Threadless BB Cartridges: Why/Why Not?

In article <[email hidden]>,

Quoted message said:

Quoted message said:

One idea I've considered is to have a bottom bracket shell cut
across the bottom, and clamp lugs (like seatpost clamp ears) across
the cut, or perhaps external clamps outside each cup. This would
allow the BB shell to be clamped down on the cups and arrest this
fretting.

That is an idea. but that makes the BB an open sided tube that has no
torsional strength, and there is a rotating force there or the right
hand cup wouldn't need a left thread.

I'm not sure I can see how a freely rotating bearing would
load the BB shell in torsion, aside from precession which this clamping
should arrest.

Quoted message said:

Quoted message said:

I'm not sure how good my intuition is for the magnitude of forces
encountered here, but the existence of bottom brackets with
extensive cutouts suggests to me this may be reasonable.

Cut-outs OK but not slotted crosswise.

Some pictures I've seen, have so little of the shell left
that I can't believe them to have any more torsional strength than the
split shell, the remaining shell being basically two independant
bands, one for each cup, and a large hole from chainstay lug to downtube.
But such extremes aren't that common and it's probably telling that
they're no longer commonplace.

I wasn't able to find any pictures to corroborate last night,
but some tandems with eccentric bottom brackets have shells that are
slotted all the way across. These are a larger diameter though, which
may help them deal with stresses.

My other thought for the moment is that since the dynamic loads
are mainly an issue on the right side, that a slot 2/3 the width of the
shell to allow clamping only on that side might be useful in its own
right without fully splitting the shell. Or, if there's merit in
clamping the left side too, then perhaps a separate parallel slot for
it - this would leave a continuous bridge of metal that can carry torsion
generated shear forces that the full split could not.

-Luns

jobst.brandt said:

Pete Cresswell said:

Thanks to Werehatrack for introducing me to the concept...

Quoted message said:

Now it begs the question:
Why are BB shells threaded in the first place? i.e. Why don't most
bikes just come with threadless
already installed?

Quoted message said:

Sounds like there's a downside...

I must have missed it but could you direct me to a web site where I can
see the cross section of a threadless BB? The only ones I know of were
on Ashtabula cranks and they had a larger diameter.

Some bikes came with pressed-in BB bearings, through the early 90s --
Klein and Fisher come to mind. I think there were others too. The
problem is getting the bearings replaced, if you can't do it yourself.

The Pinarello BB mentioned in this thread is probably pressed-in:

http://www.pinarello.com/eng/products_technology_gear.php

Pinarello uses pressed-in headsets too.

ISTR some older Kleins being creaky, and people trying to cure the
problems with Loctite. If there's enough action to wear your threads
away, there may be enough for a pressed in bearing to work loose.

The Pinarello unit has larger bearings around an ISIS spindle, requiring a
larger BB shell. Perhaps the greater outside diameter of the bearing
makes it less susceptible to working loose.

Matt O.

Quoted message said:

In article <[email hidden]>,

Quoted message said:

Just to give an idea of the fragility of BB retention, I recently had
the right hand cup loosen and not be tightenable. When I removed it,
I discovered that more than 100000 miles of riding had eroded the
threads from the steel BB shell. The right side thread was completely
gone and the left side close behind. The right hand cup had been
brutally tightened and never removed during that time. Fretting
gradually ate up the threads leaving nothing but grey paste.

Luns Tee said:

One idea I've considered is to have a bottom bracket shell cut
across the bottom, and clamp lugs (like seatpost clamp ears) across
the cut, or perhaps external clamps outside each cup. This would allow
the BB shell to be clamped down on the cups and arrest this fretting.

-snip-

I don't think that sounds too promising. But in the '50s and
'60s the British frame shops made a similar beginning. To
cure a stripped shell, they slit the bb crosswise, forced
the edges together, welded the seam and rethreaded the
resulting smaller bore.

