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Why the holes in old BB shells?



 
 
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  #1  
Old December 1st 07, 07:05 PM posted to rec.bicycles.tech
Matt O'Toole
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Posts: 657
Default Why the holes in old BB shells?

I never understood why older racing frames have big holes in their BB
shells. Is this to drain water, to allow flushing and re-greasing without
disassembly, or just to look cute, with heart shaped holes and such?

This always seemed stupid to me, because of road spray, etc.

???

Matt O.
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  #2  
Old December 1st 07, 07:26 PM posted to rec.bicycles.tech
[email protected]
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Default Why the holes in old BB shells?

Matt O'Toole writes:

I never understood why older racing frames have big holes in their
BB shells. Is this to drain water, to allow flushing and
re-greasing without disassembly, or just to look cute, with heart
shaped holes and such?


This always seemed stupid to me, because of road spray, etc.


I recall that the keyhole slot in the seat tube was deeper than the
clamping depth for the seat post and that spray from the rear wheel
could enter to fill the bottom of the frame with water. To avoid
this, we made sure there was liberal grease in that slot.

Then someone started drilling a hole in the center of the BB to let
the water out, after which the idea was widely imitated. Various
logos were cut to make even larger openings, so much so that the shell
had no lateral strength and developed nonparallel faces in use.

Yes, I found that to be stupid because it did not address the problem
of allowing water to enter, aside from being an inexcusable structural
weak spot.

Jobst Brandt
  #3  
Old December 1st 07, 07:34 PM posted to rec.bicycles.tech
Martin Borsje[_4_]
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Posts: 20
Default Why the holes in old BB shells?

explained :
Matt O'Toole writes:

I never understood why older racing frames have big holes in their
BB shells. Is this to drain water, to allow flushing and
re-greasing without disassembly, or just to look cute, with heart
shaped holes and such?


This always seemed stupid to me, because of road spray, etc.


I recall that the keyhole slot in the seat tube was deeper than the
clamping depth for the seat post and that spray from the rear wheel
could enter to fill the bottom of the frame with water. To avoid
this, we made sure there was liberal grease in that slot.

Then someone started drilling a hole in the center of the BB to let
the water out, after which the idea was widely imitated. Various
logos were cut to make even larger openings, so much so that the shell
had no lateral strength and developed nonparallel faces in use.

Yes, I found that to be stupid because it did not address the problem
of allowing water to enter, aside from being an inexcusable structural
weak spot.

Jobst Brandt


I think you can never fulle avoid water entering the frame.

Is it through the seatpost or other likely routes as the steerer tube
or the bracket itself.

What comes in must go out!

Wherefore else holes in the fork tube ends (4x)?

Martin


  #4  
Old December 1st 07, 07:42 PM posted to rec.bicycles.tech
datakoll
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Posts: 7,793
Default Why the holes in old BB shells?


either BB Borers
or an advanced thought condensation eliminator
  #5  
Old December 1st 07, 07:57 PM posted to rec.bicycles.tech
Tim McNamara
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Posts: 6,945
Default Why the holes in old BB shells?

In article ,
Martin Borsje wrote:

What comes in must go out!

Wherefore else holes in the fork tube ends (4x)?


Venting to allow hot air out of the tube when brazing, which would
otherwise force itself out through the joint causing spattering of
molten brass or silver. It's not necessary when the tube is open on the
ends, which is the case in the main frame tubes. The vent holes should
be closed by the framebuilder at the end of brazing, as they serve no
purpose after the frame is built. Indeed, they are a water infiltration
point.
  #6  
Old December 1st 07, 08:11 PM posted to rec.bicycles.tech
clare at snyder.on.ca
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Posts: 151
Default Why the holes in old BB shells?

On Sat, 01 Dec 2007 12:57:09 -0600, Tim McNamara
wrote:

In article ,
Martin Borsje wrote:

What comes in must go out!

Wherefore else holes in the fork tube ends (4x)?


Venting to allow hot air out of the tube when brazing, which would
otherwise force itself out through the joint causing spattering of
molten brass or silver. It's not necessary when the tube is open on the
ends, which is the case in the main frame tubes. The vent holes should
be closed by the framebuilder at the end of brazing, as they serve no
purpose after the frame is built. Indeed, they are a water infiltration
point.

Why not keep the bottom bracket totally sealed and vent the seat tube
externally to drain accumulated moisture?? (other than the problem of
keeping the weeping hole from plugging up??)

--
Posted via a free Usenet account from http://www.teranews.com

  #7  
Old December 1st 07, 08:43 PM posted to rec.bicycles.tech
[email protected]
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Posts: 7,934
Default Why the holes in old BB shells?

On Sat, 01 Dec 2007 13:05:49 -0500, Matt O'Toole
wrote:

I never understood why older racing frames have big holes in their BB
shells. Is this to drain water, to allow flushing and re-greasing without
disassembly, or just to look cute, with heart shaped holes and such?

This always seemed stupid to me, because of road spray, etc.

???

Matt O.


Dear Matt,

On the lower right is the largest hole in the bottom of a bike that
I've found so far, an 1890s Spalding:

http://www.nostalgic.net/pictures/1720.htm

But the two small holes suggest that there may have been a cover
plate.

Unfortunately, pictures of the underside of the bottom bracket shell
are as rare as photos peeking up the hairy nostrils of Playboy models.

Here's an extensive gallery of bike frame pornography, with nary a
shot of the underside of the BB shell:

http://www.velostuf.com/velostufgallerybikes+frames.htm

Cheers,

Carl Fogel
  #8  
Old December 1st 07, 10:33 PM posted to rec.bicycles.tech
David L. Johnson
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Posts: 1,048
Default Why the holes in old BB shells?

Matt O'Toole wrote:
I never understood why older racing frames have big holes in their BB
shells. Is this to drain water, to allow flushing and re-greasing without
disassembly, or just to look cute, with heart shaped holes and such?

This always seemed stupid to me, because of road spray, etc.


Remember the 3 Stooges? There was a standard gag they had with Curly in
a boat that was half full of water, and he drilled holes in the bottom
to let the water out. This is similar.

--

David L. Johnson

Let's not escape into mathematics. Let's stay with reality.
-- Michael Crichton
  #9  
Old December 1st 07, 10:36 PM posted to rec.bicycles.tech
David L. Johnson
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Posts: 1,048
Default Why the holes in old BB shells?

Martin Borsje wrote:

What comes in must go out!

Wherefore else holes in the fork tube ends (4x)?


Those holes have nothing to do with water. If you tried to weld or
braze a tube at both ends, the air inside would expand as you worked,
and would push out the brazing or welding you were doing. Those holes
provide pressure relief so that the brazing or welding would hold.

--

David L. Johnson

Let's not escape into mathematics. Let's stay with reality.
-- Michael Crichton
  #10  
Old December 1st 07, 10:51 PM posted to rec.bicycles.tech
datakoll
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Posts: 7,793
Default Why the holes in old BB shells?



getting into the xams cheer early ?
 




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