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#31
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Threadless BB Cartridges: Why/Why Not?
"A Muzi" wrote:
Luns Tee wrote: 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. 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 |
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#32
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Threadless BB Cartridges: Why/Why Not?
Charles Beristain writes:
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. 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 |
#33
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Threadless BB Cartridges: Why/Why Not?
Marten Gerritsen writes:
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? 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 |
#34
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Threadless BB Cartridges: Why/Why Not?
wrote:
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 |
#35
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Threadless BB Cartridges: Why/Why Not?
"James Thomson" writes:
wrote: 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 |
#36
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Threadless BB Cartridges: Why/Why Not?
"Tim McNamara" wrote:
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 |
#37
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Threadless BB Cartridges: Why/Why Not?
James Thomson writes:
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. 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 |
#38
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Threadless BB Cartridges: Why/Why Not?
On Tue, 28 Feb 2006 03:00:18 +0100, "James Thomson"
wrote: 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. |
#39
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Threadless BB Cartridges: Why/Why Not?
"Werehatrack" wrote:
"James Thomson" wrote: 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. 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. 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 |
#40
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Threadless BB Cartridges: Why/Why Not?
James Thomson writes:
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. 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. 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. 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. 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. 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? 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 |
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