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.

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

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

either BB Borers
or an advanced thought condensation eliminator

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.

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

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

David L. Johnson wrote:
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.


For air a single hole would be enough, but if you want to get water out
you'll need a vent.
Water will always find it's way in, for instance through condensation.
You either have to insure that the tube is 100% sealed or vent it to the
atmosphere. As frames with drainholes last long enough, i don't think it
is worth the bother and the risk to seal the few tubes which lend
themselves to sealing.

--
/Marten

info(apestaartje)m-gineering(punt)nl

Water drainage. And yes, they can let water in as easily as out and if
their too big, will weaken the shell.

A small hole or two won't kill anything. If you're worried about water
splash getting your spindle wet, get a plastic sleeve and slide it in
between the cups.

- -
Compliments of:
"Your Friendly Neighborhood Wheelman"

If you want to E-mail me use:
ChrisZCorner "at" webtv "dot" net

My website:
http://geocities.com/czcorner

On 1 Dec, 20:34, Martin Borsje wrote:
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- Dölj citerad text -

- Visa citerad text -

Absolutely, i have changed at least 20 Scott mtb BB this year, and
they have all been wet and rusted, so the BB should have a hole
underneath, and it has, but its blocked by the screw holding the cable
guide. Of course the best thing isnt to get the water out, but keeping
it from getting in...