Here, we're partial to building up a bronze fill then simply
cutting a new thread where the damage is half a thread deep.
Like this but inside-out:
http://www.yellowjersey.org/FORKTHRD.JPG

For fully missing threads, we bore out and either cut to
Italian or braze in threaded rings as JObst described earlier.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Luns Tee said:

Quoted message said:

Quoted message said:

One idea I've considered is to have a bottom bracket shell cut
across the bottom, and clamp lugs (like seatpost clamp ears)
across the cut, or perhaps external clamps outside each cup. This
would allow the BB shell to be clamped down on the cups and arrest
this fretting.

Quoted message said:

Quoted message said:

That is an idea. but that makes the BB an open sided tube that has
no torsional strength, and there is a rotating force there or the
right hand cup wouldn't need a left thread.

Quoted message said:

I'm not sure I can see how a freely rotating bearing would load the
BB shell in torsion, aside from precession which this clamping
should arrest.

It's not the bearing, there or in the pedal, that unscrews the thread,
but rather precession from a rotating load point. I suppose if the
clamp is sturdy, it could arrest any fretting between cup and shell.

Quoted message said:

Quoted message said:

Quoted message said:

I'm not sure how good my intuition is for the magnitude of forces
encountered here, but the existence of bottom brackets with
extensive cutouts suggests to me this may be reasonable.

Quoted message said:

Quoted message said:

Cut-outs OK but not slotted crosswise.

Quoted message said:

Some pictures I've seen, have so little of the shell left that I
can't believe them to have any more torsional strength than the
split shell, the remaining shell being basically two independent
bands, one for each cup, and a large hole from chainstay lug to
downtube. But such extremes aren't that common and it's probably
telling that they're no longer commonplace.

This is like other places on bicycles, where someone with enough
market presence can set a new standard for mechanics. It took a long
time for the four kinds of BB threads to arrive at the British
standard, odd as it is, of 1.370x24TPI Left & Right threads.

http://www.sheldonbrown.com/brandt/bb-adjust.html

Quoted message said:

I wasn't able to find any pictures to corroborate last night, but
some tandems with eccentric bottom brackets have shells that are
slotted all the way across. These are a larger diameter though,
which may help them deal with stresses.

I think that this problem could be overcome but I don't see it
happening with the extreme attention to weight savings. We won't see
a heavier BB shell with a split and clamp screws in the bear future.

Quoted message said:

My other thought for the moment is that since the dynamic loads are
mainly an issue on the right side, that a slot 2/3 the width of the
shell to allow clamping only on that side might be useful in its own
right without fully splitting the shell. Or, if there's merit in
clamping the left side too, then perhaps a separate parallel slot
for it - this would leave a continuous bridge of metal that can
carry torsion generated shear forces that the full split could not.

That would be practical, considering that the left cup does not have
any significant rotating loads, proven by the use of right hand thread
and an aluminum lock ring that seems never to change its preload.

Jobst Brandt

Does the Cannondale Hollowgram SI integrated BB qualify as threadless?

both my road bike and MTB have them with some very tough miles on the
MTB and a year of racing on the road bike. Claims to be lighter and
stiffer than the equivalent Dura-Ace.

http://www.cannondale.com/Asset/iu_files/115861a.pdf

charlieb in ct

Charles Beristain said:

Does the Cannondale Hollowgram SI integrated BB qualify as threadless?

both my road bike and MTB have them with some very tough miles on the
MTB and a year of racing on the road bike. Claims to be lighter and
stiffer than the equivalent Dura-Ace.

http://www.cannondale.com/Asset/iu_files/115861a.pdf

It's a proprietary interface crankset which requires a special BB
shell in the frame. These cranksets fit only a CDale frame that's
prepped at the factory to receive them. The frames might be
retrofittable to accept a different crank, but I can't tell; no
dimensions are given, so it's impossible for me to say whether the BB
might be threadable to accept a conventional BB.

