.
    History, photos and tech articles on my website. Also check "Dave's Bike Blog."

  8. #8
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    First I saw cut out BB shells was in the late 60's, it was on a Masi, before the M it appears. Most I would describe as ports, I guess my 2 stroke youth is showing.

    A friend ordered a Harry Quinn in 1973, he asked for a drilled BB shell, and thats what he got, about twenty .20" diameter holes neatly spaced on the underside of the BB shell.

    All Styling in my book, but fun.

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