Art makes a good point here.
While glued joints have a history of successful applications in structures of all types (yes, including torsion), all of these instances have one thing going for them that we, on the other hand, do at our own peril: TESTING. Testing, and quality control.
On another level, we should all be aware that, in the event of any of our's untimely demise, we might leave behind a fleet of bikes that ultimately go to auction. We should not assume that the next owner should, or will know of any time-bomb mechanical conditions that might have been put into place on an otherwise pristine and road-ready looking bicycle. Assembling a dangerous bike, if even for display or the occasional quick ride, could thus have disastrous consequences down the road.
I was actually thinking about this very issue this morning. I needed a longer/higher stem for my new 54cm Gitane Professional Service Course, and found a 22X25mm (french-dimensioned) 90mm neck on a discarded American Arrow (W. German) gaspipe bike that fit the bill. This neck looked like a toy, however, complete with casting flash, deep milling-error gouges and already-slender physique. I spent some hours cleaning it up and it looks absolutely perfect, and this morning's ride was improved by the addition, but is it safe? It is difinitely not "service course" grade, as was the stout 80mm Pivo it replaced. Belleri Franco (BF), btw. I plan on riding this one easy, but I'll probably sooner die from a fractured (already notched, how convenient!) BB spindle on my Viscount.
David Snyder Auburn, CA usa
Art Link wrote:
> Why screw with this at all???!!*** Throw it out and buy another on Ebay.
> Your safety and health is worth something more than saving the
> handlebar(unless it came off the Pope's gold plated Colnago). This is like
> repairing your foam core helmet after a crash to save a few bucks. Toss
> it.!! Art-lost an eye in a bike crash in 1973-Link,San Antonio,TX,USA
>
> David Snyder wrote: >
> Aldo is completely correct on both points.
>
> In particular, most bar's bends create twisting forces going into the
> clamp,
> and relatively long, slender glued or pressed joints do not fare well in
> torsion. These junctions fail starting at one end, and the failure
> progresses along the length to complete failure, due to the twisting that
> occurs along the length of tubing. I wouldn't count on the outer sleeve
> twisting along with the inner bar, since the stress on the adhesive will
> be
> localized at the outermost points of the bond (left and right in this
> case).
> Nor would I assume that any adhesive won't leave large areas un-bonded
> where
> air can become trapped, surrounded by glue.
>
> David Snyder, BSME
> theorizing in
> Auburn, CA, usa
>
>
> Aldo Ross wrote:
>
>> I've tried drilling & pinning (one pin 1/8" dia) through the
>> sleeve and bar, but the aluminum (non-heat-treated Cinelli
>> bars) is so soft that the slippage continued, while the pin
>> just gouged a slot through the bar and the sleeve.
>>
>> If you try glue or epoxy, remember that under load it could
>> shear (break loose) at any time.