Despite the fact that CDale is an established firm with a long record,
I would tend to regard these cranks as something to be avoided due to
the inherent pitfalls of the proprietary-parts problem.
--
Typoes are a feature, not a bug.
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In article <[email hidden]>,

Peter Cole said:

I have a ~30 year old frame (Belgian) that has exactly this setup. The
BB shell has 2 slots with ears and pinch bolts to clamp both the fixed
and adjustable cups. I assumed, given the age of this bike, it was a
well-known technique. I wondered why it isn't used more often.

I would imagine that the purpose of this pinching was either
simply forgotten, or deemed not worth the extra complication and
weight (and then forgotten).

I'm curious though - what's the threading of this BB? Is the
right side cup a normal or a left-handed thread?

-Luns

Luns Tee said:

In article <[email hidden]>,

Peter Cole said:

I have a ~30 year old frame (Belgian) that has exactly this setup. The
BB shell has 2 slots with ears and pinch bolts to clamp both the fixed
and adjustable cups. I assumed, given the age of this bike, it was a
well-known technique. I wondered why it isn't used more often.

I would imagine that the purpose of this pinching was either
simply forgotten, or deemed not worth the extra complication and
weight (and then forgotten).

I'm curious though - what's the threading of this BB? Is the
right side cup a normal or a left-handed thread?

-Luns

often standard BSA, but variations exist

See www.m-gineering.nl/oldtechg.htm (last entry)

--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

A Muzi said:

Luns Tee wrote:

Quoted message said:

Quoted message said:

One idea I've considered is to have a bottom bracket shell
cut across the bottom, and clamp lugs (like seatpost clamp
ears) across the cut, or perhaps external clamps outside
each cup. This would allow the BB shell to be clamped down
on the cups and arrest this fretting.

Quoted message said:

I don't think that sounds too promising. But in the '50s and
'60s the British frame shops made a similar beginning. To
cure a stripped shell, they slit the bb crosswise, forced
the edges together, welded the seam and rethreaded the
resulting smaller bore.

I had the modification that Luns describes performed as a repair to the
bottom bracket shell of a Dawes Super Galaxy touring bike in London in the
early nineties. I'd bought the frame used, and the flange of the fixed cup
sheared off when I first tried to remove it. My local repairer cut open the
shell to remove the remains of the cup, then brazed on a pair of pinch
bolts. The repair gave me no trouble for the 30,000 or so miles I
subsequently rode on that frame.

James Thomson

Charles Beristain said:

Does the Cannondale Hollowgram SI integrated BB qualify as
threadless?

I don't believe the term "threadless" does much for anything but the
steertube that has traditionally been a headache in assembly.

Quoted message said:

Both my road bike and MTB have them with some very tough miles on
the MTB and a year of racing on the road bike. Claims to be lighter
and stiffer than the equivalent Dura-Ace.

http://www.cannondale.com/Asset/iu_files/115861a.pdf

Interesting. Fig. 6, showing the BB cross section is the one that
shows what interests me. I am not so thrilled with their leaving out
the bearings, possibly because they are amazingly small and probably
not angular contact as they should be. Maybe Shimano angular contact
head bearings would fit. That would be a bonus.

There is no reference to Isis, so I guess Cannondale are using their
own spline profile. That's too bad because a bit of unity in the face
of Shimano might help.

Jobst Brandt

Marten Gerritsen said:

Quoted message said:

Quoted message said:

I have a ~30 year old frame (Belgian) that has exactly this
setup. The BB shell has 2 slots with ears and pinch bolts to clamp
both the fixed and adjustable cups. I assumed, given the age of
this bike, it was a well-known technique. I wondered why it isn't
used more often.

Quoted message said:

Quoted message said:

I would imagine that the purpose of this pinching was either simply
forgotten, or deemed not worth the extra complication and weight
(and then forgotten).

Quoted message said:

Quoted message said:

I'm curious though - what's the threading of this BB? Is the right
side cup a normal or a left-handed thread?

Quoted message said:

See www.m-gineering.nl/oldtechg.htm (last entry)

This is refreshing to see that in those days the inventor apparently
understood that a clamped BB cup doesn't need a left thread and that
the BB width could be assured with a sleeve, split so that the clamp
action would secure the threaded cups.

Elegant!

Jobst Brandt

Quoted message said:

There is no reference to Isis, so I guess Cannondale are
using their own spline profile. That's too bad because a
bit of unity in the face of Shimano might help.

To give them credit, Cannondale were selling splined cranks (initially with
external bearing cups) long before Shimano's versions and ISIS came on the
market, beginning with the M900 Magic (Magic Motorcycle) model. The axle
was designed to be made from aluminium.

http://pardo.net/pardo/bike/pic/fail/FAIL-014.html

There've been a few revisions of the design, and I'm not sure whether or
not the model pictured in the .pdf pre-dates ISIS.

James Thomson

James Thomson said:

Quoted message said:

There is no reference to Isis, so I guess Cannondale are using
their own spline profile. That's too bad because a bit of unity in
the face of Shimano might help.

To give them credit, Cannondale were selling splined cranks
(initially with external bearing cups) long before Shimano's
versions and ISIS came on the market, beginning with the M900 Magic
(Magic Motorcycle) model. The axle was designed to be made from
aluminium.

http://pardo.net/pardo/bike/pic/fail/FAIL-014.html

There've been a few revisions of the design, and I'm not sure
whether or not the model pictured in the .pdf pre-dates ISIS.

British crank maker Williams offered what appeared to be an
interference fit splined crank 40 years ago. Hilary Stone just had
one up for auction on eBay. I've never seen one in person.

http://tinyurl.com/no575

Tim McNamara said:

British crank maker Williams offered what appeared to be
an interference fit splined crank 40 years ago. Hilary Stone
just had one up for auction on eBay. I've never seen one
in person.

I have, on a mid-sixties Moulton S-Speed, and of course there were other
splined cranks even earlier: Gnutti springs to mind, though I'm no
historian.

Just to clarify, I wasn't suggesting that Cannondale produced the first
splined cranks, but only that their use of tapered splines pre-dates both
Octalink and ISIS.

James Thomson

James Thomson said:

Quoted message said:

British crank maker Williams offered what appeared to be an
interference fit splined crank 40 years ago. Hilary Stone just had
one up for auction on eBay. I've never seen one in person.

Quoted message said:

I have, on a mid-sixties Moulton S-Speed, and of course there were
other splined cranks even earlier: Gnutti springs to mind, though
I'm no historian.

Quoted message said:

Just to clarify, I wasn't suggesting that Cannondale produced the
first splined cranks, but only that their use of tapered splines
pre-dates both Octalink and ISIS.

Octalink was not a tapered spline and that was its downfall. It was a
slip fit spline that had elastic and clearance backlash that allowed
enough fretting to loosen its retaining bolt for "goofy footed" riders
of which there are enough to present systematic failures. We have had
user testimony to that effect on this forum.

I bring this up because the manufacturers involved in BB design are
not well versed in the failure modes, bringing designs to market that
have built in failures. Octalink solved spindle strength problem but
failed in crank attachment... and bearing size. All of them up to now
have failed in pedal attachment, and most fail in lateral crank
bending strength, the mode in which nearly all cranks break. Cranks
rarely break form pedaling torque. They break off at the bottom of
the pedal stroke in side bending. This is apparent from all the
failed cranks shown here and ones I have inspected.

Jobst Brandt

Quoted message said:

James Thomson writes:

Quoted message said:

Quoted message said:

Just to clarify, I wasn't suggesting that Cannondale produced
the first splined cranks, but only that their use of tapered splines
pre-dates both Octalink and ISIS.

Quoted message said:

Octalink was not a tapered spline [snip]

I'm aware of that. I wrote that Cannondale's tapered spline pre-dated
Octalink: that doesn't imply that Octalink was itself tapered. The ISIS
standard was developed as a non-proprietary answer to Shimano's Octalink. I
was pointing out that it would have been impossible for Cannondale to have
adopted the ISIS spline before both Octalink and the ISIS standard existed.
Since Cannondale seem committed to aluminium as a spindle material, I
suspect they feel that the dimensions of the ISIS interface are unsuitable
for their uses.

James Thomson

James Thomson said:

Since Cannondale seem committed to aluminium as a spindle material, I
suspect they feel that the dimensions of the ISIS interface are unsuitable
for their uses.

And they're probably right, for what it's worth. Of course, inventing
yet another proprietary interface, and then marrying it to a BB design
that is just as quirky, is hardly a route to getting the product
generally accepted in the marketplace. It may be the best thing out
there, but if it's not installable in the bikes that other people are
already riding, it's not going to catch on.

CDale seems to be making a tactical error that has been committed over
and over in the past; come up with something that may very well be
better than the competition can provide, and then ensure that it will
not be a success by keeping it from being widely available.

Someday, someone is going to recognize that the English/Italian BB
shell diameter is the real problem, and will propose a new open
standard for a larger diameter of shell that can carry a more useful
size of bearing and shaft. For those who wish to stay with the old
tech, an adapter bushing could provide backward compatibility with
prior designs.

Unfortunately, I don't think that this is a move that's likely to be
made anytime soon.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Werehatrack said:

"James Thomson" wrote:

Quoted message said:

Quoted message said:

Since Cannondale seem committed to aluminium as a
spindle material, I suspect they feel that the dimensions
of the ISIS interface are unsuitable for their uses.

Quoted message said:

And they're probably right, for what it's worth. Of course,
inventing yet another proprietary interface, and then marrying
it to a BB design that is just as quirky, is hardly a route to
getting the product generally accepted in the marketplace.
It may be the best thing out there, but if it's not installable in
the bikes that other people are already riding, it's not going
to catch on.

Quoted message said:

CDale seems to be making a tactical error that has been
committed over and over in the past; come up with something
that may very well be better than the competition can provide,
and then ensure that it will not be a success by keeping it from
being widely available.

To be frank, I doubt that Hollowgram (and Coda Magic before it) has ever
been seen by Cannondale as a bridgehead into the mass market, but rather as
a selling feature of their most expensive models. Mass market acceptance
(which is probably precluded by the extravagant machining and expensive
materials) would undermine the exclusivity necessary to marketing the
system to the elite.

I did wonder whether it was a means of seeking market acceptance for a new
bottom bracket shell standard, but whatever the intention, that hasn't
happened.

Quoted message said:

Someday, someone is going to recognize that the English/Italian BB
shell diameter is the real problem, and will propose a new open
standard for a larger diameter of shell that can carry a more useful
size of bearing and shaft.

ISIS Overdrive?

http://www.isisdrive.com/isisoverdrive/

There's an interesting contrast between the scramble to adopt a wild array
of mutually incompatible integrated headset standards that nobody seemed to
want or need, and the general disinclination of the industry to update the
bottom bracket standard to a design that would appear to have real benefits
and simple backward compatibility.

In any case, the market seems to have accepted external bearing cups (a
feature of the orginal Coda Magic system, incidentally), which may remove
any immediate impetus to update the shell standard.

James Thomson

James Thomson said:

Quoted message said:

Quoted message said:

Since Cannondale seem committed to aluminium as a spindle
material, I suspect they feel that the dimensions of the ISIS
interface are unsuitable for their uses.

Quoted message said:

Quoted message said:

And they're probably right, for what it's worth. Of course,
inventing yet another proprietary interface, and then marrying it
to a BB design that is just as quirky, is hardly a route to getting
the product generally accepted in the marketplace. It may be the
best thing out there, but if it's not installable in the bikes that
other people are already riding, it's not going to catch on.

Quoted message said:

Quoted message said:

Cannondale seems to be making a tactical error that has been
committed over and over in the past; come up with something that
may very well be better than the competition can provide, and then
ensure that it will not be a success by keeping it from being
widely available.

Quoted message said:

To be frank, I doubt that Hollowgram (and Coda Magic before it) has
ever been seen by Cannondale as a bridgehead into the mass market,
but rather as a selling feature of their most expensive models.
Mass market acceptance (which is probably precluded by the
extravagant machining and expensive materials) would undermine the
exclusivity necessary to marketing the system to the elite.

Quoted message said:

I did wonder whether it was a means of seeking market acceptance for
a new bottom bracket shell standard, but whatever the intention,
that hasn't happened.

Quoted message said:

Quoted message said:

Someday, someone is going to recognize that the English/Italian BB
shell diameter is the real problem, and will propose a new open
standard for a larger diameter of shell that can carry a more
useful size of bearing and shaft.

Not soon but in harder times, the major manufacturers will have to
bury the hatchet and have a standards agreement in which standards are
not only set but designed so that there will be interchangeability as
we have in the computer business for I/O and storage devices as well
as data formats. For that to happen a strong leader must emerge who
engages both the manufacturers and the market. That need not come
from within the industry but could be achieved by an international
trade board that sets guidelines.

Quoted message said:

ISIS Overdrive?

http://www.isisdrive.com/isisoverdrive/

This is hopelessly lost. This does not address the failures of BB
threads the under size of the shell to house both a sturdy spindle AND
bearings and above all, I find the Isis spline not ideal for the task.
Nothing on that assembly strikes me as a significant advance. As was
demonstrated, spindles have broken because the transition from spline
to shaft was too abrupt, in spite of it's larger diameter than the old
square taper.

Quoted message said:

There's an interesting contrast between the scramble to adopt a wild
array of mutually incompatible integrated headset standards that
nobody seemed to want or need, and the general disinclination of the
industry to update the bottom bracket standard to a design that
would appear to have real benefits and simple backward
compatibility.

We don't need no "integrated headsets". That's fashion. The current
external pressed-in cups are ideal mechanically, being easy to install
and weather proof (facing downward). Now that fretting damage has
been addressed they also work and work well with threadless steer
tubes. What problem is the "integration" solving?

Quoted message said:

In any case, the market seems to have accepted external bearing cups
(a feature of the original Coda Magic system, incidentally), which
may remove any immediate impetus to update the shell standard.

We'll have to see how that works. If internal cups are difficult to
install and subsequently fail even when ideally installed, external
ones with overhung loads ought to accelerate failure while being no
easier to install. Getting rid of special (maintenance) tools should
also be a goal for the industry.

Jobst Brandt

Quoted message said:

James Thomson writes:

[suggesting a current published non-proprietary standard that includes
a larger-diameter BB shell as part of the spec]

Quoted message said:

Quoted message said:

ISIS Overdrive?

http://www.isisdrive.com/isisoverdrive/

This is hopelessly lost. This does not address the failures of BB
threads the under size of the shell to house both a sturdy spindle AND
bearings

The 12mm increase in BB diameter over the current size isn't enough,
then? Granted, I'd have plumped for a bit more OD so as to allow the
use of robust and inexpensive standard ball bearing assemblies, but at
least this seems to be a potentially firmer ground for improvement
than the existing "standard" BB.

Quoted message said:

and above all, I find the Isis spline not ideal for the task.
Nothing on that assembly strikes me as a significant advance. As was
demonstrated, spindles have broken because the transition from spline
to shaft was too abrupt, in spite of it's larger diameter than the old
square taper.

No argument there; if they were going to go with a shoulder at all,
they needed a lot more radius on the transition.

Perhaps it's time for a Rev B in the ISIS standard.

I think that the real problem is Shimano, however. As long as that
monster in the marketplace categorically refuses to come to the table
for any standards discussions, it is going to remain difficult to
achieve a useful consensus on what the successor BB shell design
should be. OTOH, I think that an independent agreement implemented by
Trek, Bianchi, CDale and the other major players would ultimately
force Shimano to produce cranks and BBs that acknowledged the change,
as long as the successor design was contrived to allow the continued
use of the old tech via adapter bushings for at least a resonable
period of time.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.